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.

Fluctuation of Indoor Radon and VOC Concentrations Due to Seasonal Variations

EPA Science Inventory

This research was conducted to better characterize the spatial and temporal variability of vapor intrusion by collecting a full year’s dataset of weekly measurements of subslab soil gas, external soil gas, and indoor air, on a single house that is impacted by vapor intrusion of r...

Estimating the gas and dye quantities for modified tracer technique measurements of stream reaeration coefficients

USGS Publications Warehouse

Rathbun, R.E.

1979-01-01

Measuring the reaeration coefficient of a stream with a modified tracer technique has been accomplished by injecting either ethylene or ethylene and propane together and a rhodamine-WT dye solution into the stream. The movement of the tracers through the stream reach after injection is described by a one-dimensional diffusion equation. The peak concentrations of the tracers at the downstream end of the reach depend on the concentrations of the tracers in the stream at the injection site, the longitudinal dispersion coefficient, the mean water velocity, the length of the reach, and the duration of the injection period. The downstream gas concentrations also depend on the gas desorption coefficients of the reach. The concentrations of the tracer gases in the stream at the injection site depend on the flow rates of the gases through the injection diffusers, the efficiency of the gas absorption process, and the stream discharge. The concentration of dye in the stream at the injection site depends on the flow rate of the dye solution, the concentration of the dye solution, and the stream discharge. Equations for estimating the gas flow rates, the quantities of the gases, the dye concentration, and the quantity of dye together with procedures for determining the variables in these equations are presented. (Woodard-USGS)

Novel characterization of the aerosol and gas-phase composition of aerosolized jet fuel.

PubMed

Tremblay, Raphael T; Martin, Sheppard A; Fisher, Jeffrey W

2010-04-01

Few robust methods are available to characterize the composition of aerosolized complex hydrocarbon mixtures. The difficulty in separating the droplets from their surrounding vapors and preserving their content is challenging, more so with fuels, which contain hydrocarbons ranging from very low to very high volatility. Presented here is a novel method that uses commercially available absorbent tubes to measure a series of hydrocarbons in the vapor and droplets from aerosolized jet fuels. Aerosol composition and concentrations were calculated from the differential between measured total (aerosol and gas-phase) and measured gas-phase concentrations. Total samples were collected directly, whereas gas-phase only samples were collected behind a glass fiber filter to remove droplets. All samples were collected for 1 min at 400 ml min(-1) and quantified using thermal desorption-gas chromatography-mass spectrometry. This method was validated for the quantification of the vapor and droplet content from 4-h aerosolized jet fuel exposure to JP-8 and S-8 at total concentrations ranging from 200 to 1000 mg/m(3). Paired samples (gas-phase only and total) were collected every approximately 40 min. Calibrations were performed with neat fuel to calculate total concentration and also with a series of authentic standards to calculate specific compound concentrations. Accuracy was good when compared to an online GC-FID (gas chromatography-flame ionization detection) technique. Variability was 15% or less for total concentrations, the sum of all gas-phase compounds, and for most specific compound concentrations in both phases. Although validated for jet fuels, this method can be adapted to other hydrocarbon-based mixtures.

Tracking Dissolved Methane Concentrations near Active Seeps and Gas Hydrates: Sea of Japan.

NASA Astrophysics Data System (ADS)

Snyder, G. T.; Aoki, S.; Matsumoto, R.; Tomaru, H.; Owari, S.; Nakajima, R.; Doolittle, D. F.; Brant, B.

2015-12-01

A number of regions in the Sea of Japan are known for active gas venting and for gas hydrate exposures on the sea floor. In this investigation we employed several gas sensors mounted on a ROV in order to determine the concentrations of dissolved methane in the water near these sites. Methane concentrations were determined during two-second intervals throughout each ROV deployment during the cruise. The methane sensor deployments were coupled with seawater sampling using Niskin bottles. Dissolved gas concentrations were later measured using gas chromatography in order to compare with the sensor results taken at the same time. The observed maximum dissolved methane concentrations were much lower than saturation values, even when the ROV manipulators were in contact with gas hydrate. Nonetheless, dissolved concentrations did reach several thousands of nmol/L near gas hydrate exposures and gas bubbles, more than two orders of magnitude over the instrumental detection limits. Most of the sensors tested were able to detect dissolved methane concentrations as low as 10 nmol/L which permitted detection when the ROV approached methane plume sites, even from several tens of meters above the sea floor. Despite the low detection limits, the methane sensors showed variable response times when returning to low-background seawater (~5nM). For some of the sensors, the response time necessary to return to background values occurred in a matter of minutes, while for others it took several hours. Response time, as well as detection limit, should be an important consideration when selecting methane sensors for ROV or AUV investigations. This research was made possible, in part, through funding provided by the Japanese Ministry of Economy, Trade and Industry (METI).

Gas Contamination In Plasma-Arc-Welded Aluminum

NASA Technical Reports Server (NTRS)

Mcclure, John C.; Torres, Martin R.; Gurevitch, Alan C.; Newman, Robert A.

1992-01-01

Document describes experimental investigation on visible and tactile effects of gaseous contaminants in variable-polarity plasma arc (VPPA) welding of 2219 T-87 aluminum alloy. Contaminant gases (nitrogen, methane, oxygen, and hydrogen) introduced in argon arc and in helium shield gas in various controlled concentrations. Report represents results of experiments in form of photographs of fronts, backs, polished cross sections, and etched cross sections of welds made with various contaminants at various concentrations. Provides detailed discussion of conditions under which welds made.

Variable selection based cotton bollworm odor spectroscopic detection

NASA Astrophysics Data System (ADS)

Lü, Chengxu; Gai, Shasha; Luo, Min; Zhao, Bo

2016-10-01

Aiming at rapid automatic pest detection based efficient and targeting pesticide application and shooting the trouble of reflectance spectral signal covered and attenuated by the solid plant, the possibility of near infrared spectroscopy (NIRS) detection on cotton bollworm odor is studied. Three cotton bollworm odor samples and 3 blank air gas samples were prepared. Different concentrations of cotton bollworm odor were prepared by mixing the above gas samples, resulting a calibration group of 62 samples and a validation group of 31 samples. Spectral collection system includes light source, optical fiber, sample chamber, spectrometer. Spectra were pretreated by baseline correction, modeled with partial least squares (PLS), and optimized by genetic algorithm (GA) and competitive adaptive reweighted sampling (CARS). Minor counts differences are found among spectra of different cotton bollworm odor concentrations. PLS model of all the variables was built presenting RMSEV of 14 and RV2 of 0.89, its theory basis is insect volatilizes specific odor, including pheromone and allelochemics, which are used for intra-specific and inter-specific communication and could be detected by NIR spectroscopy. 28 sensitive variables are selected by GA, presenting the model performance of RMSEV of 14 and RV2 of 0.90. Comparably, 8 sensitive variables are selected by CARS, presenting the model performance of RMSEV of 13 and RV2 of 0.92. CARS model employs only 1.5% variables presenting smaller error than that of all variable. Odor gas based NIR technique shows the potential for cotton bollworm detection.

Applications of breath gas analysis in medicine

NASA Astrophysics Data System (ADS)

Amann, Anton; Poupart, Guy; Telser, Stefan; Ledochowski, Maximilian; Schmid, Alex; Mechtcheriakov, Sergei

2004-12-01

Volatile organic compounds (VOCs) in exhaled breath gas provide valuable information about the subjects' physiological and pathophysiological condition. Proton-transfer-reaction mass spectrometry (PTR-MS) allows rapid and online measurements of these substances. We present results of three studies illustrating the potential of breath gas analysis by PTR-MS in various contexts: long-time online monitoring of VOCs in sleeping subjects suggests that VOC profiles are related to sleep stages. Analysis of VOC concentrations in the breath of carbohydrate malabsorbers emphasizes the role played by bacteria in the gut. Finally, we demonstrate the large intra- and intersubject concentration variability of VOCs by considering one particular mass.

Experiments to Evaluate and Implement Passive Tracer Gas Methods to Measure Ventilation Rates in Homes

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

Lunden, Melissa; Faulkner, David; Heredia, Elizabeth

2012-10-01

This report documents experiments performed in three homes to assess the methodology used to determine air exchange rates using passive tracer techniques. The experiments used four different tracer gases emitted simultaneously but implemented with different spatial coverage in the home. Two different tracer gas sampling methods were used. The results characterize the factors of the execution and analysis of the passive tracer technique that affect the uncertainty in the calculated air exchange rates. These factors include uncertainties in tracer gas emission rates, differences in measured concentrations for different tracer gases, temporal and spatial variability of the concentrations, the comparison betweenmore » different gas sampling methods, and the effect of different ventilation conditions.« less

Mathematical modeling of filling of gas centrifuge cascade for nickel isotope separation by various feed flow rate

NASA Astrophysics Data System (ADS)

Ushakov, Anton; Orlov, Alexey; Sovach, Victor P.

2018-03-01

This article presents the results of research filling of gas centrifuge cascade for separation of the multicomponent isotope mixture with process gas by various feed flow rate. It has been used mathematical model of the nonstationary hydraulic and separation processes occurring in the gas centrifuge cascade. The research object is definition of the regularity transient of nickel isotopes into cascade during filling of the cascade. It is shown that isotope concentrations into cascade stages after its filling depend on variable parameters and are not equal to its concentration on initial isotope mixture (or feed flow of cascade). This assumption is used earlier any researchers for modeling such nonstationary process as set of steady-state concentration of isotopes into cascade. Article shows physical laws of isotope distribution into cascade stage after its filling. It's shown that varying each parameters of cascade (feed flow rate, feed stage number or cascade stage number) it is possible to change isotope concentration on output cascade flows (light or heavy fraction) for reduction of duration of further process to set of steady-state concentration of isotopes into cascade.

Detection of greenhouse-gas-induced climatic change. Progress report, 1 December 1991--30 June 1994

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

Wigley, T.M.L.; Jones, P.D.

1994-07-01

In addition to changes due to variations in greenhouse gas concentrations, the global climate system exhibits a high degree of internally-generated and externally-forced natural variability. To detect the enhanced greenhouse effect, its signal must be isolated from the ``noise`` of this natural climatic variability. A high quality, spatially extensive data base is required to define the noise and its spatial characteristics. To facilitate this, available land and marine data bases will be updated and expanded. The data will be analyzed to determine the potential effects on climate of greenhouse gas concentration changes and other factors. Analyses will be guided bymore » a variety of models, from simple energy balance climate models to ocean General Circulation Models. Appendices A--G contain the following seven papers: (A) Recent global warmth moderated by the effects of the Mount Pinatubo eruption; (B) Recent warming in global temperature series; (C) Correlation methods in fingerprint detection studies; (D) Balancing the carbon budget. Implications for projections of future carbon dioxide concentration changes; (E) A simple model for estimating methane concentration and lifetime variations; (F) Implications for climate and sea level of revised IPCC emissions scenarios; and (G) Sulfate aerosol and climatic change.« less

Seasonal patterns of cytokinins and microclimate and the mediation of gas exchange among canopy layers of mature Acer saccharum trees.

PubMed

Reeves, Ian; Emery, R J Neil

2007-11-01

Seasonal patterns of cytokinins (CKs) and microclimate were examined in the upper, middle and lower canopy layers of mature Acer saccharum Marsh. (sugar maple) trees to elucidate the potential role of CKs in the mediation of gas exchange. The upper canopy showed a distinctly dissimilar microclimate from the middle and lower canopy layers with higher photosynthetically active radiation and wind speed, but showed no corresponding differences in transpiration (E) or stomatal conductance (g(s)). Although E and g(s) tended to be higher in the upper canopy than in the middle and lower canopies, the differences were not significant, indicating regulation beyond the passive response to changes in microclimate. The upper canopy accumulated significantly higher concentrations of CKs, predominantly as ribosides, and all canopy layers showed distinct seasonal patterns in CK profiles. Multiple regression models showed significant relationships between both g(s) and E and foliar CK concentration, although these relationships varied among canopy layers. The relationships were strongest in the middle and lower canopy layers where there was less fluctuation in leaf water status and less variability in abiotic variables. The relationships between gas exchange parameters and leaf CK concentration began to decouple near the end of the growing season as foliar phytohormone concentrations changed with the approach of dormancy.

Assessment of Mitigation Systems on Vapor Intrusion ...

EPA Pesticide Factsheets

Vapor intrusion is the migration of subsurface vapors, including radon and volatile organic compounds (VOCs), in soil gas from the subsurface to indoor air. Vapor intrusion happens because there are pressure and concentration differentials between indoor air and soil gas. Indoor environments are often negatively pressurized with respect to outdoor air and soil gas (for example, from exhaust fans or the stack effect), and this pressure difference allows soil gas containing subsurface vapors to flow into indoor air through advection. In addition, concentration differentials cause VOCs and radon to migrate from areas of higher to lower concentrations through diffusion, which is another cause of vapor intrusion. Current practice for evaluating the vapor intrusion pathway involves a multiple line of evidence approach based on direct measurements in groundwater, external soil gas, subslab soil gas, and/or indoor air. No single line of evidence is considered definitive, and direct measurements of vapor intrusion can be costly, especially where significant spatial and temporal variability require repeated measurements at multiple locations to accurately assess the chronic risks of long-term exposure to volatile organic compounds (VOCs) like chloroform, perchloroethylene (PCE), and trichloroethylene (TCE).

Relationships between 222Rn dissolved in ground water supplies and indoor 222Rn concentrations in some Colorado front range houses

USGS Publications Warehouse

Folger, P.F.; Nyberg, P.; Wanty, R.B.; Poeter, E.

1994-01-01

Indoor 222Rn concentrations were measured in 37 houses with alpha track detectors placed in water-use rooms near water sources (bathrooms, laundry rooms, and kitchens) and in non-water-use living rooms, dining rooms, and bedrooms away from water sources. Results show that relative contributions of 222Rn to indoor air from water use are insignificant when soil-gas concentrations are high but become increasingly important as the ratio of 222Rn-in-water:222Rn-in-soil gas increases. High soil-gas 222Rn concentrations may mask 222Rn contributions from water even when waterborne 222Rn concentrations are as high as 750 kBq m-3. Ground water in Precambrian Pikes Peak granite averages 340 kBq m-3222Rn, vs. 170 kBq m-3 in Precambrian migmatite, but average 222Rn concentrations in soil gas are also lower in migmatite. Because the ratio of 222Rn-in- water:222Rn-in-soil gas may be consistently higher for houses in migmatite than in Pikes Peak granite, indoor air in houses built on migmatite may have a greater relative contribution from water use even though average 222Rn concentrations in the water are lower. Continuous monitoring of 222Rn concentrations in air on 15-min intervals also indicates that additions to indoor concentrations from water use are significant and measurable only when soil-gas concentrations are low and concentrations in water are high. When soil-gas concentrations were mitigated to less than 150 Bq m-3 in one house, water contributes 20-40% of the annual indoor 222Rn concentration in the laundry room (222Rn concentration in water of 670 kBq m-3). Conversely, when the mitigation system is inactive, diurnal fluctuations and other variations in the soil-gas 222Rn contribution swamp the variability due to water use in the house. Measurable variations in indoor concentrations from water use were not detected in one house despite a low soil-gas contribution of approximately 150 Bq m-3 because waterborne 222Rn concentrations also are low (80 kBq m-3). This result suggests that 222Rn concentrations in water near the recommended EPA limit in drinking water of 11 kBq m-3 may not contribute measurable amounts of 222Rn to indoor air in most houses.

On the role of sea-state in bubble-mediated air-sea gas flux during a winter storm

NASA Astrophysics Data System (ADS)

Liang, Jun-Hong; Emerson, Steven R.; D'Asaro, Eric A.; McNeil, Craig L.; Harcourt, Ramsey R.; Sullivan, Peter P.; Yang, Bo; Cronin, Meghan F.

2017-04-01

Oceanic bubbles play an important role in the air-sea exchange of weakly soluble gases at moderate to high wind speeds. A Lagrangian bubble model embedded in a large eddy simulation model is developed to study bubbles and their influence on dissolved gases in the upper ocean. The transient evolution of mixed-layer dissolved oxygen and nitrogen gases at Ocean Station Papa (50°N, 145°W) during a winter storm is reproduced with the model. Among different physical processes, gas bubbles are the most important in elevating dissolved gas concentrations during the storm, while atmospheric pressure governs the variability of gas saturation anomaly (the relative departure of dissolved gas concentration from the saturation concentration). For the same wind speed, bubble-mediated gas fluxes are larger during rising wind with smaller wave age than during falling wind with larger wave age. Wave conditions are the primary cause for the bubble gas flux difference: when wind strengthens, waves are less-developed with respect to wind, resulting in more frequent large breaking waves. Bubble generation in large breaking waves is favorable for a large bubble-mediated gas flux. The wave-age dependence is not included in any existing bubble-mediated gas flux parameterizations.

Interannual variability of ammonia concentrations over the United States: sources and implications

NASA Astrophysics Data System (ADS)

Schiferl, Luke D.; Heald, Colette L.; Van Damme, Martin; Clarisse, Lieven; Clerbaux, Cathy; Coheur, Pierre-François; Nowak, John B.; Neuman, J. Andrew; Herndon, Scott C.; Roscioli, Joseph R.; Eilerman, Scott J.

2016-09-01

The variability of atmospheric ammonia (NH3), emitted largely from agricultural sources, is an important factor when considering how inorganic fine particulate matter (PM2.5) concentrations and nitrogen cycling are changing over the United States. This study combines new observations of ammonia concentration from the surface, aboard aircraft, and retrieved by satellite to both evaluate the simulation of ammonia in a chemical transport model (GEOS-Chem) and identify which processes control the variability of these concentrations over a 5-year period (2008-2012). We find that the model generally underrepresents the ammonia concentration near large source regions (by 26 % at surface sites) and fails to reproduce the extent of interannual variability observed at the surface during the summer (JJA). Variability in the base simulation surface ammonia concentration is dominated by meteorology (64 %) as compared to reductions in SO2 and NOx emissions imposed by regulation (32 %) over this period. Introduction of year-to-year varying ammonia emissions based on animal population, fertilizer application, and meteorologically driven volatilization does not substantially improve the model comparison with observed ammonia concentrations, and these ammonia emissions changes have little effect on the simulated ammonia concentration variability compared to those caused by the variability of meteorology and acid-precursor emissions. There is also little effect on the PM2.5 concentration due to ammonia emissions variability in the summer when gas-phase changes are favored, but variability in wintertime emissions, as well as in early spring and late fall, will have a larger impact on PM2.5 formation. This work highlights the need for continued improvement in both satellite-based and in situ ammonia measurements to better constrain the magnitude and impacts of spatial and temporal variability in ammonia concentrations.

Quantitative measuring system for combustible gas with audible tick rate

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

Batz, J.E.

1979-09-04

Northern Illinois Gas Co.'s new gas-detection instrument is lightweight, portable, easy to use, and in compliance with industry standards as an intrinsically safe device. The instrument uses a semiconductor gas-sensor element energyzed with the regulated voltage source. Placed in the atmosphere to be tested, the detector generates a signal representative of the concentration of natural gas in the air. A meter displays the signal to determine whether the area is hazardous; a variable-repetition-rate blocking oscillator feeding a speaker responds to the signal, generating an audible tick rate useful in locating a leak.

Effect of pulsed corona discharge voltage and feed gas flow rate on dissolved ozone concentration

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

Prasetyaningrum, A., E-mail: ajiprasetyaningrum@gmail.com; Ratnawati,; Jos, B.

Ozonization is one of the methods extensively used for water purification and degradation of organic materials. Ozone (O{sub 3}) is recognized as a powerful oxidizing agent. Due to its strong oxidability and better environmental friendless, ozone increasing being used in domestic and industrial applications. Current technology in ozone production utilizes several techniques (corona discharge, ultra violet radiation and electrolysis). This experiment aimed to evaluating effect of voltage and gas flow rate on ozone production with corona discharge. The system consists of two net-type stainless steel electrode placed in a dielectric barrier. Three pulsed voltage (20, 30, 40 KV) and flowmore » rate (5, 10, 15 L/min) were prepare for operation variable at high frequency (3.7 kHz) with AC pulsed power supply. The dissolved ozone concentration depends on the applied high-voltage level, gas flow rate and the discharge exposure duration. The ozone concentration increases with decreasing gas flow rate. Dissolved ozone concentrations greater than 200 ppm can be obtained with a minimum voltage 40 kV.« less

Effect of pulsed corona discharge voltage and feed gas flow rate on dissolved ozone concentration

NASA Astrophysics Data System (ADS)

Prasetyaningrum, A.; Ratnawati, Jos, B.

2015-12-01

Ozonization is one of the methods extensively used for water purification and degradation of organic materials. Ozone (O3) is recognized as a powerful oxidizing agent. Due to its strong oxidability and better environmental friendless, ozone increasing being used in domestic and industrial applications. Current technology in ozone production utilizes several techniques (corona discharge, ultra violet radiation and electrolysis). This experiment aimed to evaluating effect of voltage and gas flow rate on ozone production with corona discharge. The system consists of two net-type stainless steel electrode placed in a dielectric barrier. Three pulsed voltage (20, 30, 40 KV) and flow rate (5, 10, 15 L/min) were prepare for operation variable at high frequency (3.7 kHz) with AC pulsed power supply. The dissolved ozone concentration depends on the applied high-voltage level, gas flow rate and the discharge exposure duration. The ozone concentration increases with decreasing gas flow rate. Dissolved ozone concentrations greater than 200 ppm can be obtained with a minimum voltage 40 kV.

Variability in the gas phase composition of fluids discharged from Los Azufres geothermal field, Mexico

NASA Astrophysics Data System (ADS)

Santoyo, E.; Verma, S. P.; Nieva, D.; Portugal, E.

1991-07-01

Studies related to hydrological structure of the Los Azufres geothermal field and its effects on the exploitation of the field for generation of electrical energy have included a program of sampling and chemical analysis of fluids discharged by a number of deep wells in continuous production. Chemical analysis of the gaseous phase includes monitoring of CO 2, H 2S, NH 3, H 2, He, N 2, CH 4 and 222Rn. Five wells in Los Azufres field were periodically sampled during 1983-1988. The monitoring program has shown considerable variability in the gas concentrations of fluids. Before mid-1985, the 'base-line' concentrations of the gases showed standard deviations between 8 and 28%. During the later period, the average concentrations of different gases ranged from 37% to much higher values above the 'base-line'. The largest variations are observed in He, CO 2 and 222Rn. This variability is interpreted in terms of (1) addition of 'excess steam', (2) a possible relationship with earthquake events that occurred in México during September 19-21, 1985, and early May to early June of 1987 and, (3) more recent variations (after mid-1987), increased exploitation of the field.

Nitrous Oxide Emissions From Northern Forested and Harvested Ecosystems

NASA Astrophysics Data System (ADS)

Kavanaugh, K. M.; Kellman, L. M.

2005-12-01

Very little is known about how deforestation alters the soil subsurface production and surface emissions of N2O from northern forest soils. Soil N2O surface fluxes and subsurface concentrations from two 3 year old harvested and intact forest pairs of contrasting soil texture were monitored during the 2004 and 2005 growing seasons in the Acadian forest of Atlantic Canada in order to: 1) quantify N2O emissions associated with each land-use type, 2) examine spatial and temporal variations in subsurface concentrations and surface fluxes at each site, and 3) determine the suitability of a photoacoustic gas monitor (PGM) for in- situ field measurements vs. field sample collection and laboratory analysis on a gas chromatograph. Each site was instrumented with 11 permanent collars for surface flux measurements designed to capture the microsite variability at the sites. Subsurface soil gas samplers, designed to identify the important zones of N2O production in the vertical profile were installed at depths of 0, 10, 20 and 35 cm below the organic-mineral soil interface. Surface fluxes were measured with non-steady-state vented surface flux chambers with measurements of all surface flux and subsurface data made on a bi-weekly basis. Results suggest that spatial and temporal variability in surface emissions are very high and routinely close to zero. Subsurface profile concentration data shows vertical concentration profiles at intact forest sites with concentrations close to atmospheric, while harvested sites show a pattern of increasing N2O concentration with depth, reaching a maximum of approximately 27000ppb at 35cm.

Impacts of climate variability and future climate change on harmful algal blooms and human health

Treesearch

Stephanie K. Moore; Vera L. Trainer; Nathan J. Mantua; Micaela S. Parker; Edward A. Laws; Lorraine C. Backer; Lora E. Fleming

2008-01-01

Anthropogenically-derived increases in atmospheric greenhouse gas concentrations have been implicated in recent climate change, and are projected to substantially impact the climate on a global scale in the future. For marine and freshwater systems, increasing concentrations of greenhouse gases are expected to increase surface temperatures, lower pH, and cause changes...

Indoor radon, geogenic radon surrogates and geology - Investigations on their correlation.

PubMed

Friedmann, H; Baumgartner, A; Bernreiter, M; Gräser, J; Gruber, V; Kabrt, F; Kaineder, H; Maringer, F J; Ringer, W; Seidel, C; Wurm, G

2017-01-01

The indoor radon concentration was measured in most houses in a couple of municipalities in Austria. At the same time the activity concentration of radium in soil, the soil gas radon concentration, the permeability of the ground and the ambient dose equivalent rate were also measured and the geological situations (geological units) were recorded too. From the indoor radon concentration and different house and living parameters a radon potential (Austrian radon potential) was derived which should represent the radon concentration in a standard room. Another radon potential (Neznal radon potential) was calculated from the soil gas radon concentration and the permeability. The aim of the investigation was to correlate all the different variables and to test if the use of surrogate data (e.g. geological information, ambient dose equivalent rate, etc.) can be used to judge the radon risk for an area without performing numerous indoor measurements. Copyright © 2016 Elsevier Ltd. All rights reserved.

Vapor concentration monitor

DOEpatents

Bayly, John G.; Booth, Ronald J.

1977-01-01

An apparatus for monitoring the concentration of a vapor, such as heavy water, having at least one narrow bandwidth in its absorption spectrum, in a sample gas such as air. The air is drawn into a chamber in which the vapor content is measured by means of its radiation absorption spectrum. High sensitivity is obtained by modulating the wavelength at a relatively high frequency without changing its optical path, while high stability against zero drift is obtained by the low frequency interchange of the sample gas to be monitored and of a reference sample. The variable HDO background due to natural humidity is automatically corrected.

Hierarchical modeling of indoor radon concentration: how much do geology and building factors matter?

PubMed

Borgoni, Riccardo; De Francesco, Davide; De Bartolo, Daniela; Tzavidis, Nikos

2014-12-01

Radon is a natural gas known to be the main contributor to natural background radiation exposure and only second to smoking as major leading cause of lung cancer. The main concern is in indoor environments where the gas tends to accumulate and can reach high concentrations. The primary contributor of this gas into the building is from the soil although architectonic characteristics, such as building materials, can largely affect concentration values. Understanding the factors affecting the concentration in dwellings and workplaces is important both in prevention, when the construction of a new building is being planned, and in mitigation when the amount of Radon detected inside a building is too high. In this paper we investigate how several factors, such as geologic typologies of the soil and a range of building characteristics, impact on indoor concentration focusing, in particular, on how concentration changes as a function of the floor level. Adopting a mixed effects model to account for the hierarchical nature of the data, we also quantify the extent to which such measurable factors manage to explain the variability of indoor radon concentration. Copyright © 2014 Elsevier Ltd. All rights reserved.

Chemical equilibrium. [maximizing entropy of gas system to derive relations between thermodynamic variables

NASA Technical Reports Server (NTRS)

1976-01-01

The entropy of a gas system with the number of particles subject to external control is maximized to derive relations between the thermodynamic variables that obtain at equilibrium. These relations are described in terms of the chemical potential, defined as equivalent partial derivatives of entropy, energy, enthalpy, free energy, or free enthalpy. At equilibrium, the change in total chemical potential must vanish. This fact is used to derive the equilibrium constants for chemical reactions in terms of the partition functions of the species involved in the reaction. Thus the equilibrium constants can be determined accurately, just as other thermodynamic properties, from a knowledge of the energy levels and degeneracies for the gas species involved. These equilibrium constants permit one to calculate the equilibrium concentrations or partial pressures of chemically reacting species that occur in gas mixtures at any given condition of pressure and temperature or volume and temperature.

Noble Gas Signatures in Snow: a New Experimental Investigation.

NASA Astrophysics Data System (ADS)

Amalberti, J.; Hall, C. M.; Castro, C.

2016-12-01

Dissolved noble gases in groundwater (He, Ne, Ar, Kr, and Xe) have been widely used to improve our knowledge of surface and groundwater dynamics. However, a recent rainwater study [1] recorded noble gas concentration anomalies originating from conditions at high altitude. Potential anomaly sources might include fog, orographic rain, synoptic rain and snow, depending on the region considered. Here, we outline a methodology for measuring noble gases in freshly collected snow samples. Their fine-grained nature leads to significant experimental challenges. Overall, our results (Fig. 1) show that snow has elevated He concentrations with depleted concentrations of all other noble gases. Similar results have been recorded in ice [2, 3]. In addition, our results show relatively homogeneous (< 14%) He and Ne concentrations while Ar, Kr and Xe display large concentration variability (> 80%). These observations led us to investigate the structure of snow and potential host-sites (available empty space) within the crystal structure. Noble gases are chemically inert and do not form bonds that could affect the ice crystal structure. Therefore, host-sites control the solubility of each noble gas. Our results show that He and Ne, which are known to have small atomic radii, are likely dissolved into the ice/snow crystal lattice, while heavy noble gas (Ar, Kr and Xe) are likely accommodated into defects. Consequently, smaller variability recorded in light noble gases, may result from He and Ne being hosted within the crystal lattice, whereas heavy noble gases rely on the presence of defects, which may randomly appear within the structure during snow formation. These new results can be used to better constrain the source of ground ice [3], groundwater systems and to investigate the structural transition mechanisms from snow to firn and ice. Figure 1: Noble gas concentrations (C) in snow (filled circles symbols) and ice (half-filled square symbols) normalized to air saturated water (ASW). [1] Warrier, et al., (2013), Geophys. Res. Lett., 40, 3248-3252. [2] Malone et al., (2010), EPSL, 289, 112-122. [3] Utting et a., (2016), Quat. Res., 85, 117-184.

Inside anesthesia breathing circuits: time to reach a set sevoflurane concentration in toddlers and newborns: simulation using a test lung.

PubMed

Kern, Delphine; Larcher, Claire; Basset, Bertrand; Alacoque, Xavier; Fesseau, Rose; Samii, Kamran; Minville, Vincent; Fourcade, Olivier

2012-08-01

We measured the time it takes to reach the desired inspired anesthetic concentration using the Primus (Drägerwerk, AG, Lübeck, Germany) and the Avance (GE Datex-Ohmeda, Munich, Germany) anesthesia machines with toddler and newborn ventilation settings. The time to reach 95% of inspired target sevoflurane concentration was measured during wash-in from 0 to 6 vol% sevoflurane and during wash-out from 6 to 0 vol% with fresh gas flows equal to 1 and 2 times the minute ventilation. The Avance was faster than the Primus (65 seconds [95% confidence interval (CI): 55 to 78] vs 310 seconds [95% CI: 261 to 359]) at 1.5 L/min fresh gas flow, tidal volume of 50 mL, and 30 breaths/min. Times were shorter by the same magnitude at higher fresh gas flows and higher minute ventilation rates. The effect of doubling fresh gas flow was variable and less than expected. The Primus is slower during newborn than toddler ventilation, whereas the Avance's response time was the same for newborn and toddler ventilation. Our data confirm that the time to reach the target-inspired anesthetic concentration depends on breathing circuit volume, fresh gas flow, and minute ventilation.

Novel models on fluid's variable thermo-physical properties for extensive study on convection heat and mass transfer

NASA Astrophysics Data System (ADS)

Shang, De-Yi; Zhong, Liang-Cai

2017-01-01

Our novel models for fluid's variable physical properties are improved and reported systematically in this work for enhancement of theoretical and practical value on study of convection heat and mass transfer. It consists of three models, namely (1) temperature parameter model, (2) polynomial model, and (3) weighted-sum model, respectively for treatment of temperature-dependent physical properties of gases, temperature-dependent physical properties of liquids, and concentration- and temperature-dependent physical properties of vapour-gas mixture. Two related components are proposed, and involved in each model for fluid's variable physical properties. They are basic physic property equations and theoretical similarity equations on physical property factors. The former, as the foundation of the latter, is based on the typical experimental data and physical analysis. The latter is built up by similarity analysis and mathematical derivation based on the former basic physical properties equations. These models are available for smooth simulation and treatment of fluid's variable physical properties for assurance of theoretical and practical value of study on convection of heat and mass transfer. Especially, so far, there has been lack of available study on heat and mass transfer of film condensation convection of vapour-gas mixture, and the wrong heat transfer results existed in widespread studies on the related research topics, due to ignorance of proper consideration of the concentration- and temperature-dependent physical properties of vapour-gas mixture. For resolving such difficult issues, the present novel physical property models have their special advantages.

Metabolic and respiratory derangements associated with death in cold-stunned Kemp's ridley turtles (Lepidochelys kempii): 32 cases (2005-2009).

PubMed

Keller, Krista A; Innis, Charles J; Tlusty, Michael F; Kennedy, Adam E; Bean, Sarah B; Cavin, Julie M; Merigo, Constance

2012-02-01

To assess selected clinicopathologic variables at hospital admission (day 1) for cold-stunned Kemp's ridley turtles (Lepidochelys kempii) that died during the first 3 days after admission (nonsurvivors) and turtles that survived (survivors) and to determine the percentage change of each variable from day 1 to day of death (nonsurvivors) or to day 2 or 3 of hospitalization (survivors). Retrospective case-control study. Animals-64 stranded, cold-stunned Kemp's ridley turtles hospitalized from October 2005 through December 2009. Blood gas, pH, Hct, and selected biochemical values in blood samples determined on day 1 and day of death (nonsurvivors; n = 32) or day 2 or 3 of hospitalization (survivors; 32) were obtained from medical records. For each variable, initial values and percentage changes (from initial values to values at the day of death or day 2 or 3 of hospitalization) were compared between survivors and nonsurvivors. Compared with blood analysis findings for survivors, nonsurvivors initially had significantly higher potassium concentration and Pco(2) and significantly lower Po(2), pH, and bicarbonate concentration than did survivors. For the first 2 or 3 days of hospitalization, percentage changes in potassium, lactate, and ionized calcium concentrations were significantly higher and percentage changes in pH and plasma glucose and bicarbonate concentrations were significantly lower in nonsurvivors. At hospital admission, cold-stunned Kemp's ridley turtles were affected by metabolic and respiratory derangements; severe derangements were associated with death. Evaluation of blood gas, pH, Hct, and selected clinicopathologic variables provided useful clinical and prognostic information during rehabilitation of cold-stunned Kemp's ridley turtles.

Time-series measurements of bubble plume variability and water column methane distribution above Southern Hydrate Ridge, Oregon

NASA Astrophysics Data System (ADS)

Philip, Brendan T.; Denny, Alden R.; Solomon, Evan A.; Kelley, Deborah S.

2016-03-01

An estimated 500-2500 gigatons of methane carbon is sequestered in gas hydrate at continental margins and some of these deposits are associated with overlying methane seeps. To constrain the impact that seeps have on methane concentrations in overlying ocean waters and to characterize the bubble plumes that transport methane vertically into the ocean, water samples and time-series acoustic images were collected above Southern Hydrate Ridge (SHR), a well-studied hydrate-bearing seep site ˜90 km west of Newport, Oregon. These data were coregistered with robotic vehicle observations to determine the origin of the seeps, the plume rise heights above the seafloor, and the temporal variability in bubble emissions. Results show that the locations of seep activity and bubble release remained unchanged over the 3 year time-series investigation, however, the magnitude of gas release was highly variable on hourly time scales. Bubble plumes were detected to depths of 320-620 m below sea level (mbsl), in several cases exceeding the upper limit of hydrate stability by ˜190 m. For the first time, sustained gas release was imaged at the Pinnacle site and in-between the Pinnacle and the Summit area of venting, indicating that the subseafloor transport of fluid and gas is not restricted to the Summit at SHR, requiring a revision of fluid-flow models. Dissolved methane concentrations above background levels from 100 to 300 mbsl are consistent with long-term seep gas transport into the upper water column, which may lead to the build-up of seep-derived carbon in regional subsurface waters and to increases in associated biological activity.

Detection of greenhouse-gas-induced climatic change. Progress report, July 1, 1994--July 31, 1995

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

Jones, P.D.; Wigley, T.M.L.

1995-07-21

The objective of this research is to assembly and analyze instrumental climate data and to develop and apply climate models as a basis for detecting greenhouse-gas-induced climatic change, and validation of General Circulation Models. In addition to changes due to variations in anthropogenic forcing, including greenhouse gas and aerosol concentration changes, the global climate system exhibits a high degree of internally-generated and externally-forced natural variability. To detect the anthropogenic effect, its signal must be isolated from the ``noise`` of this natural climatic variability. A high quality, spatially extensive data base is required to define the noise and its spatial characteristics.more » To facilitate this, available land and marine data bases will be updated and expanded. The data will be analyzed to determine the potential effects on climate of greenhouse gas and aerosol concentration changes and other factors. Analyses will be guided by a variety of models, from simple energy balance climate models to coupled atmosphere ocean General Circulation Models. These analyses are oriented towards obtaining early evidence of anthropogenic climatic change that would lead either to confirmation, rejection or modification of model projections, and towards the statistical validation of General Circulation Model control runs and perturbation experiments.« less

Characterization of VOCs Across Pennsylvania: Assessing Emissions from Rural, Forested, Agricultural and Natural Gas Drilling-Impacted Areas

NASA Astrophysics Data System (ADS)

Grannas, A. M.; Fuentes, J. D.; Ramos-Garcés, F.; Wang, D. K.; Martins, D. K.

2012-12-01

Volatile organic compounds (VOCs) of both biogenic and anthropogenic origin are important to troposphere chemistry, particularly the formation of photochemical smog and secondary organic aerosol. There is concern that increased natural gas exploration may lead to increased emissions of certain VOCs during well development and due to fugitive emissions from operational well sites and pipelines. For a six-day period in June 2012, a variety of VOCs were measured using canister sampling from a mobile measurement platform. Transects from southwestern to northeastern Pennsylvania were studied, with samples obtained in rural, forested, urban, farm-impacted and gas well-impacted sites. As expected, biogenic VOCs and isoprene oxidation products were enhanced in forested regions, while anthropogenic non-methane hydrocarbons were enhanced in urban areas. BTEX (benzene, toluene, ethylbenzene and xylenes) was enhanced in urban areas, but the concentrations of BTEX measured near developing and existing natural gas sites were similar to rural and forested sites. Halogenated hydrocarbons and Freon compounds were consistent at all site locations. We will discuss the specific concentrations and signatures of these compounds and assess the potential impact of agricultural activities and gas well development on the observed VOC concentrations and variability.

On which timescales do gas transfer velocities control North Atlantic CO2 flux variability?

NASA Astrophysics Data System (ADS)

Couldrey, Matthew; Oliver, Kevin; Yool, Andrew; Halloran, Paul; Achterberg, Eric

2016-04-01

The North Atlantic is an important basin for the global ocean's uptake of anthropogenic and natural carbon dioxide (CO2), but the mechanisms controlling this carbon flux are not fully understood. The air-sea flux of CO2, F, is the product of a gas transfer velocity, k, the air-sea CO2concentration gradient, ΔpCO2, and the temperature and salinity-dependent solubility coefficient, α. k is difficult to constrain, representing the dominant uncertainty in F on short (instantaneous to interannual) timescales. Previous work shows that in the North Atlantic, ΔpCO2and k both contribute significantly to interannual F variability, but that k is unimportant for multidecadal variability. On some timescale between interannual and multidecadal, gas transfer velocity variability and its associated uncertainty become negligible. Here, we quantify this critical timescale for the first time. Using an ocean model, we determine the importance of k, ΔpCO2and α on a range of timescales. On interannual and shorter timescales, both ΔpCO2and k are important controls on F. In contrast, pentadal to multidecadal North Atlantic flux variability is driven almost entirely by ΔpCO2; k contributes less than 25%. Finally, we explore how accurately one can estimate North Atlantic F without a knowledge of non-seasonal k variability, finding it possible for interannual and longer timescales. These findings suggest that continued efforts to better constrain gas transfer velocities are necessary to quantify interannual variability in the North Atlantic carbon sink. However, uncertainty in k variability is unlikely to limit the accuracy of estimates of longer term flux variability.

On which timescales do gas transfer velocities control North Atlantic CO2 flux variability?

NASA Astrophysics Data System (ADS)

Couldrey, Matthew P.; Oliver, Kevin I. C.; Yool, Andrew; Halloran, Paul R.; Achterberg, Eric P.

2016-05-01

The North Atlantic is an important basin for the global ocean's uptake of anthropogenic and natural carbon dioxide (CO2), but the mechanisms controlling this carbon flux are not fully understood. The air-sea flux of CO2, F, is the product of a gas transfer velocity, k, the air-sea CO2 concentration gradient, ΔpCO2, and the temperature- and salinity-dependent solubility coefficient, α. k is difficult to constrain, representing the dominant uncertainty in F on short (instantaneous to interannual) timescales. Previous work shows that in the North Atlantic, ΔpCO2 and k both contribute significantly to interannual F variability but that k is unimportant for multidecadal variability. On some timescale between interannual and multidecadal, gas transfer velocity variability and its associated uncertainty become negligible. Here we quantify this critical timescale for the first time. Using an ocean model, we determine the importance of k, ΔpCO2, and α on a range of timescales. On interannual and shorter timescales, both ΔpCO2 and k are important controls on F. In contrast, pentadal to multidecadal North Atlantic flux variability is driven almost entirely by ΔpCO2; k contributes less than 25%. Finally, we explore how accurately one can estimate North Atlantic F without a knowledge of nonseasonal k variability, finding it possible for interannual and longer timescales. These findings suggest that continued efforts to better constrain gas transfer velocities are necessary to quantify interannual variability in the North Atlantic carbon sink. However, uncertainty in k variability is unlikely to limit the accuracy of estimates of longer-term flux variability.

On which timescales do gas transfer velocities control North Atlantic CO2 flux variability?

NASA Astrophysics Data System (ADS)

Couldrey, M.; Oliver, K. I. C.; Yool, A.; Halloran, P. R.; Achterberg, E. P.

2016-02-01

The North Atlantic is an important basin for the global ocean's uptake of anthropogenic and natural carbon dioxide (CO2), but the mechanisms controlling this carbon flux are not fully understood. The air-sea flux of CO2, F, is the product of a gas transfer velocity, k, the air-sea CO2 concentration gradient, ΔpCO2, and the temperature and salinity-dependent solubility coefficient, α. k is difficult to constrain, representing the dominant uncertainty in F on short (instantaneous to interannual) timescales. Previous work shows that in the North Atlantic, ΔpCO2 and k both contribute significantly to interannual F variability, but that k is unimportant for multidecadal variability. On some timescale between interannual and multidecadal, gas transfer velocity variability and its associated uncertainty become negligible. Here, we quantify this critical timescale for the first time. Using an ocean model, we determine the importance of k, ΔpCO2 and α on a range of timescales. On interannual and shorter timescales, both ΔpCO2 and k are important controls on F. In contrast, pentadal to multidecadal North Atlantic flux variability is driven almost entirely by ΔpCO2; k contributes less than 25%. Finally, we explore how accurately one can estimate North Atlantic F without a knowledge of non-seasonal k variability, finding it possible for interannual and longer timescales. These findings suggest that continued efforts to better constrain gas transfer velocities are necessary to quantify interannual variability in the North Atlantic carbon sink. However, uncertainty in k variability is unlikely to limit the accuracy of estimates of longer term flux variability.

Study of oxygen gas production phenomenon during stand and discharge in silver-zinc batteries

NASA Technical Reports Server (NTRS)

1974-01-01

Standard production procedures for manufacturing silver zinc batteries are evaluated and modified to reduce oxygen generation during open circuit stand and discharge. Production predictions of several variable combinations using analysis models are listed for minimum gassing, with emphasis on the concentration of potassium hydroxide in plate formation. A recommendation for work optimizing the variables involved in plate processing is included.

Seasonal Variability in European Radon Measurements

NASA Astrophysics Data System (ADS)

Groves-Kirkby, C. J.; Denman, A. R.; Phillips, P. S.; Crockett, R. G. M.; Sinclair, J. M.

2009-04-01

In temperate climates, domestic radon concentration levels are generally seasonally dependent, the level in the home reflecting the convolution of two time-dependent functions. These are the source soil-gas radon concentration itself, and the principal force driving radon into the building from the soil, namely the pressure-difference between interior and exterior environment. While the meteorological influence can be regarded as relatively uniform on a European scale, its variability being defined largely by the influence of North-Atlantic weather systems, soil-gas radon is generally more variable as it is essentially geologically dependent. Seasonal variability of domestic radon concentration can therefore be expected to exhibit geographical variability, as is indeed the case. To compensate for the variability of domestic radon levels when assessing the long term radon health risks, the results of individual short-term measurements are generally converted to equivalent mean annual levels by application of a Seasonal Correction Factor (SCF). This is a multiplying factor, typically derived from measurements of a large number of homes, applied to the measured short-term radon concentration to provide a meaningful annual mean concentration for dose-estimation purposes. Following concern as to the universal applicability of a single SCF set, detailed studies in both the UK and France have reported location-specific SCF sets for different regions of each country. Further results indicate that SCFs applicable to the UK differ significantly from those applicable elsewhere in Europe and North America in both amplitude and phase, supporting the thesis that seasonal variability in indoor radon concentration cannot realistically be compensated for by a single national or international SCF scheme. Published data characterising the seasonal variability of European national domestic radon concentrations, has been collated and analysed, with the objective of identifying correlations between published datasets and local geographic/geological conditions. Available data included regional SCF figures from the United Kingdom and from France, together with nationally-consolidated results from a number of other European countries. Analysis of this data shows significant variability between different countries and from region to region within those countries where regional data is available. Overall, radon-rich sedimentary geologies, particularly high porosity limestones etc., exhibit high seasonal variation, while radon-rich igneous geologies demonstrate relatively constant, albeit somewhat higher, radon concentration levels. Examples of the former can be found in the Pennines and South Downs in England, Languedoc and Brittany in France. Greatest variability is found in Switzerland, still subject to the ongoing Alpine orogeny, where the inhabited part of the country is largely overlain with recently-deposited light, porous sediments. Low-variability high-radon regions include the granite-rich Cornwall/Devon peninsular in England, and Auvergne and the Ardennes in France, all components of the Devonian-Carboniferous Hercynian belt, which extends from the Iberian peninsular through South-West Ireland and South-West England to France and Germany.

Natural gas treating with molecular sieves. Pt. 2. Regeneration, economics

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

Harris, T.B.

1972-08-01

Regeneration considerations are often the key to successful and economical application of molecular sieves for natural gas sweetening. In effect, molecular sieves remove the sulfur compounds from the feed stream and concentrate them into a smaller regeneration gas stream. Because a molecular sieve natural gas sweetener concentrates the hydrogen sulfide from the feed stream in a smaller regeneration gas stream, the sulfur-rich gas must be subsequently treated or disposed of. Molecular sieve sweeteners afford a high degree of flexibility in operating rates. They have a very high turndown ratio limited only by the use of product gas for regeneration, whichmore » can be utilized to full advantage with a control system that provides variable cycle times. Tabular data provide a range of designed conditions for existing molecular sieve natural gas sweeteners. Actual operating experience has shown that, in most cases, the following economical advantages can be realized: (1) investment cost is competitive to alternate forms of gas treating; (2) operating cost of molecular sieve units are generally lower (3) the value of carbon dioxide left in natural gas can lead to a considerable operating credit; and (4) the incremental costs of expansion to an existing plant are normally much less. (24 refs.)« less

The Effect of Equilibration Time and Tubing Material on Soil Gas Measurements

EPA Science Inventory

The collection of soil vapor samples representative of in-situ conditions presents challenges associated with the unavoidable disturbance of the subsurface and potential losses to the atmosphere. This article evaluates the effects of two variables that influence the concentration...

Development of a Scalable Testbed for Mobile Olfaction Verification.

PubMed

Zakaria, Syed Muhammad Mamduh Syed; Visvanathan, Retnam; Kamarudin, Kamarulzaman; Yeon, Ahmad Shakaff Ali; Md Shakaff, Ali Yeon; Zakaria, Ammar; Kamarudin, Latifah Munirah

2015-12-09

The lack of information on ground truth gas dispersion and experiment verification information has impeded the development of mobile olfaction systems, especially for real-world conditions. In this paper, an integrated testbed for mobile gas sensing experiments is presented. The integrated 3 m × 6 m testbed was built to provide real-time ground truth information for mobile olfaction system development. The testbed consists of a 72-gas-sensor array, namely Large Gas Sensor Array (LGSA), a localization system based on cameras and a wireless communication backbone for robot communication and integration into the testbed system. Furthermore, the data collected from the testbed may be streamed into a simulation environment to expedite development. Calibration results using ethanol have shown that using a large number of gas sensor in the LGSA is feasible and can produce coherent signals when exposed to the same concentrations. The results have shown that the testbed was able to capture the time varying characteristics and the variability of gas plume in a 2 h experiment thus providing time dependent ground truth concentration maps. The authors have demonstrated the ability of the mobile olfaction testbed to monitor, verify and thus, provide insight to gas distribution mapping experiment.

Development of a Scalable Testbed for Mobile Olfaction Verification

PubMed Central

Syed Zakaria, Syed Muhammad Mamduh; Visvanathan, Retnam; Kamarudin, Kamarulzaman; Ali Yeon, Ahmad Shakaff; Md. Shakaff, Ali Yeon; Zakaria, Ammar; Kamarudin, Latifah Munirah

2015-01-01

The lack of information on ground truth gas dispersion and experiment verification information has impeded the development of mobile olfaction systems, especially for real-world conditions. In this paper, an integrated testbed for mobile gas sensing experiments is presented. The integrated 3 m × 6 m testbed was built to provide real-time ground truth information for mobile olfaction system development. The testbed consists of a 72-gas-sensor array, namely Large Gas Sensor Array (LGSA), a localization system based on cameras and a wireless communication backbone for robot communication and integration into the testbed system. Furthermore, the data collected from the testbed may be streamed into a simulation environment to expedite development. Calibration results using ethanol have shown that using a large number of gas sensor in the LGSA is feasible and can produce coherent signals when exposed to the same concentrations. The results have shown that the testbed was able to capture the time varying characteristics and the variability of gas plume in a 2 h experiment thus providing time dependent ground truth concentration maps. The authors have demonstrated the ability of the mobile olfaction testbed to monitor, verify and thus, provide insight to gas distribution mapping experiment. PMID:26690175

Project Rulison gas flow analysis

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

Montan, D.N.

1971-01-01

An analysis of the well performance was attempted by fitting a simple model of the chimney, gas sands, and explosively created fracturing to the 2 experimentally measured variables, flow rate, and chimney pressure. The gas-flow calculations for various trial models were done by a finite difference solution to the nonlinear partial differential equation for radial Darcy flow. The TRUMP computer program was used to perform the numerical calculations. In principle, either the flow rate or the chimney pressure could be used as the independent variable in the calculations. In the present case, the flow rate was used as the independentmore » variable, since chimney pressure measurements were not made until after the second flow period in early Nov. 1970. Furthermore, the formation pressure was not accurately known and, hence, was considered a variable parameter in the modeling process. The chimney pressure was assumed equal to the formation pressure at the beginning of the flow testing. The model consisted of a central zone, representing the chimney, surrounded by a number of concentric zones, representing the formation. The effect of explosive fracturing was simulated by increasing the permeability in the zones near the central zone.« less

A method for estimation of bias and variability of continuous gas monitor data: application to carbon monoxide monitor accuracy.

PubMed

Shulman, Stanley A; Smith, Jerome P

2002-01-01

A method is presented for the evaluation of the bias, variability, and accuracy of gas monitors. This method is based on using the parameters for the fitted response curves of the monitors. Thereby, variability between calibrations, between dates within each calibration period, and between different units can be evaluated at several different standard concentrations. By combining variability information with bias information, accuracy can be assessed. An example using carbon monoxide monitor data is provided. Although the most general statistical software required for these tasks is not available on a spreadsheet, when the same number of dates in a calibration period are evaluated for each monitor unit, the calculations can be done on a spreadsheet. An example of such calculations, together with the formulas needed for their implementation, is provided. In addition, the methods can be extended by use of appropriate statistical models and software to evaluate monitor trends within calibration periods, as well as consider the effects of other variables, such as humidity and temperature, on monitor variability and bias.

Behavior of dusty real gas on adiabatic propagation of cylindrical imploding strong shock waves

NASA Astrophysics Data System (ADS)

Gangwar, P. K.

2018-05-01

In this paper, CCW method has been used to study the behavior of dusty real gas on adiabatic propagation of cylindrical imploding strong shock waves. The strength of overtaking waves is estimated under the assumption that both C+ and C- disturbances propagate in non-uniform region of same density distribution. It is assumed that the dusty gas is the mixture of a real gas and a large number of small spherical solid particles of uniform size. The solid particles are uniformly distributed in the medium. Maintaining equilibrium flow conditions, the expressions for shock strength has been derived both for freely propagation as well as under the effect of overtaking disturbances. The variation of all flow variables with propagation distance, mass concentration of solid particles in the mixture and the ratio of solid particles to the initial density of gas have been computed and discussed through graphs. It is found that the presence of dust particles in the gases medium has significant effects on the variation of flow variables and the shock is strengthened under the influence of overtaking disturbances. The results accomplished here been compared with those for ideal gas.

Popping rocks from the Mid-Atlantic Ridge: Insights into mantle volatile concentrations and degassing dynamics

NASA Astrophysics Data System (ADS)

Jones, M.; Soule, S. A.; Kurz, M. D.; Wanless, V. D.; Le Roux, V.; Klein, F.; Mittelstaedt, E. L.; Curtice, J.

2016-12-01

During a 1985 cruise, the Mid-Atlantic Ridge (MAR) near 14°N yielded an unusually vesicular mid-ocean ridge (MOR) basalt that popped upon recovery from the seafloor due to the release of trapped volatiles. This `popping rock' has been inferred to be representative of primitive, undegassed magmas from the upper mantle due to its high volatile concentrations. Thus, the sample has been used to constrain CO2 flux from the MOR system, upper mantle volatile concentrations, and magma degassing dynamics. However, the lack of geologic context for the original popping rock raises questions about whether it truly reflects the volatile content of its mantle source. Here, we present results from a 2016 cruise to the MAR aimed at characterizing the geologic context of popping rocks and understanding their origins. The newly recovered samples display differences in volatile concentrations and vesicularities between popping and non-popping rocks. These differences may be related to geologic setting and eruption dynamics with potential implications for mantle volatile concentrations. Volatile concentrations in the outer quenched margin of new samples were measured by ion microprobe to elucidate degassing systematics, brine/magma interactions, and popping rock formation. The large variability in dissolved H2O (0.05-0.77 wt%) can be attributed to spatially variable brine contamination. Dissolved CO2 concentrations (153-356 ppm) are likely controlled by initial volatile concentrations and variable degrees of degassing. The subset of popping samples display low dissolved CO2 concentrations (161-178 ppm) and moderate dissolved H2O concentrations (.44-.50 wt%) and are at equilibrium with their eruption depth based on solubility calculations. X-ray microtomography reveals vesicularity in newly collected popping rocks exceeding 19%, making these samples the most highly vesicular recovered from the MAR. The total gas contents in the basaltic glasses are inferred from dissolved volatile concentrations and vesicularity. These calculations are aided by analysis of gas contents in vesicles by confocal Raman spectroscopy and vacuum crushing experiments. The preliminary results and seafloor observations allow an evaluation of the origins of popping rocks and their implications for mantle volatile concentrations.

Implications for carbon processing beneath the Greenland Ice Sheet from dissolved CO2 and CH4 concentrations of subglacial discharge

NASA Astrophysics Data System (ADS)

Pain, A.; Martin, J.; Martin, E. E.

2017-12-01

Subglacial carbon processes are of increasing interest as warming induces ice melting and increases fluxes of glacial meltwater into proglacial rivers and the coastal ocean. Meltwater may serve as an atmospheric source or sink of carbon dioxide (CO2) or methane (CH4), depending on the magnitudes of subglacial organic carbon (OC) remineralization, which produces CO2 and CH4, and mineral weathering reactions, which consume CO2 but not CH4. We report wide variability in dissolved CO2 and CH4 concentrations at the beginning of the melt season (May-June 2017) between three sites draining land-terminating glaciers of the Greenland Ice Sheet. Two sites, located along the Watson River in western Greenland, drain the Isunnguata and Russell Glaciers and contained 1060 and 400 ppm CO2, respectively. In-situ CO2 flux measurements indicated that the Isunnguata was a source of atmospheric CO2, while the Russell was a sink. Both sites had elevated CH4 concentrations, at 325 and 25 ppm CH4, respectively, suggesting active anaerobic OC remineralization beneath the ice sheet. Dissolved CO2 and CH4 reached atmospheric equilibrium within 2.6 and 8.6 km downstream of Isunnguata and Russell discharge sites, respectively. These changes reflect rapid gas exchange with the atmosphere and/or CO2 consumption via instream mineral weathering. The third site, draining the Kiagtut Sermiat in southern Greenland, had about half atmospheric CO2 concentrations (250 ppm), but approximately atmospheric CH4 concentrations (2.1 ppm). Downstream CO2 flux measurements indicated ingassing of CO2 over the entire 10-km length of the proglacial river. CO2 undersaturation may be due to more readily weathered lithologies underlying the Kiagtut Sermiat compared to Watson River sites, but low CH4 concentrations also suggest limited contributions of CO2 and CH4 from OC remineralization. These results suggest that carbon processing beneath the Greenland Ice Sheet may be more variable than previously recognized. Variations control whether discharge is a source or sink of atmospheric CO2 or CH4, but gas concentrations could be further modified by instream reactions. Increased meltwater fluxes should enhance the importance of greenhouse gas fluxes from subglacial discharge, and heighten the need to constrain variability in subglacial carbon processing.

Seasonal Variability in Vadose zone biodegradation at a crude oil pipeline rupture site

USGS Publications Warehouse

Sihota, Natasha J.; Trost, Jared J.; Bekins, Barbara; Berg, Andrew M.; Delin, Geoffrey N.; Mason, Brent E.; Warren, Ean; Mayer, K. Ulrich

2016-01-01

Understanding seasonal changes in natural attenuation processes is critical for evaluating source-zone longevity and informing management decisions. The seasonal variations of natural attenuation were investigated through measurements of surficial CO2 effluxes, shallow soil CO2 radiocarbon contents, subsurface gas concentrations, soil temperature, and volumetric water contents during a 2-yr period. Surficial CO2 effluxes varied seasonally, with peak values of total soil respiration (TSR) occurring in the late spring and summer. Efflux and radiocarbon data indicated that the fractional contributions of natural soil respiration (NSR) and contaminant soil respiration (CSR) to TSR varied seasonally. The NSR dominated in the spring and summer, and CSR dominated in the fall and winter. Subsurface gas concentrations also varied seasonally, with peak values of CO2 and CH4 occurring in the fall and winter. Vadose zone temperatures and subsurface CO2 concentrations revealed a correlation between contaminant respiration and temperature. A time lag of 5 to 7 mo between peak subsurface CO2 concentrations and peak surface efflux is consistent with travel-time estimates for subsurface gas migration. Periods of frozen soils coincided with depressed surface CO2 effluxes and elevated CO2 concentrations, pointing to the temporary presence of an ice layer that inhibited gas transport. Quantitative reactive transport simulations demonstrated aspects of the conceptual model developed from field measurements. Overall, results indicated that source-zone natural attenuation (SZNA) rates and gas transport processes varied seasonally and that the average annual SZNA rate estimated from periodic surface efflux measurements is 60% lower than rates determined from measurements during the summer.

Non-thermal atmospheric pressure HF plasma source: generation of nitric oxide and ozone for bio-medical applications

NASA Astrophysics Data System (ADS)

Kühn, S.; Bibinov, N.; Gesche, R.; Awakowicz, P.

2010-01-01

A new miniature high-frequency (HF) plasma source intended for bio-medical applications is studied using nitrogen/oxygen mixture at atmospheric pressure. This plasma source can be used as an element of a plasma source array for applications in dermatology and surgery. Nitric oxide and ozone which are produced in this plasma source are well-known agents for proliferation of the cells, inhalation therapy for newborn infants, disinfection of wounds and blood ozonation. Using optical emission spectroscopy, microphotography and numerical simulation, the gas temperature in the active plasma region and plasma parameters (electron density and electron distribution function) are determined for varied nitrogen/oxygen flows. The influence of the gas flows on the plasma conditions is studied. Ozone and nitric oxide concentrations in the effluent of the plasma source are measured using absorption spectroscopy and electro-chemical NO-detector at variable gas flows. Correlations between plasma parameters and concentrations of the particles in the effluent of the plasma source are discussed. By varying the gas flows, the HF plasma source can be optimized for nitric oxide or ozone production. Maximum concentrations of 2750 ppm and 400 ppm of NO and O3, correspondingly, are generated.

Instrumentation and optimization of intra-cavity fiber laser gas absorption sensing system

NASA Astrophysics Data System (ADS)

Liu, Kun; Liu, Tiegen; Jiang, Junfeng; Liang, Xiao; Zhang, Yimo

2011-11-01

Detection of pollution, inflammable, explosive gases such as methane, acetylene, carbon monoxide and so on is very important for many areas, such as environmental, mining and petrochemical industry. Intra-cavity gas absorption sensing technique (ICGAST) based on Erbium-doped fiber ring laser (EDFRL) is one of novel methods for trace gas with higher precision. It has attracted considerable attention, and many research institutes focus on it. Instrumentation and optimization of ICGAST was reported in this paper. The system consists of five parts, which are variable gain module, intelligent frequency-selection module, gas cell, DAQ module and computer respectively. Variable gain module and intelligent frequency-selection module are combined to establish the intra-cavity of the ring laser. Gas cell is used as gas sensor. DAQ module is used to realize data acquisition synchronously. And gas demodulation is finished in the computer finally. The system was optimized by adjusting the sequence of the components. Take experimental simulation as an example, the absorptance of gas was increased five times after optimization, and the sensitivity enhancement factor can reach more than twenty. By using Fabry-Perot (F-P) etalon, the absorption wavelength of the detected gas can be obtained, with error less than 20 pm. The spectra of the detected gas can be swept continuously to obtain several absorption lines in one loop. The coefficient of variation (CV) was used to show the repeatability of gas concentration detection. And results of CV value can be less than 0.014.

Gas evolution from spheres

NASA Astrophysics Data System (ADS)

Longhurst, G. R.

1991-04-01

Gas evolution from spherical solids or liquids where no convective processes are active is analyzed. Three problem classes are considered: (1) constant concentration boundary, (2) Henry's law (first order) boundary, and (3) Sieverts' law (second order) boundary. General expressions are derived for dimensionless times and transport parameters appropriate to each of the classes considered. However, in the second order case, the non-linearities of the problem require the presence of explicit dimensional variables in the solution. Sample problems are solved to illustrate the method.

Radon in indoor air of primary schools: determinant factors, their variability and effective dose.

PubMed

Madureira, Joana; Paciência, Inês; Rufo, João; Moreira, André; de Oliveira Fernandes, Eduardo; Pereira, Alcides

2016-04-01

Radon is a radioactive gas, abundant in granitic areas, such as in the city of Porto at the north-east of Portugal. This gas is a recognized carcinogenic agent, being appointed by the World Health Organization as the leading cause of lung cancer after smoking. The aim of this preliminary survey was to determine indoor radon concentrations in public primary schools, to analyse the main factors influencing their indoor concentration levels and to estimate the effective dose in students and teachers in primary schools. Radon concentrations were measured in 45 classrooms from 13 public primary schools located in Porto, using CR-39 passive radon detectors for about 2-month period. In all schools, radon concentrations ranged from 56 to 889 Bq/m(3) (mean = 197 Bq/m(3)). The results showed that the limit of 100 Bq/m(3) established by WHO IAQ guidelines was exceeded in 92 % of the measurements, as well as 8 % of the measurements exceeded the limit of 400 Bq/m(3) established by the national legislation. Moreover, the mean annual effective dose was calculated as 1.25 mSv/y (ranging between 0.58 and 3.07 mSv/y), which is below the action level (3-10 mSv). The considerable variability of radon concentration observed between and within floors indicates a need to monitor concentrations in several rooms for each floor. A single radon detector for each room can be used, provided that the measurement error is considerably lower than variability of radon concentration between rooms. The results of the present survey will provide useful baseline data for adopting safety measures and dealing effectively with radiation emergencies. In particular, radon remediation techniques should be used in buildings located in the highest radon risk areas of Portugal. The results obtained in the current study concerning radon levels and their variations will be useful to optimize the design of future research surveys.

Reduced sulfur compounds in gas from construction and demolition debris landfills.

PubMed

Lee, Sue; Xu, Qiyong; Booth, Matthew; Townsend, Timothy G; Chadik, Paul; Bitton, Gabriel

2006-01-01

The biological conversion of sulfate from disposed gypsum drywall to hydrogen sulfide (H(2)S) in the anaerobic environment of a landfill results in odor problems and possible health concerns at many disposal facilities. To examine the extent and magnitude of such emissions, landfill gas samples from wells, soil vapor samples from the interface of the waste and cover soil, and ambient air samples, were collected from 10 construction and demolition (C&D) debris landfills in Florida and analyzed for H(2)S and other reduced sulfur compounds (RSC). H(2)S was detected in the well gas and soil vapor at all 10 sites. The concentrations in the ambient air above the surface of the landfill were much lower than those observed in the soil vapor, and no direct correlation was observed between the two sampling locations. Methyl mercaptan and carbonyl sulfide were the most frequently observed other RSC, though they occurred at smaller concentrations than H(2)S. This research confirmed the presence of H(2)S at C&D debris landfills. High concentrations of H(2)S may be a concern for employees working on the landfill site. These results indicate that workers should use proper personal protection at C&D debris landfills when involved in excavation, landfill gas collection, or confined spaces. The results indicate that H(2)S is sufficiently diluted in the atmosphere to not commonly pose acute health impacts for these landfill workers in normal working conditions. H(2)S concentrations were extremely variable with measurements occurring over a very large range (from less than 3 ppbv to 12,000 ppmv in the soil vapor and from less than 3 ppbv to 50 ppmv in ambient air). Possible reasons for the large intra- and inter-site variability observed include waste and soil heterogeneities, impact of weather conditions, and different site management practices.

40 CFR 60.456 - Test methods and procedures.

Code of Federal Regulations, 2010 CFR

2010-07-01

... Section 60.456 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS... § 60.453. (2) Method 25 for the measurement of the VOC concentration in the gas stream vent. (3) Method... sampling times or smaller volumes, when necessitated by process variables or other factors, may be approved...

Macroscale hydrologic modeling of ecologically relevant flow metrics

Treesearch

Seth J. Wenger; Charles H. Luce; Alan F. Hamlet; Daniel J. Isaak; Helen M. Neville

2010-01-01

Stream hydrology strongly affects the structure of aquatic communities. Changes to air temperature and precipitation driven by increased greenhouse gas concentrations are shifting timing and volume of streamflows potentially affecting these communities. The variable infiltration capacity (VIC) macroscale hydrologic model has been employed at regional scales to describe...

The value and limitations of global air-sampling networks for improving our understanding trace gas behavior

NASA Astrophysics Data System (ADS)

Montzka, S. A.

2016-12-01

Measurements from global surface-based air sampling networks provide a fundamental understanding of how and why concentrations of long-lived trace gases are changing over time. Results from these networks are used to quantify trace-gas concentrations and their time-dependent changes on global and smaller scales, and thus provide a means to quantify emission rates, loss frequencies, and mixing processes. Substantial advances in measurement and sampling technologies and the ability of these programs to create and maintain reliable gas standards mean that spatial concentration gradients and time-dependent changes are often very reliably measured. The presence of multiple independent networks allows an assessment of this reliability. Furthermore, recent global `snap-shot' surveys (e.g., HIPPO and ATom) and ongoing atmospheric profiling programs help us assess the ability of surface-based data to describe concentration distributions throughout most of the atmosphere ( 80% of its mass). In this overview talk, I'll explore the usefulness and limitations of existing long-term, ongoing sampling network programs and their advantages and disadvantages for characterizing concentrations on global and regional scales, and how recent advances (and short-term sampling programs) help us assess the accuracy of the surface networks to provide estimates of source and sink magnitudes, and inter-annual variability in both.

Multivariate Regression Analysis of Winter Ozone Events in the Uinta Basin of Eastern Utah, USA

NASA Astrophysics Data System (ADS)

Mansfield, M. L.

2012-12-01

I report on a regression analysis of a number of variables that are involved in the formation of winter ozone in the Uinta Basin of Eastern Utah. One goal of the analysis is to develop a mathematical model capable of predicting the daily maximum ozone concentration from values of a number of independent variables. The dependent variable is the daily maximum ozone concentration at a particular site in the basin. Independent variables are (1) daily lapse rate, (2) daily "basin temperature" (defined below), (3) snow cover, (4) midday solar zenith angle, (5) monthly oil production, (6) monthly gas production, and (7) the number of days since the beginning of a multi-day inversion event. Daily maximum temperature and daily snow cover data are available at ten or fifteen different sites throughout the basin. The daily lapse rate is defined operationally as the slope of the linear least-squares fit to the temperature-altitude plot, and the "basin temperature" is defined as the value assumed by the same least-squares line at an altitude of 1400 m. A multi-day inversion event is defined as a set of consecutive days for which the lapse rate remains positive. The standard deviation in the accuracy of the model is about 10 ppb. The model has been combined with historical climate and oil & gas production data to estimate historical ozone levels.

Temporary vs. Permanent Sub-slab Ports: A Comparative ...

EPA Pesticide Factsheets

Vapor intrusion (VI) is the migration of subsurface vapors, including radon and volatile organic compounds (VOCs), from the subsurface to indoor air. The VI exposure pathway extends from the contaminant source, which can be impacted soil, non-aqueous phase liquid, or contaminated groundwater, to indoor air-exposure points. Therefore, contaminated matrices may include groundwater, soil, soil gas, and indoor air. VOC contaminants of concern typically include halogenated solvents such as trichloroethene, tetrachloroethene, and chloroform, as well as petroleum hydrocarbons, such as the aromatic VOCs benzene, toluene, and xylenes. Radon is a colorless radioactive gas that is released by radioactive decay of radionuclides in rock and soil that migrate into homes through VI in a similar fashion to VOCs. This project focused on the performance of permanent versus temporary sub-slab sampling ports for the determination of VI of halogenated VOCs and radon into an unoccupied house. VOC and radon concentrations measured simultaneously in soil gas using collocated temporary and permanent ports appeared to be independent of the type of port. The variability between collocated temporary and permanent ports was much less than the spatial variability between different locations within a single residential duplex. The agreement of the majority of VOC and radon concentrations, 0–36% relative percent difference, and 2–19% relative standard deviation respectively, of each sub-sl

Gas-assisted dispersive liquid-phase microextraction using ionic liquid as extracting solvent for spectrophotometric speciation of copper.

PubMed

Akhond, Morteza; Absalan, Ghodratollah; Pourshamsi, Tayebe; Ramezani, Amir M

2016-07-01

Gas-assisted dispersive liquid-phase microextraction (GA-DLPME) has been developed for preconcentration and spectrophotometric determination of copper ion in different water samples. The ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate and argon gas, respectively, were used as the extracting solvent and disperser. The procedure was based on direct reduction of Cu(II) to Cu(I) by hydroxylamine hydrochloride, followed by extracting Cu(I) into ionic liquid phase by using neocuproine as the chelating agent. Several experimental variables that affected the GA-DLPME efficiency were investigated and optimized. Under the optimum experimental conditions (IL volume, 50µL; pH, 6.0; acetate buffer, 1.5molL(-1); reducing agent concentration, 0.2molL(-1); NC concentration, 120µgmL(-1); Ar gas bubbling time, 6min; argon flow rate, 1Lmin(-1); NaCl concentration, 6% w/w; and centrifugation time, 3min), the calibration graph was linear over the concentration range of 0.30-2.00µgmL(-1) copper ion with a limit of detection of 0.07µgmL(-1). Relative standard deviation for five replicate determinations of 1.0µgmL(-1) copper ion was found to be 3.9%. The developed method was successfully applied to determination of both Cu(I) and Cu(II) species in water samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Evaluation of INL Supplied MOOSE/OSPREY Model: Modeling Water Adsorption on Type 3A Molecular Sieve

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

Pompilio, L. M.; DePaoli, D. W.; Spencer, B. B.

The purpose of this study was to evaluate Idaho National Lab’s Multiphysics Object-Oriented Simulation Environment (MOOSE) software in modeling the adsorption of water onto type 3A molecular sieve (3AMS). MOOSE can be thought-of as a computing framework within which applications modeling specific coupled-phenomena can be developed and run. The application titled Off-gas SeParation and REcoverY (OSPREY) has been developed to model gas sorption in packed columns. The sorbate breakthrough curve calculated by MOOSE/OSPREY was compared to results previously obtained in the deep bed hydration tests conducted at Oak Ridge National Laboratory. The coding framework permits selection of various options, whenmore » they exist, for modeling a process. For example, the OSPREY module includes options to model the adsorption equilibrium with a Langmuir model or a generalized statistical thermodynamic adsorption (GSTA) model. The vapor solid equilibria and the operating conditions of the process (e.g., gas phase concentration) are required to calculate the concentration gradient driving the mass transfer between phases. Both the Langmuir and GSTA models were tested in this evaluation. Input variables were either known from experimental conditions, or were available (e.g., density) or were estimated (e.g., thermal conductivity of sorbent) from the literature. Variables were considered independent of time, i.e., rather than having a mass transfer coefficient that varied with time or position in the bed, the parameter was set to remain constant. The calculated results did not coincide with data from laboratory tests. The model accurately estimated the number of bed volumes processed for the given operating parameters, but breakthrough times were not accurately predicted, varying 50% or more from the data. The shape of the breakthrough curves also differed from the experimental data, indicating a much wider sorption band. Model modifications are needed to improve its utility and predictive capability. Recommended improvements include: greater flexibility for input of mass transfer parameters, time-variable gas inlet concentration, direct output of loading and temperature profiles along the bed, and capability to conduct simulations of beds in series.« less

Monitoring and modeling wetland chloride concentrations in relationship to oil and gas development

USGS Publications Warehouse

Post van der Burg, Max; Tangen, Brian A.

2015-01-01

Extraction of oil and gas via unconventional methods is becoming an important aspect of energy production worldwide. Studying the effects of this development in countries where these technologies are being widely used may provide other countries, where development may be proposed, with some insight in terms of concerns associated with development. A fairly recent expansion of unconventional oil and gas development in North America provides such an opportunity. Rapid increases in energy development in North America have caught the attention of managers and scientists as a potential stressor for wildlife and their habitats. Of particular concern in the Northern Great Plains of the U.S. is the potential for chloride-rich produced water associated with unconventional oil and gas development to alter the water chemistry of wetlands. We describe a landscape scale modeling approach designed to examine the relationship between potential chloride contamination in wetlands and patterns of oil and gas development. We used a spatial Bayesian hierarchical modeling approach to assess multiple models explaining chloride concentrations in wetlands. These models included effects related to oil and gas wells (e.g. age of wells, number of wells) and surficial geology (e.g. glacial till, outwash). We found that the model containing the number of wells and the surficial geology surrounding a wetland best explained variation in chloride concentrations. Our spatial predictions showed regions of localized high chloride concentrations. Given the spatiotemporal variability of regional wetland water chemistry, we do not regard our results as predictions of contamination, but rather as a way to identify locations that may require more intensive sampling or further investigation. We suggest that an approach like the one outlined here could easily be extended to more of an adaptive monitoring approach to answer questions about chloride contamination risk that are of interest to managers.

Volatile Organic Compound Emissions from Natural Gas Facilities in the Denver-Julesburg Basin, the Uintah Basin and the Marcellus Shale

NASA Astrophysics Data System (ADS)

Li, X.; Omara, M.; Sullivan, M.; Subramanian, R.; Robinson, A. L.; Presto, A. A.

2015-12-01

Natural gas has been widely considered as a "bridge" fuel in the future. Because of the rapid advancement of horizontal drilling and hydraulic fracturing techniques, the production of crude oil and natural gas in US increased dramatically in recent years; and currently natural gas contributes to about 25% of total US energy consumption. Recent studies suggest that shale gas extraction facilities may emit Volatile Organic Compounds (VOCs), which could contribute to the formation of ozone and affect regional air quality, public health and climate change. In this study we visited 37 natural gas facilities in Denver-Julesburg and Uintah Basins from March to May, 2015. VOCs and methane concentrations were measured downwind of individual facilities with our mobile lab. In total 13 VOCs, including benzene and toluene, were measured by a SRI 8610C Gas Chromatograph. Similar measurements will be conducted in the Marcellus Shale in late August 2015. Preliminary results show that VOC emissions from individual shale gas facilities are variable, which suggests that a single VOC profile may not characterize all natural gas production facilities, though there may be some common characteristics. Measured VOC concentrations will be normalized to concurrently-measured methane emissions, and coupled with methane emission rates measured at these facilities, used to obtain VOC emission factors from natural gas production. This presentation will also compare VOC emission rates from the Marcellus shale with that from the Denver-Julesburg and Uintah basins.

An effective temperature compensation approach for ultrasonic hydrogen sensors

NASA Astrophysics Data System (ADS)

Tan, Xiaolong; Li, Min; Arsad, Norhana; Wen, Xiaoyan; Lu, Haifei

2018-03-01

Hydrogen is a kind of promising clean energy resource with a wide application prospect, which will, however, cause a serious security issue upon the leakage of hydrogen gas. The measurement of its concentration is of great significance. In a traditional approach of ultrasonic hydrogen sensing, a temperature drift of 0.1 °C results in a concentration error of about 250 ppm, which is intolerable for trace amount of gas sensing. In order to eliminate the influence brought by temperature drift, we propose a feasible approach named as linear compensation algorithm, which utilizes the linear relationship between the pulse count and temperature to compensate for the pulse count error (ΔN) caused by temperature drift. Experimental results demonstrate that our proposed approach is capable of improving the measurement accuracy and can easily detect sub-100 ppm of hydrogen concentration under variable temperature conditions.

Inversion structure and winter ozone distribution in the Uintah Basin, Utah, U.S.A.

NASA Astrophysics Data System (ADS)

Lyman, Seth; Tran, Trang

2015-12-01

The Uintah Basin in Utah, U.S.A. experiences high concentrations of ozone during some winters due to strong, multi-day temperature inversions that facilitate the buildup of pollution from local sources, including the oil and gas industry. Together, elevation of monitoring sites and proximity to oil and gas wells explain as much as 90% of spatial variability in surface ozone concentrations during inversion episodes (i.e., R2 = 0.90). Inversion conditions start earlier and last longer at lower elevations, at least in part because lower elevations are more insulated from winds aloft that degrade inversion conditions and dilute produced ozone. Surface air transport under inversions is dominated by light, diurnal upslope-downslope flow that limits net transport distances. Thus, different areas of the Basin are relatively isolated from each other, allowing spatial factors like elevation and proximity to sources to strongly influence ozone concentrations at individual sites.

Annual Greenhouse Gas (CO2, CH4, and N2O) Fluxes Via Ebullition from a Temperate Emergent Wetland

NASA Astrophysics Data System (ADS)

Mcnicol, G.; Sturtevant, C. S.; Knox, S. H.; Baldocchi, D. D.; Silver, W. L.

2014-12-01

Quantifying wetland greenhouse gas exchange is necessary to evaluate their potential for mitigating climate change via carbon sequestration. However measuring greenhouse gas fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) in wetlands is difficult due to high spatial and temporal variability, and multiple transport pathways of emission. Transport of biogenic soil gas via highly sporadic ebullition (bubbling) events is often ignored or quantified poorly in wetland greenhouse gas budgets, but can rapidly release large volumes of gas to the atmosphere. To quantify a robust annual ebullition flux we measured rates continuously for a year (2013-2014) using custom-built chambers deployed in a restored emergent wetland located in the Sacramento-San Joaquin Delta, CA. We combined ebullition flux rates with observations of gas concentrations to estimate annual ebullition emissions of CO2, CH4, and N2O and compare flux rates to whole-ecosystem exchange of CO2 and CH4 measured simultaneously by eddy covariance.Mean ebullition flux rates were 18.3 ± 5.6 L m-2 yr-1. Ebullition CH4 concentrations were very high and ranged from 23-76 % with a mean of 47 ± 2.9 %; CO2 concentrations were lower and ranged from 0.7-6.6 % with a mean of 2.8 ± 0.3 %; N2O concentrations were below atmospheric concentrations and ranged from 130-389 ppb(v) with a mean of 257 ± 13 ppb(v). We calculated well-constrained annual ebullition fluxes of: 6.2 ± 1.9 g CH4 m-2 yr-1, 1.0 ± 0.3 g CO2 m-2 yr-1 and 9.3 ± 2.8 mg N2O m-2 yr-1. Methane emissions via ebullition were very large, representing 15-25 % of total wetland CH4 emissions measured at this site, whereas ebullition released only relatively small quantities of CO2 and N2O. Our results demonstrate that large releases of CH4 via ebullition from open water surfaces can be a significant component of restored wetland greenhouse gas budgets.

Solubility of Haloether Anesthetics in Human and Animal Blood

PubMed Central

Soares, Joao H. N.; Brosnan, Robert J.; Fukushima, Fabíola B.; Hodges, Joanne; Liu, Hong

2012-01-01

Background Anesthetic blood solubility predicts pharmacokinetics for inhaled agents and is essential for determination of blood anesthetic concentrations from end-tidal gas concentrations using Henry’s Law. Though used to model anesthetic effects in humans, there are limited interspecies solubility comparisons that include modern haloethers. This study aimed to measure hematocrit-adjusted blood:gas anesthetic partition coefficients (λB:G) for desflurane, sevoflurane, isoflurane, and methoxyflurane in humans and animals. Methods Whole blood was collected from 20 rats, 8 horses, and 4 each of cats, cattle, humans, dogs, goats, pigs, rabbits, and sheep. Plasma or cell volume was removed to adjust all samples to a packed cell volume of 40%. A single agent calibration gas headspace was added to blood in a glass syringe and was mixed and equilibrated at 37°C for 2 hours. Agent concentrations in the calibration gas and syringe headspace were measured using gas chromatography. Anesthetic solubility in saline, citrate-phosphate-dextrose-adenine, and olive oil were similarly measured. Results Except for goats, all animal species had at least one λB:G measurement that differed significantly from humans. For each agent, λB:G positively correlated with serum triglyceride concentrations, but this only explained 25% of interspecies variability. Desflurane was significantly less soluble in blood than sevoflurane in some species (e.g., humans) but not in others (e.g., rabbits). Conclusions Anesthetic partition coefficients differ significantly between humans and most animals for haloether anesthetics. Because of their similar λB:G values, goats may be a better animal model for inhaled anesthetic pharmacokinetics in people. PMID:22510863

Solubility of haloether anesthetics in human and animal blood.

PubMed

Soares, Joao H N; Brosnan, Robert J; Fukushima, Fabíola B; Hodges, Joanne; Liu, Hong

2012-07-01

Anesthetic blood solubility predicts pharmacokinetics for inhaled agents and is essential for determination of blood anesthetic concentrations from end-tidal gas concentrations using Henry's Law. Though used to model anesthetic effects in humans, there are limited interspecies solubility comparisons that include modern haloethers. This study aimed to measure hematocrit-adjusted blood:gas anesthetic partition coefficients (λ B:G) for desflurane, sevoflurane, isoflurane, and methoxyflurane in humans and animals. Whole blood was collected from 20 rats, 8 horses, and 4 each of cats, cattle, humans, dogs, goats, pigs, rabbits, and sheep. Plasma or cell volume was removed to adjust all samples to a packed cell volume of 40%. A single-agent calibration gas headspace was added to blood in a glass syringe and was mixed and equilibrated at 37°C for 2 h. Agent concentrations in the calibration gas and syringe headspace were measured using gas chromatography. Anesthetic solubility in saline, citrate-phosphate-dextrose-adenine, and olive oil were similarly measured. Except for goats, all animal species had at least one λ B:G measurement that differed significantly from humans. For each agent, λ B:G positively correlated with serum triglyceride concentrations, but this only explained 25% of interspecies variability. Desflurane was significantly less soluble in blood than sevoflurane in some species (e.g., humans) but not in others (e.g., rabbits). Anesthetic partition coefficients differ significantly between humans and most animals for haloether anesthetics. Because of their similar λ B:G values, goats may be a better animal model for inhaled anesthetic pharmacokinetics in people.

Gas hydrate saturation from acoustic impedance and resistivity logs in the shenhu area, south china sea

USGS Publications Warehouse

Wang, X.; Wu, S.; Lee, M.; Guo, Y.; Yang, S.; Liang, J.

2011-01-01

During the China's first gas hydrate drilling expedition -1 (GMGS-1), gas hydrate was discovered in layers ranging from 10 to 25 m above the base of gas hydrate stability zone in the Shenhu area, South China Sea. Water chemistry, electrical resistivity logs, and acoustic impedance were used to estimate gas hydrate saturations. Gas hydrate saturations estimated from the chloride concentrations range from 0 to 43% of the pore space. The higher gas hydrate saturations were present in the depth from 152 to 177 m at site SH7 and from 190 to 225 m at site SH2, respectively. Gas hydrate saturations estimated from the resistivity using Archie equation have similar trends to those from chloride concentrations. To examine the variability of gas hydrate saturations away from the wells, acoustic impedances calculated from the 3 D seismic data using constrained sparse inversion method were used. Well logs acquired at site SH7 were incorporated into the inversion by establishing a relation between the water-filled porosity, calculated using gas hydrate saturations estimated from the resistivity logs, and the acoustic impedance, calculated from density and velocity logs. Gas hydrate saturations estimated from acoustic impedance of seismic data are ???10-23% of the pore space and are comparable to those estimated from the well logs. The uncertainties in estimated gas hydrate saturations from seismic acoustic impedances were mainly from uncertainties associated with inverted acoustic impedance, the empirical relation between the water-filled porosities and acoustic impedances, and assumed background resistivity. ?? 2011 Elsevier Ltd.

Greenhouse Gas Sensing Using Small Unmanned Aerial Systems - Field Experiment Results and Future Directions

NASA Astrophysics Data System (ADS)

Aubrey, A. D.; Christensen, L. E.; Brockers, R.; Thompson, D. R.

2014-12-01

Requirements for greenhouse gas point source detection and quantification often require high spatial resolution on the order of meters. These applications, which help close the gap in emissions estimate uncertainties, also demand sensing with high sensitivity and in a fashion that accounts for spatiotemporal variability on the order of seconds to minutes. Low-cost vertical takeoff and landing (VTOL) small unmanned aerial systems (sUAS) provide a means to detect and identify the location of point source gas emissions while offering ease of deployment and high maneuverability. Our current fielded gas sensing sUAS platforms are able to provide instantaneous in situ concentration measurements at locations within line of sight of the operator. Recent results from field experiments demonstrating methane detection and plume characterization will be discussed here, including performance assessment conducted via a controlled release experiment in 2013. The logical extension of sUAS gas concentration measurement is quantification of flux rate. We will discuss the preliminary strategy for quantitative flux determination, including intrinsic challenges and heritage from airborne science campaigns, associated with this point source flux quantification. This system approach forms the basis for intelligent autonomous quantitative characterization of gas plumes, which holds great value for applications in commercial, regulatory, and safety environments.

Hydrogen loss during N-15 nuclear reaction analysis of high strength steel

NASA Astrophysics Data System (ADS)

Larochelle, J. S.; Désilets-Benoit, A.; Borduas, G.; Laliberté-Riverin, S.; Roorda, S.; Brochu, M.

2017-10-01

High strength steel samples were analysed by N-15 nuclear reaction analysis in order to detect hydrogen that may have been introduced by electroplating process. The NRA signal decreased during exposure of the ion beam and residual gas analysis showed that the gas was desorbed by the beam interaction. The variable hydrogen signal could be well described as the sum of a constant concentration and a fraction susceptible to second order desorption. A mechanically polished bevel allowed measurements to be extended to a depth of 0.2 mm.

Analysis of real-time variables affecting children's exposure to diesel-related pollutants during school bus commutes in Los Angeles

NASA Astrophysics Data System (ADS)

Sabin, Lisa D.; Kozawa, Kathleen; Behrentz, Eduardo; Winer, Arthur M.; Fitz, Dennis R.; Pankratz, David V.; Colome, Steven D.; Fruin, Scott A.

Variables affecting children's exposure during school bus commutes were investigated using real-time measurements of black carbon (BC), particle-bound polycyclic aromatic hydrocarbons (PB-PAH) and nitrogen dioxide (NO 2) inside 3 conventional diesel school buses, a particle trap-outfitted (TO) diesel school bus and a compressed natural gas (CNG) school bus, while traveling along an urban Los Angeles Unified School District bus route. A video camera was mounted at the front of each bus to record roadway conditions ahead of the bus during each commute. The videotapes from 12 commutes, in conjunction with pollutant concentration time series, were used to determine the influence of variables such as vehicles being followed, bus type and roadway type on pollutant concentrations inside the bus. For all buses tested, the highest concentrations of BC, PB-PAH and NO 2 were observed when following a diesel school bus, especially if that bus was emitting visible exhaust. This result was important because other diesel school buses were responsible for the majority of the diesel vehicle encounters, primarily due to caravanning with each other when leaving a school at the same time. Compared with following a gasoline vehicle or no target, following a smoky diesel school bus yielded BC and PB-PAH concentrations inside the cabin 8 and 11 times higher, respectively, with windows open, and ˜1.8 times higher for both pollutants with windows closed. When other diesel vehicles were not present, pollutant concentrations were highest inside the conventional diesel buses and lowest inside the CNG bus, while the TO diesel bus exhibited intermediate concentrations. Differences in pollutant concentrations between buses were most pronounced with the bus windows closed, and were attributed to a combination of higher concentrations in the exhaust and higher exhaust gas intrusion rates for the conventional diesel buses. Conventional diesel school buses can have a double exposure impact on commuting children: first, exposures to the exhaust from other nearby diesel school buses and, second, exposure to the bus's own exhaust through "self-pollution".

Microscale profiling of photosynthesis-related variables in a highly productive biofilm photobioreactor.

PubMed

Li, Tong; Piltz, Bastian; Podola, Björn; Dron, Anthony; de Beer, Dirk; Melkonian, Michael

2016-05-01

In the present study depth profiles of light, oxygen, pH and photosynthetic performance in an artificial biofilm of the green alga Halochlorella rubescens in a porous substrate photobioreactor (PSBR) were recorded with microsensors. Biofilms were exposed to different light intensities (50-1,000 μmol photons m(-2) s(-1) ) and CO2 levels (0.04-5% v/v in air). The distribution of photosynthetically active radiation showed almost identical trends for different surface irradiances, namely: a relatively fast drop to a depth of about 250 µm, (to 5% of the incident), followed by a slower decrease. Light penetrated into the biofilm deeper than the Lambert-Beer Law predicted, which may be attributed to forward scattering of light, thus improving the overall light availability. Oxygen concentration profiles showed maxima at a depth between 50 and 150 μm, depending on the incident light intensity. A very fast gas exchange was observed at the biofilm surface. The highest oxygen concentration of 3.2 mM was measured with 1,000 μmol photons m(-2) s(-1) and 5% supplementary CO2. Photosynthetic productivity increased with light intensity and/or CO2 concentration and was always highest at the biofilm surface; the stimulating effect of elevated CO2 concentration in the gas phase on photosynthesis was enhanced by higher light intensities. The dissolved inorganic carbon concentration profiles suggest that the availability of the dissolved free CO2 has the strongest impact on photosynthetic productivity. The results suggest that dark respiration could explain previously observed decrease in growth rate over cultivation time in this type of PSBR. Our results represent a basis for understanding the complex dynamics of environmental variables and metabolic processes in artificial phototrophic biofilms exposed to a gas phase and can be used to improve the design and operational parameters of PSBRs. © 2015 Wiley Periodicals, Inc.

CO2 variability from in situ and vertical column measurements in Mexico City

NASA Astrophysics Data System (ADS)

Baylon, J. L.; Grutter, M.; Stremme, W.; Bezanilla, A.; Plaza, E.

2014-12-01

UNAM started a program to measure, among many other atmospheric parameters, greenhouse gas concentrations at six stations in the Mexican territory as part of the "Red Universitaria de Observatorios Atmosfericos", RUOA (www.ruoa.unam.mx). In this work we present recent time series of CO2 measured at the station located in the university campus in Mexico City, and compare them to total vertical columns of this gas measured at the same location. In situ measurements are continuously carried out with a cavity ring-down spectrometer (Picarro Inc., G2401) since July 2014 and the columns are retrieved from solar absorption measurements taken with a Fourier transform infrared spectrometer (Bruker, Vertex 80) when conditions allow. The retrieval method is described and results of the comparison of both techniques and a detailed analysis of the variability of this important greenhouse gas is presented. Simultaneous surface and column CO2 data are useful to constrain models and estimate emissions.

Nitrous oxide as a tracer gas in the ASHRAE 110-1995 Standard.

PubMed

Burke, Martin; Wong, Larry; Gonzales, Ben A; Knutson, Gerhard

2014-01-01

ANSI/ASHRAE Standard 110 provides a quantitative method for testing the performance of laboratory fume hoods. Through release of a known quantity (4.0 Lpm) of a tracer gas, and subsequent monitoring of the tracer gas concentration in the "breathing zone" of a mannequin positioned in front of the hood, this method allows for evaluation of laboratory hood performance. Standard 110 specifies sulfur hexafluoride (SF6) as the tracer gas; however, suitable alternatives are allowed. Through three series of performance tests, this analysis serves to investigate the use of nitrous oxide (N2O) as an alternate tracer gas for hood performance testing. Single gas tests were performed according to ASHRAE Standard 110-1995 with each tracer gas individually. These tests showed identical results using an acceptance criterion of AU 0.1 with the sash half open, nominal 18 inches (0.46m) high, and the face velocity at a nominal 60 fpm (0.3 m/s). Most data collected in these single gas tests, for both tracer gases, were below the minimum detection limit, thus two dual gas tests were developed for simultaneous sampling of both tracer gases. Dual gas dual ejector tests were performed with both tracer gases released simultaneously through two ejectors, and the concentration measured with two detectors using a common sampling probe. Dual gas single ejector tests were performed with both tracer gases released though a single ejector, and the concentration measured in the same manner as the dual gas dual ejector tests. The dual gas dual ejector tests showed excellent correlation, with R typically greater than 0.9. Variance was observed in the resulting regression line for each hood, likely due to non-symmetry between the two challenges caused by variables beyond the control of the investigators. Dual gas single ejector tests resulted in exceptional correlation, with R>0.99 typically for the consolidated data, with a slope of 1.0. These data indicate equivalent results for ASHRAE 110 performance testing using either SF6 or N2O, indicating N2O as an applicable alternate tracer gas.

Optimization of A 2-Micron Laser Frequency Stabilization System for a Double-Pulse CO2 Differential Absorption Lidar

NASA Technical Reports Server (NTRS)

Chen, Songsheng; Yu, Jirong; Bai, Yingsin; Koch, Grady; Petros, Mulugeta; Trieu, Bo; Petzar, Paul; Singh, Upendra N.; Kavaya, Michael J.; Beyon, Jeffrey

2010-01-01

A carbon dioxide (CO2) Differential Absorption Lidar (DIAL) for accurate CO2 concentration measurement requires a frequency locking system to achieve high frequency locking precision and stability. We describe the frequency locking system utilizing Frequency Modulation (FM), Phase Sensitive Detection (PSD), and Proportional Integration Derivative (PID) feedback servo loop, and report the optimization of the sensitivity of the system for the feed back loop based on the characteristics of a variable path-length CO2 gas cell. The CO2 gas cell is characterized with HITRAN database (2004). The method can be applied for any other frequency locking systems referring to gas absorption line.

Solubility of oxygen in a seawater medium in equilibrium with a high-pressure oxy-helium atmosphere.

PubMed

Taylor, C D

1979-06-01

The molar oxygen concentration in a seawater medium in equilibrium with a high-pressure oxygen-helium atmosphere was measured directly in pressurized subsamples, using a modified version of the Winkler oxygen analysis. At a partial pressure of oxygen of 1 atm or less, its concentration in the aqueous phase was adequately described by Henry's Law at total pressures up to 600 atm. This phenomenon, which permits a straightforward determination of dissolved oxygen within hyperbaric systems, resulted from pressure-induced compensatory alterations in the Henry's Law variables rather than from a true obedience to the Ideal Gas Law. If the partial pressure of a gas contributes significantly to the hydrostatic pressure, Henry's Law is no longer adequate for determining its solubility within the compressed medium.

Reconciling anthropogenic climate change with observed temperature 1998-2008.

PubMed

Kaufmann, Robert K; Kauppi, Heikki; Mann, Michael L; Stock, James H

2011-07-19

Given the widely noted increase in the warming effects of rising greenhouse gas concentrations, it has been unclear why global surface temperatures did not rise between 1998 and 2008. We find that this hiatus in warming coincides with a period of little increase in the sum of anthropogenic and natural forcings. Declining solar insolation as part of a normal eleven-year cycle, and a cyclical change from an El Nino to a La Nina dominate our measure of anthropogenic effects because rapid growth in short-lived sulfur emissions partially offsets rising greenhouse gas concentrations. As such, we find that recent global temperature records are consistent with the existing understanding of the relationship among global surface temperature, internal variability, and radiative forcing, which includes anthropogenic factors with well known warming and cooling effects.

Chamber measurement of surface-atmosphere trace gas exchange: Numerical evaluation of dependence on soil, interfacial layer, and source/sink properties

NASA Astrophysics Data System (ADS)

Hutchinson, G. L.; Livingston, G. P.; Healy, R. W.; Striegl, R. G.

2000-04-01

We employed a three-dimensional finite difference gas diffusion model to simulate the performance of chambers used to measure surface-atmosphere trace gas exchange. We found that systematic errors often result from conventional chamber design and deployment protocols, as well as key assumptions behind the estimation of trace gas exchange rates from observed concentration data. Specifically, our simulations showed that (1) when a chamber significantly alters atmospheric mixing processes operating near the soil surface, it also nearly instantaneously enhances or suppresses the postdeployment gas exchange rate, (2) any change resulting in greater soil gas diffusivity, or greater partitioning of the diffusing gas to solid or liquid soil fractions, increases the potential for chamber-induced measurement error, and (3) all such errors are independent of the magnitude, kinetics, and/or distribution of trace gas sources, but greater for trace gas sinks with the same initial absolute flux. Finally, and most importantly, we found that our results apply to steady state as well as non-steady-state chambers, because the slow rate of gas diffusion in soil inhibits recovery of the former from their initial non-steady-state condition. Over a range of representative conditions, the error in steady state chamber estimates of the trace gas flux varied from -30 to +32%, while estimates computed by linear regression from non-steady-state chamber concentrations were 2 to 31% too small. Although such errors are relatively small in comparison to the temporal and spatial variability characteristic of trace gas exchange, they bias the summary statistics for each experiment as well as larger scale trace gas flux estimates based on them.

Chamber measurement of surface-atmosphere trace gas exchange--Numerical evaluation of dependence on soil interfacial layer, and source/sink products

USGS Publications Warehouse

Hutchinson, G.L.; Livingston, G.P.; Healy, R.W.; Striegl, Robert G.

2000-01-01

We employed a three-dimensional finite difference gas diffusion model to simulate the performance of chambers used to measure surface-atmosphere tace gas exchange. We found that systematic errors often result from conventional chamber design and deployment protocols, as well as key assumptions behind the estimation of trace gas exchange rates from observed concentration data. Specifically, our simulationshowed that (1) when a chamber significantly alters atmospheric mixing processes operating near the soil surface, it also nearly instantaneously enhances or suppresses the postdeployment gas exchange rate, (2) any change resulting in greater soil gas diffusivity, or greater partitioning of the diffusing gas to solid or liquid soil fractions, increases the potential for chamber-induced measurement error, and (3) all such errors are independent of the magnitude, kinetics, and/or distribution of trace gas sources, but greater for trace gas sinks with the same initial absolute flux. Finally, and most importantly, we found that our results apply to steady state as well as non-steady-state chambers, because the slow rate of gas diffusion in soil inhibits recovery of the former from their initial non-steady-state condition. Over a range of representative conditions, the error in steady state chamber estimates of the trace gas flux varied from -30 to +32%, while estimates computed by linear regression from non-steadystate chamber concentrations were 2 to 31% too small. Although such errors are relatively small in comparison to the temporal and spatial variability characteristic of trace gas exchange, they bias the summary statistics for each experiment as well as larger scale trace gas flux estimates based on them.

Evaluation and application of static headspace-multicapillary column-gas chromatography-ion mobility spectrometry for complex sample analysis.

PubMed

Denawaka, Chamila J; Fowlis, Ian A; Dean, John R

2014-04-18

An evaluation of static headspace-multicapillary column-gas chromatography-ion mobility spectrometry (SHS-MCC-GC-IMS) has been undertaken to assess its applicability for the determination of 32 volatile compounds (VCs). The key experimental variables of sample incubation time and temperature have been evaluated alongside the MCC-GC variables of column polarity, syringe temperature, injection temperature, injection volume, column temperature and carrier gas flow rate coupled with the IMS variables of temperature and drift gas flow rate. This evaluation resulted in six sets of experimental variables being required to separate the 32 VCs. The optimum experimental variables for SHS-MCC-GC-IMS, the retention time and drift time operating parameters were determined; to normalise the operating parameters, the relative drift time and normalised reduced ion mobility for each VC were determined. In addition, a full theoretical explanation is provided on the formation of the monomer, dimer and trimer of a VC. The optimum operating condition for each VC calibration data was obtained alongside limit of detection (LOD) and limit of quantitation (LOQ) values. Typical detection limits ranged from 0.1ng bis(methylthio)methane, ethylbutanoate and (E)-2-nonenal to 472ng isovaleric acid with correlation coefficient (R(2)) data ranging from 0.9793 (for the dimer of octanal) through to 0.9990 (for isobutyric acid). Finally, the developed protocols were applied to the analysis of malodour in sock samples. Initial work involved spiking an inert matrix and sock samples with appropriate concentrations of eight VCs. The average recovery from the inert matrix was 101±18% (n=8), while recoveries from the sock samples were lower, that is, 54±30% (n=8) for sock type 1 and 78±24% (n=6) for sock type 2. Finally, SHS-MCC-GC-IMS was applied to sock malodour in a field trial based on 11 volunteers (mixed gender) over a 3-week period. By applying the SHS-MCC-GC-IMS database, four VCs were identified and quantified: ammonia, dimethyl disulphide, dimethyl trisulphide and butyric acid. A link was identified between the presence of high ammonia and dimethyl disulphide concentrations and a high malodour odour grading, that is, ≥ 6. Statistical analysis did not find any correlation between the occurrence of dimethyl disulphide and participant gender. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

Inside Story of Gas Processes within Stormwater Biofilters: Does Greenhouse Gas Production Tarnish the Benefits of Nitrogen Removal?

PubMed

Payne, Emily G I; Pham, Tracey; Cook, Perran L M; Deletic, Ana; Hatt, Belinda E; Fletcher, Tim D

2017-04-04

Stormwater biofilters are dynamic environments, supporting diverse processes that act to capture and transform incoming pollutants. However, beneficial water treatment processes can be accompanied by undesirable greenhouse gas production. This study investigated the potential for nitrous oxide (N 2 O) and methane (CH 4 ) generation in dissolved form at the base of laboratory-scale stormwater biofilter columns. The influence of plant presence, species, inflow frequency, and inclusion of a saturated zone and carbon source were studied. Free-draining biofilters remained aerobic with negligible greenhouse gas production during storm events. Designs with a saturated zone were oxygenated at their base by incoming stormwater before anaerobic conditions rapidly re-established, although extended dry periods allowed the reintroduction of oxygen by evapotranspiration. Production of CH 4 and N 2 O in the saturated zone varied significantly in response to plant presence, species, and wetting and drying. Concentrations of N 2 O typically peaked rapidly following stormwater inundation, associated with limited plant root systems and poorer nitrogen removal from biofilter effluent. Production of CH 4 also commenced quickly but continued throughout the anaerobic interevent period and lacked clear relationships with plant characteristics or nitrogen removal performance. Dissolved greenhouse gas concentrations were highly variable, but peak concentrations of N 2 O accounted for <1.5% of the incoming total nitrogen load. While further work is required to measure surface emissions, the potential for substantial release of N 2 O or CH 4 in biofilter effluent appears relatively low.

Prediction of dissolved oxygen and carbon dioxide concentration profiles in tubular photobioreactors for microalgal culture

PubMed

Rubio; Fernandez; Perez; Camacho; Grima

1999-01-05

A model is developed for prediction of axial concentration profiles of dissolved oxygen and carbon dioxide in tubular photobioreactors used for culturing microalgae. Experimental data are used to verify the model for continuous outdoor culture of Porphyridium cruentum grown in a 200-L reactor with 100-m long tubular solar receiver. The culture was carried out at a dilution rate of 0.05 h-1 applied only during a 10-h daylight period. The quasi-steady state biomass concentration achieved was 3.0 g. L-1, corresponding to a biomass productivity of 1.5 g. L-1. d-1. The model could predict the dissolved oxygen level in both gas disengagement zone of the reactor and at the end of the loop, the exhaust gas composition, the amount of carbon dioxide injected, and the pH of the culture at each hour. In predicting the various parameters, the model took into account the length of the solar receiver tube, the rate of photosynthesis, the velocity of flow, the degree of mixing, and gas-liquid mass transfer. Because the model simulated the system behavior as a function of tube length and operational variables (superficial gas velocity in the riser, composition of carbon dioxide in the gas injected in the solar receiver and its injection rate), it could potentially be applied to rational design and scale-up of photobioreactors. Copyright 1999 John Wiley & Sons, Inc.

Measurements of soil, surface water, and groundwater CO2 concentration variability within Earth's critical zone: low-cost, long-term, high-temporal resolution monitoring

NASA Astrophysics Data System (ADS)

Blackstock, J. M.; Covington, M. D.; Williams, S. G. W.; Myre, J. M.; Rodriguez, J.

2017-12-01

Variability in CO2 fluxes within Earth's Critical zone occurs over a wide range of timescales. Resolving this and its drivers requires high-temporal resolution monitoring of CO2 both in the soil and aquatic environments. High-cost (> 1,000 USD) gas analyzers and data loggers present cost-barriers for investigations with limited budgets, particularly if high spatial resolution is desired. To overcome high-costs, we developed an Arduino based CO2 measuring platform (i.e. gas analyzer and data logger). The platform was deployed at multiple sites within the Critical Zone overlying the Springfield Plateau aquifer in Northwest Arkansas, USA. The CO2 gas analyzer used in this study was a relatively low-cost SenseAir K30. The analyzer's optical housing was covered by a PTFE semi-permeable membrane allowing for gas exchange between the analyzer and environment. Total approximate cost of the monitoring platform was 200 USD (2% detection limit) to 300 USD (10% detection limit) depending on the K30 model used. For testing purposes, we deployed the Arduino based platform alongside a commercial monitoring platform. CO2 concentration time series were nearly identical. Notably, CO2 cycles at the surface water site, which operated from January to April 2017, displayed a systematic increase in daily CO2 amplitude. Preliminary interpretation suggests key observation of seasonally increasing stream metabolic function. Other interpretations of observed cyclical and event-based behavior are out of the scope of the study; however, the presented method describes an accurate near-hourly characterization of CO2 variability. The new platform has been shown to be operational for several months, and we infer reliable operation for much longer deployments (> 1 year) given adequate environmental protection and power supply. Considering cost-savings, this platform is an attractive option for continuous, accurate, low-power, and low-cost CO2 monitoring for remote locations, globally.

Greenhouse gas scenario sensitivity and uncertainties in precipitation projections for central Belgium

NASA Astrophysics Data System (ADS)

Van Uytven, E.; Willems, P.

2018-03-01

Climate change impact assessment on meteorological variables involves large uncertainties as a result of incomplete knowledge on the future greenhouse gas concentrations and climate model physics, next to the inherent internal variability of the climate system. Given that the alteration in greenhouse gas concentrations is the driver for the change, one expects the impacts to be highly dependent on the considered greenhouse gas scenario (GHS). In this study, we denote this behavior as GHS sensitivity. Due to the climate model related uncertainties, this sensitivity is, at local scale, not always that strong as expected. This paper aims to study the GHS sensitivity and its contributing role to climate scenarios for a case study in Belgium. An ensemble of 160 CMIP5 climate model runs is considered and climate change signals are studied for precipitation accumulation, daily precipitation intensities and wet day frequencies. This was done for the different seasons of the year and the scenario periods 2011-2040, 2031-2060, 2051-2081 and 2071-2100. By means of variance decomposition, the total variance in the climate change signals was separated in the contribution of the differences in GHSs and the other model-related uncertainty sources. These contributions were found dependent on the variable and season. Following the time of emergence concept, the GHS uncertainty contribution is found dependent on the time horizon and increases over time. For the most distinct time horizon (2071-2100), the climate model uncertainty accounts for the largest uncertainty contribution. The GHS differences explain up to 18% of the total variance in the climate change signals. The results point further at the importance of the climate model ensemble design, specifically the ensemble size and the combination of climate models, whereupon climate scenarios are based. The numerical noise, introduced at scales smaller than the skillful scale, e.g. at local scale, was not considered in this study.

Assessing How Water Type, Climate, and Landscape Position Correlate with Variability of Methane in Shallow Groundwater in the Marcellus Region

NASA Astrophysics Data System (ADS)

Campbell, A.; Lautz, L.; Hoke, G. D.

2017-12-01

Prior work shows that spatial differences in naturally-occurring methane concentrations in shallow groundwater in the Marcellus Shale region are correlated with water type (e.g. Ca-HCO3 vs Na-HCO3) and landscape position (e.g. valley vs upland). However, little is known about how naturally-occurring methane in groundwater varies through time, particularly on a seasonal or monthly time scale, and how temporal variability is related to seasonal changes in climate. Extensive development of the Marcellus shale gas play in northeastern Pennsylvania limits opportunities for measuring baseline water quality through time. In contrast, a ban on hydraulic fracturing in NY affords an opportunity for characterizing baseline temporal variability in methane concentrations. The objective of this study is to characterize temporal variability of naturally-occurring methane in shallow groundwater in the Marcellus region, and how such temporal variability is correlated to other well characteristics, such as water type, landscape position, and climatic conditions. We worked with homeowners to sample 11 domestic wells monthly in the Marcellus Shale region of NY for methane concentrations and major ions for a full year. Wells were grouped according to the primary source of methane (e.g. thermogenic vs microbial) based upon δ13C-DIC, δ13C-CH4, and δD-CH4 isotopes. The full dataset and the grouped data were analyzed to assess how well climatic conditions, water type, and landscape position correlate with variability of methane concentrations through time. These data provide information on within year and between year variability of methane, as well as spatial variability between wells, which fills a data gap and can be used to inform policy regulations.

Superfluid thermodynamic cycle refrigerator

DOEpatents

Swift, G.W.; Kotsubo, V.Y.

1992-12-22

A cryogenic refrigerator cools a heat source by cyclically concentrating and diluting the amount of [sup 3]He in a single phase [sup 3]He-[sup 4]He solution. The [sup 3]He in superfluid [sup 4]He acts in a manner of an ideal gas in a vacuum. Thus, refrigeration is obtained using any conventional thermal cycle, but preferably a Stirling or Carnot cycle. A single phase solution of liquid [sup 3]He at an initial concentration in superfluid [sup 4]He is contained in a first variable volume connected to a second variable volume through a superleak device that enables free passage of [sup 4]He while restricting passage of [sup 3]He. The [sup 3]He is compressed (concentrated) and expanded (diluted) in a phased manner to carry out the selected thermal cycle to remove heat from the heat load for cooling below 1 K. 12 figs.

Superfluid thermodynamic cycle refrigerator

DOEpatents

Swift, Gregory W.; Kotsubo, Vincent Y.

1992-01-01

A cryogenic refrigerator cools a heat source by cyclically concentrating and diluting the amount of .sup.3 He in a single phase .sup.3 He-.sup.4 He solution. The .sup.3 He in superfluid .sup.4 He acts in a manner of an ideal gas in a vacuum. Thus, refrigeration is obtained using any conventional thermal cycle, but preferably a Stirling or Carnot cycle. A single phase solution of liquid .sup.3 He at an initial concentration in superfluid .sup.4 He is contained in a first variable volume connected to a second variable volume through a superleak device that enables free passage of .sup.4 He while restricting passage of .sup.3 He. The .sup.3 He is compressed (concentrated) and expanded (diluted) in a phased manner to carry out the selected thermal cycle to remove heat from the heat load for cooling below 1 K.

Analysis of Atmospheric Composition and Tropospheric Variability With Integrated Open- Path and Ground-Based Solar Infrared Absorption Spectroscopy

NASA Astrophysics Data System (ADS)

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

2006-12-01

Ground-based solar infrared absorption spectroscopy coupled with open-path spectroscopy provides a means for analysis of the highly variable contribution of the boundary layer to problems of radiative transfer and atmospheric chemistry. This is of particular importance in geographic regions of significant local anthropogenic influence and large tropospheric fluctuations in general. A Bomem DA8 FT-IR integrated with a sun-tracking and open-path system (~0.5 km) is located at The University of Tennessee, in downtown Knoxville and near The Great Smoky Mountains National Park, an area known for problematic air quality. From atmospheric absorption spectra, boundary layer concentrations as well as total column abundances and vertical concentration profiles are derived. A record of more than 1000 solar-sourced atmospheric spectra covering a period greater than three years in duration is under analysis to characterize the limit of precision in total column abundance determinations for many gases such as O3, CO, CH4, N2O, HF and CO2. Initial efforts using atmospheric O2 as a calibration indicate the solar-sourced spectra may not meet the precision required for the highly accurate atmospheric CO2 quantification by such global efforts as the OCO and NDSC. However, the determined variability of CO2 and other gas concentrations is statistically significant and is indicative of local concentration fluxes pertinent to the regional atmospheric chemistry. This is therefore an important data record in the southeastern United States, a somewhat under- sampled geographic region. In addition to providing a means to improve the analysis of solar spectra, the open-path data is useful for elucidation of seasonal and diurnal trends in the trace gas concentrations. This provides an urban air quality monitor in addition to improving the description of the total atmospheric composition, as the open-path system is stable and permanent.

High resolution spatial and temporal evolution of dissolved gases in groundwater during a controlled natural gas release experiment.

PubMed

Cahill, Aaron G; Parker, Beth L; Mayer, Bernhard; Mayer, K Ulrich; Cherry, John A

2018-05-01

Fugitive gas comprised primarily of methane (CH 4 ) with traces of ethane and propane (collectively termed C 1-3 ) may negatively impact shallow groundwater when unintentionally released from oil and natural gas wells. Currently, knowledge of fugitive gas migration, subsurface source identification and oxidation potential in groundwater is limited. To advance understanding, a controlled release experiment was performed at the Borden Research Aquifer, Canada, whereby 51m 3 of natural gas was injected into an unconfined sand aquifer over 72days with dissolved gases monitored over 323days. During active gas injection, a dispersed plume of dissolved C 1-3 evolved in a depth discrete and spatially complex manner. Evolution of the dissolved gas plume was driven by free-phase gas migration controlled by small-scale sediment layering and anisotropy. Upon cessation of gas injection, C 1-3 concentrations increased to the greatest levels observed, particularly at 2 and 6m depths, reaching up to 31.5, 1.5 and 0.1mg/L respectively before stabilizing and persisting. At no time did groundwater become fully saturated with natural gas at the scale of sampling undertaken. Throughout the experiment the isotopic composition of injected methane (δ 13 C of -42.2‰) and the wetness parameter (i.e. the ratio of C 1 to C 2+ ) constituted excellent tracers for the presence of fugitive gas at concentrations >2mg/L. At discrete times C 1-3 concentrations varied by up to 4 orders of magnitude over 8m of aquifer thickness (e.g. from <0.01 to 30mg/L for CH 4 ), while some groundwater samples lacked evidence of fugitive gas, despite being within 10m of the injection zone. Meanwhile, carbon isotope ratios of dissolved CH 4 showed no evidence of oxidation. Our results show that while impacts to aquifers from a fugitive gas event are readily detectable at discrete depths, they are spatially and temporally variable and dissolved methane has propensity to persist. Copyright © 2017 Elsevier B.V. All rights reserved.

Estimating PM2.5 Concentrations in Xi'an City Using a Generalized Additive Model with Multi-Source Monitoring Data

PubMed Central

Song, Yong-Ze; Yang, Hong-Lei; Peng, Jun-Huan; Song, Yi-Rong; Sun, Qian; Li, Yuan

2015-01-01

Particulate matter with an aerodynamic diameter <2.5 μm (PM2.5) represents a severe environmental problem and is of negative impact on human health. Xi'an City, with a population of 6.5 million, is among the highest concentrations of PM2.5 in China. In 2013, in total, there were 191 days in Xi’an City on which PM2.5 concentrations were greater than 100 μg/m3. Recently, a few studies have explored the potential causes of high PM2.5 concentration using remote sensing data such as the MODIS aerosol optical thickness (AOT) product. Linear regression is a commonly used method to find statistical relationships among PM2.5 concentrations and other pollutants, including CO, NO2, SO2, and O3, which can be indicative of emission sources. The relationships of these variables, however, are usually complicated and non-linear. Therefore, a generalized additive model (GAM) is used to estimate the statistical relationships between potential variables and PM2.5 concentrations. This model contains linear functions of SO2 and CO, univariate smoothing non-linear functions of NO2, O3, AOT and temperature, and bivariate smoothing non-linear functions of location and wind variables. The model can explain 69.50% of PM2.5 concentrations, with R2 = 0.691, which improves the result of a stepwise linear regression (R2 = 0.582) by 18.73%. The two most significant variables, CO concentration and AOT, represent 20.65% and 19.54% of the deviance, respectively, while the three other gas-phase concentrations, SO2, NO2, and O3 account for 10.88% of the total deviance. These results show that in Xi'an City, the traffic and other industrial emissions are the primary source of PM2.5. Temperature, location, and wind variables also non-linearly related with PM2.5. PMID:26540446

Soil Greenhouse Gas Emissions from a Subtropical Mangrove in Hong Kong

NASA Astrophysics Data System (ADS)

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

2014-12-01

The concept of "blue carbon" has received increasing attention recently, which points to the potential role of vegetated coastal wetlands in carbon sequestration. Yet, the magnitude and controls of greenhouse gas emissions from coastal wetland ecosystems, especially mangroves in the subtropical regions, are still largely unknown. In this study, we conducted chamber measurements in the Mai Po Marshes Nature Reserve of Hong Kong at monthly intervals to characterize the spatial and temporal variability of the emission of greenhouse gases, including CO2, CH4 and N2O from mangrove soils, and examine the influence of environmental and biotic variables on greenhouse gas fluxes. We found the highest mean CH4 and N2O emissions in autumn and the highest CO2 flux in summer. Along the tidal gradient, we observed significantly higher CH4 and N2O emissions from the middle zones and landward zones, respectively, while no clear spatial variation of CO2 emissions was observed. There were significantly higher soil greenhouse gas emissions from sites dominated by Avicennia marina than those dominated by Kandelia obovata, which might be due to the presence of pneumatophores which facilitated gas transport. We found a significant, negative correlation between CH4 flux and soil NO3-N concentration, while CO2 flux was positively correlation with total Kjeldahl nitrogen content. Soil temperature was positively correlated with the emissions of all three greenhouse gases, while water table depth was positively and negatively correlated with CH4 and N2O emissions, respectively. Our findings demonstrate the high spatial and temporal variability of greenhouse gas emissions from mangrove soils which could be attributed in part to the differences in environmental conditions and dominant plant species.

Prospective targeting and control of end-tidal CO2 and O2 concentrations

PubMed Central

Slessarev, Marat; Han, Jay; Mardimae, Alexandra; Prisman, Eitan; Preiss, David; Volgyesi, George; Ansel, Cliff; Duffin, James; Fisher, Joseph A

2007-01-01

Current methods of forcing end-tidal PCO2 (PETCO2) and PO2 (PETO2) rely on breath-by-breath adjustment of inspired gas concentrations using feedback loop algorithms. Such servo-control mechanisms are complex because they have to anticipate and compensate for the respiratory response to a given inspiratory gas concentration on a breath-by-breath basis. In this paper, we introduce a low gas flow method to prospectively target and control PETCO2 and PETO2 independent of each other and of minute ventilation in spontaneously breathing humans. We used the method to change PETCO2 from control (40 mmHg for PETCO2 and 100 mmHg for PETO2) to two target PETCO2 values (45 and 50 mmHg) at iso-oxia (100 mmHg), PETO2 to two target values (200 and 300 mmHg) at normocapnia (40 mmHg), and PETCO2 with PETO2 simultaneously to the same targets (45 with 200 mmHg and 50 with 300 mmHg). After each targeted value, PETCO2 and PETO2 were returned to control values. Each state was maintained for 30 s. The average difference between target and measured values for PETCO2 was ± 1 mmHg, and for PETO2 was ± 4 mmHg. PETCO2 varied by ± 1 mmHg and PETO2 by ± 5.6 mmHg (s.d.) over the 30 s stages. This degree of control was obtained despite considerable variability in minute ventilation between subjects (± 7.6 l min−1). We conclude that targeted end-tidal gas concentrations can be attained in spontaneously breathing subjects using this prospective, feed-forward, low gas flow system. PMID:17446225

Linking carbon and hydrologic fluxes in the critical zone: Observations from high-frequency monitoring of a weathered bedrock vadose zone

NASA Astrophysics Data System (ADS)

Tune, A. K.; Druhan, J. L.; Wang, J.; Cargill, S.; Murphy, C.; Rempe, D. M.

2017-12-01

A principle challenge in quantifying feedbacks between continental weathering and atmospheric CO2 is to improve understanding of how biogeochemical processes in the critical zone influence the distribution and mobility of organic and inorganic carbon. In particular, in landscapes characterized by thin soils and heterogeneous weathered and fractured bedrock, little data exist to inform and constrain predictive models for carbon dynamics. Here, we present the results of an intensive water and gas sampling campaign across an 18 m thick, variably saturated argillite weathering profile in the Eel River CZO. We monitor water content in situ and regularly collect samples of freely-draining water, tightly-held water, and gas through wet and dry seasons using a novel Vadose-zone Monitoring System (VMS) consisting of sensors and samplers distributed across a 20 m long inclined borehole. This novel approach facilitates the interception of gas and water during transport across the entire variably saturated weathering profile. The data demonstrate that seasonal changes in saturation control the vertical distribution and mobility of carbon in the fractured critical zone. Concentrations of gaseous CO2, O2, and dissolved organic and inorganic carbon fluctuate significantly and repeatably with seasonal additions of water infiltrating the weathered bedrock. A persistent vertical structure in the concentrations of dissolved phases and gas concentrations broadly corresponds to depths associated with unsaturated, seasonally saturated, and chronically saturated zones. Associated variations in the vertical structure of mineralogy and elemental composition, including solid phase organic carbon content, are observed in core obtained during drilling. Together, our observations indicate significant respiration of organic carbon at depths greater than the base of the soil, and thus motivate further investigation of the role of heterogeneous weathered, bedrock environments, which are needed to improve quantitative models for feedbacks between terrestrial and atmospheric CO2.

Critical evaluation of connectivity-based point of care testing systems of glucose in a hospital environment.

PubMed

Floré, Katelijne M J; Fiers, Tom; Delanghe, Joris R

2008-01-01

In recent years a number of point of care testing (POCT) glucometers were introduced on the market. We investigated the analytical variability (lot-to-lot variation, calibration error, inter-instrument and inter-operator variability) of glucose POCT systems in a university hospital environment and compared these results with the analytical needs required for tight glucose monitoring. The reference hexokinase method was compared to different POCT systems based on glucose oxidase (blood gas instruments) or glucose dehydrogenase (handheld glucometers). Based upon daily internal quality control data, total errors were calculated for the various glucose methods and the analytical variability of the glucometers was estimated. The total error of the glucometers exceeded by far the desirable analytical specifications (based on a biological variability model). Lot-to-lot variation, inter-instrument variation and inter-operator variability contributed approximately equally to total variance. As in a hospital environment, distribution of hematocrit values is broad, converting blood glucose into plasma values using a fixed factor further increases variance. The percentage of outliers exceeded the ISO 15197 criteria in a broad glucose concentration range. Total analytical variation of handheld glucometers is larger than expected. Clinicians should be aware that the variability of glucose measurements obtained by blood gas instruments is lower than results obtained with handheld glucometers on capillary blood.

Temporal variations of methane concentration and isotopic composition in groundwater of the St. Lawrence Lowlands, eastern Canada

NASA Astrophysics Data System (ADS)

Rivard, Christine; Bordeleau, Geneviève; Lavoie, Denis; Lefebvre, René; Malet, Xavier

2018-03-01

Dissolved methane concentrations in shallow groundwater are known to vary both spatially and temporally. The extent of these variations is poorly documented although this knowledge is critical for distinguishing natural fluctuations from anthropogenic impacts stemming from oil and gas activities. This issue was addressed as part of a groundwater research project aiming to assess the risk of shale gas development for groundwater quality over a 500-km2 area in the St. Lawrence Lowlands (Quebec, Canada). A specific study was carried out to define the natural variability of methane concentrations and carbon and hydrogen isotope ratios in groundwater, as dissolved methane is naturally ubiquitous in aquifers of this area. Monitoring was carried out over a period of up to 2.5 years in seven monitoring wells. Results showed that for a given well, using the same sampling depth and technique, methane concentrations can vary over time from 2.5 to 6 times relative to the lowest recorded value. Methane isotopic composition, which is a useful tool to distinguish gas origin, was found to be stable for most wells, but varied significantly over time in the two wells where methane concentrations are the lowest. The use of concentration ratios, as well as isotopic composition of methane and dissolved inorganic carbon (DIC), helped unravel the processes responsible for these variations. This study indicates that both methane concentrations and isotopic composition, as well as DIC isotopes, should be regularly monitored over at least 1 year to establish their potential natural variations prior to hydrocarbon development.

Spatial and temporal variability of nitrate and nitrous oxide concentrations in the unsaturated zone at a corn field in the US Midwest

NASA Astrophysics Data System (ADS)

Gopalakrishnan, G.; Negri, C.

2011-12-01

There has been a significant increase in reactive nitrogen in the environment as a result of human activity. Reactive nitrogen of anthropogenic origin now equals that derived from natural terrestrial nitrogen fixation and is expected to exceed it by the end of the decade. Nitrogen is applied to crops as fertilizer and impacts the environment through water quality impairments (mostly as nitrate) and as greenhouse gas emissions (as nitrous oxide). Research on environmental impacts resulting from nitrogen application in the form of fertilizers has focused disproportionately on the degradation of water quality from agricultural non-point sources. The impacts of this degradation are registered both locally, with runoff and percolation of agrochemicals into local surface water and groundwater, and on a larger scale, such as the increase in the anoxic zone in the Gulf of Mexico attributed to nitrate from the Mississippi River. Impacts to the global climate from increased production of nitrous oxide as a result of increased fertilization are equally significant. Nitrous oxide is a greenhouse gas with a warming potential that is approximately 300 times greater than carbon dioxide. Direct emissions of nitrous oxide from the soil have been expressed as 1% of the applied nitrogen. Indirect emissions due to runoff, leaching and volatilization of the nitrogen from the field have been expressed as 0.75% of the applied nitrogen. Many studies have focused on processes governing nitrogen fluxes in the soil, surface water and groundwater systems. However, research on the biogeochemical processes regulating nitrogen fluxes in the unsaturated zone and consequent impacts on nitrate and nitrous oxide concentrations in groundwater are lacking. Our study explores the spatial and temporal variability of nitrate and nitrous oxide concentrations in the vadose zone at a 15 acre corn field in the US Midwest and links it to the concentrations found in the groundwater at the field site. Results indicated that nitrate concentrations in the vadose zone were an order of magnitude greater than in the groundwater. Nitrous oxide concentrations were significantly less in the vadose zone, suggesting that conditions for microbial degradation of the nitrate were not optimal. There was significant short-term variability in the nitrate concentrations as well as spatial variability over the field site. While the processes governing the linkage between nitrogen concentrations in the unsaturated and saturated zones are still unclear, our research suggests that current models may overestimate the indirect emissions of nitrous oxide produced in agricultural systems.

Using Isotope Ratio Infrared Spectrometer to determine δ13C and δ18O of carbonate samples

NASA Astrophysics Data System (ADS)

Smajgl, Danijela; Stöbener, Nils; Mandic, Magda

2017-04-01

The isotopic composition of calcifying organisms is a key tool for reconstruction past seawater temperature and water chemistry. Therefore stable carbon and oxygen isotopes (δ13C and δ18O) in carbonates have been widely used for reconstruction of paleoenvironments. Precise and accurate determination of isotopic composition of carbon (13C) and oxygen (18O) from carbonate sample with proper referencing and data evaluation algorithm presents a challenge for scientists. Mass spectrometry was the only widely used technique for this kind of analysis, but recent advances make laser based spectroscopy a viable alternative. The Thermo Scientific Delta Ray Isotope Ratio Infrared Spectrometer (IRIS) analyzer with the Universal Reference Interface (URI) Connect is one of those alternatives and with TELEDYNE Cetac ASX-7100 autosampler extends the traditional offerings with a system of high precision and throughput of samples. To establish precision and accuracy of measurements and also to develop optimal sample preparation method for measurements with Delta Ray IRIS and URI Connect, IAEA reference materials were used. Preparation is similar to a Gas Bench II method. Carbonate material is added into the vials, flushed with CO2 free synthetic air and acidified with few droplets of 104% H3PO4. Sample amount used for analysis can be as low as 200 μg. Samples are measured after acidification and equilibration time of one hour at 70°C. The CO2 gas generated by reaction is flushed into the variable volume inside the URI Connect through the Nafion based built-in water trap. For this step, carrier gas (CO2 free air) is used to flush the gas from the vial into the variable volume with a maximum volume of 100 ml. A small amount of the sample is then used for automatic concentration determination present in the variable volume. The Thermo Scientific Qtegra Software automatically adjusts any additional dilution of the sample to achieve the desired concentration (usually 400 ppm) in the analyzer. As part of the workflow, reference gas measurements are regularly measured at the same concentration as the sample to allow for automatic drift and linearity correction. With described sample preparation and measurement method, samples are measured with standard deviation less than 0.1‰ δ13C and δ18O, respectively and accuracy of <0.01‰. The system can measure up to 100 samples per day. Equivalent of about 80 µg of pure CO2 gas is needed to complete an analysis. Due to it's small weight and robustness, sample analysis can be performed in the field. Applying new technology of Isotope Ratio Infrared Spectrometers in environmental and paleoenvironmental research can extend the knowledge of complex seawater history and CO2 cycle.

Relevance of anisotropy and spatial variability of gas diffusivity for soil-gas transport

NASA Astrophysics Data System (ADS)

Schack-Kirchner, Helmer; Kühne, Anke; Lang, Friederike

2017-04-01

Models of soil gas transport generally do not consider neither direction dependence of gas diffusivity, nor its small-scale variability. However, in a recent study, we could provide evidence for anisotropy favouring vertical gas diffusion in natural soils. We hypothesize that gas transport models based on gas diffusion data measured with soil rings are strongly influenced by both, anisotropy and spatial variability and the use of averaged diffusivities could be misleading. To test this we used a 2-dimensional model of soil gas transport to under compacted wheel tracks to model the soil-air oxygen distribution in the soil. The model was parametrized with data obtained from soil-ring measurements with its central tendency and variability. The model includes vertical parameter variability as well as variation perpendicular to the elongated wheel track. Different parametrization types have been tested: [i)]Averaged values for wheel track and undisturbed. em [ii)]Random distribution of soil cells with normally distributed variability within the strata. em [iii)]Random distributed soil cells with uniformly distributed variability within the strata. All three types of small-scale variability has been tested for [j)] isotropic gas diffusivity and em [jj)]reduced horizontal gas diffusivity (constant factor), yielding in total six models. As expected the different parametrizations had an important influence to the aeration state under wheel tracks with the strongest oxygen depletion in case of uniformly distributed variability and anisotropy towards higher vertical diffusivity. The simple simulation approach clearly showed the relevance of anisotropy and spatial variability in case of identical central tendency measures of gas diffusivity. However, until now it did not consider spatial dependency of variability, that could even aggravate effects. To consider anisotropy and spatial variability in gas transport models we recommend a) to measure soil-gas transport parameters spatially explicit including different directions and b) to use random-field stochastic models to assess the possible effects for gas-exchange models.

Elimination of residual amplitude modulation in tunable diode laser wavelength modulation spectroscopy using an optical fiber delay line.

PubMed

Chakraborty, Arup Lal; Ruxton, Keith; Johnstone, Walter; Lengden, Michael; Duffin, Kevin

2009-06-08

A new fiber-optic technique to eliminate residual amplitude modulation in tunable diode laser wavelength modulation spectroscopy is presented. The modulated laser output is split to pass in parallel through the gas measurement cell and an optical fiber delay line, with the modulation frequency / delay chosen to introduce a relative phase shift of pi between them. The two signals are balanced using a variable attenuator and recombined through a fiber coupler. In the absence of gas, the direct laser intensity modulation cancels, thereby eliminating the high background. The presence of gas induces a concentration-dependent imbalance at the coupler's output from which the absolute absorption profile is directly recovered with high accuracy using 1f detection.

Reconciling anthropogenic climate change with observed temperature 1998–2008

PubMed Central

Kaufmann, Robert K.; Kauppi, Heikki; Mann, Michael L.; Stock, James H.

2011-01-01

Given the widely noted increase in the warming effects of rising greenhouse gas concentrations, it has been unclear why global surface temperatures did not rise between 1998 and 2008. We find that this hiatus in warming coincides with a period of little increase in the sum of anthropogenic and natural forcings. Declining solar insolation as part of a normal eleven-year cycle, and a cyclical change from an El Nino to a La Nina dominate our measure of anthropogenic effects because rapid growth in short-lived sulfur emissions partially offsets rising greenhouse gas concentrations. As such, we find that recent global temperature records are consistent with the existing understanding of the relationship among global surface temperature, internal variability, and radiative forcing, which includes anthropogenic factors with well known warming and cooling effects. PMID:21730180

Multi-year air monitoring of legacy and current-use brominated flame retardants in an urban center in northeastern China.

PubMed

Li, Wen-Long; Huo, Chun-Yan; Liu, Li-Yan; Song, Wei-Wei; Zhang, Zi-Feng; Ma, Wan-Li; Qiao, Li-Na; Li, Yi-Fan

2016-11-15

The occurrence and temporal trends of polybrominated diphenyl ethers (PBDEs) and non-PBDE brominated flame retardants (NBFRs) were investigated in an urban atmosphere of Northeast China in consecutive six years (2008-2013). Among all chemicals, BDE-209, l,2,5,6,9,10-hexabromocyclododecane (HBCD), and decabromodiphenylethane (DBDPE) were the three most dominant compounds. During the period, the levels of pentabromodiphenyl ethers in the gas-phase and octabromodiphenyl ethers in the particle-phase significantly decreased, while the levels of BDE-209 and NBFRs increased in either the gas-phase or particle-phase. Ambient temperature was the most significant variable that influenced the gas-phase and particle-phase concentrations of BFRs, followed by wind speed and relative humidity. A stronger temperature dependence of the atmospheric concentrations was found for lower mass BFRs. Gas-particle partitioning studies suggested PBDEs in the urban atmosphere of Northeast China were at steady-state. Steady-state equation can also well describe the partitioning behavior for NBFRs, suggesting that the atmospheric partitioning behaviors of NBFRs were similar to those of PBDEs. Copyright © 2016 Elsevier B.V. All rights reserved.

Personal exposure to metal fume, NO2, and O3 among production welders and non-welders.

PubMed

Schoonover, Todd; Conroy, Lorraine; Lacey, Steven; Plavka, Julie

2011-01-01

The objective of this study was to characterize personal exposures to welding-related metals and gases for production welders and non-welders in a large manufacturing facility. Welding fume metals and irritant gases nitrogen dioxide (NO(2)) and ozone (O(3)) were sampled for thirty-eight workers. Personal exposure air samples for welding fume metals were collected on 37 mm open face cassettes and nitrogen dioxide and ozone exposure samples were collected with diffusive passive samplers. Samples were analyzed for metals using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and welding fume metal exposure concentrations were defined as the sum of welding-related metals mass per volume of air sampled. Welding fume metal exposures were highly variable among similar types of welding while NO(2) and O(3) exposure were less variable. Welding fume metal exposures were significantly higher 474 μg/m(3) for welders than non-welders 60 μg/m(3) (p=0.001). Welders were exposed to higher concentrations of NO(2) and O(3) than non-welders but the differences were not statistically significant. Welding fume metal exposure concentrations for welders performing gas metal arc welding (GMAW) and shielded metal arc welding (SMAW) were higher than welders performing gas tungsten arc welding (GTAW). Non-welders experienced exposures similar to GTAW welders despite a curtain wall barrier separating welding and non-welding work areas.

Monitoring and modeling wetland chloride concentrations in relationship to oil and gas development.

PubMed

Post van der Burg, Max; Tangen, Brian A

2015-03-01

Extraction of oil and gas via unconventional methods is becoming an important aspect of energy production worldwide. Studying the effects of this development in countries where these technologies are being widely used may provide other countries, where development may be proposed, with some insight in terms of concerns associated with development. A fairly recent expansion of unconventional oil and gas development in North America provides such an opportunity. Rapid increases in energy development in North America have caught the attention of managers and scientists as a potential stressor for wildlife and their habitats. Of particular concern in the Northern Great Plains of the U.S. is the potential for chloride-rich produced water associated with unconventional oil and gas development to alter the water chemistry of wetlands. We describe a landscape scale modeling approach designed to examine the relationship between potential chloride contamination in wetlands and patterns of oil and gas development. We used a spatial Bayesian hierarchical modeling approach to assess multiple models explaining chloride concentrations in wetlands. These models included effects related to oil and gas wells (e.g. age of wells, number of wells) and surficial geology (e.g. glacial till, outwash). We found that the model containing the number of wells and the surficial geology surrounding a wetland best explained variation in chloride concentrations. Our spatial predictions showed regions of localized high chloride concentrations. Given the spatiotemporal variability of regional wetland water chemistry, we do not regard our results as predictions of contamination, but rather as a way to identify locations that may require more intensive sampling or further investigation. We suggest that an approach like the one outlined here could easily be extended to more of an adaptive monitoring approach to answer questions about chloride contamination risk that are of interest to managers. Published by Elsevier Ltd.

Air concentrations of volatile compounds near oil and gas production: a community-based exploratory study.

PubMed

Macey, Gregg P; Breech, Ruth; Chernaik, Mark; Cox, Caroline; Larson, Denny; Thomas, Deb; Carpenter, David O

2014-10-30

Horizontal drilling, hydraulic fracturing, and other drilling and well stimulation technologies are now used widely in the United States and increasingly in other countries. They enable increases in oil and gas production, but there has been inadequate attention to human health impacts. Air quality near oil and gas operations is an underexplored human health concern for five reasons: (1) prior focus on threats to water quality; (2) an evolving understanding of contributions of certain oil and gas production processes to air quality; (3) limited state air quality monitoring networks; (4) significant variability in air emissions and concentrations; and (5) air quality research that misses impacts important to residents. Preliminary research suggests that volatile compounds, including hazardous air pollutants, are of potential concern. This study differs from prior research in its use of a community-based process to identify sampling locations. Through this approach, we determine concentrations of volatile compounds in air near operations that reflect community concerns and point to the need for more fine-grained and frequent monitoring at points along the production life cycle. Grab and passive air samples were collected by trained volunteers at locations identified through systematic observation of industrial operations and air impacts over the course of resident daily routines. A total of 75 volatile organics were measured using EPA Method TO-15 or TO-3 by gas chromatography/mass spectrometry. Formaldehyde levels were determined using UMEx 100 Passive Samplers. Levels of eight volatile chemicals exceeded federal guidelines under several operational circumstances. Benzene, formaldehyde, and hydrogen sulfide were the most common compounds to exceed acute and other health-based risk levels. Air concentrations of potentially dangerous compounds and chemical mixtures are frequently present near oil and gas production sites. Community-based research can provide an important supplement to state air quality monitoring programs.

Using satellite-based measurements to explore ...

EPA Pesticide Factsheets

New particle formation (NPF) can potentially alter regional climate by increasing aerosol particle (hereafter particle) number concentrations and ultimately cloud condensation nuclei. The large scales on which NPF is manifest indicate potential to use satellite-based (inherently spatially averaged) measurements of atmospheric conditions to diagnose the occurrence of NPF and NPF characteristics. We demonstrate the potential for using satellite-measurements of insolation (UV), trace gas concentrations (sulfur dioxide (SO2), nitrogen dioxide (NO2), ammonia (NH3), formaldehyde (HCHO), ozone (O3)), aerosol optical properties (aerosol optical depth (AOD), Ångström exponent (AE)), and a proxy of biogenic volatile organic compound emissions (leaf area index (LAI), temperature (T)) as predictors for NPF characteristics: formation rates, growth rates, survival probabilities, and ultrafine particle (UFP) concentrations at five locations across North America. NPF at all sites is most frequent in spring, exhibits a one-day autocorrelation, and is associated with low condensational sink (AOD×AE) and HCHO concentrations, and high UV. However, there are important site-to-site variations in NPF frequency and characteristics, and in which of the predictor variables (particularly gas concentrations) significantly contribute to the explanatory power of regression models built to predict those characteristics. This finding may provide a partial explanation for the reported spatia

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

NASA Astrophysics Data System (ADS)

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

2014-12-01

The increase in the natural gas component of the energy sector has led many state and local municipalities to begin regulation of emissions from the oil and natural gas operators with air quality (AQ) as a concern. "Top-down" measurements of trace gases in the air above wells complement "bottom-up" inventories, used by EPA and AQ stakeholders, through a more accurate depiction of regional variability of methane and other species near and downwind of oil and gas operations. Satellite observations of methane, nitrogen dioxide, formaldehyde, ozone, and other carbon gases enhance the spatial and temporal coverage of the data needed to demonstrate any long-term impacts from shale gas development. As part of a NASA AQAST (Air Quality Applied Sciences Team) project, we are evaluating satellite measurements of trace gases in regions with oil and gas operations for their application as a "top-down" constraint. For validation of the satellite instruments' sensitivities to emitted gases, we focus on regions where the DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality) campaign deployed with ground and aircraft measurements, including, Maryland (2011), California and Texas (2013), and Colorado (2014). We compare vertical distributions of methane and volatile organic compounds (VOCs) nearby and downwind of oil and gas wells to locate any regional differences during the campaign time periods. This allows for better characterization of the satellite observations and their limitations for application in air quality studies in similar environments. Taking advantage of current EOS-era satellites' data records, we also analyze methane anomalies and gas correlations in the free troposphere from 2005 to present to identify trends for basins with oil and gas extraction sites and their influence on background concentrations downwind of wells. In most regions with oil and gas activity, we see continually increasing methane concentrations and about a 5-10 percent enhancement above background tropospheric concentrations. With this ongoing effort, we aim to demonstrate the benefits of satellite-derived "top-down" constraints for emissions estimates associated with oil and natural gas operations.

Oxygen in the deep-sea: The challenge of maintaining uptake rates in a changing ocean

NASA Astrophysics Data System (ADS)

Hofmann, A. F.; Peltzer, E. T.; Brewer, P. G.

2011-12-01

Although focused on recently, ocean acidification is not the only effect of anthropogenic CO2 emissions on the ocean. Ocean warming will reduce dissolved oxygen concentrations and at the hypoxic limit for a given species this can pose challenges to marine life. The limit is traditionally reported simply as the static mass concentration property [O2]; here we treat it as a dynamic gas exchange problem for the animal analogous to gas exchange at the sea surface. The diffusive limit and its relationship to water velocity is critical for the earliest stages of marine life (eggs, embryos), but the effect is present for all animals at all stages of life. We calculate the external limiting O2 conditions for several representative metabolic rates and their relationship to flow of the bulk fluid under different environmental conditions. Ocean O2 concentrations decline by ≈ 14 μmol kg-1 for a 2 °C rise in temperature. At standard 1000 m depth conditions in the Pacific, flow over the surface would have to increase by ≈ 60% from 2.0 to 3.2 cm s-1 to compensate for this change. The functions derived allow new calculations of depth profiles of limiting O2 concentrations, as well as maximal diffusively sustainable metabolic oxygen consumption rates at various places around the world. Our treatment shows that there is a large variability in the global ocean in terms of facilitating aerobic life. This variability is greater than the variability of the oxygen concentration alone. It becomes clear that temperature and pressure dependencies of diffusion and partial pressure create a region typically around 1000 m depth where a maximal [O2] is needed to sustain a given metabolic rate. This zone of greatest physical constriction on the diffusive transport in the boundary layer is broadly consistent with the oxygen minimum zone, i.e., the zone of least oxygen concentration supply, resulting in a pronounced minimum of maximal diffusively sustainable metabolic oxygen consumption rates. This least-favorable zone for aerobic respiration is bound to expand with further ocean warming.

Impact of nitrate-enhanced leachate recirculation on gaseous releases from a landfill bioreactor cell

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

Tallec, G.; Bureau, C.; Peu, P.

2009-07-15

This study evaluates the impact of nitrate injection on a full scale landfill bioreactor through the monitoring of gaseous releases and particularly N{sub 2}O emissions. During several weeks, we monitored gas concentrations in the landfill gas collection system as well as surface gas releases with a series of seven static chambers. These devices were directly connected to a gas chromatograph coupled to a flame ionisation detector and an electron capture detector (GC-FID/ECD) placed directly on the field. Measurements were performed before, during and after recirculation of raw leachate and nitrate-enhanced leachate. Raw leachate recirculation did not have a significant effectmore » on the biogas concentrations (CO{sub 2}, CH{sub 4} and N{sub 2}O) in the gas extraction network. However, nitrate-enhanced leachate recirculation induced a marked increase of the N{sub 2}O concentrations in the gas collected from the recirculation trench (100-fold increase from 0.2 ppm to 23 ppm). In the common gas collection system however, this N{sub 2}O increase was no more detectable because of dilution by gas coming from other cells or ambient air intrusion. Surface releases through the temporary cover were characterized by a large spatial and temporal variability. One automated chamber gave limited standard errors over each experimental period for N{sub 2}O releases: 8.1 {+-} 0.16 mg m{sup -2} d{sup -1} (n = 384), 4.2 {+-} 0.14 mg m{sup -2} d{sup -1} (n = 132) and 1.9 {+-} 0.10 mg m{sup -2} d{sup -1} (n = 49), during, after raw leachate and nitrate-enhanced leachate recirculation, respectively. No clear correlation between N{sub 2}O gaseous surface releases and recirculation events were evidenced. Estimated N{sub 2}O fluxes remained in the lower range of what is reported in the literature for landfill covers, even after nitrate injection.« less

Comparison of enzyme-linked immunosorbent assay and gas chromatography procedures for the detection of cyanazine and metolachlor in surface water samples

USGS Publications Warehouse

Schraer, S.M.; Shaw, D.R.; Boyette, M.; Coupe, R.H.; Thurman, E.M.

2000-01-01

Enzyme-linked immunosorbent assay (ELISA) data from surface water reconnaissance were compared to data from samples analyzed by gas chromatography for the pesticide residues cyanazine (2-[[4-chloro-6-(ethylamino)-l,3,5-triazin-2-yl]amino]-2-methylpropanenitrile ) and metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide). When ELISA analyses were duplicated, cyanazine and metolachlor detection was found to have highly reproducible results; adjusted R2s were 0.97 and 0.94, respectively. When ELISA results for cyanazine were regressed against gas chromatography results, the models effectively predicted cyanazine concentrations from ELISA analyses (adjusted R2s ranging from 0.76 to 0.81). The intercepts and slopes for these models were not different from 0 and 1, respectively. This indicates that cyanazine analysis by ELISA is expected to give the same results as analysis by gas chromatography. However, regressing ELISA analyses for metolachlor against gas chromatography data provided more variable results (adjusted R2s ranged from 0.67 to 0.94). Regression models for metolachlor analyses had two of three intercepts that were not different from 0. Slopes for all metolachlor regression models were significantly different from 1. This indicates that as metolachlor concentrations increase, ELISA will over- or under-estimate metolachlor concentration, depending on the method of comparison. ELISA can be effectively used to detect cyanazine and metolachlor in surface water samples. However, when detections of metolachlor have significant consequences or implications it may be necessary to use other analytical methods.

Seasonal dynamics of water and air chemistry in an indoor chlorinated swimming pool.

PubMed

Zare Afifi, Mehrnaz; Blatchley, Ernest R

2015-01-01

Although swimming is known to be beneficial in terms of cardiovascular health, as well as for some forms of rehabilitation, swimming is also known to present risks to human health, largely in the form of exposure to microbial pathogens and disinfection byproducts (DBPs). Relatively little information is available in the literature to characterize the seasonal dynamics of air and water chemistry in indoor chlorinated swimming pools. To address this issue, water samples were collected five days per week from an indoor chlorinated swimming pool facility at a high school during the academic year and once per week during summer over a fourteen-month period. The samples were analyzed for free and combined chlorine, urea, volatile DBPs, pH, temperature and total alkalinity. Membrane Introduction Mass Spectrometry (MIMS) was used to identify and measure the concentrations of eleven aqueous-phase volatile DBPs. Variability in the concentrations of these DBPs was observed. Factors that influenced variability included bather loading and mixing by swimmers. These compounds have the ability to adversely affect water and air quality and human health. A large fraction of the existing literature regarding swimming pool air quality has focused on trichloramine (NCl₃). For this work, gas-phase NCl₃ was analyzed by an air sparging-DPD/KI method. The results showed that gas-phase NCl₃ concentration is influenced by bather loading and liquid-phase NCl₃ concentration. Urea is the dominant organic-N compound in human urine and sweat, and is known to be an important precursor for producing NCl₃ in swimming pools. Results of daily measurements of urea indicated a link between bather load and urea concentration in the pool.

The effect of fresh gas flow rate and type of anesthesia machine on time to reach target sevoflurane concentration.

PubMed

Shin, Hye Won; Yu, Hae Na; Bae, Go Eun; Huh, Hyub; Park, Ji Yong; Kim, Ji Young

2017-01-19

Anesthesia machines have been developed by the application of new technology for rapid and easier control of anesthetic concentration. In this study, we used a test lung to investigate whether the time taken to reach the target sevoflurane concentration varies with the rate of fresh gas flow (FGF) and type of anesthesia machine (AM). We measured the times taken to reach the target sevoflurane concentration (2 minimum alveolar concentration = 4%) at variable rates of FGF (0.5, 1, or 3 L/min) and different types of AM (Primus ® , Perseus ® , and Zeus ® [Zeus ® -F; Zeus ® fresh gas mode, Zeus ® -A; Zeus ® auto-mode]). Concomitant ventilation was supplied using 100% O 2. The AMs were connected to a test lung. A sevoflurane vaporizer setting of 6% was used in Primus ® , Perseus ® , and Zeus ® -F; a target end-tidal setting of 4% was used in Zeus ® -A (from a vaporizer setting of 0%). The time taken to reach the target concentration was measured in every group. When the same AM was used (Primus ® , Perseus ® , or Zeus ® -F), the times to target concentration shortened as the FGF rate increased (P < 0.05). Conversely, when the same FGF rate was used, but with different AMs, the time to target concentration was shortest in Perseus ® , followed by Primus ® , and finally by Zeus ® -F (P < 0.05). With regards to both modes of Zeus ® , at FGF rates of 0.5 and 1 L/min, the time to target concentration was shorter in Zeus ® -A than in Zeus ® -F; however, the time was longer in Zeus ® -A than in Zeus ® -F at FGF rate of 3 L/min (P < 0.05). Shorter times taken to reach the target concentration were associated with high FGF rates, smaller internal volume of the AM, proximity of the fresh gas inlets to patients, absence of a decoupling system, and use of blower-driven ventilators in AM.

Greenhouse gases emission from the sewage draining rivers.

PubMed

Hu, Beibei; Wang, Dongqi; Zhou, Jun; Meng, Weiqing; Li, Chongwei; Sun, Zongbin; Guo, Xin; Wang, Zhongliang

2018-01-15

Carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) concentration, saturation and fluxes in rivers (Beitang drainage river, Dagu drainage rive, Duliujianhe river, Yongdingxinhe river and Nanyunhe river) of Tianjin city (Haihe watershed) were investigated during July and October in 2014, and January and April in 2015 by static headspace gas chromatography method and the two-layer model of diffusive gas exchange. The influence of environmental variables on greenhouse gases (GHGs) concentration under the disturbance of anthropogenic activities was discussed by Spearman correlative analysis and multiple stepwise regression analysis. The results showed that the concentration and fluxes of CO 2 , CH 4 and N 2 O were seasonally variable with >winter>fall>summer, spring>summer>winter>fall and summer>spring>winter>fall for concentrations and spring>summer>fall>winter, spring>summer>winter>fall and summer>spring>fall>winter for fluxes respectively. The GHGs concentration and saturation were higher in comprehensively polluted river sites and lower in lightly polluted river sites. The three GHGs emission fluxes in two sewage draining rivers of Tianjin were clearly higher than those of other rivers (natural rivers) and the spatial variation of CH 4 was more obvious than the others. CO 2 and N 2 O air-water interface emission fluxes of the sewage draining rivers in four seasons were about 1.20-2.41 times and 1.13-3.12 times of those in the natural rivers. The CH 4 emission fluxes of the sewage draining rivers were 3.09 times in fall to 10.87 times in spring of those in the natural rivers in different season. The wind speed, water temperature and air temperature were related to GHGs concentrations. Nitrate and nitrite (NO 3 - +NO 2 - -N) and ammonia (NH 4 + -N) were positively correlated with CO 2 concentration and CH 4 concentration; and dissolved oxygen (DO) concentration was negatively correlated with CH 4 concentration and N 2 O concentration. The effect of human activities on carbon and nitrogen cycling in river is great. Copyright © 2017 Elsevier B.V. All rights reserved.

Statistical evaluation of variables affecting occurrence of hydrocarbons in aquifers used for public supply, California

USGS Publications Warehouse

Landon, Matthew K.; Burton, Carmen A.; Davis, Tracy A.; Belitz, Kenneth; Johnson, Tyler D.

2014-01-01

The variables affecting the occurrence of hydrocarbons in aquifers used for public supply in California were assessed based on statistical evaluation of three large statewide datasets; gasoline oxygenates also were analyzed for comparison with hydrocarbons. Benzene is the most frequently detected (1.7%) compound among 17 hydrocarbons analyzed at generally low concentrations (median detected concentration 0.024 μg/l) in groundwater used for public supply in California; methyl tert-butyl ether (MTBE) is the most frequently detected (5.8%) compound among seven oxygenates analyzed (median detected concentration 0.1 μg/l). At aquifer depths used for public supply, hydrocarbons and MTBE rarely co-occur and are generally related to different variables; in shallower groundwater, co-occurrence is more frequent and there are similar relations to the density or proximity of potential sources. Benzene concentrations are most strongly correlated with reducing conditions, regardless of groundwater age and depth. Multiple lines of evidence indicate that benzene and other hydrocarbons detected in old, deep, and/or brackish groundwater result from geogenic sources of oil and gas. However, in recently recharged (since ~1950), generally shallower groundwater, higher concentrations and detection frequencies of benzene and hydrocarbons were associated with a greater proportion of commercial land use surrounding the well, likely reflecting effects of anthropogenic sources, particularly in combination with reducing conditions.

Numerical Investigation of the Hydrogen Jet Flammable Envelope Extent with Account for Unsteady Phenomena

NASA Astrophysics Data System (ADS)

Chernyavsky, Boris; Benard, Pierre

2010-11-01

An important aspect of safety analysis in hydrogen applications is determination of the extent of flammable gas envelope in case of hydrogen jet release. Experimental investigations had shown significant disagreements between the extent of average flammable envelope predicted by steady-state numerical methods, and the region observed to support ignition, with proposed cause being non-steady jet phenomena resulting in significant variations of instantaneous gas concentration and velocity fields in the jet. In order to investigate the influence of these transient phenomena, a numerical investigation of hydrogen jet at low Mach number had been performed using unsteady Large Eddy Simulation. Instantaneous hydrogen concentration and velocity fields were monitored to determine instantaneous flammable envelope. The evolution of the instantaneous fields, including the development of the turbulence structures carrying hydrogen, their extent and frequency, and their relation with averaged fields had been characterized. Simulation had shown significant variability of the flammable envelope, with jet flapping causing shedding of large scale rich and lean gas pockets from the main jet core, which persist for significant times and substantially alter the extent of flammability envelope.

Plasma concentrations of midazolam during continuous subcutaneous administration in palliative care.

PubMed

Bleasel, M D; Peterson, G M; Dunne, P F

1994-01-01

We have investigated the steady-state plasma concentrations of midazolam during continuous subcutaneous administration in palliative care. Using a sensitive gas chromatography with electron capture detector assay, plasma concentrations of midazolam were measured in 11 patients (median age 68 years; range 47-82 years; six females) receiving the drug by continuous subcutaneous infusion (median rate 20 mg/day; range 10-60 mg/day). While not significant, the infusion rate tended to decrease with increasing age of the patient (Spearman's p = -0.51; p = 0.11). The steady-state plasma concentration range was 10-147 ng/ml, with a median of 30 ng/ml. Infusion rates and plasma concentrations of midazolam were correlated (Spearman's p = 0.71; p < 0.05). No other significant relationships were found between plasma concentrations and the variables of age, sex and liver function.

Using Riverboat-Mounted Eddy Covariance for Direct Measurements of Air-water Gas Exchange in Amazonia

NASA Astrophysics Data System (ADS)

Miller, S. D.; Freitas, H.; Read, E.; Goulden, M. L.; Rocha, H.

2007-12-01

Gas evasion from Amazonian rivers and lakes to the atmosphere has been estimated to play an important role in the regional budget of carbon dioxide (Richey et al., 2002) and the global budget of methane (Melack et al., 2004). These flux estimates were calculated by combining remote sensing estimates of inundation area with water-side concentration gradients and gas transfer rates (piston velocities) estimated primarily from floating chamber measurements (footprint ~1 m2). The uncertainty in these fluxes was large, attributed primarily to uncertainty in the gas exchange parameterization. Direct measurements of the gas exchange coefficient are needed to improve the parameterizations in these environments, and therefore reduce the uncertainty in fluxes. The micrometeorological technique of eddy covariance is attractive since it is a direct measurement of gas exchange that samples over a much larger area than floating chambers, and is amenable to use from a moving platform. We present eddy covariance carbon dioxide exchange measurements made using a small riverboat in rivers and lakes in the central Amazon near Santarem, Para, Brazil. Water-side carbon dioxide concentration was measured in situ, and the gas exchange coefficient was calculated. We found the piston velocity at a site on the Amazon River to be similar to existing ocean-based parameterizations, whereas the piston velocity at a site on the Tapajos River was roughly a factor 5 higher. We hypothesize that the enhanced gas exchange at the Tapajos site was due to a shallow upwind fetch. Our results demonstrate the feasibility of boat-based eddy covariance on these rivers, and also the utility of a mobile platform to investigate spatial variability of gas exchange.

Metabolomic Strategies Involving Mass Spectrometry Combined with Liquid and Gas Chromatography.

PubMed

Lopes, Aline Soriano; Cruz, Elisa Castañeda Santa; Sussulini, Alessandra; Klassen, Aline

2017-01-01

Amongst all omics sciences, there is no doubt that metabolomics is undergoing the most important growth in the last decade. The advances in analytical techniques and data analysis tools are the main factors that make possible the development and establishment of metabolomics as a significant research field in systems biology. As metabolomic analysis demands high sensitivity for detecting metabolites present in low concentrations in biological samples, high-resolution power for identifying the metabolites and wide dynamic range to detect metabolites with variable concentrations in complex matrices, mass spectrometry is being the most extensively used analytical technique for fulfilling these requirements. Mass spectrometry alone can be used in a metabolomic analysis; however, some issues such as ion suppression may difficultate the quantification/identification of metabolites with lower concentrations or some metabolite classes that do not ionise as well as others. The best choice is coupling separation techniques, such as gas or liquid chromatography, to mass spectrometry, in order to improve the sensitivity and resolution power of the analysis, besides obtaining extra information (retention time) that facilitates the identification of the metabolites, especially when considering untargeted metabolomic strategies. In this chapter, the main aspects of mass spectrometry (MS), liquid chromatography (LC) and gas chromatography (GC) are discussed, and recent clinical applications of LC-MS and GC-MS are also presented.

Controls over hydrocarbon emissions from boreal forest conifers

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

Lerdau, M.; Litvak, M.; Monson, R.

1995-06-01

The emissions of monoterpenes and isoprene were measured from two species of conifers native to the boreal forest of Canada, jack pine, Pinus rigida, and black spruce, Picea Mariana. We examined the effects of phenology and needle age on the emissions of these compounds, and the variations in tissue concentrations of monoterpenes. We measured photosynthetic carbon uptake and hydrocarbon emissions at two sites in northern Saskatchewan under controlled light, temperatures, and CO{sub 2} concentrations, and analyzed carbon uptake rates using an infra-red gas analyzer and hydrocarbon emissions using a solid sorbent/thermal desorption system coupled to a gas chromatograph with amore » mass spectrometer. Our data indicate a strong effect of temperature and seasonality on emissions but only small effects of site conditions. These results suggest that regional models of hydrocarbon emissions from boreal forests should focus on temperature and phenology as the most important controlling variables.« less

Inactivation of myeloma cancer cells by helium and argon plasma jets: The effect comparison and the key reactive species

NASA Astrophysics Data System (ADS)

Chen, Zeyu; Cui, Qingjie; Chen, Chen; Xu, Dehui; Liu, Dingxin; Chen, H. L.; Kong, Michael G.

2018-02-01

In plasma cancer therapy, the inactivation of cancer cells under plasma treatment is closely related to the reactive oxygen and nitrogen species (RONS) induced by plasmas. Quantitative study on the plasma-induced RONS that related to cancer cells apoptosis is critical for advancing the research of plasma cancer therapy. In this paper, the effects of several reactive species on the inactivation of LP-1 myeloma cancer cells are comparatively studied with variable working gas composition, surrounding gas composition, and discharge power. The results show that helium plasma jet has a higher cell inactivation efficiency than argon plasma jet under the same discharge power. By comparing the concentration of aqueous phase reactive species and the cell inactivation efficiency under different working gases and discharge powers, it is demonstrated that the inactivation efficiency of LP-1 myeloma cancer cells is strongly correlated with the concentration of peroxynitrite (ONOOH/ONOO-).

Process parameters and morphology in puerarin, phospholipids and their complex microparticles generation by supercritical antisolvent precipitation.

PubMed

Li, Ying; Yang, Da-Jian; Chen, Shi-Lin; Chen, Si-Bao; Chan, Albert Sun-Chi

2008-07-09

The aim of the study was to develop and evaluate a new method for the production of puerarin phospholipids complex (PPC) microparticles. The advanced particle formation method, solution enhanced dispersion by supercritical fluids (SEDS), was used for the preparation of puerarin (Pur), phospholipids (PC) and their complex particles for the first time. Evaluation of the processing variables on PPC particle characteristics was also conducted. The processing variables included temperature, pressure, solution concentration, the flow rate of supercritical carbon dioxide (SC-CO2) and the relative flow rate of drug solution to CO2. The morphology, particle size and size distribution of the particles were determined. Meanwhile Pur and phospholipids were separately prepared by gas antisolvent precipitation (GAS) method and solid characterization of particles by the two supercritical methods was also compared. Pur formed by GAS was more orderly, purer crystal, whereas amorphous Pur particles between 0.5 and 1microm were formed by SEDS. The complex was successfully obtained by SEDS exhibiting amorphous, partially agglomerated spheres comprised of particles sized only about 1microm. SEDS method may be useful for the processing of other pharmaceutical preparations besides phospholipids complex particles. Furthermore adopting a GAS process to recrystallize pharmaceuticals will provide a highly versatile methodology to generate new polymorphs of drugs in addition to conventional techniques.

Prestack Waveform Inversion and Well Log Examination at GC955 and WR313 in the Gulf of Mexico for Estimation of Methane Hydrate Concentrations

NASA Astrophysics Data System (ADS)

Fortin, W.; Goldberg, D.; Kucuk, H. M.

2017-12-01

Gas hydrates are naturally occurring compounds, which, at a molecular scale, are lattice structures of ice embedded with various gas molecules in the lattice voids. Volumetric estimates of associated hydrocarbons vary greatly due to the difficulty in remotely estimating hydrate concentrations in marine sediments but embedded hydrocarbon stores are thought to represent a significant portion of global deposits. Inherent hydrate instabilities obscure our understanding of and complicates processes related to resource extraction and hydrate response to disturbances in the local environment. Understanding the spatial extent and variability of hydrate deposits have important implications for potential economic production, climate change, and assessing natural hazards risks. Seismic reflection techniques are capable of determining the extent of gas hydrate deposits, often through the observation of bottom simulating reflectors (BSRs). However, BSRs are not present everywhere gas hydrates exist. Using high resolution prestack time migrated seismic data and prestack waveform inversion (PWI) we produce highly resolved velocity models and compare them to co-located well logs. Coupling our PWI results with velocity-porosity relationships and nearby well control, we map hydrate properties at GC955 and WR313. Integrating small scale heterogeneities and variations along the velocity model with in-situ measurements, we develop a workflow aimed to quantify hydrate concentrations observed in seismic data over large areas in great detail regardless of the existence of a BSR.

A dynamic two-dimensional system for measuring volatile organic compound volatilization and movement in soils.

PubMed

Allaire, S E; Yates, S R; Ernst, F F; Gan, J

2002-01-01

There is an important need to develop instrumentation that allows better understanding of atmospheric emission of toxic volatile compounds associated with soil management. For this purpose, chemical movement and distribution in the soil profile should be simultaneously monitored with its volatilization. A two-dimensional rectangular soil column was constructed and a dynamic sequential volatilization flux chamber was attached to the top of the column. The flux chamber was connected through a manifold valve to a gas chromatograph (GC) for real-time concentration measurement. Gas distribution in the soil profile was sampled with gas-tight syringes at selected times and analyzed with a GC. A pressure transducer was connected to a scanivalve to automatically measure the pressure distribution in the gas phase of the soil profile. The system application was demonstrated by packing the column with a sandy loam in a symmetrical bed-furrow system. A 5-h furrow irrigation was started 24 h after the injection of a soil fumigant, propargyl bromide (3-bromo-1-propyne; 3BP). The experience showed the importance of measuring lateral volatilization variability, pressure distribution in the gas phase, chemical distribution between the different phases (liquid, gas, and sorbed), and the effect of irrigation on the volatilization. Gas movement, volatilization, water infiltration, and distribution of degradation product (Br-) were symmetric around the bed within 10%. The system saves labor cost and time. This versatile system can be modified and used to compare management practices, estimate concentration-time indexes for pest control, study chemical movement, degradation, and emissions, and test mathematical models.

The Tiptop coal-mine fire, Kentucky: Preliminary investigation of the measurement of mercury and other hazardous gases from coal-fire gas vents

USGS Publications Warehouse

Hower, J.C.; Henke, K.; O'Keefe, J.M.K.; Engle, M.A.; Blake, D.R.; Stracher, G.B.

2009-01-01

The Tiptop underground coal-mine fire in the Skyline coalbed of the Middle Pennsylvanian Breathitt Formation was investigated in rural northern Breathitt County, Kentucky, in May 2008 and January 2009, for the purpose of determining the concentrations of carbon dioxide (CO2), carbon monoxide (CO), and mercury (Hg) in the vent and for measuring gas-vent temperatures. At the time of our visits, concentrations of CO2 peaked at 2.0% and > 6.0% (v/v) and CO at 600 ppm and > 700 ppm during field analysis in May 2008 and January 2009, respectively. For comparison, these concentrations exceed the U.S. Occupational Safety & Health Administration (OSHA) eight-hour safe exposure limits (0.5% CO2 and 50 ppm CO), although the site is not currently mined. Mercury, as Hg0, in excess of 500 and 2100 ??g/m3, in May and January, respectively, in the field, also exceeded the OSHA eight-hour exposure limit (50 ??g/m3). Carbonyl sulfide, dimethyl sulfide, carbon disulfide, and a suite of organic compounds were determined at two vents for the first sampling event. All gases are diluted by air as they exit and migrate away from a gas vent, but temperature inversions and other meteorological conditions could lead to unhealthy concentrations in the nearby towns. Variation in gas temperatures, nearly 300 ??C during the January visit to the fire versus < 50 ??C in May, demonstrates the large temporal variability in fire intensity at the Tiptop mine. These preliminary results suggest that emissions from coal fires may be important, but additional data are required that address the reasons for significant variations in the composition, flow, and temperature of vent gases. ?? 2009 Elsevier B.V.

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

NASA Astrophysics Data System (ADS)

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

2014-05-01

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

New Correction Factors Based on Seasonal Variability of Outdoor Temperature for Estimating Annual Radon Concentrations in UK.

PubMed

Daraktchieva, Z

2017-06-01

Indoor radon concentrations generally vary with season. Radon gas enters buildings from beneath due to a small air pressure difference between the inside of a house and outdoors. This underpressure which draws soil gas including radon into the house depends on the difference between the indoor and outdoor temperatures. The variation in a typical house in UK showed that the mean indoor radon concentration reaches a maximum in January and a minimum in July. Sine functions were used to model the indoor radon data and monthly average outdoor temperatures, covering the period between 2005 and 2014. The analysis showed a strong negative correlation between the modelled indoor radon data and outdoor temperature. This correlation was used to calculate new correction factors that could be used for estimation of annual radon concentration in UK homes. The comparison between the results obtained with the new correction factors and the previously published correction factors showed that the new correction factors perform consistently better on the selected data sets. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Estimation of the radon production rate in granite rocks and evaluation of the implications for geogenic radon potential maps: A case study in Central Portugal.

PubMed

Pereira, A; Lamas, R; Miranda, M; Domingos, F; Neves, L; Ferreira, N; Costa, L

2017-01-01

The goal of this study was to estimate radon gas production rate in granitic rocks and identify the factors responsible for the observed variability. For this purpose, 180 samples were collected from pre-Hercynian and Hercynian rocks in north and central Portugal and analysed for a) 226 Ra activity, b) radon ( 222 Rn) per unit mass activity, and c) radon gas emanation coefficient. On a subset of representative samples from the same rock types were also measured d) apparent porosity and e) apparent density. For each of these variables, the values ranged as follows: a) 15 to 587 Bq kg -1 , b) 2 to 73 Bq kg -1 , c) 0.01 to 0.80, d) 0.3 to 11.4 % and e) 2530 to 2850 kg m -3 . Radon production rate varied between 40 to 1386 Bq m -3  h -1 . The variability observed was associated with geologically late processes of low and high temperature which led to the alteration of the granitic rock with mobilization of U and increase in radon 222 Rn gas emanation. It is suggested that, when developing geogenic radon potential maps, data on uranium concentration in soils/altered rock should be used, rather than data obtained from unaltered rock. Copyright © 2016 Elsevier Ltd. All rights reserved.

An approach toward incorporation of global warming effects into Intensity-Duration-Frequency values

NASA Astrophysics Data System (ADS)

Kunkel, K.; Easterling, D. R.

2017-12-01

Rising global temperatures from increasing greenhouse gas concentrations will increase overall atmospheric water vapor concentrations. There is a high level of scientific confidence that this will increase the future intensity and frequency of extreme precipitation events, even in regions where overall precipitation may decrease. For control of runoff from extreme rainfall, infrastructure engineering utilizes design values of rainfall known as Intensity-Duration-Frequency (IDF) values. Use of the existing IDF values, which are based solely on historical climate records, is likely to lead to under-design of runoff control structures, and associated increased flood damages. However, future changes in IDF values are uncertain and probably regionally variable. Our paradigm is that changes in IDF values will result from changes in atmospheric capacity (water vapor concentrations) and opportunity (the number and intensity of heavy precipitation-producing storm systems). Relevant storm systems being investigated include extratropical cyclones and their associated fronts, tropical cyclones, and the North American Monsoon system. The overall approach involves developing IDF adjustment factors for changes in these components of the climate system. The adjustment factors have associated uncertainties, primarily from (1) uncertainties in the future pathway of greenhouse gas emissions and (2) variations among climate models in the sensitivity of the climate system to greenhouse gas concentration changes. In addition to meteorological considerations, the lifetime of projects designed using IDF values is an essential consideration because the IDF values may change substantially during that time. The initial results of this project will be discussed.

CO2 and CH4 emissions from streams in a lake-rich landscape: Patterns, controls, and regional significance

USGS Publications Warehouse

Crawford, John T.; Lottig, Noah R.; Stanley, Emily H.; Walker, John F.; Hanson, Paul C.; Finlay, Jacques C.; Striegl, Robert G.

2014-01-01

Aquatic ecosystems are important components of landscape carbon budgets. In lake-rich landscapes, both lakes and streams may be important sources of carbon gases (CO2 and CH4) to the atmosphere, but the processes that control gas concentrations and emissions in these interconnected landscapes have not been adequately addressed. We use multiple data sets that vary in their spatial and temporal extent during 2001–2012 to investigate the carbon gas source strength of streams in a lake-rich landscape and to determine the contribution of lakes, metabolism, and groundwater to stream CO2 and CH4. We show that streams emit roughly the same mass of CO2 (23.4 Gg C yr−1; 0.49 mol CO2 m−2 d−1) as lakes at a regional scale (27 Gg C yr−1) and that stream CH4 emissions (189 Mg C yr−1; 8.46 mmol CH4 m−2 d−1) are an important component of the regional greenhouse gas balance. Gas transfer velocity variability (range = 0.34 to 13.5 m d−1) contributed to the variability of gas flux in this landscape. Groundwater inputs and in-stream metabolism control stream gas supersaturation at the landscape scale, while carbon cycling in lakes and deep groundwaters does not control downstream gas emissions. Our results indicate the need to consider connectivity of all aquatic ecosystems (lakes, streams, wetlands, and groundwater) in lake-rich landscapes and their connections with the terrestrial environment in order to understand the full nature of the carbon cycle.

Development and Testing of a Variable Conductance Thermal Acquisition, Transport, and Switching System

NASA Technical Reports Server (NTRS)

Bugby, David C.; Farmer, Jeffery T.; Stouffer, Charles J.

2013-01-01

This paper describes the development and testing of a scalable thermal management architecture for instruments, subsystems, or systems that must operate in severe space environments with wide variations in sink temperature. The architecture involves a serial linkage of one or more hot-side variable conductance heat pipes (VCHPs) to one or more cold-side loop heat pipes (LHPs). The VCHPs provide wide area heat acquisition, limited distance thermal transport, modest against gravity pumping, concentrated LHP startup heating, and high switching ratio variable conductance operation. The LHPs provide localized heat acquisition, long distance thermal transport, significant against gravity pumping, and high switching ratio variable conductance operation. The single-VCHP, single-LHP system described herein was developed to maintain thermal control of a small robotic lunar lander throughout the lunar day-night thermal cycle. It is also applicable to other variable heat rejection space missions in severe environments. Operationally, despite a 60-70% gas blocked VCHP condenser during ON testing, the system was still able to provide 2-4 W/K ON conductance, 0.01 W/K OFF conductance, and an end-to-end switching ratio of 200-400. The paper provides a detailed analysis of VCHP condenser performance, which quantified the gas blockage situation. Future multi-VCHP/multi-LHP thermal management system concepts that provide power/transport length scalability are also discussed.

Highly-resolved Modeling of Emissions and Concentrations of Carbon Monoxide, Carbon Dioxide, Nitrogen Oxides, and Fine Particulate Matter in Salt Lake City, Utah

NASA Astrophysics Data System (ADS)

Mendoza, D. L.; Lin, J. C.; Mitchell, L.; Ehleringer, J. R.

2014-12-01

Accurate, high-resolution data on air pollutant emissions and concentrations are needed to understand human exposures and for both policy and pollutant management purposes. An important step in this process is also quantification of uncertainties. We present a spatially explicit and highly resolved emissions inventory for Salt Lake County, Utah, and trace gas concentration estimates for carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides (NOx) and fine particles (PM2.5) within Salt Lake City. We assess the validity of this approach by comparing measured concentrations against simulated values derived from combining the emissions inventory with an atmospheric model. The emissions inventory for the criteria pollutants was constructed using the 2011 National Emissions Inventory (NEI). The spatial and temporal allocation methods from the Emission Modeling Clearinghouse data set are used to downscale the NEI data from annual to hourly scales and from county-level to 500 m x 500 m resolution. Onroad mobile source emissions were estimated by combining a bottom-up emissions calculation approach for large roadway links with a top-down spatial allocation approach for other roadways. Vehicle activity data for road links were derived from automatic traffic responder data. The emissions inventory for CO2 was obtained from the Hestia emissions data product at an hourly, building, facility, and road link resolution. The AERMOD and CALPUFF dispersion models were used to transport emissions and estimate air pollutant concentrations at an hourly temporal and 500 m x 500 m spatial resolution. Modeled results were compared against measurements from a mobile lab equipped with trace gas measurement equipment traveling on pre-determined routes in the Salt Lake City area. The comparison between both approaches to concentration estimation highlights spatial locations and hours of high variability/uncertainty. Results presented here will inform understanding of variability and uncertainty in emissions and concentrations to better inform future policy. This work will also facilitate the development of a systematic approach to incorporate measurement data and models to better inform estimates of pollutant concentrations that determine the extent to which urban populations are exposed to adverse air quality.

Real-time drilling mud gas monitoring for qualitative evaluation of hydrocarbon gas composition during deep sea drilling in the Nankai Trough Kumano Basin.

PubMed

Hammerschmidt, Sebastian B; Wiersberg, Thomas; Heuer, Verena B; Wendt, Jenny; Erzinger, Jörg; Kopf, Achim

2014-01-01

Integrated Ocean Drilling Program Expedition 338 was the second scientific expedition with D/V Chikyu during which riser drilling was conducted as part of the Nankai Trough Seismogenic Zone Experiment. Riser drilling enabled sampling and real-time monitoring of drilling mud gas with an onboard scientific drilling mud gas monitoring system ("SciGas"). A second, independent system was provided by Geoservices, a commercial mud logging service. Both systems allowed the determination of (non-) hydrocarbon gas, while the SciGas system also monitored the methane carbon isotope ratio (δ(13)CCH4). The hydrocarbon gas composition was predominated by methane (> 1%), while ethane and propane were up to two orders of magnitude lower. δ(13)CCH4 values suggested an onset of thermogenic gas not earlier than 1600 meter below seafloor. This study aims on evaluating the onboard data and subsequent geological interpretations by conducting shorebased analyses of drilling mud gas samples. During shipboard monitoring of drilling mud gas the SciGas and Geoservices systems recorded up to 8.64% and 16.4% methane, respectively. Ethane and propane concentrations reached up to 0.03 and 0.013%, respectively, in the SciGas system, but 0.09% and 0.23% in the Geoservices data. Shorebased analyses of discrete samples by gas chromatography showed a gas composition with ~0.01 to 1.04% methane, 2 - 18 ppmv ethane, and 2 - 4 ppmv propane. Quadruple mass spectrometry yielded similar results for methane (0.04 to 4.98%). With δD values between -171‰ and -164‰, the stable hydrogen isotopic composition of methane showed little downhole variability. Although the two independent mud gas monitoring systems and shorebased analysis of discrete gas sample yielded different absolute concentrations they all agree well with respect to downhole variations of hydrocarbon gases. The data point to predominantly biogenic methane sources but suggest some contribution from thermogenic sources at depth, probably due to mixing. In situ thermogenic gas production at depths shallower 2000 mbsf is unlikely based on in situ temperature estimations between 81°C and 85°C and a cumulative time-temperature index of 0.23. In conclusion, the onboard SciGas data acquisition helps to provide a preliminary, qualitative evaluation of the gas composition, the in situ temperature and the possibility of gas migration.

Methane Occurrence in a Drinking Water Aquifer Before and During Natural Gas Production from the Marcellus Shale

NASA Astrophysics Data System (ADS)

Saiers, J. E.; Barth-Naftilan, E.

2017-12-01

More than 4,000 thousand wells have punctured aquifers of Pennsylvania's northern tier to siphon natural gas from the underlying Marcellus Shale. As drilling and hydraulic fracturing ramped up a decade ago, homeowner reports of well water contamination by methane and other contaminants began to emerge. Although made infrequently compared to the number of gas wells drilled, these reports were troubling and motivated our two-year, prospective study of groundwater quality within the Marcellus Shale Play. We installed multi-level sampling wells within a bedrock aquifer of a 25 km2 area that was targeted for shale gas development. These wells were sampled on a monthly basis before, during, and after seven shale gas wells were drilled, hydraulically fractured, and placed into production. The groundwater samples, together with surface water samples collected from nearby streams, were analyzed for hydrocarbons, trace metals, major ions, and the isotopic compositions of methane, ethane, water, strontium, and dissolved inorganic carbon. With regard to methane in particular, concentrations ranged from under 0.1 to over 60 mg/L, generally increased with aquifer depth, and, at some sites, exhibited considerable temporal variability. The isotopic composition of methane and hydrocarbon ratios also spanned a large range, suggesting that methane origins are diverse and, notably, shift on the time scale of this study. We will present inferences on factors governing methane occurrence across our study area by interpreting time-series data on methane concentrations and isotopic composition in context of local hydrologic variation, companion measurements of groundwater chemistry, and the known timing of key stages of natural gas extraction.

Elucidating hydraulic fracturing impacts on groundwater quality using a regional geospatial statistical modeling approach.

PubMed

Burton, Taylour G; Rifai, Hanadi S; Hildenbrand, Zacariah L; Carlton, Doug D; Fontenot, Brian E; Schug, Kevin A

2016-03-01

Hydraulic fracturing operations have been viewed as the cause of certain environmental issues including groundwater contamination. The potential for hydraulic fracturing to induce contaminant pathways in groundwater is not well understood since gas wells are completed while isolating the water table and the gas-bearing reservoirs lay thousands of feet below the water table. Recent studies have attributed ground water contamination to poor well construction and leaks in the wellbore annulus due to ruptured wellbore casings. In this paper, a geospatial model of the Barnett Shale region was created using ArcGIS. The model was used for spatial analysis of groundwater quality data in order to determine if regional variations in groundwater quality, as indicated by various groundwater constituent concentrations, may be associated with the presence of hydraulically fractured gas wells in the region. The Barnett Shale reservoir pressure, completions data, and fracture treatment data were evaluated as predictors of groundwater quality change. Results indicated that elevated concentrations of certain groundwater constituents are likely related to natural gas production in the study area and that beryllium, in this formation, could be used as an indicator variable for evaluating fracturing impacts on regional groundwater quality. Results also indicated that gas well density and formation pressures correlate to change in regional water quality whereas proximity to gas wells, by itself, does not. The results also provided indirect evidence supporting the possibility that micro annular fissures serve as a pathway transporting fluids and chemicals from the fractured wellbore to the overlying groundwater aquifers. Copyright © 2015 Elsevier B.V. All rights reserved.

Optimization of headspace solid-phase microextraction by means of an experimental design for the determination of methyl tert.-butyl ether in water by gas chromatography-flame ionization detection.

PubMed

Dron, Julien; Garcia, Rosa; Millán, Esmeralda

2002-07-19

A procedure for determination of methyl tert.-butyl ether (MTBE) in water by headspace solid-phase microextraction (HS-SPME) has been developed. The analysis was carried out by gas chromatography with flame ionization detection. The extraction procedure, using a 65-microm poly(dimethylsiloxane)-divinylbenzene SPME fiber, was optimized following experimental design. A fractional factorial design for screening and a central composite design for optimizing the significant variables were applied. Extraction temperature and sodium chloride concentration were significant variables, and 20 degrees C and 300 g/l were, respectively chosen for the best extraction response. With these conditions, an extraction time of 5 min was sufficient to extract MTBE. The calibration linear range for MTBE was 5-500 microg/l and the detection limit 0.45 microg/l. The relative standard deviation, for seven replicates of 250 microg/l MTBE in water, was 6.3%.

Evaporation of LOX under supercritical and subcritical conditions

NASA Technical Reports Server (NTRS)

Yang, A. S.; Hsieh, W. H.; Kuo, K. K.; Brown, J. J.

1993-01-01

The evaporation of LOX under supercritical and subcritical conditions was studied experimentally and theoretically. In experiments, the evaporation rate and surface temperature were measured for LOX strand vaporizing in helium environments at pressures ranging from 5 to 68 atmospheres. Gas sampling and chromatography analysis were also employed to profile the gas composition above the LOX surface for the purpose of model validation. A comprehensive theoretical model was formulated and solved numerically to simulate the evaporation process of LOX at high pressures. The model was based on the conservation equations of mass, momentum, energy, and species concentrations for a multicomponent system, with consideration of gravitational body force, solubility of ambient gases in liquid, and variable thermophysical properties. Good agreement between predictions and measured oxygen mole fraction profiles was obtained. The effect of pressure on the distribution of the Lewis number, as well as the effect of variable diffusion coefficient, were further examined to elucidate the high-pressure transport behavior exhibited in the LOX vaporization process.

Research and development of a field-ready protocol for sampling of phosgene from stationary source emissions: Diethylamine reagent studies. Research report, 11 July 1995--30 September 1996

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

Steger, J.L.; Bursey, J.T.; Merrill, R.G.

1999-03-01

This report presents the results of laboratory studies to develop and evaluate a method for the sampling and analysis of phosgene from stationary sources of air emissions using diethylamine (DEA) in toluene as the collection media. The method extracts stack gas from emission sources and stabilizes the reactive gas for subsequent analysis. DEA was evaluated both in a benchtop study and in a laboratory train spiking study. This report includes results for both the benchtop study and the train spiking study. Benchtop studies to evaluate the suitability of DEA for collecting and analyzing phosgene investigated five variables: storage time, DEAmore » concentration, moisture/pH, phosgene concentration, and sample storage temperature. Prototype sampling train studies were performed to determine if the benchtop chemical studies were transferable to a Modified Method 5 sampling train collecting phosgene in the presence of clean air mixed with typical stack gas components. Four conditions, which varied the moisture and phosgene spike were evaluated in triplicate. In addition to research results, the report includes a detailed draft method for sampling and analysis of phosgene from stationary source emissions.« less

Health survey and assessment of the polymorphisms BRCA1/P871L, BRCA1/Q356R, and BRCA2/N372H in female gas station workers in Rio de Janeiro.

PubMed

Silvestre, Rafaele T; Delmonico, Lucas; Bravo, Maryah; Santiago, Fábio; Scherrer, Luciano R; Moreira, Aline Dos Santos; Tabalipa, Marianne; Otero, Ubirani; Ornellas, Maria Helena F; Alves, Gilda

2017-12-01

Gas station workers are exposed to chemicals known to be carcinogenic, especially benzene. The objective was to analyze the health problems of female gas station workers by means of sociodemographic and clinical questionnaires, and laboratorial exams. We performed the genotyping of the polymorphisms BRCA1/P871L and BRCA1/Q356R by Polymerase Chain Reaction-Restriction Fragment Length Polymorphism, and of variant allele BRCA2/N372H through direct sequencing. The female workers showed a higher concentration of monocytes (P = 0.039); a greater number of spontaneous abortions (P = 0.025, OR = 4.977, 95% CI = 1.135-30.669); higher tobacco consumption (P = 0.013); and higher alcohol consumption (P = 0.05). The statistical analysis of the polymorphisms associated with the variables monocyte concentration and miscarriage number did not reveal a significant relationship, and smoking and spontaneous abortion were not statistically associated either. Environ. Mol. Mutagen. 58:730-734, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Removal of NO from flue gas by aqueous chlorine-dioxide scrubbing solution in a lab-scale bubbling reactor.

PubMed

Deshwal, Bal Raj; Jin, Dong Seop; Lee, Si Hyun; Moon, Seung Hyun; Jung, Jong Hyeon; Lee, Hyung Keun

2008-02-11

The present study attempts to clean up nitric oxide from the simulated flue gas using aqueous chlorine-dioxide solution in the bubbling reactor. Chlorine-dioxide is generated by chloride-chlorate process. Experiments are carried out to examine the effect of various operating variables like input NO concentration, presence of SO(2), pH of the solution and NaCl feeding rate on the NO(x) removal efficiency at 45 degrees C. Complete oxidation of nitric oxide into nitrogen dioxide occurred on passing sufficient ClO(2) gas into the scrubbing solution. NO is finally converted into nitrate and ClO(2) is reduced into chloride ions. A plausible reaction mechanism concerning NO(x) removal by ClO(2) is suggested. DeNO(x) efficiency increased slightly with the increasing input NO concentration. The presence of SO(2) improved the NO(2) absorption but pH of solution showed marginal effect on NO(2) absorption. NO(x) removal mechanism changed when medium of solution changed from acidic to alkaline. A constant NO(x) removal efficiency of about 60% has been achieved in the wide pH range of 3-11 under optimized conditions.

Application of Multiple Regression and Design of Experiments for Modelling the Effect of Monoethylene Glycol in the Calcium Carbonate Scaling Process.

PubMed

Kartnaller, Vinicius; Venâncio, Fabrício; F do Rosário, Francisca; Cajaiba, João

2018-04-10

To avoid gas hydrate formation during oil and gas production, companies usually employ thermodynamic inhibitors consisting of hydroxyl compounds, such as monoethylene glycol (MEG). However, these inhibitors may cause other types of fouling during production such as inorganic salt deposits (scale). Calcium carbonate is one of the main scaling salts and is a great concern, especially for the new pre-salt wells being explored in Brazil. Hence, it is important to understand how using inhibitors to control gas hydrate formation may be interacting with the scale formation process. Multiple regression and design of experiments were used to mathematically model the calcium carbonate scaling process and its evolution in the presence of MEG. It was seen that MEG, although inducing the precipitation by increasing the supersaturation ratio, actually works as a scale inhibitor for calcium carbonate in concentrations over 40%. This effect was not due to changes in the viscosity, as suggested in the literature, but possibly to the binding of MEG to the CaCO₃ particles' surface. The interaction of the MEG inhibition effect with the system's variables was also assessed, when temperature' and calcium concentration were more relevant.

Effects of gas composition in headspace and bicarbonate concentrations in media on gas and methane production, degradability, and rumen fermentation using in vitro gas production techniques.

PubMed

Patra, Amlan Kumar; Yu, Zhongtang

2013-07-01

Headspace gas composition and bicarbonate concentrations in media can affect methane production and other characteristics of rumen fermentation in in vitro gas production systems, but these 2 important factors have not been evaluated systematically. In this study, these 2 factors were investigated with respect to gas and methane production, in vitro digestibility of feed substrate, and volatile fatty acid (VFA) profile using in vitro gas production techniques. Three headspace gas compositions (N2+ CO2+ H2 in the ratio of 90:5:5, CO2, and N2) with 2 substrate types (alfalfa hay only, and alfalfa hay and a concentrate mixture in a 50:50 ratio) in a 3×2 factorial design (experiment 1) and 3 headspace compositions (N2, N2 + CO2 in a 50:50 ratio, and CO2) with 3 bicarbonate concentrations (80, 100, and 120 mM) in a 3×3 factorial design (experiment 2) were evaluated. In experiment 1, total gas production (TGP) and net gas production (NGP) was the lowest for CO2, followed by N2, and then the gas mixture. Methane concentration in headspace gas after fermentation was greater for CO2 than for N2 and the gas mixture, whereas total methane production (TMP) and net methane production (NMP) were the greatest for CO2, followed by the gas mixture, and then N2. Headspace composition did not affect in vitro digestibility or the VFA profile, except molar percentages of propionate, which were greater for CO2 and N2 than for the gas mixture. Methane concentration in headspace gas, TGP, and NGP were affected by the interaction of headspace gas composition and substrate type. In experiment 2, increasing concentrations of CO2 in the headspace decreased TGP and NGP quadratically, but increased the concentrations of methane, NMP, and in vitro fiber digestibility linearly, and TMP quadratically. Fiber digestibility, TGP, and NGP increased linearly with increasing bicarbonate concentrations in the medium. Concentrations of methane and NMP were unaffected by bicarbonate concentration, but TMP tended to increase due to increasing bicarbonate concentration. Although total VFA concentration and molar percentage of butyrate were unchanged, the molar percentage of acetate, and acetate-to-propionate ratio decreased, whereas the molar percentage of propionate increased quadratically with increasing bicarbonate concentration. This study demonstrated for the first time that headspace composition, especially CO2 content, and bicarbonate concentration in media could significantly influence gas and methane production, and rumen fermentation in gas production techniques. Copyright © 2013 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Indirect measurement of diluents in a multi-component natural gas

DOEpatents

Morrow, Thomas B.; Owen, Thomas E.

2006-03-07

A method of indirectly measuring the diluent (nitrogen and carbon dioxide) concentrations in a natural gas mixture. The molecular weight of the gas is modeled as a function of the speed of sound in the gas, the diluent concentrations in the gas, and constant values, resulting in a model equation. A set of reference gas mixtures with known molecular weights and diluent concentrations is used to calculate the constant values. For the gas in question, if the speed of sound in the gas is measured at three states, the three resulting expressions of molecular weight can be solved for the nitrogen and carbon dioxide concentrations in the gas mixture.

Surface gas pollutants in Lhasa, a highland city of Tibet: current levels and pollution implications

NASA Astrophysics Data System (ADS)

Ran, L.; Lin, W. L.; Deji, Y. Z.; La, B.; Tsering, P. M.; Xu, X. B.; Wang, W.

2014-05-01

Through several years of development, the city of Lhasa has become one of the most populated and urbanized areas on the highest plateau in the world. In the process of urbanization, current and potential air quality issues have been gradually concerned. To investigate the current status of air pollution in Lhasa, various gas pollutants including NOx, CO, SO2 and O3 were continuously measured from June 2012 to May 2013 at an urban site (29.40° N, 91.08° E, 3650 m a.s.l.). The seasonal variations of primary gas pollutants exhibited a peak from November to January with a large variability. High concentrations of primary trace gases almost exclusively occurred under low wind speed and showed no distinct dependence on wind direction, implying local urban emissions to be predominant. A comparison of NO2, CO and SO2 concentrations in summer between 1998 and 2012 indicated a significant increase in emissions of these gas pollutants and a change in their intercorrelations, as a result of a substantial growth in the demand of energy consumption using fossil fuels instead of previously widely used biofuels. The pronounced diurnal double peaks of primary trace gases in all seasons suggested automobile exhaust to be a major emission source in Lhasa. The secondary gas pollutant O3 displayed an average diurnal cycle of a shallow flat peak for about 4-5 h in the afternoon and a minimum in the early morning. Nighttime O3 was sometimes completely consumed by the high level of NOx. Seasonally, the variations of O3 concentrations displayed a low valley in winter and a peak in spring. In autumn and winter, transport largely contributed to the observed O3 concentrations, given its dependence on wind speed and wind direction, while in spring and summer photochemistry played an important role. A more efficient buildup of O3 concentrations in the morning and a higher peak in the afternoon was found in summer 2012 than in 1998. An enhancement in O3 concentrations would be expected in the future and more attention should be given to O3 photochemistry in response to increasing precursor emissions in this area.

Isotopic composition of transpiration and rates of change in leaf water isotopologue storage in response to environmental variables.

PubMed

Simonin, Kevin A; Roddy, Adam B; Link, Percy; Apodaca, Randy; Tu, Kevin P; Hu, Jia; Dawson, Todd E; Barbour, Margaret M

2013-12-01

During daylight hours, the isotope composition of leaf water generally approximates steady-state leaf water isotope enrichment model predictions. However, until very recently there was little direct confirmation that isotopic steady-state (ISS) transpiration in fact exists. Using isotope ratio infrared spectroscopy (IRIS) and leaf gas exchange systems we evaluated the isotope composition of transpiration and the rate of change in leaf water isotopologue storage (isostorage) when leaves were exposed to variable environments. In doing so, we developed a method for controlling the absolute humidity entering the gas exchange cuvette for a wide range of concentrations without changing the isotope composition of water vapour. The measurement system allowed estimation of (18)O enrichment both at the evaporation site and for bulk leaf water, in the steady state and the non-steady state. We show that non-steady-state effects dominate the transpiration isoflux even when leaves are at physiological steady state. Our results suggest that a variable environment likely prevents ISS transpiration from being achieved and that this effect may be exacerbated by lengthy leaf water turnover times due to high leaf water contents. © 2013 John Wiley & Sons Ltd.

Chasing Sources and Transports of Methane Plumes in the Northern Gulf of Mexico Using In Situ Sensors on Untethered Landers

NASA Astrophysics Data System (ADS)

Martens, C. S.; Mendlovitz, H.; Seim, H.; Lapham, L.; Magen, C.; Joye, S. B.; MacDonald, I. R.; Asper, V. L.; Diercks, A. R.

2016-02-01

In situ time-series measurements of light hydrocarbons, oxygen, temperature and bottom currents from landers and elevators in the benthic boundary layer (BBL) at multiple sites in the northern Gulf of Mexico reveal spatial and temporal variability in methane concentrations controlled by horizontal advection of methane-rich plumes originating from nearby natural oil and gas seeps. Multi-sensor systems deployed for several weeks within 1m of the seafloor at depths from 882 to 1622m revealed methane concentrations ranging from near atmospheric saturation (<3 nM) to over 4000 nM depending on seep proximity, current speed and direction. Methane concentrations observed in the BBL equal or exceed maximum near-bottom values seen in shipboard water column profiles analyzed by conventional gas chromatography. Continuous laser sensor methane measurements from mini-landers deployed in September 2015 at our Horn Dome and Bush Hill sites featuring numerous gas seeps revealed methane concentrations ranging from <3 to over 300 nM over two-week periods. Net current speeds in the BBL at our six lander sites in blocks GC600, OC26 and MC118 ranged from near zero to over 5 cm/s; instantaneous speeds ranged from near zero to over 30 cm/s. Near real-time acquisition of continuous hydrocarbon concentration and current data within the BBL and friction layer from untethered platforms provides important new opportunities for monitoring the impacts of natural seeps and accidental hydrocarbon releases. The instrumented approaches we have developed to simultaneously monitor methane sources and physical processes controlling plume development and transport will enable more effective responses to further accidental hydrocarbon releases.

Microcosm assays and Taguchi experimental design for treatment of oil sludge containing high concentration of hydrocarbons.

PubMed

Castorena-Cortés, G; Roldán-Carrillo, T; Zapata-Peñasco, I; Reyes-Avila, J; Quej-Aké, L; Marín-Cruz, J; Olguín-Lora, P

2009-12-01

Microcosm assays and Taguchi experimental design was used to assess the biodegradation of an oil sludge produced by a gas processing unit. The study showed that the biodegradation of the sludge sample is feasible despite the high level of pollutants and complexity involved in the sludge. The physicochemical and microbiological characterization of the sludge revealed a high concentration of hydrocarbons (334,766+/-7001 mg kg(-1) dry matter, d.m.) containing a variety of compounds between 6 and 73 carbon atoms in their structure, whereas the concentration of Fe was 60,000 mg kg(-1) d.m. and 26,800 mg kg(-1) d.m. of sulfide. A Taguchi L(9) experimental design comprising 4 variables and 3 levels moisture, nitrogen source, surfactant concentration and oxidant agent was performed, proving that moisture and nitrogen source are the major variables that affect CO(2) production and total petroleum hydrocarbons (TPH) degradation. The best experimental treatment yielded a TPH removal of 56,092 mg kg(-1) d.m. The treatment was carried out under the following conditions: 70% moisture, no oxidant agent, 0.5% of surfactant and NH(4)Cl as nitrogen source.

The Intrinsic Variability in the Water Vapor Saturation Ratio Due to Turbulence

NASA Astrophysics Data System (ADS)

Anderson, Jesse Charles

The water vapor concentration plays an important role for many atmospheric processes. The mean concentration is key to understand water vapor's effect on the climate as a greenhouse gas. The fluctuations about the mean are important to understand heat fluxes between Earth's surface and the boundary layer. These fluctuations are linked to turbulence that is present in the boundary layer. Turbulent conditions are simulated in Michigan Tech's multiphase, turbulent reaction chamber, the pi chamber. Measurements for temperature and water vapor concentration were recorded under forced Rayleigh- Benard convection at several turbulent intensities. These were used to calculate the saturation ratio, often referred to as the relative humidity. The fluctuations in the water vapor concentration were found to be the more important than the temperature for the variability of the saturation ratio. The fluctuations in the saturation ratio result in some cloud droplets experiencing a higher supersaturation than other cloud droplets, causing those "lucky" droplets to grow at a faster rate than other droplets. This difference in growth rates could contribute to a broadening of the size distribution of cloud droplets, resulting in the enhancement of collision-coalescence. These fluctuations become more pronounced with more intense turbulence.

Determination of formic acid tissue and fluid concentrations in three fatalities due to methanol poisoning.

PubMed

Hantson, P; Haufroid, V; Mahieu, P

2000-12-01

Three fatalities caused by methanol ingestion are reported. Admission blood methanol concentrations ranged from 0.28 to 4.6 g/L. Two patients had been admitted after a significant delay (>20 hours), and one patient was observed within 90 minutes following ingestion. Formic acid levels were determined in blood samples at admission and ranged from 302 to 680 mg/L. The patients died 44, 55, and 82 hours after poisoning. Formic acid determinations in postmortem tissues were performed by a gas chromatograph method. The authors found great variability in formic acid distribution among the patients and among organs.

Emissions of nitrogen oxides from an experimental hydrogen-fueled gas turbine combustor

NASA Technical Reports Server (NTRS)

Norgren, C. T.; Ingebo, R. D.

1974-01-01

The effect of operating variables of a hydrogen fueled combustor on exhaust concentrations of total oxides of nitrogen was determined at inlet-air temperature levels up to 810 K, pressure of 414,000N/sa m, and reference velocity of 21.3 m/sec. The combustor, which was originally designed for hydrocarbon fuel produced a NO(x) concentration of 380 ppm with hydrogen at 810 K inlet-air temperature. A reduction in NO(x) of about 30 % was obtained by modification to a lean or rich primary zone. The lowest NO(x) levels obtained with hydrogen were equivalent to those of the reference combustor burning hydrocarbon fuels.

Temperature and precipitation drive temporal variability in aquatic carbon and GHG concentrations and fluxes in a peatland catchment.

PubMed

Dinsmore, K J; Billett, M F; Dyson, K E

2013-07-01

The aquatic pathway is increasingly being recognized as an important component of catchment carbon and greenhouse gas (GHG) budgets, particularly in peatland systems due to their large carbon store and strong hydrological connectivity. In this study, we present a complete 5-year data set of all aquatic carbon and GHG species from an ombrotrophic Scottish peatland. Measured species include particulate and dissolved forms of organic carbon (POC, DOC), dissolved inorganic carbon (DIC), CO2 , CH4 and N2 O. We show that short-term variability in concentrations exists across all species and this is strongly linked to discharge. Seasonal cyclicity was only evident in DOC, CO2 and CH4 concentration; however, temperature correlated with monthly means in all species except DIC. Although the temperature correlation with monthly DOC and POC concentrations appeared to be related to biological productivity in the terrestrial system, we suggest the temperature correlation with CO2 and CH4 was primarily due to in-stream temperature-dependent solubility. Interannual variability in total aquatic carbon concentration was strongly correlated with catchment gross primary productivity (GPP) indicating a strong potential terrestrial aquatic linkage. DOC represented the largest aquatic carbon flux term (19.3 ± 4.59 g C m(-2)  yr(-1) ), followed by CO2 evasion (10.0 g C m(-2)  yr(-1) ). Despite an estimated contribution to the total aquatic carbon flux of between 8 and 48%, evasion estimates had the greatest uncertainty. Interannual variability in total aquatic carbon export was low in comparison with variability in terrestrial biosphere-atmosphere exchange, and could be explained primarily by temperature and precipitation. Our results therefore suggest that climatic change is likely to have a significant impact on annual carbon losses through the aquatic pathway, and as such, aquatic exports are fundamental to the understanding of whole catchment responses to climate change. © 2013 Blackwell Publishing Ltd.

40 CFR 1065.672 - Drift correction.

Code of Federal Regulations, 2013 CFR

2013-07-01

... interval gas analyzer response to the span gas concentration. x postspan = post-test interval gas analyzer... = post-test interval gas analyzer response to the zero gas concentration. Example: x refzero = 0 µmol/mol... occurred before one or more previous test intervals. (4) For any post-test interval concentrations, use...

40 CFR 1065.672 - Drift correction.

Code of Federal Regulations, 2010 CFR

2010-07-01

... interval gas analyzer response to the span gas concentration. x postspan = post-test interval gas analyzer... = post-test interval gas analyzer response to the zero gas concentration. Example: x refzero = 0 µmol/mol... occurred before one or more previous test intervals. (4) For any post-test interval concentrations, use...

40 CFR 1065.672 - Drift correction.

Code of Federal Regulations, 2014 CFR

2014-07-01

... interval gas analyzer response to the span gas concentration. x postspan = post-test interval gas analyzer... = post-test interval gas analyzer response to the zero gas concentration. Example: x refzero = 0 µmol/mol... occurred before one or more previous test intervals. (4) For any post-test interval concentrations, use...

40 CFR 1065.672 - Drift correction.

Code of Federal Regulations, 2012 CFR

2012-07-01

... interval gas analyzer response to the span gas concentration. x postspan = post-test interval gas analyzer... = post-test interval gas analyzer response to the zero gas concentration. Example: x refzero = 0 µmol/mol... occurred before one or more previous test intervals. (4) For any post-test interval concentrations, use...

40 CFR 1065.672 - Drift correction.

Code of Federal Regulations, 2011 CFR

2011-07-01

... interval gas analyzer response to the span gas concentration. x postspan = post-test interval gas analyzer... = post-test interval gas analyzer response to the zero gas concentration. Example: x refzero = 0 µmol/mol... occurred before one or more previous test intervals. (4) For any post-test interval concentrations, use...

Trace level detection of analytes using artificial olfactometry

NASA Technical Reports Server (NTRS)

Wong, Bernard (Inventor); Lewis, Nathan S. (Inventor); Severin, Erik J. (Inventor)

2001-01-01

The present invention provides a device for detecting the presence of an analyte, wherein said analyte is a microorganism marker gas. The device comprises a sample chamber having a fluid inlet port for the influx of the microorganism marker gas; a fluid concentrator in flow communication with the sample chamber, wherein the fluid concentrator has an absorbent material capable of absorbing the microorganism marker gas and thereafter releasing a concentrated microorganism marker gas; and an array of sensors in fluid communication with the concentrated microorganism marker gas. The sensor array detects and identifies the marker gas upon its release from fluid concentrate.

A finite element code for modelling tracer transport in a non-isothermal two-phase flow system for CO2 geological storage characterization

NASA Astrophysics Data System (ADS)

Tong, F.; Niemi, A. P.; Yang, Z.; Fagerlund, F.; Licha, T.; Sauter, M.

2011-12-01

This paper presents a new finite element method (FEM) code for modeling tracer transport in a non-isothermal two-phase flow system. The main intended application is simulation of the movement of so-called novel tracers for the purpose of characterization of geologically stored CO2 and its phase partitioning and migration in deep saline formations. The governing equations are based on the conservation of mass and energy. Among the phenomena accounted for are liquid-phase flow, gas flow, heat transport and the movement of the novel tracers. The movement of tracers includes diffusion and the advection associated with the gas and liquid flow. The temperature, gas pressure, suction, concentration of tracer in liquid phase and concentration of tracer in gas phase are chosen as the five primary variables. Parameters such as the density, viscosity, thermal expansion coefficient are expressed in terms of the primary variables. The governing equations are discretized in space using the Galerkin finite element formulation, and are discretized in time by one-dimensional finite difference scheme. This leads to an ill-conditioned FEM equation that has many small entries along the diagonal of the non-symmetric coefficient matrix. In order to deal with the problem of non-symmetric ill-conditioned matrix equation, special techniques are introduced . Firstly, only nonzero elements of the matrix need to be stored. Secondly, it is avoided to directly solve the whole large matrix. Thirdly, a strategy has been used to keep the diversity of solution methods in the calculation process. Additionally, an efficient adaptive mesh technique is included in the code in order to track the wetting front. The code has been validated against several classical analytical solutions, and will be applied for simulating the CO2 injection experiment to be carried out at the Heletz site, Israel, as part of the EU FP7 project MUSTANG.

Patterns in CH4 and CO2 concentrations across boreal rivers: Major drivers and implications for fluvial greenhouse emissions under climate change scenarios.

PubMed

Campeau, Audrey; Del Giorgio, Paul A

2014-04-01

It is now widely accepted that boreal rivers and streams are regionally significant sources of carbon dioxide (CO2), yet their role as methane (CH4) emitters, as well as the sensitivity of these greenhouse gas (GHG) emissions to climate change, are still largely undefined. In this study, we explore the large-scale patterns of fluvial CO2 and CH4 partial pressure (pCO2 , pCH4) and gas exchange (k) relative to a set of key, climate-sensitive river variables across 46 streams and rivers in two distinct boreal landscapes of Northern Québec. We use the resulting models to determine the direction and magnitude of C-gas emissions from these boreal fluvial networks under scenarios of climate change. River pCO2 and pCH4 were positively correlated, although the latter was two orders of magnitude more variable. We provide evidence that in-stream metabolism strongly influences the dynamics of surface water pCO2 and pCH4 , but whereas pCO2 is not influenced by temperature in the surveyed streams and rivers, pCH4 appears to be strongly temperature-dependent. The major predictors of ambient gas concentrations and exchange were water temperature, velocity, and DOC, and the resulting models indicate that total GHG emissions (C-CO2 equivalent) from the entire network may increase between by 13 to 68% under plausible scenarios of climate change over the next 50 years. These predicted increases in fluvial GHG emissions are mostly driven by a steep increase in the contribution of CH4 (from 36 to over 50% of total CO2 -equivalents). The current role of boreal fluvial networks as major landscape sources of C is thus likely to expand, mainly driven by large increases in fluvial CH4 emissions. © 2013 John Wiley & Sons Ltd.

Mathematical simulation of convective-radiative heat transfer in a ventilated rectangular cavity with consideration of internal mass transfer

NASA Astrophysics Data System (ADS)

Sheremet, M. A.; Shishkin, N. I.

2012-07-01

Mathematical simulation of the nonstationary regimes of heat-and-mass transfer in a ventilated rectangular cavity with heat-conducting walls of finite thickness in the presence of a heat-generating element of constant temperature has been carried out with account for the radiative heat transfer in the Rosseland approximation. As mechanisms of energy transfer in this cavity, the combined convection and the thermal radiation in the gas space of the cavity and the heat conduction in the elements of its fencing solid shell were considered. The mathematical model formulated in the dimensionless stream function-vorticity vector-temperature-concentration variables was realized numerically with the use of the finite-difference method. The streamline, temperature-field, and concentration distributions reflecting the influence of the Rayleigh number (Ra = 104, 105, 106), the nonstationarity (0 < τ ≤ 1000), and the optical thickness of the medium (τλ = 50, 100, 200) on the regimes of the gas flow and the heat-and-mass transfer in the cavity have been obtained.

Martian atmospheric O3 retrieval development for the NOMAD-UVIS spectrometer

NASA Astrophysics Data System (ADS)

Hewson, W.; Mason, J. P.; Leese, M.; Hathi, B.; Holmes, J.; Lewis, S. R.; Iriwin, P. G. J.; Patel, M. R.

2017-09-01

The composition of atmospheric trace gases and aerosols is a highly variable and poorly constrained component of the martian atmosphere, and by affecting martian climate and UV surface dose, represents a key parameter in the assessment of suitability for martian habitability. The ExoMars Trace Gas Orbiter (TGO) carries the Open University (OU) designed Ultraviolet and VIsible Spectrometer (UVIS) instrument as part of the Belgian-led Nadir and Occultation for MArs Discovery (NOMAD) spectrometer suite. NOMAD will begin transmitting science observations of martian surface and atmosphere back-scattered UltraViolet (UV) and visible radiation in Spring 2018, which will be processed to derive spatially and temporally averaged atmospheric trace gas and aerosol concentrations, intended to provide a better understanding of martian atmospheric photo-chemistry and dynamics, and will also improve models of martian atmospheric chemistry, climate and habitability. Work presented here illustrates initial development and testing of the OU's new retrieval algorithm for determining O3 and aerosol concentrations from the UVIS instrument.

Quantifying Emissions from the Eagle Ford Shale Using Ethane Enhancement

NASA Astrophysics Data System (ADS)

Roest, G. S.; Schade, G. W.

2014-12-01

Emissions from unconventional oil and natural gas exploration in the Eagle Ford Shale have been conjectured as a contributing factor to increasing ozone concentrations in the San Antonio Metropolitan Area, which is on track to be designated as a nonattainment area by the EPA. Primary species found in natural gas emissions are alkanes, with C3 and heavier alkanes acting as short-lived VOCs contributing to regional ozone formation. Methane emissions from the industry are also a forcing mechanism for climate change as methane is a potent greenhouse gas. Recent studies have highlighted a high variability and uncertainties in oil and natural gas emissions estimates in emissions inventories. Thus, accurately quantifying oil and natural gas emissions from the Eagle Ford Shale is necessary to assess the industry's impacts on climate forcing and regional air quality. We estimate oil and natural gas emissions in the Eagle Ford Shale using in situ ethane measurements along southwesterly trajectories from the Gulf of Mexico, dominantly during the summertime. Ethane enhancement within the drilling area is estimated by comparing ethane concentrations upwind of the shale, near the Texas coastline, to downwind measurements in the San Antonio Metropolitan Area, Odessa, and Amarillo. Upwind ethane observations indicate low background levels entering Texas in the Gulf of Mexico air masses. Significant ethane enhancement is observed between the coast and San Antonio, and is attributed to oil and natural gas operations due to the concurrent enhancements of heavier alkanes. Using typical boundary layer depths and presuming homogenous emissions across the Eagle Ford shale area, the observed ethane enhancements are used to extrapolate an estimate of oil and natural gas industry emissions in the Eagle Ford. As oil and natural gas production in the area is projected to grow rapidly over the coming years, the impacts of these emissions on regional air quality will need to be thoroughly studied.

Methane from shallow seep areas of the NW Svalbard Arctic margin does not reach the sea surface

NASA Astrophysics Data System (ADS)

Silyakova, Anna; Greinert, Jens; Jansson, Pär; Ferré, Bénédicte

2015-04-01

Methane, an important greenhouse gas, leaks from large areas of the Arctic Ocean floor. One overall question is how much methane passes from the seabed through the water column, potentially reaching the atmosphere. Transport of methane from the ocean floor into and through the water column depends on many factors such as distribution of gas seeps, microbial methane oxidation, and ambient oceanographic conditions, which may trigger a change in seep activity. From June-July 2014 we investigated dissolved methane in the water column emanating from the "Prins Karls Forland seeps" area offshore the NW Svalbard Arctic margin. Measurements of the spatial variability of dissolved methane in the water column included 65 CTD stations located in a grid covering an area of 30 by 15 km. We repeated an oceanographic transect twice in a week for time lapse studies, thus documenting significant temporal variability in dissolved methane above one shallow seep site (~100 m water depth). Analysis of both nutrient concentrations and dissolved methane in water samples from the same transect, reveal striking similarities in spatial patterns of both dissolved methane and nutrients indicating that microbial community is involved in methane cycling above the gas seepage. Our preliminary results suggest that although methane release can increase in a week's time, providing twice as much dissolved gas to the water column, no methane from a seep reaches the sea surface. Instead it spreads horizontally under the pycnocline. Yet microbial communities react rapidly to the methane supply above gas seepage areas and may also have an important role as an effective filter, hindering methane release from the ocean to the atmosphere during rapid methane ebullition. This study is funded by CAGE (Centre for Arctic Gas Hydrate, Environment and Climate), Norwegian Research Council grant no. 223259.

Chemical Discrimination in Turbulent Gas Mixtures with MOX Sensors Validated by Gas Chromatography-Mass Spectrometry

PubMed Central

Fonollosa, Jordi; Rodríguez-Luján, Irene; Trincavelli, Marco; Vergara, Alexander; Huerta, Ramón

2014-01-01

Chemical detection systems based on chemo-resistive sensors usually include a gas chamber to control the sample air flow and to minimize turbulence. However, such a kind of experimental setup does not reproduce the gas concentration fluctuations observed in natural environments and destroys the spatio-temporal information contained in gas plumes. Aiming at reproducing more realistic environments, we utilize a wind tunnel with two independent gas sources that get naturally mixed along a turbulent flow. For the first time, chemo-resistive gas sensors are exposed to dynamic gas mixtures generated with several concentration levels at the sources. Moreover, the ground truth of gas concentrations at the sensor location was estimated by means of gas chromatography-mass spectrometry. We used a support vector machine as a tool to show that chemo-resistive transduction can be utilized to reliably identify chemical components in dynamic turbulent mixtures, as long as sufficient gas concentration coverage is used. We show that in open sampling systems, training the classifiers only on high concentrations of gases produces less effective classification and that it is important to calibrate the classification method with data at low gas concentrations to achieve optimal performance. PMID:25325339

Chemical discrimination in turbulent gas mixtures with MOX sensors validated by gas chromatography-mass spectrometry.

PubMed

Fonollosa, Jordi; Rodríguez-Luján, Irene; Trincavelli, Marco; Vergara, Alexander; Huerta, Ramón

2014-10-16

Chemical detection systems based on chemo-resistive sensors usually include a gas chamber to control the sample air flow and to minimize turbulence. However, such a kind of experimental setup does not reproduce the gas concentration fluctuations observed in natural environments and destroys the spatio-temporal information contained in gas plumes. Aiming at reproducing more realistic environments, we utilize a wind tunnel with two independent gas sources that get naturally mixed along a turbulent flow. For the first time, chemo-resistive gas sensors are exposed to dynamic gas mixtures generated with several concentration levels at the sources. Moreover, the ground truth of gas concentrations at the sensor location was estimated by means of gas chromatography-mass spectrometry. We used a support vector machine as a tool to show that chemo-resistive transduction can be utilized to reliably identify chemical components in dynamic turbulent mixtures, as long as sufficient gas concentration coverage is used. We show that in open sampling systems, training the classifiers only on high concentrations of gases produces less effective classification and that it is important to calibrate the classification method with data at low gas concentrations to achieve optimal performance.

Modern climate challenges and the geological record

USGS Publications Warehouse

Cronin, Thomas M.

2010-01-01

Today's changing climate poses challenges about the influence of human activity, such as greenhouse gas emissions and land use changes, the natural variability of Earth's climate, and complex feedback processes. Ice core and instrumental records show that over the last century, atmospheric carbon dioxide (CO2) concentrations have risen to 390 parts per million volume (ppmv), about 40% above pre-Industrial Age concentrations of 280 ppmv and nearly twice those of the last glacial maximum about 22,000 years ago. Similar historical increases are recorded in atmospheric methane (CH4) and nitrous oxide (N2O). There is general agreement that human activity is largely responsible for these trends. Substantial evidence also suggests that elevated greenhouse gas concentrations are responsible for much of the recent atmospheric and oceanic warming, rising sea level, declining Arctic sea-ice cover, retreating glaciers and small ice caps, decreased mass balance of the Greenland and parts of the Antarctic ice sheets, and decreasing ocean pH (ocean "acidification"). Elevated CO2 concentrations raise concern not only from observations of the climate system, but because feedbacks associated with reduced reflectivity from in land and sea ice, sea level, and land vegetation relatively slowly (centuries or longer) to elevated 2 levels. This means that additional human-induced climate change is expected even if the rate of CO2 emissions is reduced or concentrations immediately stabilized.

Sustained in situ measurements of dissolved oxygen, methane and water transport processes in the benthic boundary layer at MC118, northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Martens, Christopher S.; Mendlovitz, Howard P.; Seim, Harvey; Lapham, Laura; D'Emidio, Marco

2016-07-01

Within months of the BP Macondo Wellhead blowout, elevated methane concentrations within the water column revealed a significant retention of light hydrocarbons in deep waters plus corresponding dissolved oxygen (DO) deficits. However, chemical plume tracking efforts were hindered by a lack of in situ monitoring capabilities. Here, we describe results from in situ time-series, lander-based investigations of physical and biogeochemical processes controlling dissolved oxygen, and methane at Mississippi Canyon lease block 118 ( 18 km from the oil spill) conducted shortly after the blowout through April 2012. Multiple sensor arrays plus open-cylinder flux chambers (;chimneys;) deployed from a benthic lander collected oxygen, methane, pressure, and current speed and direction data within one meter of the seafloor. The ROVARD lander system was deployed for an initial 21-day test experiment (9/13/2010-10/04/2010) at 882 m depth before a longer 160-day deployment (10/24/2011-4/01/2012) at 884 m depth. Temporal variability in current directions and velocities and water temperatures revealed strong influences of bathymetrically steered currents and overlying along-shelf flows on local and regional water transport processes. DO concentrations and temperature were inversely correlated as a result of water mass mixing processes. Flux chamber measurements during the 160-day deployment revealed total oxygen utilization (TOU) averaging 11.6 mmol/m2 day. Chimney DO concentrations measured during the 21-day deployment exhibited quasi-daily variations apparently resulting from an interaction between near inertial waves and the steep topography of an elevated scarp immediately adjacent to the 21-day deployment site that modulated currents at the top of the chimney. Variability in dissolved methane concentrations suggested significant temporal variability in gas release from nearby hydrocarbon seeps and/or delivery by local water transport processes. Free-vehicle (lander) monitoring over time scales of months to years utilizing in situ sensors can provide an understanding of processes controlling water transport, respiration and the fate and impacts of accidental and natural gas and oil releases.

Gas concentration cells for utilizing energy

DOEpatents

Salomon, R.E.

1987-06-30

An apparatus and method are disclosed for utilizing energy, in which the apparatus may be used for generating electricity or as a heat pump. When used as an electrical generator, two gas concentration cells are connected in a closed gas circuit. The first gas concentration cell is heated and generates electricity. The second gas concentration cell repressurizes the gas which travels between the cells. The electrical energy which is generated by the first cell drives the second cell as well as an electrical load. When used as a heat pump, two gas concentration cells are connected in a closed gas circuit. The first cell is supplied with electrical energy from a direct current source and releases heat. The second cell absorbs heat. The apparatus has no moving parts and thus approximates a heat engine. 4 figs.

Gas concentration cells for utilizing energy

DOEpatents

Salomon, Robert E.

1987-01-01

An apparatus and method for utilizing energy, in which the apparatus may be used for generating electricity or as a heat pump. When used as an electrical generator, two gas concentration cells are connected in a closed gas circuit. The first gas concentration cell is heated and generates electricity. The second gas concentration cell repressurizes the gas which travels between the cells. The electrical energy which is generated by the first cell drives the second cell as well as an electrical load. When used as a heat pump, two gas concentration cells are connected in a closed gas circuit. The first cell is supplied with electrical energy from a direct current source and releases heat. The second cell absorbs heat. The apparatus has no moving parts and thus approximates a heat engine.

Winter measurements of trace gas and aerosol composition at a rural site in southern ontario

NASA Astrophysics Data System (ADS)

Daum, P. H.; Kelly, T. J.; Tanner, R. L.; Tang, X.; Anlauf, K.; Bottenheim, J.; Brice, K. A.; Wiebe, H. A.

This paper reports the results of continuous measurements of concentrations of trace gas and aerosol species at Powassan, Ontario, a rural location in southern Ontario, from 20 January to 24 February 1984. The measurements included aerosol H + , NH 4+, Na +, Ca 2+ , NO 3-, SO 42- and Cl -, gaseous SO 2, NO, NO' y; ( = NO + NO2 + PAN + HNO3), HNO 3, PAN, and O 3. Average values of concentrations for key species during the project were: SO 2, 7.3 ppb; NO y, 7.5 ppb; HNO 3, 0.85 ppb; O 3, 33 ppb; NH 4+ 1.5 ppb; NO 3-, 0.4 ppb; and SO 42-, 0.9 ppb. Concentrations of primary pollutants (e.g. SO 2) were typically much higher, and concentrations of secondary species (e.g. SO 42-) typically lower, than observed at this location in summer. However, clear-air t- NO 3-/SO 42- ratios averaged 5-10 times higher in winter than in summer which suggests that HNO 3 is a more important source of atmospheric acidity, relative to SO 42- aerosol, in winter than in summer. Pollutant concentrations were highly variable; back trajectory calculations indicate that periods of high concentrations of both primary and secondary species were typically associated with air-mass back trajectories from the southern sectors while periods of low concentrations of secondary species were associated with back trajectories from the north. Comparison of these measurements with those at other locations suggests that concentrations at Powassan were characteristic of those prevailing over a much larger, possibly regional, area.

The Intrinsic Variability in the Water Vapor Saturation Ratio due to Turbulence

NASA Astrophysics Data System (ADS)

Anderson, J. C.; Cantrell, W. H.; Chandrakar, K. K.; Kostinski, A. B.; Niedermeier, D.; Shaw, R. A.

2017-12-01

In the atmosphere, the concentration of water vapor plays an important role in Earth's weather and climate. The mean concentration of water vapor is key to its efficiency as a greenhouse gas; the fluctuations about the mean are important for heat fluxes near the surface of earth. In boundary layer clouds, fluctuations in the water vapor concentration are linked to turbulence. Conditions representative of boundary layer clouds are simulated in Michigan Tech's multiphase, turbulent reaction chamber, the ∏ chamber, where the boundary conditions are controlled and repeatable. Measurements for temperature and water vapor concentration were recorded under forced Rayleigh-Bénard convection. As expected, the distributions for temperature and water vapor concentration broaden as the turbulence becomes more vigorous. From these two measurements the saturation ratio can be calculated. The fluctuations in the water vapor concentration are more important to the variability in the saturation ratio than fluctuations in temperature. In a cloud, these fluctuations in the saturation ratio can result in some cloud droplets experiencing much higher supersaturations. Those "lucky" droplets grow by condensation at a faster rate than other cloud droplets. The difference in the droplet growth rate could contribute to a broadened droplet distribution, which leads to the onset of collision-coalescence. With more intense turbulence these effect will become more pronounced as the fluctuations about the mean saturation ratio become more pronounced.

Biotic and Human Vulnerability to Projected Changes in Ocean Biogeochemistry over the 21st Century

PubMed Central

Mora, Camilo; Wei, Chih-Lin; Rollo, Audrey; Amaro, Teresa; Baco, Amy R.; Billett, David; Bopp, Laurent; Chen, Qi; Collier, Mark; Danovaro, Roberto; Gooday, Andrew J.; Grupe, Benjamin M.; Halloran, Paul R.; Ingels, Jeroen; Jones, Daniel O. B.; Levin, Lisa A.; Nakano, Hideyuki; Norling, Karl; Ramirez-Llodra, Eva; Rex, Michael; Ruhl, Henry A.; Smith, Craig R.; Sweetman, Andrew K.; Thurber, Andrew R.; Tjiputra, Jerry F.; Usseglio, Paolo; Watling, Les; Wu, Tongwen; Yasuhara, Moriaki

2013-01-01

Ongoing greenhouse gas emissions can modify climate processes and induce shifts in ocean temperature, pH, oxygen concentration, and productivity, which in turn could alter biological and social systems. Here, we provide a synoptic global assessment of the simultaneous changes in future ocean biogeochemical variables over marine biota and their broader implications for people. We analyzed modern Earth System Models forced by greenhouse gas concentration pathways until 2100 and showed that the entire world's ocean surface will be simultaneously impacted by varying intensities of ocean warming, acidification, oxygen depletion, or shortfalls in productivity. In contrast, only a small fraction of the world's ocean surface, mostly in polar regions, will experience increased oxygenation and productivity, while almost nowhere will there be ocean cooling or pH elevation. We compiled the global distribution of 32 marine habitats and biodiversity hotspots and found that they would all experience simultaneous exposure to changes in multiple biogeochemical variables. This superposition highlights the high risk for synergistic ecosystem responses, the suite of physiological adaptations needed to cope with future climate change, and the potential for reorganization of global biodiversity patterns. If co-occurring biogeochemical changes influence the delivery of ocean goods and services, then they could also have a considerable effect on human welfare. Approximately 470 to 870 million of the poorest people in the world rely heavily on the ocean for food, jobs, and revenues and live in countries that will be most affected by simultaneous changes in ocean biogeochemistry. These results highlight the high risk of degradation of marine ecosystems and associated human hardship expected in a future following current trends in anthropogenic greenhouse gas emissions. PMID:24143135

Biotic and human vulnerability to projected changes in ocean biogeochemistry over the 21st century.

PubMed

Mora, Camilo; Wei, Chih-Lin; Rollo, Audrey; Amaro, Teresa; Baco, Amy R; Billett, David; Bopp, Laurent; Chen, Qi; Collier, Mark; Danovaro, Roberto; Gooday, Andrew J; Grupe, Benjamin M; Halloran, Paul R; Ingels, Jeroen; Jones, Daniel O B; Levin, Lisa A; Nakano, Hideyuki; Norling, Karl; Ramirez-Llodra, Eva; Rex, Michael; Ruhl, Henry A; Smith, Craig R; Sweetman, Andrew K; Thurber, Andrew R; Tjiputra, Jerry F; Usseglio, Paolo; Watling, Les; Wu, Tongwen; Yasuhara, Moriaki

2013-10-01

Ongoing greenhouse gas emissions can modify climate processes and induce shifts in ocean temperature, pH, oxygen concentration, and productivity, which in turn could alter biological and social systems. Here, we provide a synoptic global assessment of the simultaneous changes in future ocean biogeochemical variables over marine biota and their broader implications for people. We analyzed modern Earth System Models forced by greenhouse gas concentration pathways until 2100 and showed that the entire world's ocean surface will be simultaneously impacted by varying intensities of ocean warming, acidification, oxygen depletion, or shortfalls in productivity. In contrast, only a small fraction of the world's ocean surface, mostly in polar regions, will experience increased oxygenation and productivity, while almost nowhere will there be ocean cooling or pH elevation. We compiled the global distribution of 32 marine habitats and biodiversity hotspots and found that they would all experience simultaneous exposure to changes in multiple biogeochemical variables. This superposition highlights the high risk for synergistic ecosystem responses, the suite of physiological adaptations needed to cope with future climate change, and the potential for reorganization of global biodiversity patterns. If co-occurring biogeochemical changes influence the delivery of ocean goods and services, then they could also have a considerable effect on human welfare. Approximately 470 to 870 million of the poorest people in the world rely heavily on the ocean for food, jobs, and revenues and live in countries that will be most affected by simultaneous changes in ocean biogeochemistry. These results highlight the high risk of degradation of marine ecosystems and associated human hardship expected in a future following current trends in anthropogenic greenhouse gas emissions.

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 with a biogenic origin was mainly related with large-area concentration events (duration above 10 minutes). The content of C2H6 in the thermogenic-related peak events (2.7-5.9%) agreed with the composition of the NG distributed in the GHA, indicating the potential relevance of NG usage on CH4 enhancements observed in the Houston atmosphere.

Indriect Measurement Of Nitrogen In A Mult-Component Natural Gas By Heating The Gas

DOEpatents

Morrow, Thomas B.; Behring, II, Kendricks A.

2004-06-22

Methods of indirectly measuring the nitrogen concentration in a natural gas by heating the gas. In two embodiments, the heating energy is correlated to the speed of sound in the gas, the diluent concentrations in the gas, and constant values, resulting in a model equation. Regression analysis is used to calculate the constant values, which can then be substituted into the model equation. If the diluent concentrations other than nitrogen (typically carbon dioxide) are known, the model equation can be solved for the nitrogen concentration.

Circulatory and respiratory effects of methoxyflurane in dogs: comparison of halothane.

PubMed

Steffey, E P; Farver, T B; Woliner, M J

1984-12-01

Circulatory and respiratory effects of 3 alveolar concentrations (representing 1.0, 1.5, and 2.0 times the minimal alveolar concentration, MAC) of methoxyflurane in O2 were compared with similar MAC multiples of halothane in O2. Eight adult mixed breed dogs that were healthy and nonmedicated were studied in cross-over fashion with both agents during conditions of controlled ventilation (CV; PaCO2 averaged 34 to 38 mm of Hg) and spontaneous ventilation (SV). When ventilation was controlled, methoxyflurane similar to halothane caused dose-related cardiovascular depression. Except for a greater heart rate and lesser stroke volume with methoxyflurane, little difference was noticed between the anesthetics at equivalent doses during CV. There was less dose-related circulatory depression during SV with both agents but particularly with methoxyflurane. During SV, PaCO2 increased progressively with increases in alveolar concentrations of methoxyflurane and halothane. Methoxyflurane caused significantly greater (P less than 0.05) hypoventilation than halothane only at 2.0 MAC. Except for a greater respiratory gas flow and inspiratory-expiratory gas flow ratio and a lesser inspiratory-expiratory time ratio with methoxyflurane, there was no anesthetic- or dose-response effect on respiratory variables.

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

Bruffey, Stephanie H.; Jubin, Robert Thomas

U.S. regulations will require the removal of 129I from the off-gas streams of any used nuclear fuel (UNF) reprocessing plant prior to discharge of the off-gas to the environment. The required plant decontamination factor for iodine will vary based on fuel burnup, cooling time, and other factors but is very likely to be >1000 and could be as high as 8000. Multiple off-gas streams within a UNF reprocessing plant combine prior to environmental release, and each of these streams contains some amount of iodine. To achieve the decontamination factors (DFs) that are likely to be required by regulations, iodine removalmore » from the vessel off-gas will be necessary. The vessel off-gas contains iodine at very dilute concentrations (ppb levels), and will also contain water vapor. Iodine species present are likely to include both elemental and organic iodides. There will also be solvent vapors and volatile radiolysis products. The United States has considered the use of silver-based sorbents for removal of iodine from UNF off-gas streams, but little is known about the behavior of those sorbents at very dilute iodine concentrations. The purpose of this study was to expose silver-functionalized silica aerogel (AgAerogel) to a prototypical vessel off-gas stream containing 40 ppb methyl iodide to obtain information about organic iodine capture by silver-sorbents at very low iodine concentrations. The design of this extended duration testing was such that information about the rate of adsorption, the penetration of the iodine species, and the overall system DF could be obtained. Results show that CH 3I penetrates into a AgAerogel sorbent bed to a depth of 3.9 cm under prototypical vessel off-gas conditions. An iodine loading of 22 mg I/g AgAerogel was observed in the first 0.3 cm of the bed. Of the iodine delivered to the system, 48% could not be accounted for, and future efforts will investigate this concern. Direct calculation of the decontamination factor is not possible, as no iodine was observed to break through the sorbent beds. Continued studies on the adsorption of iodine from prototypical vessel off-gas streams by silver-based sorbents will attempt to resolve some of the questions raised here, both regarding mass balance and the effect of aging on iodine adsorption by AgAerogel from a dilute gas stream. Additionally, the adsorption of different iodine species, such as I 2 and C 12H 25I will be studied. Other variables that merit examination are the gas velocity of the test and the dependence of the observed results on the inlet iodine concentration. Finally, longer duration testing should be considered in an effort to determine the mass transfer zone associated with iodine adsorption by AgAerogel under prototypical vessel off-gas conditions. The estimation of mass transfer zone is required for any future industrial implementation.« less

Variable Cycle Intake for Reverse Core Engine

NASA Technical Reports Server (NTRS)

Chandler, Jesse M (Inventor); Staubach, Joseph B (Inventor); Suciu, Gabriel L (Inventor)

2016-01-01

A gas generator for a reverse core engine propulsion system has a variable cycle intake for the gas generator, which variable cycle intake includes a duct system. The duct system is configured for being selectively disposed in a first position and a second position, wherein free stream air is fed to the gas generator when in the first position, and fan stream air is fed to the gas generator when in the second position.

Indirect Measurement Of Nitrogen In A Multi-Component Gas By Measuring The Speed Of Sound At Two States Of The Gas.

DOEpatents

Morrow, Thomas B.; Behring, II, Kendricks A.

2004-10-12

A methods of indirectly measuring the nitrogen concentration in a gas mixture. The molecular weight of the gas is modeled as a function of the speed of sound in the gas, the diluent concentrations in the gas, and constant values, resulting in a model equation. Regression analysis is used to calculate the constant values, which can then be substituted into the model equation. If the speed of sound in the gas is measured at two states and diluent concentrations other than nitrogen (typically carbon dioxide) are known, two equations for molecular weight can be equated and solved for the nitrogen concentration in the gas mixture.

Analysis of illicit ecstasy tablets: implications for clinical management in the accident and emergency department.

PubMed Central

Sherlock, K; Wolff, K; Hay, A W; Conner, M

1999-01-01

OBJECTIVE: To examine the composition of illicitly manufactured "ecstasy" tablets sold on the UK drugs market. METHODS: Analysis by gas chromatography of 25 illicit ecstasy tablets handed in under amnesty to Leeds Addiction Unit. RESULTS: Illicitly manufactured ecstasy tablets contain a range of ingredients, of widely differing concentrations, and even tablets with the same brand name have variable concentrations of active ingredients. Concentrations of 3,4-methylenedioxymethamphetamine (MDMA) more popularly known as ecstasy, varied 70-fold between tablets. Nine tablets contained neither MDMA nor related analogues. CONCLUSIONS: These results have implications for emergency workers attending to those who have become casualties of the drug ecstasy. Those claiming to have ingested ecstasy may actually have taken other agents that require different clinical management. PMID:10353046

Microbial community dynamics and methane, carbon dioxide, oxygen, and nitrous oxide concentrations in upland forest and riparian soils across a seasonal gradient of fully saturated soils to completely dried soils

NASA Astrophysics Data System (ADS)

Jones, R. T.; McGlynn, B. L.; McDermott, T.; Dore, J. E.

2015-12-01

Gas concentrations (CH4, CO2, N2O, and O2), soil properties (soil water content and pH), and microbial community composition were measured from soils at 32 sites across the Stringer Creek Watershed in the Tenderfoot Creek Experimental Forest 7 times between June 3, 2013 and September 20, 2013. Soils were fully saturated during the initial sampling period and dried down over the course of the summer. Soils and gas were sampled from 5cm and 20cm at each site and also at 50cm at eight riparian sites. In total, 496 individual soil samples were collected. Soil moisture ranged from 3.7% to fully saturated; soil pH ranged from 3.60 to 6.68. Methane concentrations in soils ranged from 0.426 ppm to 218 ppm; Carbon dioxide concentrations ranged from 550 ppm to 42,990 ppm; Nitrous oxide concentrations ranged from 0.220 ppm to 2.111 ppm; Oxygen concentrations ranged from 10.2% to 21.5%. Soil microbial communities were characterized by DNA sequences covering the V4 region of the 16S rRNA gene. DNA sequences were generated (~30,000,000 sequences) from the 496 soil samples using the Illumina MiSeq platform. Operational Taxonomic Units were generated using USEARCH, and representative sequences were taxonomically classified according the Ribosomal Database Project's taxonomy scheme. Analysis of similarity revealed that microbial communities found within a landscape type (high upland forest, low upland forest, riparian) were more similar than among landscape types (R = 0.600; p<0.001). Similarly, communities from unique site x depths were similar across the 7 collection periods (R = 0.646; p<0.001) despite changes in soil moisture. Euclidean distances of soil properties and gas concentrations were compared to Bray-Curtis community dissimilarity matrices using Mantel tests to determine how community structure co-varies with the soil environment and gas concentrations. All variables measured significantly co-varied with microbial community membership (pH: R = 0.712, p < 0.001; CO2: R = 0.578, p < 0.001; O2: R = 0.517, p < 0.001; Soil moisture: R = 0.408, p < 0.001; N2O: R = 0.218, p = 0.003; CH4: R = 0.195, p = 0.008). Despite the rather low co-variation between methane concentrations and microbial community composition, relative abundances of methanotrophic and methanogenic lineages did co-vary strongly with methane concentrations.

The effect of floating vegetation on denitrification and greenhouse gas production in wetland mesocosms

NASA Astrophysics Data System (ADS)

Jacobs, A. E.; Harrison, J. A.

2012-12-01

Anthropogenic intensification of nitrogen (N) loading to aquatic ecosystems is widespread and can lead to the degradation of these systems. Wetlands are important sites for N removal via denitrification, the microbially mediated reduction of reactive nitrate to inert N2 gas, but they can also produce high levels of greenhouse gases. Floating plants play an important role in encouraging denitrification, since they create low oxygen conditions that may favor denitrification. We investigated whether wetland sediments with floating plant cover had higher denitrification and greenhouse gas production rates than wetland sediments without floating plants. Replicate flow-through mesocosms with wetland sediment and water were constructed in a growth chamber to mimic the wetland where the sediment and water were collected. Mesocosm treatments were covered with floating vegetation (duckweed), an opaque tarp, or no cover to determine how cover type affects denitrification and greenhouse gas production and whether biotic or abiotic factors are likely responsible for observed differences. Denitrification and greenhouse gas production rates were calculated by measuring excess N2 gas, methane, and nitrous oxide concentrations in the water column and measuring the gas exchange rates between the water column and the atmosphere. Gas exchange rates were measured using an inert volatile tracer added to the water column and accumulation of gas in the mesocosm headspace. Additional mesocosm experiments were performed to determine how duckweed-dominated wetland systems respond to nitrogen loading and which mechanism for lowering dissolved oxygen concentrations is important in affecting denitrification under floating vegetation. Mesocosms with floating vegetation had lower dissolved oxygen than no cover or tarp-covered mesocosms, which is consistent with field and literature observations. Water flowing out of the mesocosms had statistically lower total nitrogen and nitrate concentrations compared to inflow water, and calculated denitrification was statistically higher in the floating vegetation treatments compared to the other treatments. Greenhouse gas production, measured in CO2 equivalents for N2O and CH4, was highly variable and not statistically different between the treatments. Denitrification in the tarp covered mesocosms was similar to the no-cover treatment, indicating that biotic effects in the floating vegetation treatment may be important in lowering water column oxygen levels and increasing denitrification. Understanding how floating vegetation affects total nitrogen loss, denitrification, and greenhouse gas production can be used to weigh ecological costs and benefits of different vegetation types, especially in constructed and managed wetlands.

Integrating time-series and spatial surveys to assess annual, lake-wide emissions of carbon dioxide and methane from a eutrophic lake

NASA Astrophysics Data System (ADS)

Loken, L. C.; Crawford, J.; Schramm, P.; Stadler, P.; Stanley, E. H.

2017-12-01

Lakes are important regulators of global carbon cycling and conduits of greenhouse gases to the atmosphere; however, most efflux estimates for individual lakes are based on extrapolations from a limited number of locations. Within-lake variability in carbon dioxide (CO2) and methane (CH4) arises from differences in water sources, physical mixing, and biogeochemical transformations; all of which can vary at multiple temporal and spatial scales. We mapped surface water concentrations of CO2 and CH4 weekly across Lake Mendota (a 39.9 km2 eutrophic lake in Wisconsin, USA) spanning the majority of the 2016 ice-free season (249 days). Combining these maps with a spatially explicit gas transfer velocity (k) model, we estimated the diffusive exchange of both gases with the atmosphere taking into account both spatial and temporal heterogeneity. The cumulative efflux of CO2 (85.3 Mmol) and CH4 (9.47 Mmol) was positive, indicating that on the annual scale Lake Mendota was a net-source of both gases to the atmosphere. Although our model included variability in k, flux patterns reflected the patterns in gas concentrations. During the stratified period, CO2 was generally undersaturated throughout the pelagic zone due to high primary production and differed near river inlets and shorelines. The lake was routinely extremely supersaturated with CH4 with elevated concentrations in expansive littoral areas. During fall mixis, concentrations of both gases increased and became more variable across the lake surface, and their spatial arrangement changed reflecting hypolimentic mixing. In this system, samples collected from the lake center reasonably well-represented the lake-wide mean CO2 concentration, but they poorly represented CH4. While metabolic processes driving CO2 varied across the lake surface, pelagic phytoplankton contributed extensively to overall primary production, which acted at the lake-wide scale. Additionally Lake Mendota's high alkalinity may have masked the metabolic imprint on CO2 patterns. In contrast, heterogeneous CH4 transformations and transport lead to remarkable variation in CH4 across the lake surface that was dynamic through time. Thus, extrapolations from a limited number of locations or timepoints may not adequately describe lake-wide CH4 dynamics.

Detection of haemoglobins with abnormal oxygen affinity by single blood gas analysis and 2,3-diphosphoglycerate measurement.

PubMed

Guerrini, G; Morabito, A; Samaja, M

2000-10-01

The aim is to determine if a single measurement of blood 2,3-diphosphoglycerate combined with gas analysis (pH, PCO2, PO2 and saturation) can identify the cause of an altered blood-oxygen affinity: the presence of an abnormal haemoglobin or a red cell disorder. The population (n=94) was divided into healthy controls (A, n=14), carriers of red cell disorders (B, n=72) and carriers of high oxygen affinity haemoglobins (C, n=8). Those variables were measured both in samples equilibrated at selected PCO2 and PO2 and in venous blood. In the univariable approach applied to equilibrated samples, we correctly identified C subjects in 93.6% or 96.8% of the cases depending on the selected variable, the standard P50 (PO2 at which 50% of haemoglobin is oxygenated) or a composite variable calculated from the above measurements. After introducing the haemoglobin concentration as a further discriminating variable, the A and B subjects were correctly identified in 91.9% or 94.2% of the cases, respectively. These figures become 93.0% or 86.1%, and 93.7% or 94.9% of the cases when using direct readings from venous blood, thereby avoiding the blood equilibration step. This test is feasible also in blood samples stored at 4 degrees C for 48 h, or at room temperature for 8 h.

Measuring Spatial Variability of Vapor Flux to Characterize Vadose-zone VOC Sources: Flow-cell Experiments

DOE PAGES

Mainhagu, Jon; Morrison, C.; Truex, Michael J.; ...

2014-08-05

A method termed vapor-phase tomography has recently been proposed to characterize the distribution of volatile organic contaminant mass in vadose-zone source areas, and to measure associated three-dimensional distributions of local contaminant mass discharge. The method is based on measuring the spatial variability of vapor flux, and thus inherent to its effectiveness is the premise that the magnitudes and temporal variability of vapor concentrations measured at different monitoring points within the interrogated area will be a function of the geospatial positions of the points relative to the source location. A series of flow-cell experiments was conducted to evaluate this premise. Amore » well-defined source zone was created by injection and extraction of a non-reactive gas (SF6). Spatial and temporal concentration distributions obtained from the tests were compared to simulations produced with a mathematical model describing advective and diffusive transport. Tests were conducted to characterize both areal and vertical components of the application. Decreases in concentration over time were observed for monitoring points located on the opposite side of the source zone from the local–extraction point, whereas increases were observed for monitoring points located between the local–extraction point and the source zone. We found that the results illustrate that comparison of temporal concentration profiles obtained at various monitoring points gives a general indication of the source location with respect to the extraction and monitoring points.« less

The development and trial of an unmanned aerial system for the measurement of methane flux from landfill and greenhouse gas emission hotspots.

PubMed

Allen, Grant; Hollingsworth, Peter; Kabbabe, Khristopher; Pitt, Joseph R; Mead, Mohammed I; Illingworth, Samuel; Roberts, Gareth; Bourn, Mark; Shallcross, Dudley E; Percival, Carl J

2018-01-09

This paper describes the development of a new sampling and measurement method to infer methane flux using proxy measurements of CO 2 concentration and wind data recorded by Unmanned Aerial Systems (UAS). The flux method described and trialed here is appropriate to the spatial scale of landfill sites and analogous greenhouse gas emission hotspots, making it an important new method for low-cost and rapid case study quantification of fluxes from currently uncertain (but highly important) greenhouse gas sources. We present a case study using these UAS-based measurements to derive instantaneous methane fluxes from a test landfill site in the north of England using a mass balance model tailored for UAS sampling and co-emitted CO 2 concentration as a methane-emission proxy. Methane flux (and flux uncertainty) during two trials on 27 November 2014 and 5 March 2015, were found to be 0.140 kg s -1 (±61% at 1σ), and 0.050 kg s -1 (±54% at 1σ), respectively. Uncertainty contributing to the flux was dominated by ambient variability in the background (inflow) concentration (>40%) and wind speed (>10%); with instrumental error contributing only ∼1-2%. The approach described represents an important advance concerning the challenging problem of greenhouse gas hotspot flux calculation, and offers transferability to a wide range of analogous environments. This new measurement solution could add to a toolkit of approaches to better validate source-specific greenhouse emissions inventories - an important new requirement of the UNFCCC COP21 (Paris) climate change agreement. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

Comparison of mercury retention by fly ashes using different experimental devices

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

Lopez-Anton, M.A.; Abad-Valle, P.; Diaz-Somoano, M.

2009-12-15

To study mercury (Hg) retention in solid sorbents, researchers generally employ similar laboratory-scale devices. However, despite their similarities, these devices are generally used under different experimental conditions. The Hg concentration in the gas phase, gas flow, and sorbent-bed characteristics are variables that influence the contact time, mass transfer, and kinetics and may greatly modify the quantities of Hg retained when the same sorbents are compared. These differences in the experimental conditions do not impede an evaluation of the sorbents as long as the results obtained points toward the same qualitative conclusions. However, the extent of variation needs to be definedmore » to avoid misinterpretation. To illustrate the range of interpretations, the results of a preliminary approach using four experimental devices in two laboratories have been compared in this work. All the experiments were carried out under a nitrogen atmosphere and Hg{sup 0} in the gas phase. The same sorbents were employed in all the devices. These were fly ashes obtained from the combustion of coals of different rank and with different unburned carbon contents. From the results obtained it can be inferred that it is necessary to strictly control the influence of the experimental variables to infer a correct interpretation of the results.« less

System and method to determine thermophysical properties of a multi-component gas

DOEpatents

Morrow, Thomas B.; Behring, II, Kendricks A.

2003-08-05

A system and method to characterize natural gas hydrocarbons using a single inferential property, such as standard sound speed, when the concentrations of the diluent gases (e.g., carbon dioxide and nitrogen) are known. The system to determine a thermophysical property of a gas having a first plurality of components comprises a sound velocity measurement device, a concentration measurement device, and a processor to determine a thermophysical property as a function of a correlation between the thermophysical property, the speed of sound, and the concentration measurements, wherein the number of concentration measurements is less than the number of components in the gas. The method includes the steps of determining the speed of sound in the gas, determining a plurality of gas component concentrations in the gas, and determining the thermophysical property as a function of a correlation between the thermophysical property, the speed of sound, and the plurality of concentrations.

40 CFR 86.1437 - Test run-manufacturer.

Code of Federal Regulations, 2010 CFR

2010-07-01

... pipes. Exhaust gas concentrations from vehicle engines equipped with multiple exhaust pipes must be... apply. (1) Exhaust gas sampling algorithm. The analysis of exhaust gas concentrations begins ten seconds after the applicable test mode begins. Exhaust gas concentrations must be analyzed at a minimum rate of...

Joint inversion of acoustic and resistivity data for the estimation of gas hydrate concentration

USGS Publications Warehouse

Lee, Myung W.

2002-01-01

Downhole log measurements, such as acoustic or electrical resistivity logs, are frequently used to estimate in situ gas hydrate concentrations in the pore space of sedimentary rocks. Usually the gas hydrate concentration is estimated separately based on each log measurement. However, measurements are related to each other through the gas hydrate concentration, so the gas hydrate concentrations can be estimated by jointly inverting available logs. Because the magnitude of slowness of acoustic and resistivity values differs by more than an order of magnitude, a least-squares method, weighted by the inverse of the observed values, is attempted. Estimating the resistivity of connate water and gas hydrate concentration simultaneously is problematic, because the resistivity of connate water is independent of acoustics. In order to overcome this problem, a coupling constant is introduced in the Jacobian matrix. In the use of different logs to estimate gas hydrate concentration, a joint inversion of different measurements is preferred to the averaging of each inversion result.

Photochemical aging of volatile organic compounds associated with oil and natural gas extraction in the Uintah Basin, UT, during a wintertime ozone formation event

NASA Astrophysics Data System (ADS)

Koss, A. R.; de Gouw, J.; Warneke, C.; Gilman, J. B.; Lerner, B. M.; Graus, M.; Yuan, B.; Edwards, P.; Brown, S. S.; Wild, R.; Roberts, J. M.; Bates, T. S.; Quinn, P. K.

2015-05-01

High concentrations of volatile organic compounds (VOCs) associated with oil and natural gas extraction were measured during a strong temperature inversion in the winter of 2013 at a rural site in the Uintah Basin, Utah. During this period, photochemistry enhanced by the stagnant meteorological conditions and concentrated VOCs led to high ozone mixing ratios (150 ppbv). A simple analysis of aromatic VOCs measured by proton-transfer-reaction mass-spectrometry (PTR-MS) is used to estimate (1) VOC emission ratios (the ratio of two VOCs at the time of emission) relative to benzene, (2) aromatic VOC emission rates, and (3) ambient OH radical concentrations. These quantities are determined from a best fit to VOC : benzene ratios as a function of time. The main findings are that (1) emission ratios are consistent with contributions from both oil and gas producing wells; (2) the emission rate of methane (27-57 x 103 kg methane h-1), extrapolated from the emission rate of benzene (4.1 ± 0.4 x 105 molecules cm-3 s-1), agrees with an independent estimate of methane emissions from aircraft measurements in 2012; and (3) calculated daily OH concentrations are low, peaking at 1 x 106 molecules cm-3, and are consistent with Master Chemical Mechanism (MCM) modeling. The analysis is extended to photochemical production of oxygenated VOCs measured by PTR-MS and is able to explain daytime variability of these species. It is not able to completely reproduce nighttime behavior, possibly due to surface deposition. Using results from this analysis, the carbon mass of secondary compounds expected to have formed by the sixth day of the stagnation event was calculated, then compared to the measured mass of primary and secondary compounds. Only 17% of the expected secondary carbon mass is accounted for by gas phase, aerosol, and snow organic carbon measurements. The disparity is likely due to substantial amounts of unquantified oxygenated products.

Photochemical aging of volatile organic compounds associated with oil and natural gas extraction in the Uintah Basin, UT, during a wintertime ozone formation event

NASA Astrophysics Data System (ADS)

Koss, A. R.; de Gouw, J.; Warneke, C.; Gilman, J. B.; Lerner, B. M.; Graus, M.; Yuan, B.; Edwards, P.; Brown, S. S.; Wild, R.; Roberts, J. M.; Bates, T. S.; Quinn, P. K.

2015-03-01

High concentrations of volatile organic compounds (VOCs) associated with oil and natural gas extraction were measured during a strong temperature inversion in winter of 2013 at a rural site in the Uintah Basin, Utah. During this period, photochemistry enhanced by the stagnant meteorological conditions and concentrated VOCs led to high ozone mixing ratios (150 ppbv). A simple analysis of aromatic VOCs measured by proton-transfer-reaction mass-spectrometry (PTR-MS) is used to estimate (1) VOC emission ratios (the ratio of two VOCs at the time of emission) relative to benzene, (2) aromatic VOC emission rates, and (3) ambient OH radical concentrations. These quantities are determined from a best fit to VOC : benzene ratios as a function of time. The main findings are that (1) emission ratios are consistent with contributions from both oil and gas producing wells, (2) the emission rate of methane (27-57 × 103 kg methane h-1), extrapolated from the emission rate of benzene (4.1 ± 0.4 × 105 molecules cm-3 s-1), agrees with an independent estimate of methane emissions from aircraft measurements in 2012, and (3) calculated daily OH concentrations are low, peaking at 1× 106 molecules cm-3, and are consistent with Master Chemical Mechanism (MCM) modeling. The analysis is extended to photochemical production of oxygenated VOCs measured by PTRMS and is able to explain daytime variability of these species. It is not able to completely reproduce nighttime behavior, possibly due to surface deposition. Using results from this analysis, the carbon mass of secondary compounds expected to have formed by the sixth day of the stagnation event was calculated, then compared to the measured mass of primary and secondary compounds. Only 17% of the expected secondary carbon mass is accounted for by gas phase, aerosol, and snow organic carbon measurements. The disparity is likely due to substantial amounts of unquantified oxygenated products.

Analysis of gas absorption to a thin liquid film in the presence of a zero-order chemical reaction

NASA Technical Reports Server (NTRS)

Rajagopalan, S.; Rahman, M. M.

1995-01-01

The paper presents a detailed theoretical analysis of the process of gas absorption to a thin liquid film adjacent to a horizontal rotating disk. The film is formed by the impingement of a controlled liquid jet at the center of the disk and subsequent radial spreading of liquid along the disk. The chemical reaction between the gas and the liquid film can be expressed as a zero-order homogeneous reaction. The process was modeled by establishing equations for the conservation of mass, momentum, and species concentration and solving them analytically. A scaling analysis was used to determine dominant transport processes. Appropriate boundary conditions were used to solve these equations to develop expressions for the local concentration of gas across the thickness of the film and distributions of film height, bulk concentration, and Sherwood number along the radius of the disk. The partial differential equation for species concentration was solved using the separation of variables technique along with the Duhamel's theorem and the final analytical solution was expressed using confluent hypergeometric functions. Tables for eigenvalues and eigenfunctions are presented for a number of reaction rate constants. A parametric study was performed using Reynolds number, Ekman number, and dimensionless reaction rate as parameters. At all radial locations, Sherwood number increased with Reynolds number (flow rate) as well as Ekman number (rate of rotation). The enhancement of mass transfer due to chemical reaction was found to be small when compared to the case of no reaction (pure absorption), but the enhancement factor was very significant when compared to pure absorption in a stagnant liquid film. The zero-order reaction processes considered in the present investigation included the absorption of oxygen in aqueous alkaline solutions of sodiumdithionite and rhodium complex catalyzed carbonylation of methanol. Present analytical results were compared to previous theoretical results for limiting conditions, and were found to have very good agreement.

Detecting the effects of coal mining, acid rain, and natural gas extraction in Appalachian basin streams in Pennsylvania (USA) through analysis of barium and sulfate concentrations.

PubMed

Niu, Xianzeng; Wendt, Anna; Li, Zhenhui; Agarwal, Amal; Xue, Lingzhou; Gonzales, Matthew; Brantley, Susan L

2018-04-01

To understand how extraction of different energy sources impacts water resources requires assessment of how water chemistry has changed in comparison with the background values of pristine streams. With such understanding, we can develop better water quality standards and ecological interpretations. However, determination of pristine background chemistry is difficult in areas with heavy human impact. To learn to do this, we compiled a master dataset of sulfate and barium concentrations ([SO 4 ], [Ba]) in Pennsylvania (PA, USA) streams from publically available sources. These elements were chosen because they can represent contamination related to oil/gas and coal, respectively. We applied changepoint analysis (i.e., likelihood ratio test) to identify pristine streams, which we defined as streams with a low variability in concentrations as measured over years. From these pristine streams, we estimated the baseline concentrations for major bedrock types in PA. Overall, we found that 48,471 data values are available for [SO 4 ] from 1904 to 2014 and 3243 data for [Ba] from 1963 to 2014. Statewide [SO 4 ] baseline was estimated to be 15.8 ± 9.6 mg/L, but values range from 12.4 to 26.7 mg/L for different bedrock types. The statewide [Ba] baseline is 27.7 ± 10.6 µg/L and values range from 25.8 to 38.7 µg/L. Results show that most increases in [SO 4 ] from the baseline occurred in areas with intensive coal mining activities, confirming previous studies. Sulfate inputs from acid rain were also documented. Slight increases in [Ba] since 2007 and higher [Ba] in areas with higher densities of gas wells when compared to other areas could document impacts from shale gas development, the prevalence of basin brines, or decreases in acid rain and its coupled effects on [Ba] related to barite solubility. The largest impacts on PA stream [Ba] and [SO 4 ] are related to releases from coal mining or burning rather than oil and gas development.

Multi-scale variability and long-range memory in indoor Radon concentrations from Coimbra, Portugal

NASA Astrophysics Data System (ADS)

Donner, Reik V.; Potirakis, Stelios; Barbosa, Susana

2014-05-01

The presence or absence of long-range correlations in the variations of indoor Radon concentrations has recently attracted considerable interest. As a radioactive gas naturally emitted from the ground in certain geological settings, understanding environmental factors controlling Radon concentrations and their dynamics is important for estimating its effect on human health and the efficiency of possible measures for reducing the corresponding exposition. In this work, we re-analyze two high-resolution records of indoor Radon concentrations from Coimbra, Portugal, each of which spans several months of continuous measurements. In order to evaluate the presence of long-range correlations and fractal scaling, we utilize a multiplicity of complementary methods, including power spectral analysis, ARFIMA modeling, classical and multi-fractal detrended fluctuation analysis, and two different estimators of the signals' fractal dimensions. Power spectra and fluctuation functions reveal some complex behavior with qualitatively different properties on different time-scales: white noise in the high-frequency part, indications of some long-range correlated process dominating time scales of several hours to days, and pronounced low-frequency variability associated with tidal and/or meteorological forcing. In order to further decompose these different scales of variability, we apply two different approaches. On the one hand, applying multi-resolution analysis based on the discrete wavelet transform allows separately studying contributions on different time scales and characterize their specific correlation and scaling properties. On the other hand, singular system analysis (SSA) provides a reconstruction of the essential modes of variability. Specifically, by considering only the first leading SSA modes, we achieve an efficient de-noising of our environmental signals, highlighting the low-frequency variations together with some distinct scaling on sub-daily time-scales resembling the properties of a long-range correlated process.

Dissolved radon and uranium in groundwater in a potential coal seam gas development region (Richmond River Catchment, Australia).

PubMed

Atkins, Marnie L; Santos, Isaac R; Perkins, Anita; Maher, Damien T

2016-04-01

The extraction of unconventional gas resources such as shale and coal seam gas (CSG) is rapidly expanding globally and often prevents the opportunity for comprehensive baseline groundwater investigations prior to drilling. Unconventional gas extraction often targets geological layers with high naturally occurring radioactive materials (NORM) and extraction practices may possibly mobilise radionuclides into regional and local drinking water resources. Here, we establish baseline groundwater radon and uranium levels in shallow aquifers overlying a potential CSG target formation in the Richmond River Catchment, Australia. A total of 91 groundwater samples from six different geological units showed highly variable radon activities (0.14-20.33 Bq/L) and uranium levels (0.001-2.77 μg/L) which were well below the Australian Drinking Water Guideline values (radon; 100 Bq/L and uranium; 17 μg/L). Therefore, from a radon and uranium perspective, the regional groundwater does not pose health risks to consumers. Uranium could not explain the distribution of radon in groundwater. Relatively high radon activities (7.88 ± 0.83 Bq/L) in the fractured Lismore Basalt aquifer coincided with very low uranium concentrations (0.04 ± 0.02 μg/L). In the Quaternary Sediments aquifers, a positive correlation between U and HCO3(-) (r(2) = 0.49, p < 0.01) implied the uranium was present as uranyl-carbonate complexes. Since NORM are often enriched in target geological formations containing unconventional gas, establishing radon and uranium concentrations in overlying aquifers comprises an important component of baseline groundwater investigations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Biogeochemical and microbiological characteristic of the pockmark sediments, the Gdansk Deep, The Baltic Sea

NASA Astrophysics Data System (ADS)

Pimenov, Nikolay; Kanapatskiy, Timur; Sivkov, Vadim; Toshchakov, Stepan; Korzhenkov, Aleksei; Ulyanova, Marina

2016-04-01

Comparison of the biogeochemical and microbial features was done for the gas-bearing and background sediments as well as near-bottom water of the Gdansk Deep, The Baltic Sea. Data were received in October, 2015 during 64th cruise of the R/V Akademik Mstislav Keldysh. Gas-bearing sediments were sampled within the known pockmark (Gas-Point, depth 94 m). Background sediments area (BG-Point, depth 86 m) was located several km off the pockmark area. The sulphate concentration in the pore water of the surface sediment layer (0-5 cm) of Gas-Point was 9,7 mmol/l, and sharply decreased with depth (did not exceed 1 mmol/l deeper than 50 cm). The sulphate concentration decrease at BG-Point also took place but was not so considerable. Sulphate concentration decrease is typical for the organic rich sediments of the high productive areas, both as for the methane seep areas. Fast sulphate depletion occurs due to active processes of its microbial reduction by consortium of the sulphate-reduction bacteria, which may use low-molecular organic compounds or hydrogen, formed at the different stages of the organic matter destruction; as well as within the process of the anaerobic methane oxidation by consortium of the methane-trophic archaea and sulphate-reduction bacteria. Together with sulphate concentration decrease the methane content increase, typical for the marine sediments, occurred. At the Gas-Point the methane concentration varied within 10 μmol/dm3 in the surface layer till its maximum at sediment horizon of 65 cm (5 mmol/dm3), and decreased to 1.5 mmol/dm3 at depth of 300 cm. The BG-Point maximum values were defined at sediment horizon 6 cm (2,6 μmol/dm3). Methane sulfate transition zone at the Gas-Point sediments was at 25-35 cm depth; whereas it was not defined at the BG-Point mud. High methane concentration in the gas-bearing sediments results in the formation of the methane seep from the sediments to the near-bottom water. So the Gas-Point near-bottom waters were characterized by high methane concentration (0.36-0.50 μmol/l) even in the water 2-5 m above the bottom (0.08-0.28 μmol/l), whereas at the BG-Point sediments methane concentration in the near-bottom water was 0.06-0.08 μmol/l. In order to get insights into the structure of microbial community responsible for realization of these redox processes we performed microbial community profiling using high-throughput 16S amplicon sequencing. DNA was extracted from sediments and water column in pockmark and background zones. NGS libraries were prepared with fusion primers for V4 variable region (Caporaso et al., 2012) and sequenced on the MiSeq system. Results well correlated with new data obtained from the analysis of the intensity of microbial processes. The study was financed by the Russian Scientific Fund (grant 14-37-00047). Caporaso JG, Lauber CL, Walters WA, Berg-Lyons D, Huntley J, Fierer N, Owens SM, Betley J, Fraser L, Bauer M, Gormley N, Gilbert JA, Smith G, Knight R. Ultra-high-throughput microbial community analysis on the Illumina HiSeq and MiSeq platforms. ISME J. 2012 Aug;6(8):1621-4

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

Porta, Miquel; Facultat de Medicina, Universitat Autonoma de Barcelona; CIBER en Epidemiologia y Salud Publica

Background: The relationships between social factors and body concentrations of environmental chemical agents are unknown in many human populations. Some chemical compounds may play an etiopathogenic role in pancreatic cancer. Objective: To analyze the relationships between occupational social class and serum concentrations of seven selected organochlorine compounds (OCs) in exocrine pancreatic cancer: dichlorodiphenyltrichloroethane (p,p'-DDT), dichlorodiphenyldichloroethene (p,p'-DDE), 3 polychlorinated biphenyls (PCBs), hexachlorobenzene, and {beta}-hexachlorocyclohexane. Methods: Incident cases of exocrine pancreatic cancer were prospectively identified, and interviewed face-to-face during hospital admission (n=135). Serum concentrations of OCs were analyzed by high-resolution gas chromatography with electron-capture detection. Social class was classified according to occupation.more » Results: Multivariate-adjusted concentrations of all seven compounds were higher in occupational social classes IV-V (the less affluent) than in classes I-II; they were higher as well in class III than in classes I-II for four compounds. Concentrations of six OCs were higher in manual workers than in non-manual workers (p<0.05 for PCBs). Social class explained statistically between 3.7% and 5.7% of the variability in concentrations of PCBs, and 2% or less variability in the other OCs. Conclusions: Concentrations of most OCs were higher in the less affluent occupational social classes. In pancreatic cancer the putative causal role of these persistent organic pollutants may not be independent of social class. There is a need to integrate evidence on the contribution of different social processes and environmental chemical exposures to the etiology of pancreatic and other cancers.« less

Artifacts in measuring aerosol uptake kinetics: the roles of time, concentration and adsorption

NASA Astrophysics Data System (ADS)

Renbaum, L. H.; Smith, G. D.

2011-03-01

In laboratory studies of organic aerosol particles reacting with gas-phase oxidants, high concentrations of radicals are often used to study on the timescale of seconds reactions which may be occurring over days or weeks in the troposphere. Implicit in this approach is the assumption that radical concentration and time are interchangeable parameters, though this has not been established. Here, the kinetics of OH- and Cl-initiated oxidation reactions of model single-component liquid organic aerosols (squalane, brassidic acid and 2-octyldodecanoic acid) are studied by varying separately the radical concentration and the reaction time. Two separate flow tubes with residence times of 2 and 66 s are used, and [OH] and [Cl] are varied by adjusting either the laser photolysis fluence or the radical precursor concentration ([O3] or [Cl2], respectively) used to generate the radicals. It is found that the rates measured by varying the radical concentration and the reaction time are equal only if the precursor concentrations are the same in the two approaches. Further, the rates depend on the concentrations of the precursor species with a Langmuir-type functional form suggesting that O3 and Cl2 saturate the surface of the liquid particles. It is believed that the presence of O3 inhibits the rate of OH reaction, perhaps by reacting with OH radicals or blocking surface sites, while Cl2 enhances the rate of Cl reaction by participating in a radical chain mechanism. These results have important implications for laboratory experiments in which high concentrations of gas-phase oxidants are used to study atmospheric reactions over short timescales and may explain the variability in recent measurements of the reactive uptake of OH on squalane particles in reactor systems used in this and other laboratories.

Microfabricated gas chromatograph for on-site determinations of TCE in indoor air arising from vapor intrusion. 2. Spatial/temporal monitoring.

PubMed

Kim, Sun Kyu; Burris, David R; Bryant-Genevier, Jonathan; Gorder, Kyle A; Dettenmaier, Erik M; Zellers, Edward T

2012-06-05

We demonstrate the use of two prototype Si-microfabricated gas chromatographs (μGC) for continuous, short-term measurements of indoor trichloroethylene (TCE) vapor concentrations related to the investigation of TCE vapor intrusion (VI) in two houses. In the first house, with documented TCE VI, temporal variations in TCE air concentrations were monitored continuously for up to 48 h near the primary VI entry location under different levels of induced differential pressure (relative to the subslab). Concentrations ranged from 0.23 to 27 ppb by volume (1.2-150 μg/m(3)), and concentration trends agreed closely with those determined from concurrent reference samples. The sensitivity and temporal resolution of the measurements were sufficiently high to detect transient fluctuations in concentration resulting from short-term changes in variables affecting the extent of VI. Spatial monitoring showed a decreasing TCE concentration gradient with increasing distance from the primary VI entry location. In the second house, with no TCE VI, spatial profiles derived from the μGC prototype data revealed an intentionally hidden source of TCE within a closet, demonstrating the capability for locating non-VI sources. Concentrations measured in this house ranged from 0.51 to 56 ppb (2.7-300 μg/m(3)), in good agreement with reference method values. This first field demonstration of μGC technology for automated, near-real-time, selective VOC monitoring at low- or subppb levels augurs well for its use in short- and long-term on-site analysis of indoor air in support of VI assessments.

Positional stability as the light emission limit in sonoluminescence with sulfuric acid.

PubMed

Urteaga, Raúl; Dellavale, Damián H; Puente, Gabriela F; Bonetto, Fabián J

2007-11-01

We studied a single bubble sonoluminescence system consisting of an argon bubble in a sulfuric acid aq. solution. We experimentally determined the relevant variables of the system. We also measured the bubble position, extent of the bubble orbits, and light intensity as a function of acoustic pressure for different argon concentrations. We find that the Bjerknes force is responsible for the bubble mean position and this imposes a limitation in the maximum acoustic pressure that can be applied to the bubble. The Rayleigh-Taylor instability does not play a role in this system and, at a given gas concentration, the SL intensity depends more on the bubble time of collapse than any other investigated parameter.

Amines in boreal forest air at SMEAR II station in Finland

NASA Astrophysics Data System (ADS)

Hemmilä, Marja; Hellén, Heidi; Virkkula, Aki; Makkonen, Ulla; Praplan, Arnaud P.; Kontkanen, Jenni; Ahonen, Lauri; Kulmala, Markku; Hakola, Hannele

2018-05-01

We measured amines in boreal forest air in Finland both in gas and particle phases with 1 h time resolution using an online ion chromatograph (instrument for Measuring AeRosols and Gases in Ambient Air - MARGA) connected to an electrospray ionization quadrupole mass spectrometer (MS). The developed MARGA-MS method was able to separate and detect seven different amines: monomethylamine (MMA), dimethylamine (DMA), trimethylamine (TMA), ethylamine (EA), diethylamine (DEA), propylamine (PA), and butylamine (BA). The detection limits of the method for amines were low (0.2-3.1 ng m-3), the accuracy of IC-MS analysis was 11-37 %, and the precision 10-15 %. The proper measurements in the boreal forest covered about 8 weeks between March and December 2015. The amines were found to be an inhomogeneous group of compounds, showing different seasonal and diurnal variability. Total MMA (MMA(tot)) peaked together with the sum of ammonia and ammonium ions already in March. In March, monthly means for MMA were < 2.4 and 6.8 ± 9.1 ng m-3 in gas and aerosol phases, respectively, and for NH3 and NH4+ these were 52 ± 16 and 425 ± 371 ng m-3, respectively. Monthly medians in March for MMA(tot), NH3, and NH4+ were < 2.4, 19 and 90 ng m-3, respectively. DMA(tot) and TMA(tot) had summer maxima indicating biogenic sources. We observed diurnal variation for DMA(tot) but not for TMA(tot). The highest concentrations of these compounds were measured in July. Then, monthly means for DMA were < 3.1 and 8.4 ± 3.1 ng m-3 in gas and aerosol phases, respectively, and for TMA these were 0.4 ± 0.1 and 1.8 ± 0.5 ng m-3. Monthly medians in July for DMA were below the detection limit (DL) and 4.9 ng m-3 in gas and aerosol phases, respectively, and for TMA these were 0.4 and 1.4 ng m-3. When relative humidity of air was > 90 %, gas-phase DMA correlated well with 1.1-2 nm particle number concentration (R2 = 0.63) suggesting that it participates in atmospheric clustering. EA concentrations were low all the time. Its July means were < 0.36 and 0.4 ± 0.4 ng m-3 in gas and aerosol phases, respectively, but individual concentration data correlated well with monoterpene concentrations in July. Monthly means of PA and BA were below detection limits at all times.

Patterns in stream greenhouse gas dynamics from mountains to plains in northcentral Wyoming

NASA Astrophysics Data System (ADS)

Kuhn, C.; Bettigole, C.; Glick, H. B.; Seegmiller, L.; Oliver, C. D.; Raymond, P.

2017-09-01

Quantification of small stream contributions to global carbon cycling is key to understanding how freshwater systems transmit and transform carbon between terrestrial and atmospheric pools. To date, greenhouse gas emissions of carbon dioxide and methane from freshwaters, particularly in mountainous regions, remain poorly characterized due to a lack of direct field observations. Using a unique longitudinal approach, we conducted field surveys across two ecoregions (Middle Rockies and Great Plains) in the Clear Creek watershed, a subwatershed of Wyoming's Powder River Basin. We took direct measurements of stream gases using headspace sampling at 30 sites (8 June to 23 October). We observed the lowest and most variable concentrations in headwaters, which flow through a federally designated alpine wilderness area. By contrast, the Great Plains exhibited 1.45 and 4 times higher pCO2 and pCH4 concentrations and the relative contributions of methane increased downstream. Fluxes during snowmelt were 45% and 58% higher for CO2 and CH4 than during base flow but overall were lower than estimates for other systems. Variability for pCO2 was highest during late summer and in the uppermost sections of the headwaters. The high heterogeneity and common undersaturation observed through space and time, especially in the mountains, suggest that downscaled regional estimates may fail to capture variability in fluxes observed at these smaller scales. Based on these results, we strongly recommend higher resolution time series studies and increased scrutiny of systems at near equilibrium, inclusive of winter storage and ice-off events, to improve our understanding of the effects of seasonal dynamics on these processes.

Variable leak gas source

DOEpatents

Henderson, Timothy M.; Wuttke, Gilbert H.

1977-01-01

A variable leak gas source and a method for obtaining the same which includes filling a quantity of hollow glass micro-spheres with a gas, storing said quantity in a confined chamber having a controllable outlet, heating said chamber above room temperature, and controlling the temperature of said chamber to control the quantity of gas passing out of said controllable outlet. Individual gas filled spheres may be utilized for calibration purposes by breaking a sphere having a known quantity of a known gas to calibrate a gas detection apparatus.

Plasma processing of large curved surfaces for superconducting rf cavity modification

DOE PAGES

Upadhyay, J.; Im, Do; Popović, S.; ...

2014-12-15

In this study, plasma based surface modification of niobium is a promising alternative to wet etching of superconducting radio frequency (SRF) cavities. The development of the technology based on Cl 2/Ar plasma etching has to address several crucial parameters which influence the etching rate and surface roughness, and eventually, determine cavity performance. This includes dependence of the process on the frequency of the RF generator, gas pressure, power level, the driven (inner) electrode configuration, and the chlorine concentration in the gas mixture during plasma processing. To demonstrate surface layer removal in the asymmetric non-planar geometry, we are using a simplemore » cylindrical cavity with 8 ports symmetrically distributed over the cylinder. The ports are used for diagnosing the plasma parameters and as holders for the samples to be etched. The etching rate is highly correlated with the shape of the inner electrode, radio-frequency (RF) circuit elements, chlorine concentration in the Cl 2/Ar gas mixtures, residence time of reactive species and temperature of the cavity. Using cylindrical electrodes with variable radius, large-surface ring-shaped samples and d.c. bias implementation in the external circuit we have demonstrated substantial average etching rates and outlined the possibility to optimize plasma properties with respect to maximum surface processing effect.« less

Modes of interannual variability in northern hemisphere winter atmospheric circulation in CMIP5 models: evaluation, projection and role of external forcing

NASA Astrophysics Data System (ADS)

Frederiksen, Carsten S.; Ying, Kairan; Grainger, Simon; Zheng, Xiaogu

2018-04-01

Models from the coupled model intercomparison project phase 5 (CMIP5) dataset are evaluated for their ability to simulate the dominant slow modes of interannual variability in the Northern Hemisphere atmospheric circulation 500 hPa geopotential height in the twentieth century. A multi-model ensemble of the best 13 models has then been used to identify the leading modes of interannual variability in components related to (1) intraseasonal processes; (2) slowly-varying internal dynamics; and (3) the slowly-varying response to external changes in radiative forcing. Modes in the intraseasonal component are related to intraseasonal variability in the North Atlantic, North Pacific and North American, and Eurasian regions and are little affected by the larger radiative forcing of the Representative Concentration Pathways 8.5 (RCP8.5) scenario. The leading modes in the slow-internal component are related to the El Niño-Southern Oscillation, Pacific North American or Tropical Northern Hemisphere teleconnection, the North Atlantic Oscillation, and the Western Pacific teleconnection pattern. While the structure of these slow-internal modes is little affected by the larger radiative forcing of the RCP8.5 scenario, their explained variance increases in the warmer climate. The leading mode in the slow-external component has a significant trend and is shown to be related predominantly to the climate change trend in the well mixed greenhouse gas concentration during the historical period. This mode is associated with increasing height in the 500 hPa pressure level. A secondary influence on this mode is the radiative forcing due to stratospheric aerosols associated with volcanic eruptions. The second slow-external mode is shown to be also related to radiative forcing due to stratospheric aerosols. Under RCP8.5 there is only one slow-external mode related to greenhouse gas forcing with a trend over four times the historical trend.

Geochemical and isotopic features of geothermal fluids around the Sea of Marmara, NW Turkey

NASA Astrophysics Data System (ADS)

Italiano, Francesco; Woith, Heiko; Seyis, Cemil; Pizzino, Luca; Sciarra, Alessandra

2016-04-01

Earthquake processes provoke modifications of the crust affecting the fluid regime with changes in water level in wells, in temperature and/or chemical composition of groundwaters, in the flow-rate of gas discharges and in their chemical and isotopic composition. In the frame of MARsite (MARsite has received funding from the European Union's Seventh Programme for research, technological development and demonstration under grant agreement No 308417) the relationship between fluids and seismogenesis has been approached collecting geochemical data of local significance and evaluating them in geochemical interpretative models of fluids circulation and interactions as well as defining their behaviour over a seismic-prone area. During three fluid sampling campaigns in 2013, 2014, and 2015 a suite of 120 gas samples were collected from 72 thermal and mineral water springs/wells in the wider Marmara region along the Northern and Southern branches of the North Anatolian Fault Zone (NAFZ). Bubbling gases were collected if available, in all other cases the gas phase was extracted from water samples collected on that purpose. Gas samples were analyzed for the main chemical composition as well as their isotopic composition (He and C). The results highlight that the vented gases are a binary mixture of two end-members having nitrogen and carbon dioxide as main components. The geochemical features of the gas phase are the result of several processes that have modified their pristine composition. Atmospheric and deep-originated volatiles mix at variable extents and interact with cold and hot groundwaters. CO2 is normally the main gas species. But it's concentration may decrease due to gas-water interactions (GWI) increasing the relative concentration of N2 and other less soluble gases. A high CO2 content indicates minor interactions. Thus, the easier and faster the pathways are from the deep layers toward the Earth's surface, the lower are the interactions. The volatiles keep their pristine composition. Faults represent a preferential way for rising volatiles due to local high permeability. 3He/4He ratios ranging from 0.1 to 4.8Ra (Ra = 3He/4He atmospheric ratio) indicate the presence of mantle contribution. The highest ratio was found at the eastern end of the Ganos fault. Mantle degassing is not obvious in non-volcanic areas, however the measured helium isotopic ratios indicate mantle degassing likely through lithospheric faults. All the information we got indicate that the fluids circulating over this area are the result of fluid mixing at variable extents of three end-members: mantle, crust and atmosphere.

Impacts of climate variability and future climate change on harmful algal blooms and human health.

PubMed

Moore, Stephanie K; Trainer, Vera L; Mantua, Nathan J; Parker, Micaela S; Laws, Edward A; Backer, Lorraine C; Fleming, Lora E

2008-11-07

Anthropogenically-derived increases in atmospheric greenhouse gas concentrations have been implicated in recent climate change, and are projected to substantially impact the climate on a global scale in the future. For marine and freshwater systems, increasing concentrations of greenhouse gases are expected to increase surface temperatures, lower pH, and cause changes to vertical mixing, upwelling, precipitation, and evaporation patterns. The potential consequences of these changes for harmful algal blooms (HABs) have received relatively little attention and are not well understood. Given the apparent increase in HABs around the world and the potential for greater problems as a result of climate change and ocean acidification, substantial research is needed to evaluate the direct and indirect associations between HABs, climate change, ocean acidification, and human health. This research will require a multidisciplinary approach utilizing expertise in climatology, oceanography, biology, epidemiology, and other disciplines. We review the interactions between selected patterns of large-scale climate variability and climate change, oceanic conditions, and harmful algae.

Gas dynamics and mixture formation in swirled flows with precession of air flow

NASA Astrophysics Data System (ADS)

Tretyakov, V. V.; Sviridenkov, A. A.

2017-10-01

The effect of precessing air flow on the processes of mixture formation in the wake of the front winding devices of the combustion chambers is considered. Visual observations have shown that at different times the shape of the atomized jet is highly variable and has signs of precessing motion. The experimental data on the distribution of the velocity and concentration fields of the droplet fuel in the working volume of the flame tube of a typical combustion chamber are obtained. The method of calculating flows consisted in integrating the complete system of Reynolds equations written in Euler variables and closed with the two-parameter model of turbulence k-ε. Calculation of the concentration fields of droplet and vapor fuel is based on the use of models for disintegration into droplets of fuel jets, fragmentation of droplets and analysis of motion and evaporation of individual droplets in the air flow. Comparison of the calculation results with experimental data showed their good agreement.

Impacts of climate variability and future climate change on harmful algal blooms and human health

PubMed Central

Moore, Stephanie K; Trainer, Vera L; Mantua, Nathan J; Parker, Micaela S; Laws, Edward A; Backer, Lorraine C; Fleming, Lora E

2008-01-01

Anthropogenically-derived increases in atmospheric greenhouse gas concentrations have been implicated in recent climate change, and are projected to substantially impact the climate on a global scale in the future. For marine and freshwater systems, increasing concentrations of greenhouse gases are expected to increase surface temperatures, lower pH, and cause changes to vertical mixing, upwelling, precipitation, and evaporation patterns. The potential consequences of these changes for harmful algal blooms (HABs) have received relatively little attention and are not well understood. Given the apparent increase in HABs around the world and the potential for greater problems as a result of climate change and ocean acidification, substantial research is needed to evaluate the direct and indirect associations between HABs, climate change, ocean acidification, and human health. This research will require a multidisciplinary approach utilizing expertise in climatology, oceanography, biology, epidemiology, and other disciplines. We review the interactions between selected patterns of large-scale climate variability and climate change, oceanic conditions, and harmful algae. PMID:19025675

Amount of gas hydrate estimated from compressional- and shear-wave velocities at the JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well

USGS Publications Warehouse

Lee, M.W.

1999-01-01

The amount of in situ gas hydrate concentrated in the sediment pore space at the JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well was estimated by using compressional-wave (P-wave) and shear-wave (S-wave) downhole log measurements. A weighted equation developed for relating the amount of gas hydrate concentrated in the pore space of unconsolidated sediments to the increase of seismic velocities was applied to the acoustic logs with porosities derived from the formation density log. A weight of 1.56 (W=1.56) and the exponent of 1 (n=1) provided consistent estimates of gas hydrate concentration from the S-wave and the P-wave logs. Gas hydrate concentration is as much as 80% in the pore spaces, and the average gas hydrate concentration within the gas-hydrate-bearing section from 897 m to 1110 m (excluding zones where there is no gas hydrate) was calculated at 39.0% when using P-wave data and 37.8% when using S-wave data.

Time-Lapse Geophysical Measurements targeting Spatial and Temporal Variability in Biogenic Gas Production from Peat Soils in a Hydrologically Controlled Wetland in the Florida Everglades

NASA Astrophysics Data System (ADS)

Wright, W. J.; Shahan, T.; Sharp, N.; Comas, X.

2015-12-01

Peat soils are known to release globally significant amounts of methane (CH4) and carbon dioxide (CO2) to the atmosphere. However, uncertainties still remain regarding the spatio-temporal distribution of gas accumulations and triggering mechanisms of gas releasing events. Furthermore, most research on peatland gas dynamics has traditionally been focused on high latitude peatlands. Therefore, understanding gas dynamics in low-latitude peatlands (e.g. the Florida Everglades) is key to global climate research. Recent studies in the Everglades have demonstrated that biogenic gas flux values may vary when considering different temporal and spatial scales of measurements. The work presented here targets spatial variability in gas production and release at the plot scale in an approximately 85 m2 area, and targets temporal variability with data collected during the spring months of two different years. This study is located in the Loxahatchee Impoundment Landscape Assessment (LILA), a hydrologically controlled, landscape scale (30 Ha) model of the Florida Everglades. Ground penetrating radar (GPR) has been used in the past to investigate biogenic gas dynamics in peat soils, and is used in this study to monitor changes of in situ gas storage. Each year, a grid of GPR profiles was collected to image changes in gas distribution in 2d on a weekly basis, and several flux chambers outfitted with time-lapse cameras captured high resolution (hourly) gas flux measurements inside the GPR grid. Combining these methods allows us to use a mass balance approach to estimate spatial variability in gas production rates, and capture temporal variability in gas flux rates.

Polycyclic Aromatic Hydrocarbons in Residential Dust: Sources of Variability

PubMed Central

Metayer, Catherine; Petreas, Myrto; Does, Monique; Buffler, Patricia A.; Rappaport, Stephen M.

2013-01-01

Background: There is interest in using residential dust to estimate human exposure to environmental contaminants. Objectives: We aimed to characterize the sources of variability for polycyclic aromatic hydrocarbons (PAHs) in residential dust and provide guidance for investigators who plan to use residential dust to assess exposure to PAHs. Methods: We collected repeat dust samples from 293 households in the Northern California Childhood Leukemia Study during two sampling rounds (from 2001 through 2007 and during 2010) using household vacuum cleaners, and measured 12 PAHs using gas chromatography–mass spectrometry. We used a random- and a mixed-effects model for each PAH to apportion observed variance into four components and to identify sources of variability. Results: Median concentrations for individual PAHs ranged from 10 to 190 ng/g of dust. For each PAH, total variance was apportioned into regional variability (1–9%), intraregional between-household variability (24–48%), within-household variability over time (41–57%), and within-sample analytical variability (2–33%). Regional differences in PAH dust levels were associated with estimated ambient air concentrations of PAH. Intraregional differences between households were associated with the residential construction date and the smoking habits of residents. For some PAHs, a decreasing time trend explained a modest fraction of the within-household variability; however, most of the within-household variability was unaccounted for by our mixed-effects models. Within-household differences between sampling rounds were largest when the interval between dust sample collections was at least 6 years in duration. Conclusions: Our findings indicate that it may be feasible to use residential dust for retrospective assessment of PAH exposures in studies of health effects. PMID:23461863

Recharge processes and vertical transfer investigated through long-term monitoring of dissolved gases in shallow groundwater

NASA Astrophysics Data System (ADS)

de Montety, V.; Aquilina, L.; Labasque, T.; Chatton, E.; Fovet, O.; Ruiz, L.; Fourré, E.; de Dreuzy, J. R.

2018-05-01

We investigated temporal variations and vertical evolution of dissolved gaseous tracers (CFC-11, CFC-12, SF6, and noble gases), as well as 3H/3He ratio to determine groundwater recharge processes of a shallow unconfined, hard-rock aquifer in an agricultural catchment. We sampled dissolved gas concentration at 4 locations along the hillslope of a small experimental watershed, over 6 hydrological years, between 2 and 6 times per years, for a total of 20 field campaigns. We collected groundwater samples in the fluctuation zone and the permanently saturated zone using piezometers from 5 to 20 m deep. The purpose of this work is i) to assess the benefits of using gaseous tracers like CFCs and SF6 to study very young groundwater with flows suspected to be heterogeneous and variable in time, ii) to characterize the processes that control dissolved gas concentrations in groundwater during the recharge of the aquifer, and iii) to understand the evolution of recharge flow processes by repeated measurement campaigns, taking advantage of a long monitoring in a site devoted to recharge processes investigation. Gas tracer profiles are compared at different location of the catchment and for different hydrologic conditions. In addition, we compare results from CFCs and 3H/3He analysis to define the flow model that best explains tracer concentrations. Then we discuss the influence of recharge events on tracer concentrations and residence time and propose a temporal evolution of residence times for the unsaturated zone and the permanently saturated zone. These results are used to gain a better understanding of the conceptual model of the catchment and flow processes especially during recharge events.

Comparison of an infrared anaesthetic agent analyser (Datex-Ohmeda) with refractometry for measurement of isoflurane, sevoflurane and desflurane concentrations.

PubMed

Rudolff, Andrea S; Moens, Yves P S; Driessen, Bernd; Ambrisko, Tamas D

2014-07-01

To assess agreement between infrared (IR) analysers and a refractometer for measurements of isoflurane, sevoflurane and desflurane concentrations and to demonstrate the effect of customized calibration of IR analysers. In vitro experiment. Six IR anaesthetic monitors (Datex-Ohmeda) and a single portable refractometer (Riken). Both devices were calibrated following the manufacturer's recommendations. Gas samples were collected at common gas outlets of anaesthesia machines. A range of agent concentrations was produced by stepwise changes in dial settings: isoflurane (0-5% in 0.5% increments), sevoflurane (0-8% in 1% increments), or desflurane (0-18% in 2% increments). Oxygen flow was 2 L minute(-1) . The orders of testing IR analysers, agents and dial settings were randomized. Duplicate measurements were performed at each setting. The entire procedure was repeated 24 hours later. Bland-Altman analysis was performed. Measurements on day-1 were used to yield calibration equations (IR measurements as dependent and refractometry measurements as independent variables), which were used to modify the IR measurements on day-2. Bias ± limits of agreement for isoflurane, sevoflurane and desflurane were 0.2 ± 0.3, 0.1 ± 0.4 and 0.7 ± 0.9 volume%, respectively. There were significant linear relationships between differences and means for all agents. The IR analysers became less accurate at higher gas concentrations. After customized calibration, the bias became almost zero and the limits of agreement became narrower. If similar IR analysers are used in research studies, they need to be calibrated against a reference method using the agent in question at multiple calibration points overlapping the range of interest. © 2013 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia.

Variable gas leak rate valve

DOEpatents

Eernisse, Errol P.; Peterson, Gary D.

1976-01-01

A variable gas leak rate valve which utilizes a poled piezoelectric element to control opening and closing of the valve. The gas flow may be around a cylindrical rod with a tubular piezoelectric member encircling the rod for seating thereagainst to block passage of gas and for reopening thereof upon application of suitable electrical fields.

Stream macroinvertebrate communities across a gradient of natural gas development in the Fayetteville Shale.

PubMed

Johnson, Erica; Austin, Bradley J; Inlander, Ethan; Gallipeau, Cory; Evans-White, Michelle A; Entrekin, Sally

2015-10-15

Oil and gas extraction in shale plays expanded rapidly in the U.S. and is projected to expand globally in the coming decades. Arkansas has doubled the number of gas wells in the state since 2005 mostly by extracting gas from the Fayetteville Shale with activity concentrated in mixed pasture-deciduous forests. Concentrated well pads in close proximity to streams could have adverse effects on stream water quality and biota if sedimentation associated with developing infrastructure or contamination from fracturing fluid and waste occurs. Cumulative effects of gas activity and local habitat conditions on macroinvertebrate communities were investigated across a gradient of gas well activity (0.2-3.6 wells per km(2)) in ten stream catchments in spring 2010 and 2011. In 2010, macroinvertebrate density was positively related to well pad inverse flowpath distance from streams (r=0.84, p<0.001). Relatively tolerant mayflies Baetis and Caenis (r=0.64, p=0.04), filtering hydropsychid caddisflies (r=0.73, p=0.01), and chironomid midge densities (r=0.79, p=0.008) also increased in streams where more well pads were closer to stream channels. Macroinvertebrate trophic structure reflected environmental conditions with greater sediment and primary production in streams with more gas activity close to streams. However, stream water turbidity (r=0.69, p=0.02) and chlorophyll a (r=0.89, p<0.001) were the only in-stream variables correlated with gas well activities. In 2011, a year with record spring flooding, a different pattern emerged where mayfly density (p=0.74, p=0.01) and mayfly, stonefly, and caddisfly richness (r=0.78, p=0.008) increased in streams with greater well density and less silt cover. Hydrology and well pad placement in a catchment may interact to result in different relationships between biota and catchment activity between the two sample years. Our data show evidence of different macroinvertebrate communities expressed in catchments with different levels of gas activity that reinforce the need for more quantitative analyses of cumulative freshwater-effects from oil and gas development. Copyright © 2015 Elsevier B.V. All rights reserved.

Nebulization reflux concentrator

NASA Technical Reports Server (NTRS)

Collins, V. G.; Cofer, W. R., III

1986-01-01

A nebulization reflux concentrator for removing trace gas contaminants from a sample gas is described. Sample gas from a gas supply is drawn by a suction source into a vessel. The gas enters the vessel through an atomizing nozzle, thereby atomizing and entraining a scrubbing liquid solvent drawn through a siphon tube from a scrubbing liquid reservoir. The gas and entrained liquid rise through a concentrator and impinge upon a solvent phobic filter, whereby purified gas exits through the filter housing and contaminated liquid coalesces on the solvent phobic filter and falls into the reservoir.

Optimisation of gellan gum edible coating for ready-to-eat mango (Mangifera indica L.) bars.

PubMed

Danalache, Florina; Carvalho, Claudia Y; Alves, Vitor D; Moldão-Martins, Margarida; Mata, Paulina

2016-03-01

The optimisation of an edible coating based on low acyl (L)/high acyl (H) gellan gum for ready-to-eat mango bars was performed through a central composite rotatable design (CCRD). The independent variables were the concentration of gellan (L/H90/10) and the concentration of Ca(2+) in the coating solution, as well as the storage time after coating application. The response variables studied were the coating thickness, mango bars firmness, syneresis, and colour alterations. Gellan concentration was the independent variable that most influenced the thickness of the coating. Syneresis was quite low for the conditions tested (<1.64%). Similarly, the colour alterations were low during the entire storage time (ΔE<5). Considering the model predictions, 1.0%wt L/H90/10 with addition of 6 mM Ca(2+) could represent the optimal coating formulation for the mango bars. The release of eight volatile compounds from the uncoated and coated mango bars with the selected formulation was analysed by Headspace - Solid Phase Micro Extraction-Gas Chromatography during 9 days of refrigerated storage. This work showed that the coating can improve mango bars sensory characteristics (appearance and firmness) and stability in terms of syneresis, colour and volatiles content during storage increasing the commercial value of the final product. Crown Copyright © 2015. Published by Elsevier B.V. All rights reserved.

Modeling of Blast Furnace with Layered Cohesive Zone

NASA Astrophysics Data System (ADS)

Dong, X. F.; Yu, A. B.; Chew, S. J.; Zulli, P.

2010-04-01

An ironmaking blast furnace (BF) is a moving bed reactor involving counter-, co-, and cross-current flows of gas, powder, liquids, and solids, coupled with heat exchange and chemical reactions. The behavior of multiple phases directly affects the stability and productivity of the furnace. In the present study, a mathematical model is proposed to describe the behavior of fluid flow, heat and mass transfer, as well as chemical reactions in a BF, in which gas, solid, and liquid phases affect each other through interaction forces, and their flows are competing for the space available. Process variables that characterize the internal furnace state, such as reduction degree, reducing gas and burden concentrations, as well as gas and condensed phase temperatures, have been described quantitatively. In particular, different treatments of the cohesive zone (CZ), i.e., layered, isotropic, and anisotropic nonlayered, are discussed, and their influence on simulation results is compared. The results show that predicted fluid flow and thermochemical phenomena within and around the CZ and in the lower part of the BF are different for different treatments. The layered CZ treatment corresponds to the layered charging of burden and naturally can predict the CZ as a gas distributor and liquid generator.

CO2 Absorption from Biogas by Glycerol: Conducted in Semi-Batch Bubble Column

NASA Astrophysics Data System (ADS)

puji lestari, Pratiwi; Mindaryani, Aswati; Wirawan, S. K.

2018-03-01

Biogas is a renewable energy source that has been developed recently. The main contents of Biogas itself are Methane and carbon dioxide (CO2) where Methane is the main component of biogas with CO2 as the highest impurities. The quality of biogas depends on the CO2 content, the lower CO2 levels, the higher biogas quality. Absorption is one of the methods to reduce CO2 level. The selections of absorbent and appropriate operating parameters are important factors in the CO2 absorption from biogas. This study aimed to find out the design parameters for CO2 absorption using glycerol that represented by the overall mass transfer coefficient (KLa) and Henry’s constant (H). This study was conducted in semi-batch bubble column. Mixed gas was contacted with glycerol in a bubble column. The concentration of CO2 in the feed gas inlet and outlet columns were analysed by Gas Chromatograph. The variables observed in this study were superficial gas velocity and temperatures. The results showed that higher superficial gas velocity and lower temperature increased the rate of absorption process and the amount of CO2 absorbed.

Hydrogen production by the hyperthermophilic bacterium Thermotoga maritima Part II: modeling and experimental approaches for hydrogen production.

PubMed

Auria, Richard; Boileau, Céline; Davidson, Sylvain; Casalot, Laurence; Christen, Pierre; Liebgott, Pierre Pol; Combet-Blanc, Yannick

2016-01-01

Thermotoga maritima is a hyperthermophilic bacterium known to produce hydrogen from a large variety of substrates. The aim of the present study is to propose a mathematical model incorporating kinetics of growth, consumption of substrates, product formations, and inhibition by hydrogen in order to predict hydrogen production depending on defined culture conditions. Our mathematical model, incorporating data concerning growth, substrates, and products, was developed to predict hydrogen production from batch fermentations of the hyperthermophilic bacterium, T. maritima . It includes the inhibition by hydrogen and the liquid-to-gas mass transfer of H 2 , CO 2 , and H 2 S. Most kinetic parameters of the model were obtained from batch experiments without any fitting. The mathematical model is adequate for glucose, yeast extract, and thiosulfate concentrations ranging from 2.5 to 20 mmol/L, 0.2-0.5 g/L, or 0.01-0.06 mmol/L, respectively, corresponding to one of these compounds being the growth-limiting factor of T. maritima . When glucose, yeast extract, and thiosulfate concentrations are all higher than these ranges, the model overestimates all the variables. In the window of the model validity, predictions of the model show that the combination of both variables (increase in limiting factor concentration and in inlet gas stream) leads up to a twofold increase of the maximum H 2 -specific productivity with the lowest inhibition. A mathematical model predicting H 2 production in T. maritima was successfully designed and confirmed in this study. However, it shows the limit of validity of such mathematical models. Their limit of applicability must take into account the range of validity in which the parameters were established.

A new exposure metric for traffic-related air pollution? An analysis of determinants of hopanes in settled indoor house dust.

PubMed

Sbihi, Hind; Brook, Jeffrey R; Allen, Ryan W; Curran, Jason H; Dell, Sharon; Mandhane, Piush; Scott, James A; Sears, Malcolm R; Subbarao, Padmaja; Takaro, Timothy K; Turvey, Stuart E; Wheeler, Amanda J; Brauer, Michael

2013-06-19

Exposure to traffic-related air pollution (TRAP) can adversely impact health but epidemiologic studies are limited in their abilities to assess long-term exposures and incorporate variability in indoor pollutant infiltration. In order to examine settled house dust levels of hopanes, engine lubricating oil byproducts found in vehicle exhaust, as a novel TRAP exposure measure, dust samples were collected from 171 homes in five Canadian cities and analyzed by gas chromatography-mass spectrometry. To evaluate source contributions, the relative abundance of the highest concentration hopane monomer in house dust was compared to that in outdoor air. Geographic variables related to TRAP emissions and outdoor NO2 concentrations from city-specific TRAP land use regression (LUR) models were calculated at each georeferenced residence location and assessed as predictors of variability in dust hopanes. Hopanes relative abundance in house dust and ambient air were significantly correlated (Pearson's r=0.48, p<0.05), suggesting that dust hopanes likely result from traffic emissions. The proportion of variance in dust hopanes concentrations explained by LUR NO2 was less than 10% in Vancouver, Winnipeg and Toronto while the correlations in Edmonton and Windsor explained 20 to 40% of the variance. Modeling with household factors such as air conditioning and shoe removal along with geographic predictors related to TRAP generally increased the proportion of explained variability (10-80%) in measured indoor hopanes dust levels. Hopanes can consistently be detected in house dust and may be a useful tracer of TRAP exposure if determinants of their spatiotemporal variability are well-characterized, and when home-specific factors are considered.

A new exposure metric for traffic-related air pollution? An analysis of determinants of hopanes in settled indoor house dust

PubMed Central

2013-01-01

Background Exposure to traffic-related air pollution (TRAP) can adversely impact health but epidemiologic studies are limited in their abilities to assess long-term exposures and incorporate variability in indoor pollutant infiltration. Methods In order to examine settled house dust levels of hopanes, engine lubricating oil byproducts found in vehicle exhaust, as a novel TRAP exposure measure, dust samples were collected from 171 homes in five Canadian cities and analyzed by gas chromatography–mass spectrometry. To evaluate source contributions, the relative abundance of the highest concentration hopane monomer in house dust was compared to that in outdoor air. Geographic variables related to TRAP emissions and outdoor NO2 concentrations from city-specific TRAP land use regression (LUR) models were calculated at each georeferenced residence location and assessed as predictors of variability in dust hopanes. Results Hopanes relative abundance in house dust and ambient air were significantly correlated (Pearson’s r=0.48, p<0.05), suggesting that dust hopanes likely result from traffic emissions. The proportion of variance in dust hopanes concentrations explained by LUR NO2 was less than 10% in Vancouver, Winnipeg and Toronto while the correlations in Edmonton and Windsor explained 20 to 40% of the variance. Modeling with household factors such as air conditioning and shoe removal along with geographic predictors related to TRAP generally increased the proportion of explained variability (10-80%) in measured indoor hopanes dust levels. Conclusions Hopanes can consistently be detected in house dust and may be a useful tracer of TRAP exposure if determinants of their spatiotemporal variability are well-characterized, and when home-specific factors are considered. PMID:23782977

The distribution of methylated sulfur compounds, DMS and DMSP, in Canadian subarctic and Arctic marine waters during summer 2015

NASA Astrophysics Data System (ADS)

Jarníková, Tereza; Dacey, John; Lizotte, Martine; Levasseur, Maurice; Tortell, Philippe

2018-04-01

We present seawater concentrations of dimethyl sulfide (DMS) and dimethylsulfoniopropionate (DMSP) measured across a transect from the Labrador Sea to the Canadian Arctic Archipelago during summer 2015. Using an automated ship-board gas chromatography system and a membrane-inlet mass spectrometer, we measured a wide range of DMS (˜ 1 to 18 nM) and DMSP (˜ 1 to 150 nM) concentrations. The highest DMS and DMSP concentrations occurred in a localized region of Baffin Bay, where surface waters were characterized by high chlorophyll a (chl a) fluorescence, indicative of elevated phytoplankton biomass. Across the full sampling transect, there were only weak relationships between DMS(P), chl a fluorescence and other measured variables, including positive relationships between DMSP : chl a ratios and several taxonomic marker pigments, and elevated DMS(P) concentrations in partially ice-covered areas. Our high spatial resolution measurements allowed us to examine DMS variability over small scales (< 1 km), documenting strong DMS concentration gradients across surface hydrographic frontal features. Our new observations fill in an important observational gap in the Arctic Ocean and provide additional information on sea-air DMS fluxes from this ocean region. In addition, this study constitutes a significant contribution to the existing Arctic DMS(P) dataset and provides a baseline for future measurements in the region.

Deep-Water Acoustic Anomalies from Methane Hydrate in the Bering Sea

USGS Publications Warehouse

Wood, Warren T.; Barth, Ginger A.; Scholl, David W.; Lebedeva-Ivanova, Nina

2015-01-01

A recent expedition to the central Bering Sea, one of the most remote locations in the world, has yielded observations confirming gas and gas hydrates in this deep ocean basin. Significant sound speed anomalies found using inversion of pre-stack seismic data are observed in association with variable seismic amplitude anomalies in the thick sediment column. The anomalously low sound speeds below the inferred base of methane hydrate stability indicate the presence of potentially large quantities of gas-phase methane associated with each velocity-amplitude anomaly (VAMP). The data acquired are of such high quality that quantitative estimates of the concentrations of gas hydrates in the upper few hundred meters of sediment are also possible, and analyses are under way to make these estimates. Several VAMPs were specifically targeted in this survey; others were crossed incidentally. Indications of many dozens or hundreds of these features exist throughout the portion of the Bering Sea relevant to the U.S. extended continental shelf (ECS) consistent with the United Nations Convention on the Law of the Sea. 

Electrical properties of methane hydrate + sediment mixtures

USGS Publications Warehouse

Du Frane, Wyatt L.; Stern, Laura A.; Constable, Steven; Weitemeyer, Karen A.; Smith, Megan M; Roberts, Jeffery J.

2015-01-01

Knowledge of the electrical properties of multicomponent systems with gas hydrate, sediments, and pore water is needed to help relate electromagnetic (EM) measurements to specific gas hydrate concentration and distribution patterns in nature. Toward this goal, we built a pressure cell capable of measuring in situ electrical properties of multicomponent systems such that the effects of individual components and mixing relations can be assessed. We first established the temperature-dependent electrical conductivity (σ) of pure, single-phase methane hydrate to be ~5 orders of magnitude lower than seawater, a substantial contrast that can help differentiate hydrate deposits from significantly more conductive water-saturated sediments in EM field surveys. Here we report σ measurements of two-component systems in which methane hydrate is mixed with variable amounts of quartz sand or glass beads. Sand by itself has low σ but is found to increase the overall σ of mixtures with well-connected methane hydrate. Alternatively, the overall σ decreases when sand concentrations are high enough to cause gas hydrate to be poorly connected, indicating that hydrate grains provide the primary conduction path. Our measurements suggest that impurities from sand induce chemical interactions and/or doping effects that result in higher electrical conductivity with lower temperature dependence. These results can be used in the modeling of massive or two-phase gas-hydrate-bearing systems devoid of conductive pore water. Further experiments that include a free water phase are the necessary next steps toward developing complex models relevant to most natural systems.

Gas/particle partitioning of 2-methyltetrols and levoglucosan at an urban site in Denver.

PubMed

Xie, Mingjie; Hannigan, Michael P; Barsanti, Kelley C

2014-01-01

In this study, a medium volume sampler incorporating quartz fiber filters (QFFs) and a polyurethane foam (PUF)/XAD/PUF sandwich (PXP) was used to collect 2-methyltetrols (isoprene tracer) and levoglucosan (biomass burning tracer) in gaseous and particle (PM2.5) phases. The measured gas/particle (G/P) partitioning coefficients (Kp,OMm) of 2-methyltetrols and levoglucosan were calculated and compared to their predicted G/P partitioning coefficients (Kp,OMt) based on an absorptive partitioning theory. The breakthrough experiments showed that gas-phase 2-methyltetrols and levoglucosan could be collected using the PXP or PUF adsorbent alone, with low breakthrough; however, the recoveries of levoglucosan in PXP samples were lower than 70% (average of 51.9–63.3%). The concentration ratios of 2-methyltetrols and levoglucosan in the gas phase to those in the particle phase were often close to or higher than unity in summer, indicating that these polar species are semi-volatile and their G/P partitioning should be considered when applying particle-phase data for source apportionment. The Kp,OMm values of 2-methyltetrols had small variability in summer Denver, which was ascribed to large variations in concentrations of particulate organic matter (5.14 ± 3.29 μg m–3) and small changes in ambient temperature (21.8 ± 4.05 °C). The regression between log Kp,OMm and log Kp,OMt suggested that the absorptive G/P partitioning theory could reasonably predict the measured G/P partitioning of levoglucosan in ambient samples.

Investigation into adsorption and photocatalytic degradation of gaseous benzene in an annular fluidized bed photocatalytic reactor.

PubMed

Geng, Qijin; Tang, Shankang; Wang, Lintong; Zhang, Yunchen

2015-01-01

The adsorption and photocatalytic degradation of gaseous benzene were investigated considering the operating variables and kinetic mechanism using nano-titania agglomerates in an annular fluidized bed photocatalytic reactor (AFBPR) designed. The special adsorption equilibrium constant, adsorption active sites, and apparent reaction rate coefficient of benzene were determined by linear regression analysis at various gas velocities and relative humidities (RH). Based on a series of photocatalytic degradation kinetic equations, the influences of operating variables on degradation efficiency, apparent reaction rate coefficient and half-life were explored. The findings indicated that the operating variables have obviously influenced the adsorption/photocatalytic degradation and corresponding kinetic parameters. In the photocatalytic degradation process, the relationship between photocatalytic degradation efficiency and RH indicated that water molecules have a dual-function which was related to the structure characteristics of benzene. The optimal operating conditions for photocatalytic degradation of gaseous benzene in AFBPR were determined as the fluidization number at 1.9 and RH required related to benzene concentration. This investigation highlights the importance of controlling RH and benzene concentration in order to obtain the desired synergy effect in photocatalytic degradation processes.

Pollutant exposures from natural gas cooking burners: a simulation-based assessment for Southern California.

PubMed

Logue, Jennifer M; Klepeis, Neil E; Lobscheid, Agnes B; Singer, Brett C

2014-01-01

Residential natural gas cooking burners (NGCBs) can emit substantial quantities of pollutants, and they are typically used without venting range hoods. We quantified pollutant concentrations and occupant exposures resulting from NGCB use in California homes. A mass-balance model was applied to estimate time-dependent pollutant concentrations throughout homes in Southern California and the exposure concentrations experienced by individual occupants. We estimated nitrogen dioxide (NO2), carbon monoxide (CO), and formaldehyde (HCHO) concentrations for 1 week each in summer and winter for a representative sample of Southern California homes. The model simulated pollutant emissions from NGCBs as well as NO2 and CO entry from outdoors, dilution throughout the home, and removal by ventilation and deposition. Residence characteristics and outdoor concentrations of NO2 and CO were obtained from available databases. We inferred ventilation rates, occupancy patterns, and burner use from household characteristics. We also explored proximity to the burner(s) and the benefits of using venting range hoods. Replicate model executions using independently generated sets of stochastic variable values yielded estimated pollutant concentration distributions with geometric means varying by <10%. The simulation model estimated that-in homes using NGCBs without coincident use of venting range hoods-62%, 9%, and 53% of occupants are routinely exposed to NO2, CO, and HCHO levels that exceed acute health-based standards and guidelines. NGCB use increased the sample median of the highest simulated 1-hr indoor concentrations by 100, 3,000, and 20 ppb for NO2, CO, and HCHO, respectively. Reducing pollutant exposures from NGCBs should be a public health priority. Simulation results suggest that regular use of even moderately effective venting range hoods would dramatically reduce the percentage of homes in which concentrations exceed health-based standards.

Noble Gas Signatures in Antrim Shale Gas in the Michigan Basin - Assessing Compositional Variability and Transport Processes

NASA Astrophysics Data System (ADS)

Wen, T.; Castro, M. C.; Ellis, B. R.; Hall, C. M.; Lohmann, K. C.; Bouvier, L.

2014-12-01

Recent studies in the Michigan Basin looked at the atmospheric and terrigenic noble gas signatures of deep brines to place constraints on the past thermal history of the basin and to assess the extent of vertical transport processes within this sedimentary system. In this contribution, we present noble gas data of shale gas samples from the Antrim shale formation in the Michigan Basin. The Antrim shale was one of the first economic shale-gas plays in the U.S. and has been actively developed since the 1980's. This study pioneers the use of noble gases in subsurface shale gas in the Michigan Basin to clarify the nature of vertical transport processes within the sedimentary sequence and to assess potential variability of noble gas signatures in shales. Antrim Shale gas samples were analyzed for all stable noble gases (He, Ne, Ar, Kr, Xe) from samples collected at depths between 300 and 500m. Preliminary results show R/Ra values (where R and Ra are the measured and atmospheric 3He/4He ratios, respectively) varying from 0.022 to 0.21. Although most samples fall within typical crustal R/Ra range values (~0.02-0.05), a few samples point to the presence of a mantle He component with higher R/Ra ratios. Samples with higher R/Ra values also display higher 20Ne/22Ne ratios, up to 10.4, and further point to the presence of mantle 20Ne. The presence of crustally produced nucleogenic 21Ne and radiogenic 40Ar is also apparent with 21Ne/22Ne ratios up to 0.033 and 40Ar/36Ar ratios up to 312. The presence of crustally produced 4He, 21Ne and 40Ar is not spatially homogeneous within the Antrim shale. Areas of higher crustal 4He production appear distinct to those of crustally produced 21Ne and 40Ar and are possibly related the presence of different production levels within the shale with varying concentrations of parent elements.

Characterization of a nose-only inhalation exposure system for hydrocarbon mixtures and jet fuels.

PubMed

Martin, Sheppard A; Tremblay, Raphael T; Brunson, Kristyn F; Kendrick, Christine; Fisher, Jeffrey W

2010-04-01

A directed-flow nose-only inhalation exposure system was constructed to support development of physiologically based pharmacokinetic (PBPK) models for complex hydrocarbon mixtures, such as jet fuels. Due to the complex nature of the aerosol and vapor-phase hydrocarbon exposures, care was taken to investigate the chamber hydrocarbon stability, vapor and aerosol droplet compositions, and droplet size distribution. Two-generation systems for aerosolizing fuel and hydrocarbons were compared and characterized for use with either jet fuels or a simple mixture of eight hydrocarbons. Total hydrocarbon concentration was monitored via online gas chromatography (GC). Aerosol/vapor (A/V) ratios, and total and individual hydrocarbon concentrations, were determined using adsorbent tubes analyzed by thermal desorption-gas chromatography-mass spectrometry (TDS-GC-MS). Droplet size distribution was assessed via seven-stage cascade impactor. Droplet mass median aerodynamic diameter (MMAD) was between 1 and 3 mum, depending on the generator and mixture utilized. A/V hydrocarbon concentrations ranged from approximately 200 to 1300 mg/m(3), with between 20% and 80% aerosol content, depending on the mixture. The aerosolized hydrocarbon mixtures remained stable during the 4-h exposure periods, with coefficients of variation (CV) of less than 10% for the total hydrocarbon concentrations. There was greater variability in the measurement of individual hydrocarbons in the A-V phase. In conclusion, modern analytical chemistry instruments allow for improved descriptions of inhalation exposures of rodents to aerosolized fuel.

Above- and below-ground methane fluxes and methanotrophic activity in a landfill-cover soil

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

Schroth, M.H., E-mail: martin.schroth@env.ethz.ch; Eugster, W.; Gomez, K.E.

2012-05-15

Highlights: Black-Right-Pointing-Pointer We quantify above- and below-ground CH{sub 4} fluxes in a landfill-cover soil. Black-Right-Pointing-Pointer We link methanotrophic activity to estimates of CH{sub 4} loading from the waste body. Black-Right-Pointing-Pointer Methane loading and emissions are highly variable in space and time. Black-Right-Pointing-Pointer Eddy covariance measurements yield largest estimates of CH{sub 4} emissions. Black-Right-Pointing-Pointer Potential methanotrophic activity is high at a location with substantial CH{sub 4} loading. - Abstract: Landfills are a major anthropogenic source of the greenhouse gas methane (CH{sub 4}). However, much of the CH{sub 4} produced during the anaerobic degradation of organic waste is consumed by methanotrophic microorganismsmore » during passage through the landfill-cover soil. On a section of a closed landfill near Liestal, Switzerland, we performed experiments to compare CH{sub 4} fluxes obtained by different methods at or above the cover-soil surface with below-ground fluxes, and to link methanotrophic activity to estimates of CH{sub 4} ingress (loading) from the waste body at selected locations. Fluxes of CH{sub 4} into or out of the cover soil were quantified by eddy-covariance and static flux-chamber measurements. In addition, CH{sub 4} concentrations at the soil surface were monitored using a field-portable FID detector. Near-surface CH{sub 4} fluxes and CH{sub 4} loading were estimated from soil-gas concentration profiles in conjunction with radon measurements, and gas push-pull tests (GPPTs) were performed to quantify rates of microbial CH{sub 4} oxidation. Eddy-covariance measurements yielded by far the largest and probably most representative estimates of overall CH{sub 4} emissions from the test section (daily mean up to {approx}91,500 {mu}mol m{sup -2} d{sup -1}), whereas flux-chamber measurements and CH{sub 4} concentration profiles indicated that at the majority of locations the cover soil was a net sink for atmospheric CH{sub 4} (uptake up to -380 {mu}mol m{sup -2} d{sup -1}) during the experimental period. Methane concentration profiles also indicated strong variability in CH{sub 4} loading over short distances in the cover soil, while potential methanotrophic activity derived from GPPTs was high (v{sub max} {approx} 13 mmol L{sup -1}(soil air) h{sup -1}) at a location with substantial CH{sub 4} loading. Our results provide a basis to assess spatial and temporal variability of CH{sub 4} dynamics in the complex terrain of a landfill-cover soil.« less

Factors Controlling Diffusive CO2 Transport and Production in the Cedarburg Bog, Saukville, Wisconsin

NASA Astrophysics Data System (ADS)

Joynt, E.; Grundl, T.; Han, W. S.; Gulbranson, E. L.

2016-12-01

Wetlands are vital components of the carbon cycle containing an estimated 20-30% of the global soil carbon store. The Cedarburg Bog of southeastern Wisconsin contains multiple wetland types, including the southernmost string bog found in North America. Carbon dioxide (CO2) behavior in wetland systems respond to multiple interdependent variables that are collectively not well understood. Modeling CO2 behavior in wetland environments requires a detailed representation of these variables. In 2014 a LI-COR 8100A automated soil gas flux system was installed in the string bog, measuring CO2 concentration and flux. Groundwater data, soil temperature, and weather data (temperature, pressure, precipitation, etc.) were included to reveal correlations between soil CO2 flux/concentration and external forces. In 2015 field data were complemented with soil moisture data and depth profiles of pore water chemistry and stable carbon isotopes from peat and soil gas to discern source and evolution of CO2 at depth. Initial gaseous δ13C(CO2) average -18‰ and deplete overnight suggesting increasing microbial metabolic efficiency. δ13C soil microbial biomass measure roughly -21‰ to -22‰. LI-COR data show diurnal and seasonal trends; CO2 concentration builds overnight while flux increases during the day. CO2 flux magnitude and CO2 concentration range peak in mid-summer, but frequency of increased CO2 flux events varies seasonally each year. Flux averages 7.55 mgCO2/min-m2 during the day but reaches 530 mgCO2/min-m2. Increased atmospheric and soil temperatures and decreasing atmospheric pressure prelude increasing CO2 flux intensity, though correlation strengths vary. Water level may influence CO2 flux, but observations suggest a mobile peat surface with the water table. 2016 imagery from trail cameras will determine extent of peat/well casing movement with water level changes. Further interpretation of data trends will utilize HYDRUS-1D to quantify relationships under changing environmental conditions.

Chemometrics comparison of gas chromatography with mass spectrometry and comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry Daphnia magna metabolic profiles exposed to salinity.

PubMed

Parastar, Hadi; Garreta-Lara, Elba; Campos, Bruno; Barata, Carlos; Lacorte, Silvia; Tauler, Roma

2018-06-01

The performances of gas chromatography with mass spectrometry and of comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry are examined through the comparison of Daphnia magna metabolic profiles. Gas chromatography with mass spectrometry and comprehensive two-dimensional gas chromatography with mass spectrometry were used to compare the concentration changes of metabolites under saline conditions. In this regard, a chemometric strategy based on wavelet compression and multivariate curve resolution-alternating least squares is used to compare the performances of gas chromatography with mass spectrometry and comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry for the untargeted metabolic profiling of Daphnia magna in control and salinity-exposed samples. Examination of the results confirmed the outperformance of comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry over gas chromatography with mass spectrometry for the detection of metabolites in D. magna samples. The peak areas of multivariate curve resolution-alternating least squares resolved elution profiles in every sample analyzed by comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry were arranged in a new data matrix that was then modeled by partial least squares discriminant analysis. The control and salt-exposed daphnids samples were discriminated and the most relevant metabolites were estimated using variable importance in projection and selectivity ratio values. Salinity de-regulated 18 metabolites from metabolic pathways involved in protein translation, transmembrane cell transport, carbon metabolism, secondary metabolism, glycolysis, and osmoregulation. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A novel additive for the reduction of acid gases and NO(x) in municipal waste incinerator flue gas.

PubMed

Hall, William J; Williams, Paul T

2006-08-01

The reduction of SO2, HCl, and NO(x) concentrations using calcium magnesium acetate (CMA) as a novel sorbent in a simulated municipal waste incinerator flue gas was investigated. The reduction of individual SO2, HCl, and NO(x) concentrations was tested at 850 degrees C and it was found that CMA could reduce the SO2 concentration by 74%, HCl concentration by 64%, or NO(x) concentration by 94%. It was observed that individual SO2 or HCl capture increased with increasing initial oxygen concentration in the reacting gas or increasing sorbent input. NO(x) reduction decreased with increasing initial oxygen concentration in the reacting gas. The simultaneous reduction of SO2, HCl, and NO(x) concentrations by CMA was also investigated. It was found that CMA could simultaneously capture 60% SO2 and 61% HCl and reduce NO(x) concentrations by 26%, when the initial oxygen concentration in the reacting gas was 4%. During the simultaneous reduction of SO2, HCl, and NO(x), it was noted that as the initial oxygen concentration in the reacting gas increased, the efficiency of SO2 capture increased too, but the efficiency of HCl capture and the efficiency of NO(x) destruction decreased.

Stability of thiopental and pentobarbital in human plasma determined with a new easy and specific gas chromatography-mass spectrometry assay.

PubMed

Martens-Lobenhoffer, J

1999-08-01

A gas chromatographic-mass spectrometric (GC-MS) assay for the determination of thiopental and its main metabolite pentobarbital in human plasma is presented in this study. The sample preparation consists only in the addition of the internal standard barbital and an acidic extraction with ethyl acetate. Analytical separation is accomplished on a RTX-1 15 m x 0.25 mm capillary column with a film thickness of 0.5 micron. The effluent is observed by a mass selective detector operating in the single ion monitoring mode. The limits of detection are 5 ng/ml for pentobarbital and 10 ng/ml for thiopental, the intra-day variabilities are 2.2% and 4.0% and the inter-day variabilities are 3.3% and 7.1% at concentrations of 5 micrograms/ml, respectively. Applying this assay, the stability of thiopental and pentobarbital in human plasma was tested at concentrations of 5 micrograms/ml each. Thiopental is stable in human plasma at least over 41 days stored at -20 degrees C and 5 degrees C, respectively. A decay of about 2%/day is observed under storage at ambient temperature (19-20 degrees C). Pentobarbital is stable under all storage conditions. Methanolic solutions of thiopental are stable for 83 days under storage at 5 degrees C. Aqueous solutions of thiopental-sodium are stable for at least 23 days under storage at 5 degrees C or ambient temperature.

Overview of Sea-Ice Properties, Distribution and Temporal Variations, for Application to Ice-Atmosphere Chemical Processes.

NASA Astrophysics Data System (ADS)

Moritz, R. E.

2005-12-01

The properties, distribution and temporal variation of sea-ice are reviewed for application to problems of ice-atmosphere chemical processes. Typical vertical structure of sea-ice is presented for different ice types, including young ice, first-year ice and multi-year ice, emphasizing factors relevant to surface chemistry and gas exchange. Time average annual cycles of large scale variables are presented, including ice concentration, ice extent, ice thickness and ice age. Spatial and temporal variability of these large scale quantities is considered on time scales of 1-50 years, emphasizing recent and projected changes in the Arctic pack ice. The amount and time evolution of open water and thin ice are important factors that influence ocean-ice-atmosphere chemical processes. Observations and modeling of the sea-ice thickness distribution function are presented to characterize the range of variability in open water and thin ice.

Trace gas transport out of the Indian Summer Monsoon

NASA Astrophysics Data System (ADS)

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

2016-04-01

The trace gas transport out of the Indian summer monsoon was investigated during the aircraft campaign OMO (Oxidation Mechanism Observations) with the German research aircraft HALO (High Altitude and Long Range Research Aircraft) in July/August 2015. HALO was based at Paphos/Cyprus and also on Gan/Maledives. Flights took place over the Mediterranean Sea, the Arabian Peninsula and the Arabian Sea. In this work the focus is on the distribution of carbon monoxide (CO) and methane (CH4) in the upper troposphere. They were measured with the laser absorption spectrometer TRISTAR on board of HALO. During the Indian summer monsoon strong convection takes place over India and the Bay of Bengal. In this area the population is high accompanied by many emission sources e.g. wetlands and cultivation of rice. Consequently the boundary layer is polluted containing high concentrations of trace gases like methane and carbon monoxide. Due to vertical transport these polluted air masses are lifted to the upper troposphere. Here they circulate with the so called Asian monsoon anticyclone. In the upper troposphere polluted air masses lead to a change in the chemical composition thus influence the chemical processes. Furthermore the anticyclone spreads the polluted air masses over a larger area. Thus the outflow of the anticyclone in the upper troposphere leads to higher concentrations of trace gases over the Arabian Sea, the Arabian Peninsula and also over the eastern part of North Africa and the eastern part of the Mediterranean Sea. During OMO higher concentrations of methane and carbon monoxide were detected at altitudes between 11km and 15km. The highest measured concentrations of carbon monoxide and methane were observed over Oman. The CO concentration in the outflow of the monsoon exceeds background levels by 10-15ppb. However the enhancement in the concentration is not obviously connected to the monsoon due to the natural variability in the troposphere. The enhancement in the methane concentration (30-40ppb) is more obviously connected to the monsoon because it is much higher than the natural variability. Consequently methane is a very good tracer for the monsoon influenced air masses. Beside flights into the outflow of the Indian summer monsoon, there were also measurements of background concentrations in the upper troposphere in air not influenced by the monsoon. Profiles have shown that the high concentrations of trace gases are only observed in the upper troposphere. The high concentrations in the upper troposphere cannot be explained by vertical transport form local ground sources.

Performance of an exhaled nitric oxide and carbon dioxide sensor using quantum cascade laser-based integrated cavity output spectroscopy.

PubMed

McCurdy, Matthew R; Bakhirkin, Yury; Wysocki, Gerard; Tittel, Frank K

2007-01-01

Exhaled nitric oxide (NO) is an important biomarker in asthma and other respiratory disorders. The optical performance of a NOCO(2) sensor employing integrated cavity output spectroscopy (ICOS) with a quantum cascade laser operating at 5.22 microm capable of real-time NO and CO(2) measurements in a single breath cycle is reported. A NO noise-equivalent concentration of 0.4 ppb within a 1-sec integration time is achieved. The off-axis ICOS sensor performance is compared to a chemiluminescent NO analyzer and a nondispersive infrared (NDIR) CO(2) absorption capnograph. Differences between the gas analyzers are assessed by the Bland-Altman method to estimate the expected variability between the gas sensors. The off-axis ICOS sensor measurements are in good agreement with the data acquired with the two commercial gas analyzers. This work demonstrates the performance characteristics and merits of mid-infrared spectroscopy for exhaled breath analysis.

Fluxes of CO2, CH4 and N2O at two European beech forests: linking soil gas production profiles with soil and stem fluxes

NASA Astrophysics Data System (ADS)

Maier, Martin; Machacova, Katerina; Halaburt, Ellen; Haddad, Sally; Urban, Otmar; Lang, Friederike

2016-04-01

Soil and plant surfaces are known to exchange greenhouse gases with the atmosphere. Some gases like nitrous oxide (N2O) and methane (CH4) can be produced and re-consumed in different soil depths and soil compartments, so that elevated concentrations of CH4 or N2O in the soil do not necessarily mean a net efflux from the soil into the atmosphere. Soil aeration, and thus the oxygen status can underlay a large spatial variability within the soil on the plot and profile scale, but also within soil aggregates. Thus, conditions suitable for production and consumption of CH4 and N2O can vary on different scales in the soil. Plant surfaces can also emit or take up CH4 and N2O, and these fluxes can significantly contribute to the net ecosystem exchange. Since roots usually have large intercellular spaces or aerenchyma they may represent preferential transport ways for soil gases, linking possibly elevated soil gas concentrations in the subsoil in a "shortcut" to the atmosphere. We tested the hypothesis that the spatial variability of the soil-atmosphere fluxes of CO2, CH4 and N2O is caused by the heterogeneity in soil properties. Therefore, we measured soil-atmosphere gas fluxes, soil gas concentrations and soil diffusivity profiles and did a small scale field assessment of soil profiles on the measurments plots. We further tried to link vertical profiles of soil gas concentrations and diffusivity to derive the production and consumption profiles, and to link these profiles to the stem-atmosphere flux rates of individual trees. Measurements were conducted in two mountain beech forests with different geographical and climatic conditions (White Carpathians, Czech Republic; Black Forest, Germany). Gas fluxes at stem and soil levels were measured simultaneously using static chamber systems and chromatographic and continuous laser analyses. Monitoring simultaneously vertical soil gas profiles allowed to assess the within-soil gas fluxes, and thus to localize the production and consumption sites of soil gases in the adjacent soil. Soils at both sites took up CH4 and N2O and emitted CO2. Soil gas profiles at the Black Forest showed only CH4 and N2O consumption. CH4 uptake was much larger by the well aerated Black Forest soil than by the loamy-clay soil in the White Carpathians. Here, it was possible to stratify the apparently homogenous site into two plots, one having redoximorphic features in the soil profiles, the other plot without. It seemed that CH4 and N2O were mainly produced in the deeper soil at the plot with temporarily reducing conditions. Beech stems mostly took up N2O from the atmosphere at both sites, whereas CH4 was emitted. The stem CH4 flux was higher for the White Carpathians than for the Black Forest site. Thus, the tree and soil flux of CH4 seems to be affected by soil structure, soil water content and the redox potential in the rooting space. We conclude from our results that trees might provide preferential pathways for greenhouse gases produced in the subsoil thereby enhancing the release of greenhouse gases. Acknowledgement This research was financially supported by the Czech Academy of Sciences and the German Academic Exchange Service within the project "Methane (CH4) and nitrous oxide (N2O) emissions from Fagus sylvatica trees" (DAAD-15-03), National Programme for Sustainability I (LO1415) and project DFG (MA 5826/2-1). We would like to thank Marek Jakubik for technical support and Sinikka Paulus for help by field measurements.

Enceladus Plume Structure and Time Variability: Comparison of Cassini Observations

PubMed Central

Perry, Mark E.; Hansen, Candice J.; Waite, J. Hunter; Porco, Carolyn C.; Spencer, John R.; Howett, Carly J. A.

2017-01-01

Abstract During three low-altitude (99, 66, 66 km) flybys through the Enceladus plume in 2010 and 2011, Cassini's ion neutral mass spectrometer (INMS) made its first high spatial resolution measurements of the plume's gas density and distribution, detecting in situ the individual gas jets within the broad plume. Since those flybys, more detailed Imaging Science Subsystem (ISS) imaging observations of the plume's icy component have been reported, which constrain the locations and orientations of the numerous gas/grain jets. In the present study, we used these ISS imaging results, together with ultraviolet imaging spectrograph stellar and solar occultation measurements and modeling of the three-dimensional structure of the vapor cloud, to constrain the magnitudes, velocities, and time variability of the plume gas sources from the INMS data. Our results confirm a mixture of both low and high Mach gas emission from Enceladus' surface tiger stripes, with gas accelerated as fast as Mach 10 before escaping the surface. The vapor source fluxes and jet intensities/densities vary dramatically and stochastically, up to a factor 10, both spatially along the tiger stripes and over time between flyby observations. This complex spatial variability and dynamics may result from time-variable tidal stress fields interacting with subsurface fissure geometry and tortuosity beyond detectability, including changing gas pathways to the surface, and fluid flow and boiling in response evolving lithostatic stress conditions. The total plume gas source has 30% uncertainty depending on the contributions assumed for adiabatic and nonadiabatic gas expansion/acceleration to the high Mach emission. The overall vapor plume source rate exhibits stochastic time variability up to a factor ∼5 between observations, reflecting that found in the individual gas sources/jets. Key Words: Cassini at Saturn—Geysers—Enceladus—Gas dynamics—Icy satellites. Astrobiology 17, 926–940. PMID:28872900

Method for mapping a natural gas leak

DOEpatents

Reichardt, Thomas A [Livermore, CA; Luong, Amy Khai [Dublin, CA; Kulp, Thomas J [Livermore, CA; Devdas, Sanjay [Albany, CA

2009-02-03

A system is described that is suitable for use in determining the location of leaks of gases having a background concentration. The system is a point-wise backscatter absorption gas measurement system that measures absorption and distance to each point of an image. The absorption measurement provides an indication of the total amount of a gas of interest, and the distance provides an estimate of the background concentration of gas. The distance is measured from the time-of-flight of laser pulse that is generated along with the absorption measurement light. The measurements are formatted into an image of the presence of gas in excess of the background. Alternatively, an image of the scene is superimposed on the image of the gas to aid in locating leaks. By further modeling excess gas as a plume having a known concentration profile, the present system provides an estimate of the maximum concentration of the gas of interest.

Natural gas leak mapper

DOEpatents

Reichardt, Thomas A [Livermore, CA; Luong, Amy Khai [Dublin, CA; Kulp, Thomas J [Livermore, CA; Devdas, Sanjay [Albany, CA

2008-05-20

A system is described that is suitable for use in determining the location of leaks of gases having a background concentration. The system is a point-wise backscatter absorption gas measurement system that measures absorption and distance to each point of an image. The absorption measurement provides an indication of the total amount of a gas of interest, and the distance provides an estimate of the background concentration of gas. The distance is measured from the time-of-flight of laser pulse that is generated along with the absorption measurement light. The measurements are formated into an image of the presence of gas in excess of the background. Alternatively, an image of the scene is superimosed on the image of the gas to aid in locating leaks. By further modeling excess gas as a plume having a known concentration profile, the present system provides an estimate of the maximum concentration of the gas of interest.

Anaerobic soil volume as a major controlling factor for soil denitrification and respiration

NASA Astrophysics Data System (ADS)

Reent Köster, Jan; Tong, Bingxin; Grosz, Balázs; Burkart, Stefan; Ruoss, Nicolas; Well, Reinhard

2017-04-01

Gas diffusion in soil is a key variable to control denitrification and its N2O to N2 product ratio since it affects two major proximal denitrification factors, i.e. the concentrations of O2 and of N2O. Gas diffusivity is governed by the structure and the state of water saturation of the pore system. At a given O2 consumption rate decreasing diffusivity causes an enhanced anaerobic soil volume where denitrification can occur. Gas diffusivity is generally quantified as bulk diffusion coefficients that represent the lineal diffusive gas flux through the soil matrix. However, the spatial distribution of respiratory O2 consumption and denitrification - and hence the local concentration of O2 and N2O - is highly non-homogeneous. Knowledge of the anaerobic soil volume fraction (ansvf) has been proposed as a key control on denitrification, and has subsequently been used in many denitrification models. The ansvf has previously been quantified by direct measurement of O2 distribution in individual soil aggregates using microsensors. The measured ansvf corresponded to modelled values based on measured aggregate diffusivity and respiration, but was not yet correlated with measured denitrification rates. In the present ongoing study, we are incubating soil cores amended with nitrate and organic litter in an automated mesocosm system under aerobic as well as anaerobic conditions. An N2 depleted incubation atmosphere and the 15N labeled soil nitrate pool facilitate quantification of the N2 production in the soil by IRMS, and fluxes of N2O and CO2 are monitored via gas chromatography. The ansvf and the measured denitrification and respiration rates will then be used for model validation. During the session we will present first results of this study.

Ambient air/near-field measurements of methane and Volatile Organic Compounds (VOCs) from a natural gas facility in Northern Europe

NASA Astrophysics Data System (ADS)

Baudic, Alexia; Gros, Valérie; Bonsang, Bernard; Baisnee, Dominique; Vogel, Félix; Yver Kwok, Camille; Ars, Sébastien; Finlayson, Andrew; Innocenti, Fabrizio; Robinson, Rod

2015-04-01

Since the 1970's, the natural gas consumption saw a rapid growth in large urban centers, thus becoming an important energy resource to meet continuous needs of factories and inhabitants. Nevertheless, it can be a substantial source of methane (CH4) and pollutants in urban areas. For instance, we have determined that about 20% of Volatile Organic Compounds (VOCs) in downtown Paris are originating from this emission source (Baudic, Gros et al., in preparation). Within the framework of the "Fugitive Methane Emissions" (FuME) project (Climate-KIC, EIT); 2-weeks gas measurements were conducted at a gas compressor station in Northern Europe. Continuous ambient air measurements of methane and VOCs concentrations were performed using a cavity ring-down spectrometer (model G2201, Picarro Inc., Santa Clara, USA) and two portable GC-FID (Chromatotec, Saint-Antoine, France), respectively. On-site near-field samplings were also carried out at the source of two pipelines using stainless steel flasks (later analyzed with a laboratory GC-FID). The objective of this study aims to use VOCs as additional tracers in order to better characterize the fugitive methane emissions in a complex environment, which can be affected by several urban sources (road-traffic, others industries, etc.). Moreover, these measurements have allowed determining the chemical composition of this specific source. Our results revealed that the variability of methane and some VOCs was (rather) well correlated, especially for alkanes (ethane, propane, etc.). An analysis of selected events with strong concentrations enhancement was performed using ambient air measurements; thus allowing the preliminary identification of different emission sources. In addition, some flasks were also sampled in Paris to determine the local natural gas composition. A comparison between both was then performed. Preliminary results from these experiments will be presented here.

Modular Analytical Multicomponent Analysis in Gas Sensor Aarrays

PubMed Central

Chaiyboun, Ali; Traute, Rüdiger; Kiesewetter, Olaf; Ahlers, Simon; Müller, Gerhard; Doll, Theodor

2006-01-01

A multi-sensor system is a chemical sensor system which quantitatively and qualitatively records gases with a combination of cross-sensitive gas sensor arrays and pattern recognition software. This paper addresses the issue of data analysis for identification of gases in a gas sensor array. We introduce a software tool for gas sensor array configuration and simulation. It concerns thereby about a modular software package for the acquisition of data of different sensors. A signal evaluation algorithm referred to as matrix method was used specifically for the software tool. This matrix method computes the gas concentrations from the signals of a sensor array. The software tool was used for the simulation of an array of five sensors to determine gas concentration of CH4, NH3, H2, CO and C2H5OH. The results of the present simulated sensor array indicate that the software tool is capable of the following: (a) identify a gas independently of its concentration; (b) estimate the concentration of the gas, even if the system was not previously exposed to this concentration; (c) tell when a gas concentration exceeds a certain value. A gas sensor data base was build for the configuration of the software. With the data base one can create, generate and manage scenarios and source files for the simulation. With the gas sensor data base and the simulation software an on-line Web-based version was developed, with which the user can configure and simulate sensor arrays on-line.

Ecophysiological Significance of CO2-Recycling via Crassulacean Acid Metabolism in Talinum calycinum Engelm. (Portulacaceae) 1

PubMed Central

Martin, Craig E.; Higley, Michael; Wang, Wei-Zhong

1988-01-01

High levels of variability in gas exchange characteristics and degree of CAM-cycling were found in the same and different individuals of Talinum calycinum Engelm. collected from rock outcrops in Missouri. Differences in CO2 assimilation were mostly correlated with differences in shoot conductance to CO2 not shoot internal CO2 concentration. As found previously, CAM acid fluctuations were evident in well-watered plants exhibiting C3 gas exchange patterns (CAM-cycling) and also in drought-stressed plants with stomata closed, or nearly so, day and night (CAM-idling). Drought stress also resulted in rapid stomatal closure, conserving water during droughts. Maximal CO2 uptake rates occurred below 35°C; higher temperatures induced decreases in CO2 assimilation and conductance while shoot internal CO2 concentrations remained similar. Plant water-use-efficiency was severely curtailed at temperatures above 30°C. Tissue acid fluctuations were the result of changes in malic acid concentrations. Calculations of the amount of water potentially conserved by CAM-cycling yielded values of approximately 5 to 44% of daytime water loss. Thus, CAM-cycling may be an important adaptation minimizing water loss by perennial succulents growing in shallow soil on rock outcrops. PMID:16665946

Constraining wintertime sources of inorganic chlorine over the northeast United States

NASA Astrophysics Data System (ADS)

Haskins, J.; Jaegle, L.; Shah, V.; Lopez-Hilfiker, F.; Lee, B. H.; Campuzano Jost, P.; Schroder, J. C.; Day, D. A.; Fiddler, M. N.; Holloway, J. S.; Sullivan, A.; Veres, P. R.; Weber, R. J.; Dibb, J. E.; Brown, S. S.; Jimenez, J. L.; Thornton, J. A.

2017-12-01

Wintertime multiphase chlorine chemistry is thought to play a significant role in the regional distribution of oxidants, the lifetime of VOCs, and the transport of NOx downwind of urban sources. However, the sources and chemistry of reactive chlorine remain highly uncertain. During the WINTER 2015 aircraft campaign, the inorganic chlorine budget was dominated by HCl (g) and total particulate chloride, accounting for greater than 85% of the total chlorine budget within the boundary layer. The total concentration of inorganic chlorine compounds found over marine regions was 1014 pptv and 609 pptv over continental regions with variability found to be driven by changes in meteorological conditions, particle liquid water content, particle pH, and proximity to large anthropogenic sources. However, displacement of particle chloride was often not a large enough source to fully explain the concentrations of gas phase Cly compounds. We use the GEOS-Chem global chemical transport model to simulate the emissions, gas-particle partitioning, and downwind transport and deposition of Cly during winter. Simulated concentrations of HCl, particle chloride, and other dominant Cly compounds are compared to measurements made during the WINTER aircraft campaign. The relative roles of Cly sources from sea-salt aerosol and anthropogenic sources such as power plants, biomass burning and road salt are explored.

Measuring Concentrations of Dissolved Methane and Ethane and the 13 C of Methane in Shale and Till.

PubMed

Hendry, M Jim; Barbour, S Lee; Schmeling, Erin E; Mundle, Scott O C

2017-01-01

Baseline characterization of concentrations and isotopic values of dissolved natural gases is needed to identify contamination caused by the leakage of fugitive gases from oil and gas activities. Methods to collect and analyze baseline concentration-depth profiles of dissolved CH 4 and C 2 H 6 and δ 13 C-CH 4 in shales and Quaternary clayey tills were assessed at two sites in the Williston Basin, Canada. Core and cuttings samples were stored in Isojars ® in a low O 2 headspace prior to analysis. Measurements and multiphase diffusion modeling show that the gas concentrations in core samples yield well-defined and reproducible depth profiles after 31-d equilibration. No measurable oxidative loss or production during core sample storage was observed. Concentrations from cuttings and mud gas logging (including IsoTubes ® ) were much lower than from cores, but correlated well. Simulations suggest the lower concentrations from cuttings can be attributed to drilling time, and therefore their use to define gas concentration profiles may have inherent limitations. Calculations based on mud gas logging show the method can provide estimates of core concentrations if operational parameters for the mud gas capture cylinder are quantified. The δ 13 C-CH 4 measured from mud gas, IsoTubes ® , cuttings, and core samples are consistent, exhibiting slight variations that should not alter the implications of the results in identifying the sources of the gases. This study shows core and mud gas techniques and, to a lesser extent, cuttings, can generate high-resolution depth profiles of dissolved hydrocarbon gas concentrations and their isotopes. © 2016, National Ground Water Association.

The features of chlorophyll concentration long-standing dynamics in the ocean surface layer (comparison of czcs and seawifs data)

NASA Astrophysics Data System (ADS)

Shevyrnogov, A.; Vysotskaya, G.

To preserve biosphere and make its utilization expedient makes imperative to comprehend in depth long-standing dynamics of the primary production process on our planet. Variability of chlorophyll concentration in the ocean is one of the most important components of this process. However, hard access and large size of the water surface make its investigation labor-consuming. Besides, the dependence of primary production on high variability of hydrophysical phenomena in the ocean (fluctuations of currents, frontal zones, etc.) makes the location of points for measuring the chlorophyll concentration dynamics significant. In this work the long-standing changes in chlorophyll concentration in the surface layer of the ocean have been analyzed on the basis of the CZCS data for 7.5 years and the SeaWiFS data from 1997 to 2003. It was shown that the average chlorophyll concentration calculated at all investigated area is varied moderately. However when analyzing spatially local trends, it was detected that areas exist with stable rise and fall of chlorophyll concentration. Some interesting features of the long-standing dynamics of chlorophyll concentration several interesting features were found. There are the various directions of long-term trends (constant increase or decrease) that cannot be explained only by large-scale hydrological phenomena in the ocean (currents, upwellings etc.). The next feature is a difference between the trends revealed by using the CZCS data and the trends based on the SeaWiFS data. Thus, the obtained results allow the possibility of identification of the ocean biota role in the global biospheric gas exchange.

A reactive transport modelling approach to assess the leaching potential of hydraulic fracturing fluids associated with coal seam gas extraction

NASA Astrophysics Data System (ADS)

Mallants, Dirk; Simunek, Jirka; Gerke, Kirill

2015-04-01

Coal Seam Gas production generates large volumes of "produced" water that may contain compounds originating from the use of hydraulic fracturing fluids. Such produced water also contains elevated concentrations of naturally occurring inorganic and organic compounds, and usually has a high salinity. Leaching of produced water from storage ponds may occur as a result of flooding or containment failure. Some produced water is used for irrigation of specific crops tolerant to elevated salt levels. These chemicals may potentially contaminate soil, shallow groundwater, and groundwater, as well as receiving surface waters. This paper presents an application of scenario modelling using the reactive transport model for variably-saturated media HP1 (coupled HYDRUS-1D and PHREEQC). We evaluate the fate of hydraulic fracturing chemicals and naturally occurring chemicals in soil as a result of unintentional release from storage ponds or when produced water from Coal Seam Gas operations is used in irrigation practices. We present a review of exposure pathways and relevant hydro-bio-geo-chemical processes, a collation of physico-chemical properties of organic/inorganic contaminants as input to a set of generic simulations of transport and attenuation in variably saturated soil profiles. We demonstrate the ability to model the coupled processes of flow and transport in soil of contaminants associated with hydraulic fracturing fluids and naturally occurring contaminants.

Sources and migration pathways of natural gas in near-surface ground water beneath the Animas River valley, Colorado and New Mexico

USGS Publications Warehouse

Chafin, Daniel T.

1994-01-01

In July 1990, the U.S. Geological Survey began a study of the occurrence of natural gas in near-surface ground water in the Animas River valley in the San Juan Basin between Durango, Colorado, and Aztec, New Mexico. The general purpose of the study was to identify the sources and migration pathways of natural gas in nearsurface ground water in the study area. The purpose of this report is to present interpretive conclusions for the study, primarily based on data collected by the U.S. Geological Survey from August 1990 to May 1991.Seventy of the 205 (34 percent) groundwater samples collected during August-November 1990 had methane concentrations that exceeded the reporting limit of 0.005 milligram per liter. The maximum concentration was 39 milligrams per liter, and the mean concentration was 1.3 milligrams per liter. Samples from wells completed in bedrock have greater mean concentrations of methane than samples from wells completed in alluvium. Correlations indicate weak or nonexistent associations between dissolved-methane concentrations and concentrations of dissolved solids, major ions, bromide, silica, iron, manganese, and carbon dioxide. Dissolved methane was associated with hydrogen sulfide.Soil-gas-methane concentrations were measurable at few of 192 ground-water sites, even at sites at which ground water contained large concentrations of dissolved methane, which indicates that soil-gas surveys are not useful to delineate areas of gas-affected ground water. The reporting limit of 0.005 milligram per liter of gas was equaled or exceeded by 40 percent of soil-gas measurements adjacent to 352 gas-well casings. Concentrations of at least 100 milligrams per liter of gas were measured at 25 (7 percent) of the sites.Potential sources of gases in water, soil, gas-well surface casings, and cathodic-protection wells were determined on the basis of their isotopic and molecular compositions and available information about gas-well construction or leaks. Biogenic and thermogenic sources of gas exist in the near-surface environment of the study area. Biogenic gas is present locally in the near-surface Animas and Nacimiento formations, and biogenic gas has been detected in water wells completed in those rocks. Most gas probably is thermogenic gas from deep reservoirs, including the Dakota Sandstone, Mesaverde Group, Lewis Shale, Pictured Cliffs Sandstone, and coals in the Fruitland Formation. Less important sources include sandstones in the upper Fruitland Formation and the Kirtland Shale.Although migration of gas by diffusion or through natural fractures is possible, manmade conduits probably account for most of the upward migration of gas to the near-surface environment of the study area. Primary migration pathways largely consist of 1) leaking, conventional gas wells and 2) uncemented annuli of conventional gas wells along coals in the Fruitland Formation. Secondary migration pathways are gas-well annuli, cathodic-protection wells, seismic-test holes, and bedrock water wells.

Gas Exchange of Algae

PubMed Central

Ammann, Elizabeth C. B.; Lynch, Victoria H.

1967-01-01

The oxygen production of a photosynthetic gas exchanger containing Chlorella pyrenoidosa (1% packed cell volume) was measured when various concentrations of carbon dioxide were present within the culture unit. The internal carbon dioxide concentrations were obtained by manipulating the entrance gas concentration and the flow rate. Carbon dioxide percentages were monitored by means of electrodes placed directly in the nutrient medium. The concentration of carbon dioxide in the nutrient medium which produced maximal photosynthesis was in the range of 1.5 to 2.5% by volume. Results were unaffected by either the level of carbon dioxide in the entrance gas or the rate of gas flow. Entrance gases containing 2% carbon dioxide flowing at 320 ml/min, 3% carbon dioxide at 135 ml/min, and 4% carbon dioxide at 55 ml/min yielded optimal carbon dioxide concentrations in the particular unit studied. By using carbon dioxide electrodes implanted directly in the gas exchanger to optimize the carbon dioxide concentration throughout the culture medium, it should be possible to design more efficient large-scale units. PMID:4382391

Carbon Monoxide as an Electron Donor for the Biological Reduction of Sulphate

PubMed Central

Parshina, Sofiya N.; Sipma, Jan; Henstra, Anne Meint; Stams, Alfons J. M.

2010-01-01

Several strains of Gram-negative and Gram-positive sulphate-reducing bacteria (SRB) are able to use carbon monoxide (CO) as a carbon source and electron donor for biological sulphate reduction. These strains exhibit variable resistance to CO toxicity. The most resistant SRB can grow and use CO as an electron donor at concentrations up to 100%, whereas others are already severely inhibited at CO concentrations as low as 1-2%. Here, the utilization, inhibition characteristics, and enzymology of CO metabolism as well as the current state of genomics of CO-oxidizing SRB are reviewed. Carboxydotrophic sulphate-reducing bacteria can be applied for biological sulphate reduction with synthesis gas (a mixture of hydrogen and carbon monoxide) as an electron donor. PMID:20628586

Gas hydrate saturations estimated from fractured reservoir at Site NGHP-01-10, Krishna-Godavari Basin, India

USGS Publications Warehouse

Lee, M.W.; Collett, T.S.

2009-01-01

During the Indian National Gas Hydrate Program Expedition 01 (NGHP-Ol), one of the richest marine gas hydrate accumulations was discovered at Site NGHP-01-10 in the Krishna-Godavari Basin. The occurrence of concentrated gas hydrate at this site is primarily controlled by the presence of fractures. Assuming the resistivity of gas hydratebearing sediments is isotropic, th?? conventional Archie analysis using the logging while drilling resistivity log yields gas hydrate saturations greater than 50% (as high as ???80%) of the pore space for the depth interval between ???25 and ???160 m below seafloor. On the other hand, gas hydrate saturations estimated from pressure cores from nearby wells were less than ???26% of the pore space. Although intrasite variability may contribute to the difference, the primary cause of the saturation difference is attributed to the anisotropic nature of the reservoir due to gas hydrate in high-angle fractures. Archie's law can be used to estimate gas hydrate saturations in anisotropic reservoir, with additional information such as elastic velocities to constrain Archie cementation parameters m and the saturation exponent n. Theory indicates that m and n depend on the direction of the measurement relative to fracture orientation, as well as depending on gas hydrate saturation. By using higher values of m and n in the resistivity analysis for fractured reservoirs, the difference between saturation estimates is significantly reduced, although a sizable difference remains. To better understand the nature of fractured reservoirs, wireline P and S wave velocities were also incorporated into the analysis.

Control of exposure to hexavalent chromium and ozone in gas metal arc welding of stainless steels by use of a secondary shield gas.

PubMed

Dennis, John H; French, Michael J; Hewitt, Peter J; Mortazavi, Seyed B; Redding, Christopher A J

2002-01-01

Previous work has demonstrated that the shield gas composition in gas metal arc welding can have a considerable effect on hexavalent chromium [Cr(VI)] concentration in the fume and on ozone concentrations near the arc. Normally a single shield gas is used. This paper describes a double shroud torch that allows used of concentric shield gases of different compositions. A solid stainless steel wire was used for welding. The double shroud torch used secondary shield gases containing small amounts of the reducing agents NO and C2H4. The Cr(VI) concentration in the fume and ozone concentration at a fixed point relative to the arc were measured and compared with results when using a single shield gas. Use of the reducing agents in secondary shielding using the double shroud torch was found to offer advantages for ozone concentration reduction compared with use in a conventional torch, but this was not found to be an advantage for reducing Cr(VI) concentrations.

Seasonal variability and source apportionment of volatile organic compounds (VOCs) in the Paris megacity (France)

NASA Astrophysics Data System (ADS)

Baudic, Alexia; Gros, Valérie; Sauvage, Stéphane; Locoge, Nadine; Sanchez, Olivier; Sarda-Estève, Roland; Kalogridis, Cerise; Petit, Jean-Eudes; Bonnaire, Nicolas; Baisnée, Dominique; Favez, Olivier; Albinet, Alexandre; Sciare, Jean; Bonsang, Bernard

2016-09-01

Within the framework of air quality studies at the megacity scale, highly time-resolved volatile organic compound (C2-C8) measurements were performed in downtown Paris (urban background sites) from January to November 2010. This unique dataset included non-methane hydrocarbons (NMHCs) and aromatic/oxygenated species (OVOCs) measured by a GC-FID (gas chromatograph with a flame ionization detector) and a PTR-MS (proton transfer reaction - mass spectrometer), respectively. This study presents the seasonal variability of atmospheric VOCs being monitored in the French megacity and their various associated emission sources. Clear seasonal and diurnal patterns differed from one VOC to another as the result of their different origins and the influence of environmental parameters (solar radiation, temperature). Source apportionment (SA) was comprehensively conducted using a multivariate mathematical receptor modeling. The United States Environmental Protection Agency's positive matrix factorization tool (US EPA, PMF) was used to apportion and quantify ambient VOC concentrations into six different sources. The modeled source profiles were identified from near-field observations (measurements from three distinct emission sources: inside a highway tunnel, at a fireplace and from a domestic gas flue, hence with a specific focus on road traffic, wood-burning activities and natural gas emissions) and hydrocarbon profiles reported in the literature. The reconstructed VOC sources were cross validated using independent tracers such as inorganic gases (NO, NO2, CO), black carbon (BC) and meteorological data (temperature). The largest contributors to the predicted VOC concentrations were traffic-related activities (including motor vehicle exhaust, 15 % of the total mass on the annual average, and evaporative sources, 10 %), with the remaining emissions from natural gas and background (23 %), solvent use (20 %), wood-burning (18 %) and a biogenic source (15 %). An important finding of this work is the significant contribution from wood-burning, especially in winter, where it could represent up to ˜ 50 % of the total mass of VOCs. Biogenic emissions also surprisingly contributed up to ˜ 30 % in summer (due to the dominating weight of OVOCs in this source). Finally, the mixed natural gas and background source exhibited a high contribution in spring (35 %, when continental air influences were observed) and in autumn (23 %, for home heating consumption).

Helium ionization detection apparatus

NASA Technical Reports Server (NTRS)

Nagai, R.

1984-01-01

In a gas chromatograph apparatus comprising a gas supply (He carrier gas), a sample injection apparatus, a chromatograph column, a He ion detector, and connecting tubes, a foreign gas (other than He) injection apparatus is installed between the sample injection apparatus and the detector. Mixing of the sample gas and foreign gas takes place readily, the sample gas is always maintained at a stable concentrator range, and accurate measurements are possible, especially at low sample gas concentrations.

Reconstructing mantle volatile contents through the veil of degassing

NASA Astrophysics Data System (ADS)

Tucker, J.; Mukhopadhyay, S.; Gonnermann, H. M.

2014-12-01

The abundance of volatile elements in the mantle reveals critical information about the Earth's origin and evolution such as the chemical constituents that built the Earth and material exchange between the mantle and exosphere. However, due to magmatic degassing, volatile element abundances measured in basalts usually do not represent those in undegassed magmas and hence in the mantle source of the basalts. While estimates of average mantle concentrations of some volatile species can be obtained, such as from the 3He flux into the oceans, volatile element variability within the mantle remains poorly constrained. Here, we use CO2-He-Ne-Ar-Xe measurements in basalts and a new degassing model to reconstruct the initial volatile contents of 8 MORBs from the Mid-Atlantic Ridge and Southwest Indian Ridge that span a wide geochemical range from depleted to enriched MORBs. We first show that equilibrium degassing (e.g. Rayleigh degassing), cannot simultaneously fit the measured CO2-He-Ne-Ar-Xe compositions in MORBs and argue that kinetic fractionation between bubbles and melt lowers the dissolved ratios of light to heavy noble gas species in the melt from that expected at equilibrium. We present a degassing model (after Gonnermann and Mukhopadhyay, 2007) that explicitly accounts for diffusive fractionation between melt and bubbles. The model computes the degassed composition based on an initial volatile composition and a diffusive timescale. To reconstruct the undegassed volatile content of a sample, we find the initial composition and degassing timescale which minimize the misfit between predicted and measured degassed compositions. Initial 3He contents calculated for the 8 MORB samples vary by a factor of ~7. We observe a correlation between initial 3He and CO2 contents, indicating relatively constant CO2/3He ratios despite the geochemical diversity and variable gas content in the basalts. Importantly, the gas-rich popping rock from the North Atlantic, as well as the average mantle ratio computed from the ridge 3He flux and independently estimated CO2 content fall along the same correlation. This observation suggests that undegassed CO2 and noble gas concentrations can be reconstructed in individual samples through measurement of noble gases and CO2 in erupted basalts.

Methods for in situ Mesocosm Water Table Manipulation in Amazon Peatlands

NASA Astrophysics Data System (ADS)

Sarno, B. G.; Guardia, J. R.; Torres, M. G.; Lopez, J. G.; Rios, M. L.; Saquiray, L. M.; Rodriguez, T. C.; Rivera, P. V.; Van Haren, J. L. M.; Cadillo-Quiroz, H.

2016-12-01

Rainfall manipulation in tropical Amazon rainforests has previously been used to analyze the effects of rapidly changing drought and flood seasons on canopy dynamics, above-ground ecological function and greenhouse gas cycles. We chose to focus on variance below the rootline due to the greater carbon mass and impact of this region and the variables affecting it. We designed and implemented a system that manipulates above and below ground water exposure to control soil saturation. Isolation of soil sample was collected using a PVC pipe submerged 50 cm into the ground with an overhead watershed and an underground water filter. Similarly, a control sample of the above ground water was collected. Above ground water control was performed, not unlike previous systems, using overhead cover, drainage and rerouting, constructed using 1 inch PVC sections configured to allow 25% shed, 50% shed, and 75% increase. Underground filters were designed using variable clay concentrations to achieve desired permeability and flow rate. We selected kiln-fire pure clay discs, instead of poly-acrylamide discs, to enable a steady flow of 0.83 mL/hr. In addition, we adjusted the concentration of the clay disc with sand buffering and carbon lacing at different mass concentrations to allow direct controls of the flow rate, as high as 12.45 mL/hr. Using pure clay concentrations of 100%, 75%, and 50% by mass, and lacing the filters with carbon fill of 10%, 20%, and 30% by volume, before kiln firing, allows much more desirable flow rates. These significant increases in flow rate allow for better control of both above and below ground water exposure. Such a system will enable a more complete geochemical and microbiological analysis of soil and water within this highly variable region of the rain forest. Construction and installation of the submerged towers has been performed at numerous sites along the Peruvian Amazon River basin. Monitoring soil respiration will be performed on the current installations on a continuous schedule for 6 months, in efforts to understand the effects of water table control on the microbial community respiration and greenhouse gases production in the tropical rainforest peatlands. Our work will allow for a more complete understanding of variation in greenhouse gas sources and the ecological carbon cycle due to water table change.

Controlling dust from concrete saw cutting.

PubMed

Shepherd, Susan; Woskie, Susan

2013-01-01

Cutting concrete with gas-powered saws is ubiquitous in the construction industry and a source of exposure to respirable crystalline silica. Volunteers from the New England Laborers Training Center were recruited to participate in a field experiment examining dust reductions through the use of water, from a hose and from a sprayer, as a dust control. In four series of tests, reinforced concrete pipe was cut under both "dry" and "wet" control conditions. Overall, the geometric mean respirable dust concentration for "dry" cutting (14.396 mg/m³) exceeded both types of water-based controls by more than tenfold. Wet cutting reduced the respirable dust concentration by 85% compared with dry cutting when comparing tests paired by person and saw blade (n = 79 pairs). Using a respirable cyclone, a total of 178 samples were taken. Due to the high variability in dust exposure found in this and other studies of saw cutting, the data were examined for potential exposure determinants that contribute to that variability. Using mixed models, three fixed effects were statistically significant: control condition, worker experience, and location. A random effect for subject was included in the model to account for repeated measures. When each of the significant fixed effects was included with the random effect, it was apparent that inclusion of worker experience or location reduced the between-worker component of exposure variability, while inclusion of control condition (wet vs. dry) explained a large portion of the within-subject variability. Overall, the fixed effect variable for control condition explained the largest fraction of the total exposure variability.

Preliminary measurement of gas concentrations of perfluropropane using an analytical weighing balance.

PubMed

Clarkson, Douglas McG; Manna, Avinish; Hero, Mark

2014-02-01

We describe the use of an analytical weighing balance of measurement accuracy 0.00001g for determination of concentrations of perfluropropane (C3F8) gas used in ophthalmic surgical vitrectomy procedures. A range of test eyes corresponding to an eye volume of 6.1ml were constructed using 27 gauge needle exit ducts and separately 20 gauge (straight) and 23 gauge (angled) entrance ports. This method allowed determination of concentration levels in the sample preparation syringe and also levels in test eyes. It was determined that a key factor influencing gas concentrations accuracy related to the method of gas fill and the value of dead space of the gas preparation/delivery system and with a significant contribution arising from the use of the particle filter. The weighing balance technique was identified as an appropriate technique for estimation of gas concentrations. Copyright © 2013 IPEM. Published by Elsevier Ltd. All rights reserved.

Confirmation of the sterilization effect using a high concentration of ozone gas for the bio-clean room.

PubMed

Iwamura, Takuji; Nagano, Katsunori; Nogami, Toshihiro; Matsuki, Noritomo; Kosaka, Noriyoshi; Shintani, Hideharu; Katoh, Miyoshi

2013-01-01

A high-level aseptic environment must be maintained in bio-cleanrooms used for the manufacture of sterile products. In the past, formaldehyde gas was most commonly used to sterilize bio-cleanrooms, but due to strict residual limitations there has been a need to develop a less toxic alternative choice. The authors have developed a revolutionary new sterilization system using a high concentration of ozone gas and used this system to sterilize an actual bio-cleanroom. This system integrates the ozone gas generator with the air conditioning system by proper control. The design specifications for the system included an ozone gas concentration of 200 ppm or more, relative humidity of 80% or more, and a sterilizing time of 120 min. Blow vents and suction ports were placed to ensure a uniform airflow which would extend through the entire room during ozone gas sterilization. Tests regarding long-term material exposure to ozone gas were conducted when the system was introduced to distinguish usable and unusable materials. In an actually constructed cleanroom, simulations were used to predict the evenness of the diffusion of ozone gas concentration and relative humidity during ozone gas sterilization, and measurements of the actual indoor ozone gas concentration, temperature and relative humidity during sterilization revealed that the ozone concentration and relative humidity needed for sterilization had been achieved generally throughout the entire environment. In addition, the CT value (mg/m(3) (=ppm) × min) , derived by multiplying the ozone gas concentration during ozone gas sterilization by the sterilization time, was equal to or greater than the target value of 24 × 10(3) (ppm·min) . When the results of sterilization in a cleanroom were confirmed using a biological indicator (BI) , negative results were obtained at all measurement points, demonstrating that sterilization was being performed effectively in the actual factory at which the ozone gas sterilization system had been introduced.

Reservoir controls on the occurrence and production of gas hydrates in nature

USGS Publications Warehouse

Collett, Timothy Scott

2014-01-01

modeling has shown that concentrated gas hydrate occurrences in sand reservoirs are conducive to existing well-based production technologies. The resource potential of gas hydrate accumulations in sand-dominated reservoirs have been assessed for several polar terrestrial basins. In 1995, the U.S. Geological Survey (USGS) assigned an in-place resource of 16.7 trillion cubic meters of gas for hydrates in sand-dominated reservoirs on the Alaska North Slope. In a more recent assessment, the USGS indicated that there are about 2.42 trillion cubic meters of technically recoverable gas resources within concentrated, sand-dominated, gas hydrate accumulations in northern Alaska. Estimates of the amount of in-place gas in the sand dominated gas hydrate accumulations of the Mackenzie Delta Beaufort Sea region of the Canadian arctic range from 1.0 to 10 trillion cubic meters of gas. Another prospective gas hydrate resources are those of moderate-to-high concentrations within sandstone reservoirs in marine environments. In 2008, the Bureau of Ocean Energy Management estimated that the Gulf of Mexico contains about 190 trillion cubic meters of gas in highly concentrated hydrate accumulations within sand reservoirs. In 2008, the Japan Oil, Gas and Metals National Corporation reported on a resource assessment of gas hydrates in which they estimated that the volume of gas within the hydrates of the eastern Nankai Trough at about 1.1 trillion cubic meters, with about half concentrated in sand reservoirs. Because conventional production technologies favor sand-dominated gas hydrate reservoirs, sand reservoirs are considered to be the most viable economic target for gas hydrate production and will be the prime focus of most future gas hydrate exploration and development projects.

Multi-year application of WRF-CAM5 over East Asia-Part II: Interannual variability, trend analysis, and aerosol indirect effects

NASA Astrophysics Data System (ADS)

Zhang, Yang; Wang, Kai; He, Jian

2017-09-01

Following a comprehensive evaluation of WRF-CAM5 in Part I, Part II describes analyses of interannual variability, multi-year variation trends, and the direct, indirect, and total effects of anthropogenic aerosols. The interannual variations of chemical column and surface concentrations, and ozone (O3)/particulate matter (PM) indicators are strongly correlated to anthropogenic emission changes. Despite model biases, the model captures well the observed interannual variations of temperature at 2-m, cloud fraction, shortwave cloud forcing, downwelling shortwave radiation, cloud droplet number concentration, column O3, and column formaldehyde (HCHO) for the whole domain. While the model reproduces the volatile organic compound (VOC)-limited regimes of O3 chemistry at sites in Hong Kong, Taiwan, Japan, South Korea, and from the Acid Deposition Monitoring Network in East Asia (EANET) and the degree of sulfate neutralization at the EANET sites, it has limited capability in capturing the interannual variations of the ratio of O3 and nitrogen dioxide (O3/NO2) and PM chemical regime indicators, due to uncertainties in the emissions of precursors for O3 and secondary PM, the model assumption for ammonium bisulfate (NH4HSO4) as well as lack of gas/particle partitioning of total ammonia and total nitrate. While the variation trends in multi-year periods in aerosol optical depth and column concentrations of carbon monoxide, sulfur dioxide, and NO2 are mainly caused by anthropogenic emissions, those of major meteorological and cloud variables partly reflect feedbacks of chemistry to meteorological variables. The impacts of anthropogenic aerosol indirect effects either dominate or play an important role in the aerosol total effects for most cloud and chemical predictions, whereas anthropogenic aerosol direct effects influence most meteorological and radiation variables. The direct, indirect, and total effects of anthropogenic aerosols exhibit a strong interannual variability in 2001, 2006, and 2011.

40 CFR 52.277 - Oxides of nitrogen, combustion gas concentration limitations.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 3 2010-07-01 2010-07-01 false Oxides of nitrogen, combustion gas concentration limitations. 52.277 Section 52.277 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Oxides of nitrogen, combustion gas concentration limitations. (a) The following rules are being retained...

40 CFR 52.277 - Oxides of nitrogen, combustion gas concentration limitations.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 3 2014-07-01 2014-07-01 false Oxides of nitrogen, combustion gas concentration limitations. 52.277 Section 52.277 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Oxides of nitrogen, combustion gas concentration limitations. (a) The following rules are being retained...

40 CFR 52.277 - Oxides of nitrogen, combustion gas concentration limitations.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 3 2011-07-01 2011-07-01 false Oxides of nitrogen, combustion gas concentration limitations. 52.277 Section 52.277 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Oxides of nitrogen, combustion gas concentration limitations. (a) The following rules are being retained...

40 CFR 52.277 - Oxides of nitrogen, combustion gas concentration limitations.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 3 2012-07-01 2012-07-01 false Oxides of nitrogen, combustion gas concentration limitations. 52.277 Section 52.277 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Oxides of nitrogen, combustion gas concentration limitations. (a) The following rules are being retained...

40 CFR 52.277 - Oxides of nitrogen, combustion gas concentration limitations.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 3 2013-07-01 2013-07-01 false Oxides of nitrogen, combustion gas concentration limitations. 52.277 Section 52.277 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Oxides of nitrogen, combustion gas concentration limitations. (a) The following rules are being retained...

Origin, speciation, and fluxes of trace-element gases at Augustine volcano, Alaska: Insights into magma degassing and fumarolic processes

NASA Astrophysics Data System (ADS)

Symonds, Robert B.; Reed, Mark H.; Rose, William I.

1992-02-01

Thermochemical modeling predicts that trace elements in the Augustine gas are transported from near-surface magma as simple chloride (NaCl, KCl, FeCl 2, ZnCl 2, PbCl 2, CuCl, SbCl 3, LiCl, MnCl 2, NiCl 2, BiCl, SrCl 2), oxychloride (MoO 2Cl 2), sulfide (AsS), and elemental (Cd) gas species. However, Si, Ca, Al, Mg, Ti, V, and Cr are actually more concentrated in solids, beta-quartz (SiO 2), wollastonite (CaSiO 3), anorthite (CaAl 2Si 2O 8), diopside (CaMgSi 2O 6), sphene (CaTiSiO 5), V 2O 3(c), and Cr 2O 3(c), respectively, than in their most abundant gaseous species, SiF 4, CaCl 2, AlF 2O, MgCl 2 TiCl 4, VOCl 3, and CrO 2Cl 2. These computed solids are not degassing products, but reflect contaminants in our gas condensates or possible problems with our modeling due to "missing" gas species in the thermochemical data base. Using the calculated distribution of gas species and the COSPEC SO 2 fluxes, we have estimated the emission rates for many species (e.g., COS, NaCl, KCl, HBr, AsS, CuCl). Such forecasts could be useful to evaluate the effects of these trace species on atmospheric chemistry. Because of the high volatility of metal chlorides (e.g., FeCl 2, NaCl, KCl, MnCl 2, CuCl), the extremely HCl-rich Augustine volcanic gases are favorable for transporting metals from magma. Thermochemical modeling shows that equilibrium degassing of magma near 870°C can account for the concentrations of Fe, Na, K, Mn, Cu, Ni and part of the Mg in the gases escaping from the dome fumaroles on the 1986 lava dome. These calculations also explain why gases escaping from the lower temperature but highly oxidized moat vents on the 1976 lava dome should transport less Fe, Na, K, Mn and Ni, but more Cu; oxidation may also account for the larger concentrations of Zn and Mo in the moat gases. Nonvolatile elements (e.g., Al, Ca, Ti, Si) in the gas condensates came from eroded rock particles that dissolved in our samples or, for Si, from contamination from the silica sampling tube. Only a very small amount of rock contamination occurred (water/rock ratios between 10 4 and 10 6). Erosion is more prevalent in the pyroclastic flow fumaroles than in the summit vents, reflecting physical differences in the fumarole walls: ash vs. lava. Trace element contents of volcanic gases show enormous variability because of differences in the intensive parameters of degassing magma and variable amounts of wall rock erosion in volcanic fumaroles.

Shale gas development impacts on surface water quality in Pennsylvania.

PubMed

Olmstead, Sheila M; Muehlenbachs, Lucija A; Shih, Jhih-Shyang; Chu, Ziyan; Krupnick, Alan J

2013-03-26

Concern has been raised in the scientific literature about the environmental implications of extracting natural gas from deep shale formations, and published studies suggest that shale gas development may affect local groundwater quality. The potential for surface water quality degradation has been discussed in prior work, although no empirical analysis of this issue has been published. The potential for large-scale surface water quality degradation has affected regulatory approaches to shale gas development in some US states, despite the dearth of evidence. This paper conducts a large-scale examination of the extent to which shale gas development activities affect surface water quality. Focusing on the Marcellus Shale in Pennsylvania, we estimate the effect of shale gas wells and the release of treated shale gas waste by permitted treatment facilities on observed downstream concentrations of chloride (Cl(-)) and total suspended solids (TSS), controlling for other factors. Results suggest that (i) the treatment of shale gas waste by treatment plants in a watershed raises downstream Cl(-) concentrations but not TSS concentrations, and (ii) the presence of shale gas wells in a watershed raises downstream TSS concentrations but not Cl(-) concentrations. These results can inform future voluntary measures taken by shale gas operators and policy approaches taken by regulators to protect surface water quality as the scale of this economically important activity increases.

Pathlength Determination for Gas in Scattering Media Absorption Spectroscopy

PubMed Central

Mei, Liang; Somesfalean, Gabriel; Svanberg, Sune

2014-01-01

Gas in scattering media absorption spectroscopy (GASMAS) has been extensively studied and applied during recent years in, e.g., food packaging, human sinus monitoring, gas diffusion studies, and pharmaceutical tablet characterization. The focus has been on the evaluation of the gas absorption pathlength in porous media, which a priori is unknown due to heavy light scattering. In this paper, three different approaches are summarized. One possibility is to simultaneously monitor another gas with known concentration (e.g., water vapor), the pathlength of which can then be obtained and used for the target gas (e.g., oxygen) to retrieve its concentration. The second approach is to measure the mean optical pathlength or physical pathlength with other methods, including time-of-flight spectroscopy, frequency-modulated light scattering interferometry and the frequency domain photon migration method. By utilizing these methods, an average concentration can be obtained and the porosities of the material are studied. The last method retrieves the gas concentration without knowing its pathlength by analyzing the gas absorption line shape, which depends upon the concentration of buffer gases due to intermolecular collisions. The pathlength enhancement effect due to multiple scattering enables also the use of porous media as multipass gas cells for trace gas monitoring. All these efforts open up a multitude of different applications for the GASMAS technique. PMID:24573311

SAFETY OF MANNITOL USE IN BOWEL PREPARATION: a prospective assessment of intestinal methane (CH4) levels during colonoscopy after mannitol and sodium phosphate (NaP) bowel cleansing.

PubMed

Paulo, Gustavo Andrade de; Martins, Fernanda Prata Borges; Macedo, Erika Pereira de; Gonçalves, Manoel Ernesto Peçanha; Ferrari, Angelo Paulo

2016-01-01

- Adequate bowel preparation is critical for the quality of colonoscopy. Despite reported occurrence of colonic explosion due to methane and hydrogen production by bacterial fermentation during colonoscopy, gas exchange during the procedure is believed to be effective in lowering existing methane concentration, allowing for safe utilization of mannitol for bowel preparation. Thus, mannitol is widely used for bowel cleansing prior to colonoscopy, considering its low cost and effectiveness for bowel preparation. - The aim of this study was to assess the safety of mannitol for bowel preparation, when compared to sodium phosphate (NaP). - We conducted a prospective observational study in which 250 patients undergoing colonoscopy at Universidade Federal de São Paulo and Hospital Albert Einstein (São Paulo, Brazil) were approached for inclusion in the study. Patients received either mannitol (n=50) or NaP (n=200) for bowel preparation, based on physician indication. Study was conducted from August 2009 to December 2009. The main outcome of interest was presence of detectable levels of methane (CH4) during colonoscopy and reduction in such levels after gas exchange during the procedure. Methane concentrations were measured in three intestinal segments during scope introduction and withdrawal. Safety was assessed as the absence of high levels of methane, defined as 5%. Measurements were made using a multi-gas monitor (X-am 7000, Dräger Safety AG & Co. KGaA, Lübeck, Germany) connected to a plastic catheter introduced into the working channel of the colonoscope. Additional outcomes of interest included levels of O2. Methane and O2 levels are reported as ppm. Mean, difference and standard deviation of levels of gas measured in both moments were calculated and compared in both groups. Proportions of patients with detectable or high levels of methane in both groups were compared. Continuous variables were analyzed using t test and categorical variables using qui-square tests. The Ethics Committee in both study sites approved the study protocol. - Patients in both groups were similar regarding demographics, colonoscopy indication, ASA status and quality of bowel preparation. Seven (3.5%) patients in the NaP group had methane detected during introduction of the endoscope. Methane levels became undetectable during withdrawal of the scope. None of the patients in the mannitol group had detectable levels of methane. O2 levels did not differ in the groups. - This is the largest study to assess the safety of mannitol for bowel preparation, considering methane measurements. Our results indicate that mannitol use is as safe as NaP, and gas exchange was efficient in reducing methane concentrations.

A Priori Subgrid Scale Modeling for a Droplet Laden Temporal Mixing Layer

NASA Technical Reports Server (NTRS)

Okongo, Nora; Bellan, Josette

2000-01-01

Subgrid analysis of a transitional temporal mixing layer with evaporating droplets has been performed using a direct numerical simulation (DNS) database. The DNS is for a Reynolds number (based on initial vorticity thickness) of 600, with droplet mass loading of 0.2. The gas phase is computed using a Eulerian formulation, with Lagrangian droplet tracking. Since Large Eddy Simulation (LES) of this flow requires the computation of unfiltered gas-phase variables at droplet locations from filtered gas-phase variables at the grid points, it is proposed to model these by assuming the gas-phase variables to be given by the filtered variables plus a correction based on the filtered standard deviation, which can be computed from the sub-grid scale (SGS) standard deviation. This model predicts unfiltered variables at droplet locations better than simply interpolating the filtered variables. Three methods are investigated for modeling the SGS standard deviation: Smagorinsky, gradient and scale-similarity. When properly calibrated, the gradient and scale-similarity methods give results in excellent agreement with the DNS.

Evaluation of H2O2 and pH in exhaled breath condensate samples: methodical and physiological aspects.

PubMed

Knobloch, Henri; Becher, Gunther; Decker, Manfred; Reinhold, Petra

2008-05-01

This veterinary study is aimed at further standardization of H(2)O(2) and pH measurements in exhaled breath condensate (EBC). Data obtained in the study provide valuable information for many mammalian species including humans, and may help to avoid general pitfalls in interpretation of EBC data. EBC was sampled via the 'ECoScreen' in healthy calves (body weight 63-98 kg). Serum samples and condensates of ambient (indoor) air were collected in parallel. In the study on H(2)O(2), concentrations of H(2)O(2) in EBC, blood and ambient air were determined with the biosensor system 'ECoCheck'. In EBC, the concentration of H(2)O(2) was found to be dependent on food intake and increased significantly in the course of the day. Physiologically, lowest H(2)O(2) concentrations at 06:00 varied within the range 138-624 nmol l(-1) EBC or 0.10-0.94 nmol per 100 l exhaled breath and individual concentrations were significantly different indicating a remarkable intersubject variability. Highly reproducible results were seen within each subject (three different days within 4 weeks). No correlation existed between H(2)O(2) concentrations in EBC and blood, and EBC-H(2)O(2) was not influenced by variables of spontaneous breathing. Further results confirmed that standardization of H(2)O(2) measurements in EBC requires (1) the re-calculation of the concentration exhaled per 100 l exhaled breath (because the analyzed concentration in the liquid condensate underlies multiple methodological sources of variability given by the collection process), and (2) subtracting the concentration of inspired indoor H(2)O(2). In the study on pH use of the ISFET electrode (Sentron, the Netherlands) and a blood gas analyzer ABL 550 (Radiometer, Denmark) led to comparable results for EBC-pH (r=0.89, R(2)=79.3%, p

Constraints of gas venting activity for the interstitial water geochemistry at the shallow gas hydrate site, eastern margin of the Japan Sea; results from high resolution time-series fluid sampling by OsmoSampler

NASA Astrophysics Data System (ADS)

Owari, S.; Tomaru, H.; Matsumoto, R.

2016-12-01

We have conducted ROV researches in the eastern margin of the Japan Sea where active gas venting and outcropping of gas hydrates were observed near the seafloor and have found the strength and location of venting had changed within a few days. These observations indicate the seafloor environments with the shallow gas hydrate system could have changed for short period compared to a geological time scale. We have applied a long-term osmotic fluid sampling system "OsmoSampler" on the active gas hydrate system for one year in order to document how the gas venting and gas hydrate activity have changed the geochemical environments near the seafloor. All the major ion concentrations in the interstitial water show synchronous increase and decrease repeatedly in three to five days, reflecting the incorporation and release of fresh water in gas hydrates in response to the gas concentration change near the sampling site. Dissolved methane concentration increases rapidly and excessively (over several mM) in the first 40 days corresponding to the active gas venting. The increases of methane concentration are often associated with high ion concentration during high water pressure period, indicating excess gas release from shallow gas pockets. Contrarily, enhanced gas hydrate growth may plug the fluid-gas paths in shallow sediment, reducing gas hydrate formation due to the decrease of methane flux. This study was conducted under the commission from AIST as a part of the methane hydrate research project funded by METI (the Ministry of Economy, Trade and Industry, Japan).

Decadal evaluation of regional climate, air quality, and their interactions using WRF/Chem Version 3.6.1

NASA Astrophysics Data System (ADS)

Yahya, K.; Wang, K.; Campbell, P.; Glotfelty, T.; He, J.; Zhang, Y.

2015-08-01

The Weather Research and Forecasting model with Chemistry (WRF/Chem) v3.6.1 with the Carbon Bond 2005 (CB05) gas-phase mechanism is evaluated for its first decadal application during 2001-2010 using the Representative Concentration Pathway (RCP 8.5) emissions to assess its capability and appropriateness for long-term climatological simulations. The initial and boundary conditions are downscaled from the modified Community Earth System Model/Community Atmosphere Model (CESM/CAM5) v1.2.2. The meteorological initial and boundary conditions are bias-corrected using the National Center for Environmental Protection's Final (FNL) Operational Global Analysis data. Climatological evaluations are carried out for meteorological, chemical, and aerosol-cloud-radiation variables against data from surface networks and satellite retrievals. The model performs very well for the 2 m temperature (T2) for the 10 year period with only a small cold bias of -0.3 °C. Biases in other meteorological variables including relative humidity at 2 m, wind speed at 10 m, and precipitation tend to be site- and season-specific; however, with the exception of T2, consistent annual biases exist for most of the years from 2001 to 2010. Ozone mixing ratios are slightly overpredicted at both urban and rural locations but underpredicted at rural locations. PM2.5 concentrations are slightly overpredicted at rural sites, but slightly underpredicted at urban/suburban sites. In general, the model performs relatively well for chemical and meteorological variables, and not as well for aerosol-cloud-radiation variables. Cloud-aerosol variables including aerosol optical depth, cloud water path, cloud optical thickness, and cloud droplet number concentration are generally underpredicted on average across the continental US. Overpredictions of several cloud variables over eastern US result in underpredictions of radiation variables and overpredictions of shortwave and longwave cloud forcing which are important climate variables. While the current performance is deemed to be acceptable, improvements to the bias-correction method for CESM downscaling and the model parameterizations of cloud dynamics and thermodynamics, as well as aerosol-cloud interactions can potentially improve model performance for long-term climate simulations.

PM2.5 and gaseous pollutants in New York State during 2005-2016: Spatial variability, temporal trends, and economic influences

NASA Astrophysics Data System (ADS)

Squizzato, Stefania; Masiol, Mauro; Rich, David Q.; Hopke, Philip K.

2018-06-01

Over the past decades, mitigation strategies have been adopted both by federal and state agencies in the United States (US) to improve air quality. Between 2007 and 2009, the US faced a financial/economic crisis that lowered activity and reduced emissions. At the same time, changes in the prices of coal and natural gas drove a shift in fuels used for electricity generation. Seasonal patterns, diel cycles, spatial gradients, and trends in PM2.5 and gaseous pollutants concentrations (NOx, SO2, CO and O3) monitored in New York State (NYS) from 2005 to 2016 were examined. Relationships between ambient concentrations, changes in NYS emissions retrieved from the US EPA trends inventory, and economic indicators were studied. PM2.5 and primary gaseous pollutants concentrations decreased across NYS. By 2016, PM2.5 and SO2 attained relatively homogeneous concentrations across the state. PM2.5 concentrations decreased significantly at all sites. Similarly, SO2 concentrations declined at all sites within this period, with the highest slopes observed at the urban sites. Reductions in NOx emissions likely contributed to summertime average ozone reductions. NOx and VOCs controls reduced O3 peak concentrations as seen in significant relationships between the annual O3 4th-highest daily maximum 8-h concentrations and estimated NOx emissions at rural and suburban sites (r2 ∼ 0.7). Spring maxima were not reduced with most sites showing insignificant slopes or significant positive slopes (e.g., +2.6% y-1 and +2% y-1, at CCNY and PFI, respectively). Increases in autumn and winter ozone concentrations were found (e,g., 6.6 ± 0.4% y-1 on average in New York City). Significant relationships were observed between PM2.5, primary pollutants, and economic indicators. Overall, a decrease in electricity generation with coal, and the simultaneous increase in natural gas consumption for power generation, led to a decrease in PM2.5 and gaseous pollutants concentrations.

The composition of volcanic gas issuing from Pu`u `O`o, Kilauea Volcano, Hawaii, 2004-5

NASA Astrophysics Data System (ADS)

Edmonds, M.; Gerlach, T. M.; Herd, R. A.; Sutton, A. J.; Elias, T.

2005-12-01

The eruption of lava is accompanied by prodigious quantities of volcanic gases at Kilauea Volcano. Although sophisticated gas monitoring methods have been implemented at Pu`u `O`o, it is logistically difficult to gather data regularly on the full suite of volcanic gases emitted from crater and flank vents. Since March 2004, Open Path Fourier Transform Infrared Spectroscopy has been carried out, using incandescent vents as a source of infra red (IR) radiation. Strong IR sources, high gas concentrations and short optical pathlengths allow the regular determination of 7 volcanic gas species from vents which are usually too dangerous to approach for direct gas sampling. The data show that a) the gas composition exhibits a significant amount of variation over time and b) different crater vents, just 40-100 metres apart, emit different gas compositions and the gas composition is generally highly variable spatially around the cone and upper flow-field degassing sources (vents, skylights, hornitos). The main degassing site within Pu`u `O`o, the East Pond vent, has emitted gas of a very similar composition to that measured in 1983-5, throughout most of 2004-5: typically 75-85 mol% H2O, 10-13% SO2, 0.1-3.0% CO2, 0.3-0.6% HCl, 0.1-0.5% HF, 0.1-0.8% H2S and 0.015-0.025% CO. The most highly variable species over time and space are CO2, HF, H2S and CO. Data collected during February 2005 show cyclic variations in gas composition during lava spattering activity, which occurred every 10-20 minutes at the East Pond vent inside the crater of Pu`u `O`o. The volcanic gas was rich in CO2, HCl, H2S and CO during and immediately after the spatter episode, which involved the spray of lava from the vent 10-30 metres into the air. During the next 10-15 minutes, after spattering, the volcanic gas gradually became more water-rich, it lost its CO2 and H2S components and the HCl/HF ratio decreased. We interpret these changes to be due to the upward migration of discrete bubbles from tens of metres depth beneath the volcanic vent, which burst at the surface and cause expulsion of lava and gas. Between larger, deep-derived bubbles bursting at the surface, degassing, of mainly water, takes place from the topmost part of the magma column.

[Generation of Superoxide Radicals by Complex III in Heart Mitochondria and Antioxidant Effect of Dinitrosyl Iron Complexes at Different Partial Pressure of Oxygen].

PubMed

Dudylina, A L; Ivanova, M V; Shumaev, K B; Ruuge, E K

2016-01-01

The EPR spin-trapping technique and EPR-oximetry were used to study generation of superoxide radicals in heart mitochondria isolated from Wistar rats under conditions of variable oxygen concentration. Lithium phthalocyanine and TEMPONE-15N-D16 were chosen to determine oxygen content in a gas-permeable capillary tube containing mitochondria. TIRON was used as a spin trap. We investigated the influence of different oxygen concentrations in incubation mixture and demonstrated that heart mitochondria can generate superoxide in complex III at different partial pressure of oxygen as well as under the conditions of deep hypoxia (< 5% O2). Dinitrosyl iron complexes with glutathione (the pharmaceutical drug "Oxacom") exerted an antioxidant effect, regardless of the value of the partial pressure of oxygen, but the magnitude and kinetic characteristics of the effect depended on the concentration of the drug.

Pharmacokinetics of ethanol and its metabolite, acetaldehyde, and fetolethality in the third-trimester pregnant guinea pig for oral administration of acute, multiple-dose ethanol.

PubMed

Clarke, D W; Steenaart, N A; Slack, C J; Brien, J F

1986-08-01

The pharmacokinetics of ethanol and its metabolite, acetaldehyde, were determined in the third-trimester pregnant guinea pig (56-59 days gestation) for oral intubation of four doses of 1 g ethanol/kg maternal body weight, administered at 1-h intervals. Animals (n = 4-7) were sacrificed at each of selected times during the 26-h study. Ethanol and acetaldehyde concentrations were determined by headspace gas-liquid chromatography. The maternal and fetal blood ethanol concentration-time curves were virtually superimposable, which indicated unimpeded bidirectional placental transfer of ethanol in the maternal-fetal unit. The blood and brain ethanol concentrations were similar in each of the maternal and fetal compartments during the study, which indicated rapid equilibrium distribution of ethanol. There was accumulation of ethanol in the amniotic fluid resulting in higher ethanol concentration compared with maternal and fetal blood during the elimination phase, which indicated that the amniotic fluid may serve as a reservoir for ethanol in utero. Acetaldehyde was measurable in all the biological fluids and tissues at concentrations that were at least 1,000-fold less than the respective ethanol concentrations and were variable. There was ethanol-induced fetolethality that was delayed and variable among animals, and was 55% at 23 h. At this time interval, the ethanol concentrations in maternal blood and brain, fetal brain, and amniotic fluid were 35- to 53-fold greater and the acetaldehyde concentrations in maternal blood and fetal brain were four- to five-fold higher in the animals with dead fetuses compared with the guinea pigs with live litters. These data indicated that decreased ethanol elimination from the maternal-fetal unit was related temporally to the fetolethality.

Geochemical Variability and the Potential for Beneficial Use of Waste Water Coproduced with Oil from Permian Basin of the Southwest USA

NASA Astrophysics Data System (ADS)

Khan, N. A.; Holguin, F. O.; Xu, P.; Engle, M.; Dungan, B.; Hunter, B.; Carroll, K. C.

2014-12-01

The U.S. generates 21 billion barrels/year of coproduced water from oil and gas exploration, which is generally considered waste water. Growth in unconventional oil and gas production has spurred interest in beneficial uses of produced water, especially in arid regions such as the Permian Basin of Texas and New Mexico, the largest U.S. tight oil producer. Produced waters have variable chemistries, but generally contain high levels of organics and salts. In order to evaluate the environmental impact, treatment, and reuse potential, there is a need to characterize the compositional variability of produced water. In the present study, produced water samples were collected from 12 wells across the Permian Basin. Compositional analyses including coupled gas chromatography-time of flight-mass spectrometry and inductively coupled plasma-optical emission spectroscopy were conducted. The samples show elevated benzene, ethylbenzene, toluene, xylene, alkyl benzenes, propyl-benzene, and naphthalene compared to other heteroaromatics; they also contain complex hydrocarbon compounds containing oxygen, nitrogen, and sulfur. Van Krevelen diagrams show an increase in the concentration of heteroaromatic hydrocarbons with increasing well depth. The salinity, dominated by sodium-chloride, also increases with depth, ranging from 37-150 g/L TDS. Depth of wells (or producing formation) is a primary control on predicting water quality for treatment and beneficial use. Our results suggest that partial treatment by removing suspended solids and organic contaminants would support some beneficial uses such as onsite reuse, bioenergy production, and other industrial uses. Due to the high salinity, conventional desalination processes are not applicable or very costly, making beneficial uses requiring low salinity not feasible.

Global performance parameters for different pneumatic bioreactors operating with water and glycerol solution: experimental data and CFD simulation.

PubMed

Rodriguez, G Y; Valverde-Ramírez, M; Mendes, C E; Béttega, R; Badino, A C

2015-11-01

Global variables play a key role in evaluation of the performance of pneumatic bioreactors and provide criteria to assist in system selection and design. The purpose of this work was to use experimental data and computational fluid dynamics (CFD) simulations to determine the global performance parameters gas holdup ([Formula: see text]) and volumetric oxygen transfer coefficient (k L a), and conduct an analysis of liquid circulation velocity, for three different geometries of pneumatic bioreactors: bubble column, concentric-tube airlift, and split tube airlift. All the systems had 5 L working volumes and two Newtonian fluids of different viscosities were used in the experiments: distilled water and 10 cP glycerol solution. Considering the high oxygen demand in certain types of aerobic fermentations, the assays were carried out at high flow rates. In the present study, the performances of three pneumatic bioreactors with different geometries and operating with two different Newtonian fluids were compared. A new CFD modeling procedure was implemented, and the simulation results were compared with the experimental data. The findings indicated that the concentric-tube airlift design was the best choice in terms of both gas holdup and volumetric oxygen transfer coefficient. The CFD results for gas holdup were consistent with the experimental data, and indicated that k L a was strongly influenced by bubble diameter and shape.

Measuring temporal variability in pore-fluid chemistry to assess gas hydrate stability: development of a continuous pore-fluid array.

PubMed

Lapham, Laura L; Chanton, Jeffrey P; Martens, Christopher S; Higley, Paul D; Jannasch, Hans W; Woolsey, J Robert

2008-10-01

A specialized pore-fluid array (PFA) sampler was designed to collect and store pore fluids to monitor temporal changes of ions and gases in gas hydrate bearing sediments. We tested the hypothesis that pore-fluid chemistry records hydrate formation or decomposition events and reflects local seismic activity. The PFA is a seafloor probe that consists of an interchangeable instrument package that houses OsmoSamplers, long-term pore-fluid samplers, a specialized low-dead volume fluid coupler, and eight sample ports along a 10 m sediment probe shaft. The PFA was deployed at Mississippi Canyon 118, a Gulf of Mexico hydrate site. A 170 day record was acquired from the overlying water and 1.3 m below seafloor (mbsf). Fluids were measured for dissolved chloride, sulfate, and methane concentrations and dissolved inorganic carbon and methane stable carbon and deuterium isotope ratios. Chloride and sulfate did not change significantly over time, suggesting the absence of gas hydrate formation or decomposition events. Over the temporal record, methane concentrations averaged 4 mM at 1.3 mbsf, and methane was thermogenic in origin (delta13C-CH4 = -32.4 +/- 3.4 per thousand). The timing of an anomalous 14 mM methane spike coincided with a nearby earthquake (Mw = 5.8), consistent with the hypothesis that pore-fluid chemistry reflects seismic events.

Gas storage and separation by electric field swing adsorption

DOEpatents

Currier, Robert P; Obrey, Stephen J; Devlin, David J; Sansinena, Jose Maria

2013-05-28

Gases are stored, separated, and/or concentrated. An electric field is applied across a porous dielectric adsorbent material. A gas component from a gas mixture may be selectively separated inside the energized dielectric. Gas is stored in the energized dielectric for as long as the dielectric is energized. The energized dielectric selectively separates, or concentrates, a gas component of the gas mixture. When the potential is removed, gas from inside the dielectric is released.

Spatial and Temporal Variability of CO2 and CH4 Concentrations in the Atmospheric Surface Layer over West Siberia

NASA Astrophysics Data System (ADS)

Belan, Boris D.; Machida, Toshinobu; Sasakawa, Motoki; Davydov, Denis K.; Fofonov, Alexander V.; Krasnov, Oleg A.; Maksyutov, Shamil; Arshinov, Mikhail Yu.

2015-04-01

The investigation of greenhouse gas behavior in the atmosphere plays a key role in predicting the global changes of Earth's climate. In this connection, of particular importance is the study of the distribution of sources/sinks of trace gases in the atmospheric surface layer over the different regions of the globe. In order to fill a gap in the data on greenhouse gas concentrations in Russia, National Institute for Environmental Studies (NIES, Japan) and Institute of Atmospheric Optics (IAO SB RAS, Russia) established a network for GHG monitoring (JR-STATION, Japan-Russia Siberian Tall Tower Inland Observation Network). Gas analyzers and meteorological sensors were mounted at radio relay towers located in different regions of West Siberia. The checking equipment was placed in containers at the tower base. In the containers, the climatic parameters optimal for gas analyzer operation were maintained. The work on the network development started in 2001. Since at each of the sites the measurement duration could be different, in this paper we present the data of the greenhouse gas monitoring for eight sites which give the primary idea on the spatial distribution and temporal dynamics of CO2 and CH4 in the atmospheric surface layer over West Siberia. The analysis of the data showed that the average increase in concentration of carbon dioxide by results of our measurements in this territory increases within 1.95 - 2.53 ppm/year, depending on the area. The analysis of long-term data testifies about existence of growth of concentration of methane within 3.2 - 7.2 ppb / year. The presence of a distributed network of the sites operating in the monitoring regime makes it possible not only to investigate the temporal dynamics of CO2 and CH4 at each site and to determine the spatial differences between the concentrations by comparing the data, but also to plot the distribution charts for different moments of time. This work was supported by the Global Environment Research Account for National Institutes of the Ministry of the Environment (Japan), the Branch of Geology, Geophysics and Mining Sciences of RAS (Program No. 5); State contracts of the Ministry of Education and Science of Russia No. 14.604.21.0100, (RFMTFIBBB210290) and No. 14.613.21.0013 (RFMEFI61314X0013); Interdisciplinary integration projects of the Siberian Branch of the Russian Academy of Science No. 35, No. 70 and No. 131; and Russian Foundation for Basic Research (grants No. 14-05-00526 and 14-05-00590).

Constraining Methane Emissions from Natural Gas Production in Northeastern Pennsylvania Using Aircraft Observations and Mesoscale Modeling

NASA Astrophysics Data System (ADS)

Barkley, Z.; Davis, K.; Lauvaux, T.; Miles, N.; Richardson, S.; Martins, D. K.; Deng, A.; Cao, Y.; Sweeney, C.; Karion, A.; Smith, M. L.; Kort, E. A.; Schwietzke, S.

2015-12-01

Leaks in natural gas infrastructure release methane (CH4), a potent greenhouse gas, into the atmosphere. The estimated fugitive emission rate associated with the production phase varies greatly between studies, hindering our understanding of the natural gas energy efficiency. This study presents a new application of inverse methodology for estimating regional fugitive emission rates from natural gas production. Methane observations across the Marcellus region in northeastern Pennsylvania were obtained during a three week flight campaign in May 2015 performed by a team from the National Oceanic and Atmospheric Administration (NOAA) Global Monitoring Division and the University of Michigan. In addition to these data, CH4 observations were obtained from automobile campaigns during various periods from 2013-2015. An inventory of CH4 emissions was then created for various sources in Pennsylvania, including coalmines, enteric fermentation, industry, waste management, and unconventional and conventional wells. As a first-guess emission rate for natural gas activity, a leakage rate equal to 2% of the natural gas production was emitted at the locations of unconventional wells across PA. These emission rates were coupled to the Weather Research and Forecasting model with the chemistry module (WRF-Chem) and atmospheric CH4 concentration fields at 1km resolution were generated. Projected atmospheric enhancements from WRF-Chem were compared to observations, and the emission rate from unconventional wells was adjusted to minimize errors between observations and simulation. We show that the modeled CH4 plume structures match observed plumes downwind of unconventional wells, providing confidence in the methodology. In all cases, the fugitive emission rate was found to be lower than our first guess. In this initial emission configuration, each well has been assigned the same fugitive emission rate, which can potentially impair our ability to match the observed spatial variability. The current model also does not distinguish between natural gas emissions during the different stages of transportation. We finally discuss the use of additional tracers such as the 13CH4 isotopic ratio and ethane concentrations to separate the various contributors to the regional atmospheric CH4 enhancement.

Electrical properties of methane hydrate + sediment mixtures: The σ of CH 4 Hydrate + Sediment

DOE PAGES

Du Frane, Wyatt L.; Stern, Laura A.; Constable, Steven; ...

2015-07-30

Knowledge of the electrical properties of multicomponent systems with gas hydrate, sediments, and pore water is needed to help relate electromagnetic (EM) measurements to specific gas hydrate concentration and distribution patterns in nature. We built a pressure cell capable of measuring in situ electrical properties of multicomponent systems such that the effects of individual components and mixing relations can be assessed. We first established the temperature-dependent electrical conductivity (σ) of pure, single-phase methane hydrate to be ~5 orders of magnitude lower than seawater, a substantial contrast that can help differentiate hydrate deposits from significantly more conductive water-saturated sediments in EMmore » field surveys. We report σ measurements of two-component systems in which methane hydrate is mixed with variable amounts of quartz sand or glass beads. Sand by itself has low σ but is found to increase the overall σ of mixtures with well-connected methane hydrate. Alternatively, the overall σ decreases when sand concentrations are high enough to cause gas hydrate to be poorly connected, indicating that hydrate grains provide the primary conduction path. Our measurements suggest that impurities from sand induce chemical interactions and/or doping effects that result in higher electrical conductivity with lower temperature dependence. Finally, these results can be used in the modeling of massive or two-phase gas-hydrate-bearing systems devoid of conductive pore water. Further experiments that include a free water phase are the necessary next steps toward developing complex models relevant to most natural systems.« less

Electrical properties of methane hydrate + sediment mixtures: The σ of CH 4 Hydrate + Sediment

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

Du Frane, Wyatt L.; Stern, Laura A.; Constable, Steven

Knowledge of the electrical properties of multicomponent systems with gas hydrate, sediments, and pore water is needed to help relate electromagnetic (EM) measurements to specific gas hydrate concentration and distribution patterns in nature. We built a pressure cell capable of measuring in situ electrical properties of multicomponent systems such that the effects of individual components and mixing relations can be assessed. We first established the temperature-dependent electrical conductivity (σ) of pure, single-phase methane hydrate to be ~5 orders of magnitude lower than seawater, a substantial contrast that can help differentiate hydrate deposits from significantly more conductive water-saturated sediments in EMmore » field surveys. We report σ measurements of two-component systems in which methane hydrate is mixed with variable amounts of quartz sand or glass beads. Sand by itself has low σ but is found to increase the overall σ of mixtures with well-connected methane hydrate. Alternatively, the overall σ decreases when sand concentrations are high enough to cause gas hydrate to be poorly connected, indicating that hydrate grains provide the primary conduction path. Our measurements suggest that impurities from sand induce chemical interactions and/or doping effects that result in higher electrical conductivity with lower temperature dependence. Finally, these results can be used in the modeling of massive or two-phase gas-hydrate-bearing systems devoid of conductive pore water. Further experiments that include a free water phase are the necessary next steps toward developing complex models relevant to most natural systems.« less

Biodegradation of effluent contaminated with diesel fuel and gasoline.

PubMed

Vieira, P A; Vieira, R B; de França, F P; Cardoso, V L

2007-02-09

We studied the effects of fuel concentration (diesel and gasoline), nitrogen concentration and culture type on the biodegradation of synthetic effluent similar to what was found at inland fuel distribution terminals. An experimental design with two levels and three variables (2(3)) was used. The mixed cultures used in this study were obtained from lake with a history of petroleum contamination and were named culture C(1) (collected from surface sediment) and C(2) (collected from a depth of approximately 30cm). Of the parameters studied, the ones that had the greatest influence on the removal of total petroleum hydrocarbons (TPH) were a nitrogen concentration of 550mg/L and a fuel concentration of 4% (v/v) in the presence of culture C(1). The biodegradability study showed a TPH removal of 90+/-2% over a process period of 49 days. Analysis using gas chromatography identified 16 hydrocarbons. The aromatic compounds did not degrade as readily as the other hydrocarbons that were identified.

The distribution of methane in groundwater in Alberta (Canada) and associated aqueous geochemistry conditions

NASA Astrophysics Data System (ADS)

Humez, Pauline; Mayer, Bernhard; Nightingale, Michael; Becker, Veith; Kingston, Andrew; Taylor, Stephen; Millot, Romain; Kloppmann, Wolfram

2016-04-01

Development of unconventional energy resources such as shale gas and coalbed methane has generated some public concern with regard to the protection of groundwater and surface water resources from leakage of stray gas from the deep subsurface. In terms of environmental impact to and risk assessment of shallow groundwater resources, the ultimate challenge is to distinguish: (a) natural in-situ production of biogenic methane, (b) biogenic or thermogenic methane migration into shallow aquifers due to natural causes, and (c) thermogenic methane migration from deep sources due to human activities associated with the exploitation of conventional or unconventional oil and gas resources. We have conducted a NSERC-ANR co-funded baseline study investigating the occurrence of methane in shallow groundwater of Alberta (Canada), a province with a long record of conventional and unconventional hydrocarbon exploration. Our objective was to assess the occurrence and sources of methane in shallow groundwaters and to also characterize the hydrochemical environment in which the methane was formed or transformed through redox processes. Ultimately our aim was to determine whether methane was formed in-situ or whether it migrated from deeper formations into shallow aquifers. Combining hydrochemical and dissolved and free geochemical gas data from 372 groundwater samples obtained from 186 monitoring wells of the provincial groundwater observation well network (GOWN) in Alberta, it was found that methane is ubiquitous in groundwater in Alberta and is predominantly of biogenic origin. The highest concentrations of dissolved biogenic methane (> 0.01 mM or > 0.2 mg/L), characterized by δ13CCH4 values < -55‰, occurred in anoxic Na-Cl, Na-HCO3 and Na-HCO3-Cl type groundwater with negligible concentrations of nitrate and sulfate suggesting that methane was formed in-situ under methanogenic conditions consistent with the redox ladder concept. Despite quite variable gas concentrations and a wide range of δ13CCH4 values in baseline groundwater samples, no conclusive evidence was found for deep thermogenic gas that had migrated in significant amounts into shallow aquifers either naturally or via anthropogenically induced pathways. This study shows that the combined interpretation of aqueous geochemistry data in concert with the chemical and isotopic composition of dissolved and/or free gas can yield unprecedented insights into formation or migration of methane in shallow groundwater. This enables the assessment of cross-formational methane migration and provides an understanding of alkane gas sources and pathways necessary for a stringent baseline definition in the context of current and future unconventional hydrocarbon exploration and exploitation.

Toward refined estimates of ambient PM2.5 exposure: Evaluation of a physical outdoor-to-indoor transport model

NASA Astrophysics Data System (ADS)

Hodas, Natasha; Meng, Qingyu; Lunden, Melissa M.; Turpin, Barbara J.

2014-02-01

Because people spend the majority of their time indoors, the variable efficiency with which ambient PM2.5 penetrates and persists indoors is a source of error in epidemiologic studies that use PM2.5 concentrations measured at central-site monitors as surrogates for ambient PM2.5 exposure. To reduce this error, practical methods to model indoor concentrations of ambient PM2.5 are needed. Toward this goal, we evaluated and refined an outdoor-to-indoor transport model using measured indoor and outdoor PM2.5 species concentrations and air exchange rates from the Relationships of Indoor, Outdoor, and Personal Air Study. Herein, we present model evaluation results, discuss what data are most critical to prediction of residential exposures at the individual-subject and populations levels, and make recommendations for the application of the model in epidemiologic studies. This paper demonstrates that not accounting for certain human activities (air conditioning and heating use, opening windows) leads to bias in predicted residential PM2.5 exposures at the individual-subject level, but not the population level. The analyses presented also provide quantitative evidence that shifts in the gas-particle partitioning of ambient organics with outdoor-to-indoor transport contribute significantly to variability in indoor ambient organic carbon concentrations and suggest that methods to account for these shifts will further improve the accuracy of outdoor-to-indoor transport models.

Real-time CO2 sensor for the optimal control of electronic EGR system

NASA Astrophysics Data System (ADS)

Kim, Gwang-jung; Choi, Byungchul; Choi, Inchul

2013-12-01

In modern diesel engines, EGR (Exhaust Gas Recirculation) is an important technique used in nitrogen oxide (NOx) emission reduction. This paper describes the development and experimental results of a fiber-optical sensor using a 2.7 μm wavelength absorption to quantify the simultaneous CO2 concentration which is the primary variable of EGR rate (CO2 in the exhaust gas versus CO2 in the intake gas, %). A real-time laser absorption method was developed using a DFB (distributed feedback) diode laser and waveguide to make optimal design and control of electronic EGR system required for `Euro-6' and `Tier 4 Final' NOx emission regulations. While EGR is effective to reduce NOx significantly, the amount of HC and CO is increased in the exhaust gas if EGR rate is not controlled based on driving conditions. Therefore, it is important to recirculate an appropriate amount of exhaust gas in the operation condition generating high volume of NOx. In this study, we evaluated basic characteristics and functions of our optical sensor and studied basically in order to find out optimal design condition. We demonstrated CO2 measurement speed, accuracy and linearity as making a condition similar to real engine through the bench-scale experiment.

Flexible LNG supply, storage and price formation in a global natural gas market

NASA Astrophysics Data System (ADS)

Hayes, Mark Hanley

The body of work included in this dissertation explores the interaction of the growing, flexible liquefied natural gas (LNG) trade with the fundamentals of pipeline gas supply, gas storage, and gas consumption. By nature of its uses---largely for residential heating and electric power generation---the consumption of natural gas is highly variable both seasonally and on less predictable daily and weekly timescales. Flexible LNG trade will interconnect previously isolated regional gas markets, each with non-correlated variability in gas demand, differing gas storage costs, and heterogeneous institutional structures. The dissertation employs a series of analytical models to address key issues that will affect the expansion of the LNG trade and the implications for gas prices, investment and energy policy. First, I employ an optimization model to evaluate the fundamentals of seasonal LNG swing between markets with non-correlated gas demand (the U.S. and Europe). The model provides insights about the interaction of LNG trade with gas storage and price formation in interconnected regional markets. I then explore how random (stochastic) variability in gas demand will drive spot cargo movements and covariation in regional gas prices. Finally, I analyze the different institutional structures of the gas markets in the U.S. and Europe and consider how managed gas markets in Europe---without a competitive wholesale gas market---may effectively "export" supply and price volatility to countries with more competitive gas markets, such as the U.S.

Viewing inside Pyroclastic Flows - Large-scale Experiments on hot pyroclast-gas mixture flows

NASA Astrophysics Data System (ADS)

Breard, E. C.; Lube, G.; Cronin, S. J.; Jones, J.

2014-12-01

Pyroclastic density currents are the largest threat from volcanoes. Direct observations of natural flows are persistently prevented because of their violence and remain limited to broad estimates of bulk flow behaviour. The Pyroclastic Flow Generator - a large-scale experimental facility to synthesize hot gas-particle mixture flows scaled to pyroclastic flows and surges - allows investigating the physical processes behind PDC behaviour in safety. The ability to simulate natural eruption conditions and to view and measure inside the hot flows allows deriving validation and calibration data sets for existing numerical models, and to improve the constitutive relationships necessary for their effective use as powerful tools in hazard assessment. We here report on a systematic series of large-scale experiments on up to 30 ms-1 fast, 2-4.5 m thick, 20-35 m long flows of natural pyroclastic material and gas. We will show high-speed movies and non-invasive sensor data that detail the internal structure of the analogue pyroclastic flows. The experimental PDCs are synthesized by the controlled 'eruption column collapse' of variably diluted suspensions into an instrumented channel. Experiments show four flow phases: mixture acceleration and dilution during free fall; impact and lateral blasting; PDC runout; and co-ignimbrite cloud formation. The fully turbulent flows reach Reynolds number up to 107 and depositional facies similar to natural deposits. In the PDC runout phase, the shear flows develop a four-partite structure from top to base: a fully turbulent, strongly density-stratified ash cloud with average particle concentrations <<1vol%; a transient, turbulent dense suspension region with particle concentrations between 1 and 10 vol%; a non-turbulent, aerated and highly mobile dense underflows with particle concentrations between 40 and 50 vol%; and a vertically aggrading bed of static material. We characterise these regions and the exchanges of energy and momentum through their interfaces via vertical time-series profiles of velocity, particle concentration, gas and particle transport directionality and turbulent eddy characteristics. We highlight the importance of each region for the PDC runout dynamics and introduce a new transport and sedimentation model for downslope evolving pyroclastic flows.

The Breakup Mechanism and the Spray Pulsation Behavior of a Three-Stream Atomizer

NASA Astrophysics Data System (ADS)

Ng, Chin; Dord, Anne; Aliseda, Alberto

2011-11-01

In many processes of industrial importance, such as gasification, the liquid to gas mass ratio injected at the atomizer exceeds the limit of conventional two-fluid coaxial atomizers. To maximize the shear rate between the atomization gas and the liquid while maintaining a large contact area, a secondary gas stream is added at the centerline of the spray, interior to the liquid flow, which is annular in this configuration. This cylindrical gas jet has low momentum and does not contribute to the breakup process, which is still dominated by the high shear between the concentric annular liquid flow and the high momentum gas stream. The presence of two independently controlled gas streams leads to the appearance of a hydrodynamic instability that manifests itself in pulsating liquid flow rates and droplet sizes. We study the dependency of the atomization process on the relative flow rates of the three streams. We measure the size distribution, droplet number density and total liquid volumetric flow rate as a function of time, for realistic Weber and Ohnesorge numbers. Analysis of the temporal evolution of these physical variables reveals the dominant frequency of the instability and its effect on the breakup and dispersion of droplets in the spray. We present flow visualization and Phase Doppler Particle Analyzer results that provide insight into the behavior of this complex coaxial shear flow.

Functional Leaf Traits and Diurnal Dynamics of Photosynthetic Parameters Predict the Behavior of Grapevine Varieties Towards Ozone

PubMed Central

Pellegrini, Elisa; Campanella, Alessandra; Paolocci, Marco; Trivellini, Alice; Gennai, Clizia; Muganu, Massimo; Nali, Cristina; Lorenzini, Giacomo

2015-01-01

A comparative study on functional leaf treats and the diurnal dynamics of photosynthetic processes was conducted on 2-year-old potted plants of two grape (Vitis vinifera L.) varieties (Aleatico, ALE, and Trebbiano giallo, TRE), exposed under controlled conditions to realistic concentrations of the pollutant gas ozone (80 ppb for 5 h day-1, 8:00–13:00 h, + 40 ppb for 5 h day-1, 13:00–18:00 h). At constitutive levels, the morphological functional traits of TRE improved leaf resistance to gas exchange, suggesting that TRE is characterized by a potential high degree of tolerance to ozone. At the end of the treatment, both varieties showed typical visible injuries on fully expanded leaves and a marked alteration in the diurnal pattern of photosynthetic activity. This was mainly due to a decreased stomatal conductance (-27 and -29% in ALE and TRE, in terms of daily values in comparison to controls) and to a reduced mesophyllic functioning (+33 and +16% of the intercellular carbon dioxide concentration). Although the genotypic variability of grape regulates the response to oxidative stress, similar detoxification processes were activated, such as an increased content of total carotenoids (+64 and +30%, in ALE and TRE), enhanced efficiency of thermal energy dissipation within photosystem II (+32 and +20%) closely correlated with the increased de-epoxidation index (+26 and +22%) and variations in content of some osmolytes. In summary, we can conclude that: the daily photosynthetic performance of grapevine leaves was affected by a realistic exposure to ozone. In addition, the gas exchange and chlorophyll a fluorescence measurements revealed a different quali-quantitative response in the two varieties. The genotypic variability of V. vinifera and the functional leaf traits would seem to regulate the acclimatory response to oxidative stress and the degree of tolerance to ozone. Similar photoprotective mechanisms were activated in the two varieties, though to a different extent. PMID:26270333

Greenhouse Gas Dynamics in Streams and Riparian Floodplains located within Forested Landscapes of the US Northeast: Impact of Key Floodplain Geomorphic Features on Greenhouse Gas Production in a Forested Watershed in Northern New York State, USA.

NASA Astrophysics Data System (ADS)

Serchan, S. P.; Vidon, P.

2015-12-01

This study measured dissolved greenhouse gas (GHG) concentrations in interstitial water and stream across various "hotspots" in headwater catchments of Archer Creek watershed, New York, USA. Results indicated that stream water was hyper saturated with methane (CH4), and moderately saturated with carbon dioxide (CO2), and nitrous oxide (N2O). The values of dissolved CO2 (88.3 μmol/L), dissolved CH4 (1.2 μmol/L), and dissolved N2O (0.02 μmol/L) found in the stream were 5.8, 432, and 2.3 times in excess of atmospheric equilibrium, respectively. Results of dissolved GHG measured in interstitial water across various sites: riparian dry (RZ-Dry), riparian wet (RZ-Wet), riparian mucky (RZ-Mucky), pool with fine textured bed sediments (IS-fine-sedpool), pool with coarse textured bed sediments (IS-coarse-sed-pool), and riffles (Riffle) indicated high variations in the degree of saturation of all three GHG. RZ-Mucky, RZ-Wet, and IS-fine-sedpool sites were hotspots of CH4 and CO2 relative to other sites. RZ-Dry sites were hotspots of N2O. Multiple linear regression models indicated that dissolved oxygen (D.O.) and dissolved organic carbon (DOC) influenced dissolved CO2 and CH4 at most of the sites. Relationships between dissolved N2O and predictor variables were highly variable across all sites. Patterns of dissolved N2O in relatively oxic RZ-Dry sites (D.O. 5.3 mg/L) were positively correlated with nitrate (NO3) indicating nitrification as a dominant process in N2O production. In contrast, patterns of dissolved N2O were positively correlated with ammonium (NH4+) at RZ-Wet and RZ-Mucky sites where concentrations of D.O. were significantly lower compared to other sites.

Variable orifice using an iris shutter

DOEpatents

Beeman, Raymond; Brajkovich, Steven J.

1978-01-01

A variable orifice forming mechanism utilizing an iris shutter arrangement adapted to control gas flow, conductance in vacuum systems, as a heat shield for furnace windows, as a beam shutter in sputtering operations, and in any other application requiring periodic or continuously-variable control of material, gas, or fluid flow.

Relationship of gas hydrate concentration to porosity and reflection amplitude in a research well, Mackenzie Delta, Canada

USGS Publications Warehouse

Jin, Y.K.; Lee, M.W.; Collett, T.S.

2002-01-01

Well logs acquired at the Mallik 2L-38 gas hydrate research well. Mackenzie Delta, Canada, reveal a distinct trend showing that the resistivity of gas-hydrate-bearing sediments increases with increases in density porosities. This trend, opposite to the general trend of decrease in resistivity with porosity, implies that gas hydrates are more concentrated in the higher porosity. Using the Mallik 2L-38 well data, a proportional gas hydrate concentration (PGHC) model, which states that the gas hydrate concentration in the sediment's pore space is linearly proportional to porosity, is proposed for the general habitat of gas hydrate in sediments. Anomalous data (less than 6% of the total data) outside the dominant observed trend can be explained by local geological characteristics. The anomalous data analysis indicates that highly concentrated gas-hydrate-bearing layers would be expected where sediments have high proportions of gravel and coarse sand. Using the parameters in the PGHC model determined from resistivity-porosity logs, it is possible to qualitatively predict the degree of reflection amplitude variations in seismic profiles. Moderate-to-strong reflections are expected for the Mallik 2L-38 well. ?? 2002 Elsevier Science Ltd. All rights reserved.

46 CFR 154.1350 - Flammable gas detection system.

Code of Federal Regulations, 2013 CFR

2013-10-01

... flammable gas concentration over the concentration or volume ranges under paragraph (t) or (u) of this... a cargo concentration that is 30% or less of the lower flammable limit in air of the cargo carried... the space where the gas detection system's readout is located and must meet § 154.1365. (h) Remote...

Methods of Si based ceramic components volatilization control in a gas turbine engine

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

Garcia-Crespo, Andres Jose; Delvaux, John; Dion Ouellet, Noemie

A method of controlling volatilization of silicon based components in a gas turbine engine includes measuring, estimating and/or predicting a variable related to operation of the gas turbine engine; correlating the variable to determine an amount of silicon to control volatilization of the silicon based components in the gas turbine engine; and injecting silicon into the gas turbine engine to control volatilization of the silicon based components. A gas turbine with a compressor, combustion system, turbine section and silicon injection system may be controlled by a controller that implements the control method.

Seasonal variation of benzo(a)pyrene in the Spanish airborne PM10. Multivariate linear regression model applied to estimate BaP concentrations.

PubMed

Callén, M S; López, J M; Mastral, A M

2010-08-15

The estimation of benzo(a)pyrene (BaP) concentrations in ambient air is very important from an environmental point of view especially with the introduction of the Directive 2004/107/EC and due to the carcinogenic character of this pollutant. A sampling campaign of particulate matter less or equal than 10 microns (PM10) carried out during 2008-2009 in four locations of Spain was collected to determine experimentally BaP concentrations by gas chromatography mass-spectrometry mass-spectrometry (GC-MS-MS). Multivariate linear regression models (MLRM) were used to predict BaP air concentrations in two sampling places, taking PM10 and meteorological variables as possible predictors. The model obtained with data from two sampling sites (all sites model) (R(2)=0.817, PRESS/SSY=0.183) included the significant variables like PM10, temperature, solar radiation and wind speed and was internally and externally validated. The first validation was performed by cross validation and the last one by BaP concentrations from previous campaigns carried out in Zaragoza from 2001-2004. The proposed model constitutes a first approximation to estimate BaP concentrations in urban atmospheres with very good internal prediction (Q(CV)(2)=0.813, PRESS/SSY=0.187) and with the maximal external prediction for the 2001-2002 campaign (Q(ext)(2)=0.679 and PRESS/SSY=0.321) versus the 2001-2004 campaign (Q(ext)(2)=0.551, PRESS/SSY=0.449). Copyright 2010 Elsevier B.V. All rights reserved.

Survey of polyfluorinated chemicals (PFCs) in the atmosphere over the northeast Atlantic Ocean

NASA Astrophysics Data System (ADS)

Shoeib, Mahiba; Vlahos, Penny; Harner, Tom; Peters, Andrew; Graustein, Margaret; Narayan, Julie

2010-08-01

High volume air sampling in Bermuda, Sable Island (Nova Scotia) and along a cruise track from the Gulf of Mexico to northeast coast of the USA, was carried out to assess air concentrations, particle-gas partitioning and transport of polyfluorinated chemicals (PFCs) in this region. Samples were collected in the summer of 2007. Targeted compounds included the neutral PFCs: fluorotelomer alcohols (FTOHs), perfluoroalkyl sulfonamides (FOSAs) and perfluoroalkyl sulfonamido ethanols (FOSEs). Among the FTOHs, 8:2 FTOH was dominant in all samples. Sum of the concentration of FTOHs (gas+particle phase) were higher in Bermuda (mean, 34 pg m -3) compared to Sable Island (mean, 16 pg m -3). In cruise samples, sum of FTOHs were highly variable (mean, 81 pg m -3) reflecting contributions from land-based sources in the northeast USA with concentrations reaching as high as 156 pg m -3. Among the FOSAs and FOSEs, MeFOSE was dominant in all samples. In Bermuda, levels of MeFOSE were exceptionally high (mean, 62 pg m -3), exceeding the FTOHs. Sable Island samples also exhibited the dominance of MeFOSE but at a lower concentration (mean, 15 pg m -3). MeFOSE air concentrations (pg m -3) in cruise samples ranged from 1.6 to 73 and were not linked to land-based sources. In fact high concentrations of MeFOSE observed in Bermuda were associated with air masses that originated over the Atlantic Ocean. The partitioning to particles for 8:2 FTOH, 10:2 FTOH, MeFOSE and EtFOSE ranged from as high as 15 to 42% for cruise samples to 0.9 to 14% in Bermuda. This study provides key information for validating and developing partitioning and transport models for the PFCs.

Remote Sensing of Tropospheric Pollution from Space

NASA Technical Reports Server (NTRS)

Fishman, Jack; Bowman, Kevin W.; Burrows, John P.; Chance, Kelly V.; Edwards, David P.; Martin, Randall V.; Morris, Gary A.; Pierce, R. Bradley; Ziemke, Jerald R.; Al-Saadi, Jassim A.;

ADA Title I allegations and the Mining, Quarrying, and Oil/Gas Extraction industry.

PubMed

Van Wieren, Todd A; Rhoades, Laura; McMahon, Brian T

2017-01-01

The majority of research about employment discrimination in the U.S. Mining, Quarrying, and Oil/Gas (MQOGE) industries has concentrated on gender and race, while little attention has focused on disability. To explore allegations of Americans with Disabilities Act (ADA) Title I discrimination made to the Equal Employment Opportunity Commission (EEOC) by individuals with disabilities against MQOGE employers. Key data available to this study included demographic characteristics of charging parties, size of employers, types of allegations, and case outcomes. Using descriptive analysis, allegation profiles were developed for MQOGE's three main sectors (i.e., Oil/Gas Extraction, Mining except Oil/Gas, and Support Activities). These three profiles where then comparatively analyzed. Lastly, regression analysis explored whether some of the available data could partially predict MQOGE case outcomes. The predominant characteristics of MQOGE allegations were found to be quite similar to the allegation profile of U.S. private-sector industry as a whole, and fairly representative of MQOGE's workforce demographics. Significant differences between MQOGE's three main sector profiles were noted on some important characteristics. Lastly, it was found that MQOGE case outcomes could be partially predicted via some of the available variables. The study's limitations were presented and recommendations were offered for further research.

Interlaboratory variability in the quantification of new generation antiepileptic drugs based on external quality assessment data.

PubMed

Williams, John; Bialer, Meir; Johannessen, Svein I; Krämer, Günther; Levy, René; Mattson, Richard H; Perucca, Emilio; Patsalos, Philip N; Wilson, John F

2003-01-01

To assess interlaboratory variability in the determination of serum levels of new antiepileptic drugs (AEDs). Lyophilised serum samples containing clinically relevant concentrations of felbamate (FBM), gabapentin (GBP), lamotrigine (LTG), the monohydroxy derivative of oxcarbazepine (OCBZ; MHD), tiagabine (TGB), topiramate (TPM), and vigabatrin (VGB) were distributed monthly among 70 laboratories participating in the international Heathcontrol External Quality Assessment Scheme (EQAS). Assay results returned over a 15-month period were evaluated for precision and accuracy. The most frequently measured compound was LTG (65), followed by MHD (39), GBP (19), TPM (18), VGB (15), FBM (16), and TGB (8). High-performance liquid chromatography was the most commonly used assay technique for all drugs except for TPM, for which two thirds of laboratories used a commercial immunoassay. For all assay methods combined, precision was <11% for MHD, FBM, TPM, and LTG, close to 15% for GBP and VGB, and as high as 54% for TGB (p < 0.001). Mean accuracy values were <10% for all drugs other than TGB, for which measured values were on average 13.9% higher than spiked values, with a high variability around the mean (45%). No differences in precision and accuracy were found between methods, except for TPM, for which gas chromatography showed poorer accuracy compared with immunoassay and gas chromatography-mass spectrometry. With the notable exception of TGB, interlaboratory variability in the determination of new AEDs was comparable to that reported with older-generation agents. Poor assay performance is related more to individual operators than to the intrinsic characteristics of the method applied. Participation in an EQAS scheme is recommended to ensure adequate control of assay variability in therapeutic drug monitoring.

Shale gas development impacts on surface water quality in Pennsylvania

PubMed Central

Olmstead, Sheila M.; Muehlenbachs, Lucija A.; Shih, Jhih-Shyang; Chu, Ziyan; Krupnick, Alan J.

2013-01-01

Concern has been raised in the scientific literature about the environmental implications of extracting natural gas from deep shale formations, and published studies suggest that shale gas development may affect local groundwater quality. The potential for surface water quality degradation has been discussed in prior work, although no empirical analysis of this issue has been published. The potential for large-scale surface water quality degradation has affected regulatory approaches to shale gas development in some US states, despite the dearth of evidence. This paper conducts a large-scale examination of the extent to which shale gas development activities affect surface water quality. Focusing on the Marcellus Shale in Pennsylvania, we estimate the effect of shale gas wells and the release of treated shale gas waste by permitted treatment facilities on observed downstream concentrations of chloride (Cl−) and total suspended solids (TSS), controlling for other factors. Results suggest that (i) the treatment of shale gas waste by treatment plants in a watershed raises downstream Cl− concentrations but not TSS concentrations, and (ii) the presence of shale gas wells in a watershed raises downstream TSS concentrations but not Cl− concentrations. These results can inform future voluntary measures taken by shale gas operators and policy approaches taken by regulators to protect surface water quality as the scale of this economically important activity increases. PMID:23479604

Exploratory study of atmospheric methane enhancements derived from natural gas use in the Houston urban area

DOE PAGES

Sanchez, Nancy P.; Zheng, Chuantao; Ye, Weilin; ...

2018-01-04

Here, the extensive use of natural gas (NG) in urban areas for heating, cooking and as a vehicular fuel is associated with potentially significant emissions of methane (CH 4) to the atmosphere. Methane, a potent greenhouse gas that influences the chemistry of the atmosphere, can be emitted from different sources including leakage from NG infrastructure, transportation activities, end-use uncombusted NG, landfills and livestock. Although significant CH 4 leakage associated with aging local NG distribution systems in the U.S. has been reported, further investigation is required to study the role of this infrastructure component and other NG-related sources in atmospheric CHmore » 4 enhancements in urban centers. In this study, neighborhood-scale mobile-based monitoring of potential CH 4 emissions associated with NG in the Greater Houston area (GHA) is reported. A novel dual-gas 3.337 μm interband cascade laser-based sensor system was developed and mobile-mode deployed for simultaneous CH 4 and ethane (C 2H 6) monitoring during a period of over 14 days, corresponding to ~ 90 hours of effective data collection during summer 2016. The sampling campaign covered ~ 250 road miles and was primarily concentrated on eight residential zones with distinct infrastructure age and NG usage levels. A moderate number of elevated CH 4 concentration events (37 episodes) with mixing ratios not exceeding 3.60 ppmv and associated with atmospheric background enhancements below 1.21 ppmv were observed during the field campaign. Source discrimination analyses based on the covariance between CH 4 and C 2H 6 levels indicated the predominance of thermogenic sources (e.g., NG) in the elevated CH 4 concentration episodes. The volumetric fraction of C 2H 6 in the sources associated with the thermogenic CH 4 spikes varied between 2.7 and 5.9%, concurring with the C 2H 6 content in NG distributed in the GHA. Isolated CH 4 peak events with significantly higher C 2H 6 enhancements (~11 %) were observed at industrial areas and locations with high density of petroleum and gas pipelines in the GHA, indicating potential variability in Houston’s thermogenic CH 4 sources.« less

Exploratory study of atmospheric methane enhancements derived from natural gas use in the Houston urban area

NASA Astrophysics Data System (ADS)

Sanchez, Nancy P.; Zheng, Chuantao; Ye, Weilin; Czader, Beata; Cohan, Daniel S.; Tittel, Frank K.; Griffin, Robert J.

2018-03-01

The extensive use of natural gas (NG) in urban areas for heating and cooking and as a vehicular fuel is associated with potentially significant emissions of methane (CH4) to the atmosphere. Methane, a potent greenhouse gas that influences the chemistry of the atmosphere, can be emitted from different sources including leakage from NG infrastructure, transportation activities, end-use uncombusted NG, landfills and livestock. Although significant CH4 leakage associated with aging local NG distribution systems in the U.S. has been reported, further investigation is required to study the role of this infrastructure component and other NG-related sources in atmospheric CH4 enhancements in urban centers. In this study, neighborhood-scale mobile-based monitoring of potential CH4 emissions associated with NG in the Greater Houston area (GHA) is reported. A novel dual-gas 3.337 μm interband cascade laser-based sensor system was developed and mobile-mode deployed for simultaneous CH4 and ethane (C2H6) monitoring during a period of over 14 days, corresponding to ∼ 90 h of effective data collection during summer 2016. The sampling campaign covered ∼250 exclusive road miles and was primarily concentrated on eight residential zones with distinct infrastructure age and NG usage levels. A moderate number of elevated CH4 concentration events (37 episodes) with mixing ratios not exceeding 3.60 ppmv and associated with atmospheric background enhancements below 1.21 ppmv were observed during the field campaign. Source discrimination analyses based on the covariance between CH4 and C2H6 levels indicated the predominance of thermogenic sources (e.g., NG) in the elevated CH4 concentration episodes. The volumetric fraction of C2H6 in the sources associated with the thermogenic CH4 spikes varied between 2.7 and 5.9%, concurring with the C2H6 content in NG distributed in the GHA. Isolated CH4 peak events with significantly higher C2H6 enhancements (∼11%) were observed at industrial areas and locations with high density of petroleum and gas pipelines in the GHA, indicating potential variability in Houston's thermogenic CH4 sources.

Exploratory study of atmospheric methane enhancements derived from natural gas use in the Houston urban area

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

Sanchez, Nancy P.; Zheng, Chuantao; Ye, Weilin

Here, the extensive use of natural gas (NG) in urban areas for heating, cooking and as a vehicular fuel is associated with potentially significant emissions of methane (CH 4) to the atmosphere. Methane, a potent greenhouse gas that influences the chemistry of the atmosphere, can be emitted from different sources including leakage from NG infrastructure, transportation activities, end-use uncombusted NG, landfills and livestock. Although significant CH 4 leakage associated with aging local NG distribution systems in the U.S. has been reported, further investigation is required to study the role of this infrastructure component and other NG-related sources in atmospheric CHmore » 4 enhancements in urban centers. In this study, neighborhood-scale mobile-based monitoring of potential CH 4 emissions associated with NG in the Greater Houston area (GHA) is reported. A novel dual-gas 3.337 μm interband cascade laser-based sensor system was developed and mobile-mode deployed for simultaneous CH 4 and ethane (C 2H 6) monitoring during a period of over 14 days, corresponding to ~ 90 hours of effective data collection during summer 2016. The sampling campaign covered ~ 250 road miles and was primarily concentrated on eight residential zones with distinct infrastructure age and NG usage levels. A moderate number of elevated CH 4 concentration events (37 episodes) with mixing ratios not exceeding 3.60 ppmv and associated with atmospheric background enhancements below 1.21 ppmv were observed during the field campaign. Source discrimination analyses based on the covariance between CH 4 and C 2H 6 levels indicated the predominance of thermogenic sources (e.g., NG) in the elevated CH 4 concentration episodes. The volumetric fraction of C 2H 6 in the sources associated with the thermogenic CH 4 spikes varied between 2.7 and 5.9%, concurring with the C 2H 6 content in NG distributed in the GHA. Isolated CH 4 peak events with significantly higher C 2H 6 enhancements (~11 %) were observed at industrial areas and locations with high density of petroleum and gas pipelines in the GHA, indicating potential variability in Houston’s thermogenic CH 4 sources.« less

Characterizing spatial and temporal variability of dissolved gases in aquatic environments with in situ mass spectrometry.

PubMed

Camilli, Richard; Duryea, Anthony N

2009-07-01

The TETHYS mass spectrometer is intended for long-term in situ observation of dissolved gases and volatile organic compounds in aquatic environments. Its design maintains excellent low mass range sensitivity and stability during long-term operations, enabling characterization of low-frequency variability in many trace dissolved gases. Results are presented from laboratory trials and a 300-h in situ trial in a shallow marine embayment in Massachusetts, U.S.A. This time series consists of over 15000 sample measurements and represents the longest continuous record made by an in situ mass spectrometer in an aquatic environment. These measurements possess sufficient sampling density and duration to apply frequency analysis techniques for study of temporal variability in dissolved gases. Results reveal correlations with specific environmental periodicities. Numerical methods are presented for converting mass spectrometer ion peak ratios to absolute-scale dissolved gas concentrations across wide temperature regimes irrespective of ambient pressure, during vertical water column profiles in a hypoxic deep marine basin off the coast of California, U.S.A. Dissolved oxygen concentration values obtained with the TETHYS instrument indicate close correlation with polarographic oxygen sensor data across the entire depth range. These methods and technology enable observation of aquatic environmental chemical distributions and dynamics at appropriate scales of resolution.

Artifacts in measuring aerosol uptake kinetics: the roles of time, concentration and adsorption

NASA Astrophysics Data System (ADS)

Renbaum, L. H.; Smith, G. D.

2011-07-01

In laboratory studies of organic aerosol particles reacting with gas-phase oxidants, high concentrations of radicals are often used to study on the timescale of seconds reactions which may be occurring over days or weeks in the troposphere. Implicit in this approach is the assumption that radical concentration and time are interchangeable parameters, though this has not been established. Here, the kinetics of OH- and Cl-initiated oxidation reactions of model single-component liquid (squalane) and supercooled (brassidic acid and 2-octyldodecanoic acid) organic aerosols are studied by varying separately the radical concentration and the reaction time. Two separate flow tubes with residence times of 2 and 66 s are used, and [OH] and [Cl] are varied by adjusting either the laser photolysis fluence or the radical precursor concentration ([O3] or [Cl2], respectively) used to generate the radicals. It is found that the rates measured by varying the radical concentration and the reaction time are equal only if the precursor concentrations are the same in the two approaches. Further, the rates depend on the concentrations of the precursor species with a Langmuir-type functional form suggesting that O3 and Cl2 saturate the surface of the liquid particles. It is believed that the presence of O3 inhibits the rate of OH reaction, perhaps by reacting with OH radicals or by O3 or intermediate species blocking surface sites, while Cl2 enhances the rate of Cl reaction by participating in a radical chain mechanism. These results have important implications for laboratory experiments in which high concentrations of gas-phase oxidants are used to study atmospheric reactions over short timescales and may explain the variability in recent measurements of the reactive uptake of OH on squalane particles in reactor systems used in this and other laboratories.

Modeling of crude oil biodegradation using two phase partitioning bioreactor.

PubMed

Fakhru'l-Razi, A; Peyda, Mazyar; Ab Karim Ghani, Wan Azlina Wan; Abidin, Zurina Zainal; Zakaria, Mohamad Pauzi; Moeini, Hassan

2014-01-01

In this work, crude oil biodegradation has been optimized in a solid-liquid two phase partitioning bioreactor (TPPB) by applying a response surface methodology based d-optimal design. Three key factors including phase ratio, substrate concentration in solid organic phase, and sodium chloride concentration in aqueous phase were taken as independent variables, while the efficiency of the biodegradation of absorbed crude oil on polymer beads was considered to be the dependent variable. Commercial thermoplastic polyurethane (Desmopan®) was used as the solid phase in the TPPB. The designed experiments were carried out batch wise using a mixed acclimatized bacterial consortium. Optimum combinations of key factors with a statistically significant cubic model were used to maximize biodegradation in the TPPB. The validity of the model was successfully verified by the good agreement between the model-predicted and experimental results. When applying the optimum parameters, gas chromatography-mass spectrometry showed a significant reduction in n-alkanes and low molecular weight polycyclic aromatic hydrocarbons. This consequently highlights the practical applicability of TPPB in crude oil biodegradation. © 2014 American Institute of Chemical Engineers.

Plasma lactate concentrations and blood gas values in dogs undergoing surgical attenuation of a single congenital portosystemic shunt.

PubMed

Cariou, M P; Lipscomb, V J; Hughes, D; Brodbelt, D; Brockman, D J

2009-08-22

Plasma concentration of lactate and the values of pH, pO(2) and pCO(2) were measured in the portal, systemic venous and, when possible, systemic arterial blood of 31 dogs with a single congenital portosystemic shunt, before and shortly after the temporary complete occlusion of the shunt, and at the end of surgery. At completion of the surgery, the shunt in 16 of the dogs had been occluded completely whereas in the other 15 it had been occluded only partially. There were no significant differences between any of the measurements of these variables in the portal venous, systemic venous or arterial plasma of any of the dogs, or between the values measured in the groups in which the shunts had been occluded completely or partially. Furthermore, there were no significant differences between the two groups of dogs in the arteriovenous gradients calculated at any of the sampling sites or sampling times. None of the variables was associated with the development of postoperative complications.

Dynamic Control of Adsorption Sensitivity for Photo-EMF-Based Ammonia Gas Sensors Using a Wireless Network

PubMed Central

Vashpanov, Yuriy; Choo, Hyunseung; Kim, Dongsoo Stephen

2011-01-01

This paper proposes an adsorption sensitivity control method that uses a wireless network and illumination light intensity in a photo-electromagnetic field (EMF)-based gas sensor for measurements in real time of a wide range of ammonia concentrations. The minimum measurement error for a range of ammonia concentration from 3 to 800 ppm occurs when the gas concentration magnitude corresponds with the optimal intensity of the illumination light. A simulation with LabView-engineered modules for automatic control of a new intelligent computer system was conducted to improve measurement precision over a wide range of gas concentrations. This gas sensor computer system with wireless network technology could be useful in the chemical industry for automatic detection and measurement of hazardous ammonia gas levels in real time. PMID:22346680

Effects of landfill gas on subtropical woody plants

NASA Astrophysics Data System (ADS)

Chan, G. Y. S.; Wong, M. H.; Whitton, B. A.

1991-05-01

An account is given of the influence of landfill gas on tree growth in the field at Gin Drinkers' Bay (GDB) landfill, Hong Kong, and in the laboratory. Ten species ( Acacia confusa, Albizzia lebbek, Aporusa chinensis, Bombax malabaricum, Castanopsis fissa, Liquidambar formosana, Litsea glutinosa, Machilus breviflora, Pinus elliottii, and Tristania conferta), belonging to eight families, were transplanted to two sites, one with a high concentration of landfill gas in the cover soil (high-gas site, HGS) and the other with a relatively low concentration of gas (low-gas site, LGS). Apart from the gaseous composition, the general soil properties were similar. A strong negative correlation between tree growth and landfill gas concentration was observed. A laboratory study using the simulated landfill gas to fumigate seedlings of the above species showed that the adventitious root growth of Aporusa chinensis, Bombax malabaricum, Machilus breviflora, and Tristania confera was stimulated by the gas, with shallow root systems being induced. Acacia confusa, Albizzia lebbek, and Litsea glutinosa were gas-tolerant, while root growth of Castanopsis fissa, Liquidambar formosana, and Pinus elliottii was inhibited. In most cases, shoot growth was not affected, exceptions being Bombax malabaricum, Liquidambar formosana, and Tristania conferta, where stunted growth and/or reduced foliation was observed. A very high CO2 concentration in cover soil limits the depth of the root system. Trees with a shallow root system become very susceptible to water stress. The effects of low O2 concentration in soil are less important than the effects of high CO2 concentration. Acacia confusa, Albizzia lebbek, and Tristania conferta are suited for growth on subtropical completed landfills mainly due to their gas tolerance and/or drought tolerance.

Experimental assessment of indoor radon and soil gas variability: the RADON project

NASA Astrophysics Data System (ADS)

Barbosa, S. M.; Pereira, A. J. S. C.; Neves, L. J. P. F.; Steinitz, G.; Zafrir, H.; Donner, R.; Woith, H.

2012-04-01

Radon is a radioactive noble gas naturally present in the environment, particularly in soils derived from rocks with high uranium content. Radon is formed by alpha decay from radium within solid mineral grains, but can migrate via diffusion and/or advection into the air space of soils, as well as into groundwater and the atmosphere. The exhalation of radon from the pore space of porous materials into the atmosphere of indoor environments is well known to cause adverse health effects due to the inhalation of radon's short-lived decay products. The danger to human health is particularly acute in the case of poorly ventilated dwellings located in geographical areas of high radon potential. The RADON project, funded by the Portuguese Science Foundation (FCT), aims to evaluate the temporal variability of radon in the soil and atmosphere and to examine the influence of meteorological effects in radon concentration. For that purpose an experimental monitoring station is being installed in an undisturbed dwelling located in a region of high radon potential near the old uranium mine of Urgeiriça (central Portugal). The rationale of the project, the set-up of the experimental radon monitoring station, and preliminary monitoring results will be presented.

Catalyzed pyrolysis of grape and olive bagasse. Influence of catalyst type and chemical treatment

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

Encinar, J.M.; Beltran, F.J.; Ramiro, A.

1997-10-01

Catalyzed pyrolysis of grape and olive bagasse under different experimental conditions has been studied. Variables investigated were temperature and type and concentration of catalysts. Experiments were carried out in an isothermal manner. Products of pyrolysis are gases (H{sub 2}, CO, CO{sub 2}, and CH{sub 4}), liquids (methanol, acetone, furfurylic alcohol, phenol, furfural, naphthalene, and o-cresol), and solids (chars). Temperature is a significant variable, yielding increases of fixed carbon content, gases, and to a lesser extent, ash percentage. Catalyst presence also yields increases of solid phase content, but the amount of liquid components decrease. Among catalysts applied those of Fe andmore » Zn are the most advisable to obtain gases. Chemical treatment of bagasses with sulfuric or phosphoric acid washing leads to lower char yields, although fixed carbon content is higher and ash presence diminishes with respect to catalyst pyrolysis without chemical pretreatment. A pyrolysis kinetic study based on gas generation from thermal decomposition of residues has been carried out. From the model proposed, rate constants for the formation of each gas, reaction order of the catalyst, and activation energies were determined.« less

Indoor air quality inspection and analysis system based on gas sensor array

NASA Astrophysics Data System (ADS)

Gao, Xiang; Wang, Mingjiang; Fan, Binwen

2017-08-01

A detection and analysis system capable of measuring the concentration of four major gases in indoor air is designed. It uses four gas sensors constitute a gas sensor array, to achieve four indoor gas concentration detection, while the detection of data for further processing to reduce the cross-sensitivity between the gas sensor to improve the accuracy of detection.

Laboratory Connections--Gas Monitoring Transducers Part III: Combustible Gas Sensors.

ERIC Educational Resources Information Center

Powers, Michael H.; Dahman, Doug

1989-01-01

Describes an interface that uses semiconductor metal oxides to detect low gas concentrations. Notes the detector has long life, high stability, good reproducibility, low cost, and is able to convert the gas concentration to an electrical signal with a simple circuit. Theory, schematic, and applications are provided. (MVL)

Iodine and Bromine Distributions in Pore Waters: A Comparison Between Permafrost and Marine Gas Hydrate Fields

NASA Astrophysics Data System (ADS)

Tomaru, H.; Fehn, U.; Lu, Z.

2005-12-01

Iodine and, to a lesser degree, bromine are commonly enriched in waters associated with hydrocarbons. The concentrations of these halogens and their ratios can thus be used to identify potential source formations for hydrocarbons such as gas hydrates. While the largest reservoir of gas hydrates is found in marine sediments, permafrost locations are also an important source of gas hydrates. We measured iodine and bromine concentrations in pore waters associated with gas hydrates in the Mallik exploration well, a permafrost location in the Mackenzie delta, Northwest Territory, Canada and compared them to results from gas hydrates in marine sediments. Gas hydrates are found in the Mallik site in two horizons below the permafrost layer which reaches a depth of about 600 m in this location. We measured concentrations in samples collected from depths between 850 and 1150 m. Large sections of the test well have iodine concentrations around 1 μM, but the concentrations increase to values between 10 and 20 μM at the gas hydrate horizons. Bromine concentrations show a similar pattern, with maxima reaching values between 700 and 800 μM. Although iodine concentrations are considerably higher than in seawater (0.4 μM), they are much lower than in marine gas hydrate locations such as Nankai (200 μM); Blake Ridge (2 mM) or Hydrate Ridge (2.5 mM). Bromine concentrations at Mallik do not reach the seawater value (840 μM) in contrast to marine hydrate locations where Br is enriched by factors of four or more compared to seawater. Chlorine concentrations at Mallik are close to that of seawater, in this case similar to the marine hydrate locations. The comparison between marine hydrate locations and Mallik suggests that the organic sources responsible for the methane at Mallik are considerably different from those in marine situations. Since iodine concentrations are generally higher in marine organisms than in terrestrial organisms, the relatively low concentrations of iodine and bromine at Mallik suggest that the source material there is of more terrestrial character than in the marine locations, a observation supported by the presence of several coal seams at Mallik. The large volume of methane in this region suggests that terrestrial sources may play an important role in the accumulation of gas hydrates.

Detection of ethylene gas in exhaled breath of people living in landfill using CO{sub 2} laser photoacoustic spectroscopy with multicomponent analysis

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

Oktafiani, Fitri, E-mail: fitri.oktafiani@mail.ugm.ac.id; Stiyabudi, Rizky; Amin, Mochamad Nurul

The photoacoustic spectrometer (PAS) had been built and the performance had been determined. The research was based on the conversion of the absorbed middle infra red (IR) radiation by gas confined in a closed PAS cell into standing acoustic wave, which could be detected by a suitable electroacoustic transducer such as a microphone. The lowest detection limit for this setup was (57,1 ± 0,3) ppb and quality factor was (14,5 ± 0,6) for ethylene gas in 10P14 CO{sub 2} laser line. Then, this PAS was used to measure of ethylene gas concentration in breath sample of people living in nearmore » the Piyungan Bantul Yogyakarta landfill. The result from multicomponent analysis showed that PAS enable to measure the lowest concentration of volatile organic compound (VOC), such as ethylene, which occured on ambien air in Piyungan landfill. Variaty of distance area applied in this research. In the range of ±0,5 km from landfill, we obtained the concentration of ethylene gas concentration for human breath was (1,520 ± 0,002) ppm, while in the range of ±45 km, the ethylene gas concentration for human breath was (0,424 ± 0,002) ppm. Ethylene gas concentrations in exhaled gas decreased along with increasing distance variation of the landfill.« less

Arterial stress hormones during scuba diving with different breathing gases.

PubMed

Weist, Frank; Strobel, Günther; Hölzl, Mathias; Böning, Dieter

2012-07-01

The purpose of the study was to determine whether the conditions during scuba diving without exercise (e.g., submersion, restricted breathing) stimulate the activities of the sympathoadrenergic system and the hypothalamic-pituitary-adrenal axis. This might facilitate panic reactions in dangerous situations. Fifteen experienced rescue divers participated in three experiments with two submersions each in a diving tower where ambient pressure could be varied. During submersion (duration = 15 min), they were breathing either pure oxygen (ambient pressure = 1.1 bar) or air (1.1 and 5.3 bar) or Heliox21 (21% O(2) and 79% He, 1.1 and 5.3 bar). The subjects stayed upright immediately below the water surface holding one hand with a cannulated radial artery out in the air. Noradrenaline, adrenaline, and dopamine concentrations in arterial blood and heart rate (HR) variability as indicators of sympathoadrenergic activity and cortisol and adrenocorticotropic hormone concentrations as strain indicators were measured. [Noradrenaline] and [adrenaline] (initial values (mean ± SE) = 1616 ± 93 and 426 ± 38 pmol·L(-1)) decreased significantly by up to 30% and 50%, respectively, after 11 min of submersion, independent of pressure and inspired gas. HR variability showed roughly corresponding changes and also indications for parasympathetic stimulation, but artifacts by interference among HR monitors reduced the number of usable measurements. The other hormone concentrations did not change significantly. There was no increase of stress hormone concentrations in experienced subjects. The reduction of [noradrenaline] and [adrenaline] during scuba diving seems to be a reaction to orthostatic relief caused by external hydrostatic pressure on peripheral vasculature. The activity of the vegetative nervous system might be estimated from HR variability if interference among pulse watches can be avoided.

Intrinsic vs. spurious long-range memory in high-frequency records of environmental radioactivity. Critical re-assessment and application to indoor 222Rn concentrations from Coimbra, Portugal

NASA Astrophysics Data System (ADS)

Donner, R. V.; Potirakis, S. M.; Barbosa, S. M.; Matos, J. A. O.; Pereira, A. J. S. C.; Neves, L. J. P. F.

2015-05-01

The presence or absence of long-range correlations in the environmental radioactivity fluctuations has recently attracted considerable interest. Among a multiplicity of practically relevant applications, identifying and disentangling the environmental factors controlling the variable concentrations of the radioactive noble gas radon is important for estimating its effect on human health and the efficiency of possible measures for reducing the corresponding exposition. In this work, we present a critical re-assessment of a multiplicity of complementary methods that have been previously applied for evaluating the presence of long-range correlations and fractal scaling in environmental radon variations with a particular focus on the specific properties of the underlying time series. As an illustrative case study, we subsequently re-analyze two high-frequency records of indoor radon concentrations from Coimbra, Portugal, each of which spans several weeks of continuous measurements at a high temporal resolution of five minutes.Our results reveal that at the study site, radon concentrations exhibit complex multi-scale dynamics with qualitatively different properties at different time-scales: (i) essentially white noise in the high-frequency part (up to time-scales of about one hour), (ii) spurious indications of a non-stationary, apparently long-range correlated process (at time scales between some hours and one day) arising from marked periodic components, and (iii) low-frequency variability indicating a true long-range dependent process. In the presence of such multi-scale variability, common estimators of long-range memory in time series are prone to fail if applied to the raw data without previous separation of time-scales with qualitatively different dynamics.

Demonstration of a diel trend in sensitivity of Gossypium to ozone: a step toward relating O3 injury to exposure or flux

PubMed Central

Grantz, D.A.

2013-01-01

Plant injury by ozone (O3) occurs in three stages, O3 entrance through stomata, overcoming defences, and attack on bioreceptors. Concentration, deposition, and uptake of O3 are accessible by observation and modelling, while injury can be assessed visually or through remote sensing. However, the relationship between O3 metrics and injury is confounded by variation in sensitivity to O3. Sensitivity weighting parameters have previously been assigned to different plant functional types and growth stages, or by differentially weighting O3 concentrations, but diel and seasonal variability have not been addressed. Here a plant sensitivity parameter (S) is introduced, relating injury to O3 dose (uptake) using three independent injury endpoints in the crop species, Pima cotton (Gossypium barbadense). The diel variability of S was determined by assessment at 2h intervals. Pulses of O3 (15min) were used to assess passive (constitutive) defence mechanisms and dose was used rather than concentration to avoid genetic or environmental effects on stomatal regulation. A clear diel trend in S was apparent, with maximal sensitivity in mid-afternoon, not closely related to gas exchange, whole leaf ascorbate, or total antioxidant capacity. This physiologically based sensitivity parameter provides a novel weighting factor to improve modelled relationships between either flux or exposure to O3, and O3 impacts. This represents a substantial improvement over concentration- or phenology-based weighting factors currently in use. Future research will be required to characterize the variability and metabolic drivers of diel changes in S, and the performance of this parameter in prediction of O3 injury. PMID:23404900

High-sensitivity gas-mapping 3D imager and method of operation

DOEpatents

Kreitinger, Aaron; Thorpe, Michael

2018-05-15

Measurement apparatuses and methods are disclosed for generating high-precision and -accuracy gas concentration maps that can be overlaid with 3D topographic images by rapidly scanning one or several modulated laser beams with a spatially-encoded transmitter over a scene to build-up imagery. Independent measurements of the topographic target distance and path-integrated gas concentration are combined to yield a map of the path-averaged concentration between the sensor and each point in the image. This type of image is particularly useful for finding localized regions of elevated (or anomalous) gas concentration making it ideal for large-area leak detection and quantification applications including: oil and gas pipeline monitoring, chemical processing facility monitoring, and environmental monitoring.

Infrared Camera System for Visualization of IR-Absorbing Gas Leaks

NASA Technical Reports Server (NTRS)

Youngquist, Robert; Immer, Christopher; Cox, Robert

2010-01-01

Leak detection and location remain a common problem in NASA and industry, where gas leaks can create hazardous conditions if not quickly detected and corrected. In order to help rectify this problem, this design equips an infrared (IR) camera with the means to make gas leaks of IR-absorbing gases more visible for leak detection and location. By comparing the output of two IR cameras (or two pictures from the same camera under essentially identical conditions and very closely spaced in time) on a pixel-by-pixel basis, one can cancel out all but the desired variations that correspond to the IR absorption of the gas of interest. This can be simply done by absorbing the IR lines that correspond to the gas of interest from the radiation received by one of the cameras by the intervention of a filter that removes the particular wavelength of interest from the "reference" picture. This can be done most sensitively with a gas filter (filled with the gas of interest) placed in front of the IR detector array, or (less sensitively) by use of a suitable line filter in the same location. This arrangement would then be balanced against the unfiltered "measurement" picture, which will have variations from IR absorption from the gas of interest. By suitable processing of the signals from each pixel in the two IR pictures, the user can display only the differences in the signals. Either a difference or a ratio output of the two signals is feasible. From a gas concentration viewpoint, the ratio could be processed to show the column depth of the gas leak. If a variation in the background IR light intensity is present in the field of view, then large changes in the difference signal will occur for the same gas column concentration between the background and the camera. By ratioing the outputs, the same signal ratio is obtained for both high- and low-background signals, even though the low-signal areas may have greater noise content due to their smaller signal strength. Thus, one embodiment would use a ratioed output signal to better represent the gas column concentration. An alternative approach uses a simpler multiplication of the filtered signal to make the filtered signal equal to the unfiltered signal at most locations, followed by a subtraction to remove all but the wavelength-specific absorption in the unfiltered sample. This signal processing can also reveal the net difference signal representing the leaking gas absorption, and allow rapid leak location, but signal intensity would not relate solely to gas absorption, as raw signal intensity would also affect the displayed signal. A second design choice is whether to use one camera with two images closely spaced in time, or two cameras with essentially the same view and time. The figure shows the two-camera version. This choice involves many tradeoffs that are not apparent until some detailed testing is done. In short, the tradeoffs involve the temporal changes in the field picture versus the pixel sensitivity curves and frame alignment differences with two cameras, and which system would lead to the smaller variations from the uncontrolled variables.

Radiation Re-solution Calculation in Uranium-Silicide Fuels

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

Matthews, Christopher; Andersson, Anders David Ragnar; Unal, Cetin

The release of fission gas from nuclear fuels is of primary concern for safe operation of nuclear power plants. Although the production of fission gas atoms can be easily calculated from the fission rate in the fuel and the average yield of fission gas, the actual diffusion, behavior, and ultimate escape of fission gas from nuclear fuel depends on many other variables. As fission gas diffuses through the fuel grain, it tends to collect into intra-granular bubbles, as portrayed in Figure 1.1. These bubbles continue to grow due to absorption of single gas atoms. Simultaneously, passing fission fragments can causemore » collisions in the bubble that result in gas atoms being knocked back into the grain. This so called “re-solution” event results in a transient equilibrium of single gas atoms within the grain. As single gas atoms progress through the grain, they will eventually collect along grain boundaries, creating inter-granular bubbles. As the inter-granular bubbles grow over time, they will interconnect with other grain-face bubbles until a pathway is created to the outside of the fuel surface, at which point the highly pressurized inter-granular bubbles will expel their contents into the fuel plenum. This last process is the primary cause of fission gas release. From the simple description above, it is clear there are several parameters that ultimately affect fission gas release, including the diffusivity of single gas atoms, the absorption and knockout rate of single gas atoms in intra-granular bubbles, and the growth and interlinkage of intergranular bubbles. Of these, the knockout, or re-solution rate has an particularly important role in determining the transient concentration of single gas atoms in the grain. The re-solution rate will be explored in the following sections with regards to uranium-silicide fuels in order to support future models of fission gas bubble behavior.« less

Evolution of Size and Chemical Composition of Copper Concentrate Particles Oxidized Under Simulated Flash Smelting Conditions

NASA Astrophysics Data System (ADS)

Pérez-Tello, Manuel; Parra-Sánchez, Víctor R.; Sánchez-Corrales, Víctor M.; Gómez-Álvarez, Agustín; Brown-Bojórquez, Francisco; Parra-Figueroa, Roberto A.; Balladares-Varela, Eduardo R.; Araneda-Hernández, Eugenia A.

2018-04-01

An experimental study was conducted to elucidate the evolution of size and chemical composition of La Caridad copper concentrate particles during oxidation under simulated flash smelting conditions. Input variables tested included particle size and oxygen concentration in the process gas. The response variables included the size distributions, chemical composition, and morphology of the reacted particles at seven locations along a laboratory reactor. Particles with initial size < 45 µm contained mostly chalcopyrite, they increased their mean size and decreased the amount of dust in the population during oxidation. This was explained by a reaction path involving rapid melting followed by collision and coalescence of reacting droplets during flight. Particles with sizes > 45 µm contained varying amounts of chalcopyrite and pyrite, and tended to either maintain or decrease their mean size upon oxidation. When size reduction was observed, dust was produced because of fragmentation, and the particles showed no evidence of collisions during flight. The main oxidation products detected in the particles consisted of matte, cuprospinel, and magnetite. A plot of the mean size divided by the mean size in the feed against the fraction of sulfur eliminated generalized the experimental data so far reported in the literature, and helped identify the reaction path followed by the particles.

Calibration-free wavelength modulation spectroscopy for gas concentration measurements using a quantum cascade laser

NASA Astrophysics Data System (ADS)

Wei, Min; Kan, RuiFeng; Chen, Bing; Xu, ZhenYu; Yang, ChenGuang; Chen, Xiang; Xia, HuiHui; Hu, Mai; He, Yabai; Liu, JianGuo; Fan, XueLi; Wang, Wei

2017-05-01

We report the development of an accurate calibration-free wavelength-scanned wavelength modulation spectroscopy system based on the temporal wavelength response of a current-modulated quantum cascade laser (QCL) for gas concentration detections. Accurate measurements and determination of the QCL output intensity and wavelength response to current modulation enabled calculations of 1f-normalized 2f signal to obtain spectroscopic information with and without gas absorption in the beam path. The gas concentration was retrieved by fitting a simulation spectrum based on spectral line parameters to the background-subtracted 1f-normalized 2f signal based on measurements. In this paper, we demonstrate the performance of the developed system for the CH4 detection by applying an infrared QCL (at 7.84 µm or 1275 cm-1) to probe its two infrared transition lines at 1275.042 cm-1 and 1275.387 cm-1. The experimental results indicated very good agreements between measurements and modeling, for integrated absorbance ranging from 0.0057 cm-1 to 0.11 cm-1 (or absorbance ranging from 0.029 to 0.57). The extracted integrated absorbance was highly linear ( R = 0.99996) to the gas sample concentration. Deviations between the nominal sample gas concentrations and the extracted gas concentrations calculated based on HITRAN spectroscopic parameters were within 3.5%.

Redox controls on methane formation, migration and fate in shallow aquifers

NASA Astrophysics Data System (ADS)

Humez, Pauline; Mayer, Bernhard; Nightingale, Michael; Becker, Veith; Kingston, Andrew; Taylor, Stephen; Bayegnak, Guy; Millot, Romain; Kloppmann, Wolfram

2016-07-01

Development of unconventional energy resources such as shale gas and coalbed methane has generated some public concern with regard to the protection of groundwater and surface water resources from leakage of stray gas from the deep subsurface. In terms of environmental impact to and risk assessment of shallow groundwater resources, the ultimate challenge is to distinguish (a) natural in situ production of biogenic methane, (b) biogenic or thermogenic methane migration into shallow aquifers due to natural causes, and (c) thermogenic methane migration from deep sources due to human activities associated with the exploitation of conventional or unconventional oil and gas resources. This study combines aqueous and gas (dissolved and free) geochemical and isotope data from 372 groundwater samples obtained from 186 monitoring wells of the provincial Groundwater Observation Well Network (GOWN) in Alberta (Canada), a province with a long record of conventional and unconventional hydrocarbon exploration. We investigated whether methane occurring in shallow groundwater formed in situ, or whether it migrated into the shallow aquifers from elsewhere in the stratigraphic column. It was found that methane is ubiquitous in groundwater in Alberta and is predominantly of biogenic origin. The highest concentrations of biogenic methane (> 0.01 mM or > 0.2 mgL-1), characterized by δ13CCH4 values < -55 ‰, occurred in anoxic Na-Cl, Na-HCO3, and Na-HCO3-Cl type groundwaters with negligible concentrations of nitrate and sulfate suggesting that methane was formed in situ under methanogenic conditions for 39.1 % of the samples. In only a few cases (3.7 %) was methane of biogenic origin found in more oxidizing shallow aquifer portions suggesting limited upward migration from deeper methanogenic aquifers. Of the samples, 14.1 % contained methane with δ13CCH4 values > -54 ‰, potentially suggesting a thermogenic origin, but aqueous and isotope geochemistry data revealed that the elevated δ13CCH4 values were caused by microbial oxidation of biogenic methane or post-sampling degradation of low CH4 content samples rather than migration of deep thermogenic gas. A significant number of samples (39.2 %) contained methane with predominantly biogenic C isotope ratios (δ13CCH4 < -55 ‰) accompanied by elevated concentrations of ethane and sometimes trace concentrations of propane. These gases, observed in 28.1 % of the samples, bearing both biogenic (δ13C) and thermogenic (presence of C3) characteristics, are most likely derived from shallow coal seams that are prevalent in the Cretaceous Horseshoe Canyon and neighboring formations in which some of the groundwater wells are completed. The remaining 3.7 % of samples were not assigned because of conflicting parameters in the data sets or between replicates samples. Hence, despite quite variable gas concentrations and a wide range of δ13CCH4 values in baseline groundwater samples, we found no conclusive evidence for deep thermogenic gas migration into shallow aquifers either naturally or via anthropogenically induced pathways in this baseline groundwater survey. This study shows that the combined interpretation of aqueous geochemistry data in concert with chemical and isotopic compositions of dissolved and/or free gas can yield unprecedented insights into formation and potential migration of methane in shallow groundwater. This enables the assessment of cross-formational methane migration and provides an understanding of alkane gas sources and pathways necessary for a stringent baseline definition in the context of current and future unconventional hydrocarbon exploration and exploitation.

Detecting small holes in packages

DOEpatents

Kronberg, James W.; Cadieux, James R.

1996-01-01

A package containing a tracer gas, and a method for determining the presence of a hole in the package by sensing the presence of the gas outside the package. The preferred tracer gas, especially for food packaging, is sulfur hexafluoride. A quantity of the gas is added to the package and the package is closed. The concentration of the gas in the atmosphere outside the package is measured and compared to a predetermined value of the concentration of the gas in the absence of the package. A measured concentration greater than the predetermined value indicates the presence of a hole in the package. Measuring may be done in a chamber having a lower pressure than that in the package.

A study for health hazard evaluation of methylene chloride evaporated from the tear gas mixture.

PubMed

Park, Seung-Hyun; Chung, Eun-Kyo; Yi, Gwang-Yong; Chung, Kwang-Jae; Shin, Jung-Ah; Lee, In-Seop

2010-09-01

This study explored the health hazard of those exposed to methylene chloride by assessing its atmospheric concentration when a tear gas mixture was aerially dispersed. The concentration of methylene chloride ranged from 311.1-980.3 ppm (geometric mean, 555.8 ppm), 30 seconds after the dispersion started. However, the concentration fell rapidly to below 10 ppm after dispersion was completed. The concentration during the dispersion did not surpass the National Institute for Occupational Safety and Health 'immediately dangerous to life or health' value of 2,300 ppm, but did exceed the American Conference of Governmental Industrial Hygienists excursion limit of 250 ppm. Since methylene chloride is highly volatile (vapor pressure, 349 mmHg at 20℃), the postdispersion atmospheric concentration can rise instantaneously. Moreover, the o-chlorobenzylidenemalononitrile formulation of tear gas (CS gas) is an acute upper respiratory tract irritant. Therefore, tear gas mixtures should be handled with delicate care.

Increased stray gas abundance in a subset of drinking water wells near Marcellus shale gas extraction

PubMed Central

Jackson, Robert B.; Vengosh, Avner; Darrah, Thomas H.; Warner, Nathaniel R.; Down, Adrian; Poreda, Robert J.; Osborn, Stephen G.; Zhao, Kaiguang; Karr, Jonathan D.

2013-01-01

Horizontal drilling and hydraulic fracturing are transforming energy production, but their potential environmental effects remain controversial. We analyzed 141 drinking water wells across the Appalachian Plateaus physiographic province of northeastern Pennsylvania, examining natural gas concentrations and isotopic signatures with proximity to shale gas wells. Methane was detected in 82% of drinking water samples, with average concentrations six times higher for homes <1 km from natural gas wells (P = 0.0006). Ethane was 23 times higher in homes <1 km from gas wells (P = 0.0013); propane was detected in 10 water wells, all within approximately 1 km distance (P = 0.01). Of three factors previously proposed to influence gas concentrations in shallow groundwater (distances to gas wells, valley bottoms, and the Appalachian Structural Front, a proxy for tectonic deformation), distance to gas wells was highly significant for methane concentrations (P = 0.007; multiple regression), whereas distances to valley bottoms and the Appalachian Structural Front were not significant (P = 0.27 and P = 0.11, respectively). Distance to gas wells was also the most significant factor for Pearson and Spearman correlation analyses (P < 0.01). For ethane concentrations, distance to gas wells was the only statistically significant factor (P < 0.005). Isotopic signatures (δ13C-CH4, δ13C-C2H6, and δ2H-CH4), hydrocarbon ratios (methane to ethane and propane), and the ratio of the noble gas 4He to CH4 in groundwater were characteristic of a thermally postmature Marcellus-like source in some cases. Overall, our data suggest that some homeowners living <1 km from gas wells have drinking water contaminated with stray gases. PMID:23798404

Increased stray gas abundance in a subset of drinking water wells near Marcellus shale gas extraction.

PubMed

Jackson, Robert B; Vengosh, Avner; Darrah, Thomas H; Warner, Nathaniel R; Down, Adrian; Poreda, Robert J; Osborn, Stephen G; Zhao, Kaiguang; Karr, Jonathan D

2013-07-09

Horizontal drilling and hydraulic fracturing are transforming energy production, but their potential environmental effects remain controversial. We analyzed 141 drinking water wells across the Appalachian Plateaus physiographic province of northeastern Pennsylvania, examining natural gas concentrations and isotopic signatures with proximity to shale gas wells. Methane was detected in 82% of drinking water samples, with average concentrations six times higher for homes <1 km from natural gas wells (P = 0.0006). Ethane was 23 times higher in homes <1 km from gas wells (P = 0.0013); propane was detected in 10 water wells, all within approximately 1 km distance (P = 0.01). Of three factors previously proposed to influence gas concentrations in shallow groundwater (distances to gas wells, valley bottoms, and the Appalachian Structural Front, a proxy for tectonic deformation), distance to gas wells was highly significant for methane concentrations (P = 0.007; multiple regression), whereas distances to valley bottoms and the Appalachian Structural Front were not significant (P = 0.27 and P = 0.11, respectively). Distance to gas wells was also the most significant factor for Pearson and Spearman correlation analyses (P < 0.01). For ethane concentrations, distance to gas wells was the only statistically significant factor (P < 0.005). Isotopic signatures (δ(13)C-CH4, δ(13)C-C2H6, and δ(2)H-CH4), hydrocarbon ratios (methane to ethane and propane), and the ratio of the noble gas (4)He to CH4 in groundwater were characteristic of a thermally postmature Marcellus-like source in some cases. Overall, our data suggest that some homeowners living <1 km from gas wells have drinking water contaminated with stray gases.

Microbial succession and stimulation following a test well injection simulating CO2 leakage into shallow Newark Basin aquifers

NASA Astrophysics Data System (ADS)

Dueker, M.; Clauson, K.; Yang, Q.; Umemoto, K.; Seltzer, A. M.; Zakharova, N. V.; Matter, J. M.; Stute, M.; Takahashi, T.; Goldberg, D.; O'Mullan, G. D.

2012-12-01

Despite growing appreciation for the importance of microbes in altering geochemical reactions in the subsurface, the microbial response to geological carbon sequestration injections and the role of microbes in altering metal mobilization following leakage scenarios in shallow aquifers remain poorly constrained. A Newark Basin test well was utilized in field experiments to investigate patterns of microbial succession following injection of CO2 saturated water into isolated aquifer intervals. Additionally, laboratory mesocosm experiments, including microbially-active and inactive (autoclave sterilized) treatments, were used to constrain the microbial role in mineral dissolution, trace metal release, and gas production (e.g. hydrogen and methane). Hydrogen production was detected in both sterilized and unsterilized laboratory mesocosm treatments, indicating abiotic hydrogen production may occur following CO2 leakage, and methane production was detected in unsterilized, microbially active mesocosms. In field experiments, a decrease in pH following injection of CO2 saturated aquifer water was accompanied by mobilization of trace elements (e.g. Fe and Mn), the production of hydrogen gas, and increased bacterial cell concentrations. 16S ribosomal RNA clone libraries, from samples collected before and after the test well injection, were compared in an attempt to link variability in geochemistry to changes in aquifer microbiology. Significant changes in microbial composition, compared to background conditions, were found following the test well injection, including a decrease in Proteobacteria, and an increased presence of Firmicutes, Verrucomicrobia, Acidobacteria and other microbes associated with iron reducing and syntrophic metabolism. The concurrence of increased microbial cell concentration, and rapid microbial community succession, with increased concentrations of hydrogen gas suggests that abiotically produced hydrogen may serve as an ecologically-relevant energy source stimulating changes in aquifer microbial communities immediately following CO2 leakage.

Measurement of IL-13–Induced iNOS-Derived Gas Phase Nitric Oxide in Human Bronchial Epithelial Cells

PubMed Central

Suresh, Vinod; Mih, Justin D.; George, Steven C.

2007-01-01

Exhaled nitric oxide (NO) is altered in numerous diseases including asthma, and is thought broadly to be a noninvasive marker of inflammation. However, the precise source of exhaled NO has yet to be identified, and the interpretation is further hampered by significant inter-subject variation. Using fully differentiated normal human bronchial epithelial (NHBE) cells, we sought to determine (1) the rate of NO release (flux, pl·s−1.cm−2) into the gas; (2) the effect of IL-13, a prominent mediator of allergic inflammation, on NO release; and (3) inter-subject/donor variability in NO release. NHBE cells from three different donors were cultured at an air–liquid interface and stimulated with different concentrations of IL-13 (0, 1, and 10 ng/ml) for 48 h. Gas phase NO concentrations in the headspace over the cells were measured using a chemiluminescence analyzer. The basal NO flux from the three donors (0.05 ± 0.03) is similar in magnitude to that estimated from exhaled NO concentrations, and was significantly increased by IL-13 in a donor-specific fashion. The increase in NO release was strongly correlated with inducible nitric oxide synthase (iNOS) gene and protein expression. There was a trend toward enhanced production of nitrate relative to nitrite as an end product of NO metabolism in IL-13–stimulated cells. NO release from airway epithelial cells can be directly measured. The rate of release in response to IL-13 is strongly dependent on the individual donor, but is primarily due to the expression of iNOS. PMID:17347445

Measurement of radon concentration in super-Kamiokande's buffer gas

NASA Astrophysics Data System (ADS)

Nakano, Y.; Sekiya, H.; Tasaka, S.; Takeuchi, Y.; Wendell, R. A.; Matsubara, M.; Nakahata, M.

2017-09-01

To precisely measure radon concentrations in purified air supplied to the Super-Kamiokande detector as a buffer gas, we have developed a highly sensitive radon detector with an intrinsic background as low as 0 . 33 ± 0 . 07 mBq /m3. In this article, we discuss the construction and calibration of this detector as well as results of its application to the measurement and monitoring of the buffer gas layer above Super-Kamiokande. In March 2013, the chilled activated charcoal system used to remove radon in the input buffer gas was upgraded. After this improvement, a dramatic reduction in the radon concentration of the supply gas down to 0 . 08 ± 0 . 07 mBq /m3. Additionally, the Rn concentration of the in-situ buffer gas has been measured 28 . 8 ± 1 . 7 mBq /m3 using the new radon detector. Based on these measurements we have determined that the dominant source of Rn in the buffer gas arises from contamination from the Super-Kamiokande tank itself.

Interannual Variability of Carbon Dioxide, Methane and Nitrous Oxide Fluxes in Subarctic European Russian Tundra

NASA Astrophysics Data System (ADS)

Marushchak, M. E.; Voigt, C.; Gil, J.; Lamprecht, R. E.; Trubnikova, T.; Virtanen, T.; Kaverin, D.; Martikainen, P. J.; Biasi, C.

2017-12-01

Southern tundra landscapes are particularly vulnerable to climate warming, permafrost thaw and associated landscape rearrangement due to near-zero permafrost temperatures. The large soil C and N stocks of subarctic tundra may create a positive feedback for warming if released to the atmosphere at increased rates. Subarctic tundra in European Russia is a mosaic of land cover types, which all play different roles in the regional greenhouse gas budget. Peat plateaus - massive upheaved permafrost peatlands - are large storehouses of soil carbon and nitrogen, but include also bare peat surfaces that act as hot-spots for both carbon dioxide and nitrous oxide emissions. Tundra wetlands are important for the regional greenhouse gas balance since they show high rates of methane emissions and carbon uptake. The most dominant land-form is upland tundra vegetated by shrubs, lichens and mosses, which displays a close-to-neutral balance with respect to all three greenhouse gases. The study site Seida (67°03'N, 62°56'E), located in the discontinuous permafrost zone of Northeast European Russia, incorporates all these land forms and has been an object for greenhouse gas investigations since 2007. Here, we summarize the growing season fluxes of carbon dioxide, methane and nitrous oxide measured by chamber techniques over the study years. We analyzed the flux time-series together with the local environmental data in order to understand the drivers of interannual variability. Detailed soil profile measurements of greenhouse gas concentrations, soil moisture and temperature provide insights into soil processes underlying the net emissions to the atmosphere. The multiannual time-series allows us to assess the importance of the different greenhouse gases and landforms to the overall climate forcing of the study region.

Single-breath diffusing capacity for carbon monoxide instrument accuracy across 3 health systems.

PubMed

Hegewald, Matthew J; Markewitz, Boaz A; Wilson, Emily L; Gallo, Heather M; Jensen, Robert L

2015-03-01

Measuring diffusing capacity of the lung for carbon monoxide (DLCO) is complex and associated with wide intra- and inter-laboratory variability. Increased D(LCO) variability may have important clinical consequences. The objective of the study was to assess instrument performance across hospital pulmonary function testing laboratories using a D(LCO) simulator that produces precise and repeatable D(LCO) values. D(LCO) instruments were tested with CO gas concentrations representing medium and high range D(LCO) values. The absolute difference between observed and target D(LCO) value was used to determine measurement accuracy; accuracy was defined as an average deviation from the target value of < 2.0 mL/min/mm Hg. Accuracy of inspired volume measurement and gas sensors were also determined. Twenty-three instruments were tested across 3 healthcare systems. The mean absolute deviation from the target value was 1.80 mL/min/mm Hg (range 0.24-4.23) with 10 of 23 instruments (43%) being inaccurate. High volume laboratories performed better than low volume laboratories, although the difference was not significant. There was no significant difference among the instruments by manufacturers. Inspired volume was not accurate in 48% of devices; mean absolute deviation from target value was 3.7%. Instrument gas analyzers performed adequately in all instruments. D(LCO) instrument accuracy was unacceptable in 43% of devices. Instrument inaccuracy can be primarily attributed to errors in inspired volume measurement and not gas analyzer performance. D(LCO) instrument performance may be improved by regular testing with a simulator. Caution should be used when comparing D(LCO) results reported from different laboratories. Copyright © 2015 by Daedalus Enterprises.

The Effects of Surface Properties and Albedo on Methane Retrievals with the Airborne Visible/Infrared Imaging Spectrometer Next Generation (AVIRIS-NG)

NASA Astrophysics Data System (ADS)

Ayasse, A.; Thorpe, A. K.; Roberts, D. A.

2017-12-01

Atmospheric methane has increased by a factor of 2.5 since the beginning of the industrial era in response to anthropogenic emissions (Ciais et al., 2013). Although it is less abundant than carbon dioxide it is 86 time more potent on a 20 year time scale (Myhre et al., 2013) and is therefore responsible for about 20% of the total global warming induced by anthropogenic greenhouse gasses (Kirschke et al., 2013). Given the importance of methane to global climate change, monitoring and measuring methane emissions using techniques such as remote sensing is of increasing interest. Recently the Airborne Visible-Infrared Imaging Spectrometer - Next Generation (AVIRIS-NG) has proven to be a valuable instrument for quantitative mapping of methane plumes (Frankenberg et al., 2016; Thorpe et al., 2016; Thompson et al., 2015). In this study, we applied the Iterative Maximum a Posterior Differential Optical Spectroscopy (IMAP-DOAS) methane retrieval algorithm to a synthetic image with variable methane concentrations, albedo, and land cover. This allowed for characterizing retrieval performance, including potential sensitivity to variable land cover, low albedo surfaces, and surfaces known to cause spurious signals. We conclude that albedo had little influence on the IMAP-DOAS results except at very low radiance levels. Water (without sun glint) was found to be the most challenging surface for methane retrievals while hydrocarbons and some green vegetation also caused error. Understanding the effect of surface properties on methane retrievals is important given the increased use of AVIRIS-NG to map gas plumes over diverse locations and methane sources. This analysis could be expanded to include additional gas species like carbon dioxide and to further investigate gas sensitivity of proposed instruments for dedicated gas mapping from airborne and spaceborne platforms.

Dynamic evaluation of airflow rates for a variable air volume system serving an open-plan office.

PubMed

Mai, Horace K W; Chan, Daniel W T; Burnett, John

2003-09-01

In a typical air-conditioned office, the thermal comfort and indoor air quality are sustained by delivering the amount of supply air with the correct proportion of outdoor air to the breathing zone. However, in a real office, it is not easy to measure these airflow rates supplied to space, especially when the space is served by a variable air volume (VAV) system. The most accurate method depends on what is being measured, the details of the building and types of ventilation system. The constant concentration tracer gas method as a means to determine ventilation system performance, however, this method becomes more complicated when the air, including the tracer gas is allowed to recirculate. An accurate measurement requires significant resource support in terms of instrumentation set up and also professional interpretation. This method deters regular monitoring of the performance of an airside systems by building managers, and hence the indoor environmental quality, in terms of thermal comfort and indoor air quality, may never be satisfactory. This paper proposes a space zone model for the calculation of all the airflow parameters based on tracer gas measurements, including flow rates of outdoor air, VAV supply, return space, return and exfiltration. Sulphur hexafluoride (SF6) and carbon dioxide (CO2) are used as tracer gases. After using both SF6 and CO2, the corresponding results provide a reference to justify the acceptability of using CO2 as the tracer gas. The validity of using CO2 has the significance that metabolic carbon dioxide can be used as a means to evaluate real time airflow rates. This approach provides a practical protocol for building managers to evaluate the performance of airside systems.

Propagation of exponential shock wave in an axisymmetric rotating non-ideal dusty gas

NASA Astrophysics Data System (ADS)

Nath, G.

2016-09-01

One-dimensional unsteady isothermal and adiabatic flow behind a strong exponential shock wave propagating in a rotational axisymmetric mixture of non-ideal gas and small solid particles, which has variable azimuthal and axial fluid velocities, is analyzed. The shock wave is driven out by a piston moving with time according to exponential law. The azimuthal and axial components of the fluid velocity in the ambient medium are assumed to be varying and obeying exponential laws. In the present work, small solid particles are considered as pseudo-fluid with the assumption that the equilibrium flow-conditions are maintained in the flow-field, and the viscous-stress and heat conduction of the mixture are negligible. Solutions are obtained in both the cases, when the flow between the shock and the piston is isothermal or adiabatic by taking into account the components of vorticity vector and compressibility. It is found that the assumption of zero temperature gradient brings a profound change in the density, axial component of vorticity vector and compressibility distributions as compared to that of the adiabatic case. To investigate the behavior of the flow variables and the influence on the shock wave propagation by the parameter of non-idealness of the gas overline{b} in the mixture as well as by the mass concentration of solid particles in the mixture Kp and by the ratio of the density of solid particles to the initial density of the gas G1 are worked out in detail. It is interesting to note that the shock strength increases with an increase in G1 ; whereas it decreases with an increase in overline{b} . Also, a comparison between the solutions in the cases of isothermal and adiabatic flows is made.

Rapid fluctuations in the northern Baltic Sea H2S layer

NASA Astrophysics Data System (ADS)

Kankaanpää, Harri T.; Virtasalo, Joonas J.

2017-12-01

Hydrogen sulfide (H2S) is linked to water quality deterioration in the Baltic Sea, with widespread seafloor hypoxia. We examined the vertical and temporal variability of in situ [H2S], oxygen concentration ([O2]), temperature (T) and pH at weekly, hourly and minute intervals at 13 locations in the western Gulf of Finland in 2013-2014. The main target was the 60-100 m water depth range, containing 3.2-290 μM O2 and 6.3-22.6 μM H2S. Where gas was detected by acoustic surveys, the structure of the H2S layer was more complex compared to stations devoid of gas. Local minima and maxima in pH frequently occurred near the H2S upper boundary (redox transition zone). Except for the homogeneous, tranquil zone above the seafloor at some stations, substantial rapid changes in hydrographic conditions were common. Typically, a layer of marked temporal T variability was present atop or within the topmost H2S layers. The largest temporal changes over a weekly period were - 0.44 °C/- 10.8 μM H2S/- 0.12 pH units (at seafloor level), + 0.18 °C/+7.9 μM H2S between casts (1 h) and + 0.03 °C/- 2.5 μM H2S per minute (high resolution logging). Abrupt [H2S] changes were recorded at two stations with sediments containing free gas. The T and [H2S] changes were synchronous at several layers, reflecting water movement. We conclude that rapid changes occur in hydrographic conditions in the near-bottom H2S layer in the northern Baltic Sea, especially at locations where free gas is present in the underlying sediments.

Active Stand-off Detection of Gas Leaks Using a Short Range Hard-target Backscatter Differential Optical Absorption System Based on a Quantum Cascade Laser Transmitter

NASA Astrophysics Data System (ADS)

Diaz, Adrian; Thomas, Benjamin; Castillo, Paulo; Gross, Barry; Moshary, Fred

2016-06-01

Fugitive gas emissions from agricultural or industrial plants and gas pipelines are an important environmental concern as they can contribute to the global increase of greenhouse gas concentration. Moreover, they are also a security and safety concern because of possible risk of fire/explosion or toxicity. This study presents gas concentration measurements using a quantum cascade laser open path system (QCLOPS). The system retrieves the pathaveraged concentration of N2O and CH4 by collecting the backscattered light from a scattering target. The gas concentration measurements have a high temporal resolution (68 ms) and are achieved at sufficient range (up to 40 m, ~ 130 feet) with a detection limit of 2.6 ppm CH4 and 0.4 ppm for N2O. Given these characteristics, this system is promising for mobile/multidirectional remote detection and evaluation of gas leaks. The instrument is monostatic with a tunable QCL emitting at ~ 7.7 μm wavelength range. The backscattered radiation is collected by a Newtonian telescope and focused on an infrared light detector. Puffs of N2O and CH4 are released along the optical path to simulate a gas leak. The measured absorption spectrum is obtained using the thermal intra-pulse frequency chirped DFB QCL and is analyzed to obtain path averaged gas concentrations.

Using Bayesian Inference Framework towards Identifying Gas Species and Concentration from High Temperature Resistive Sensor Array Data

DOE PAGES

Liu, Yixin; Zhou, Kai; Lei, Yu

2015-01-01

High temperature gas sensors have been highly demanded for combustion process optimization and toxic emissions control, which usually suffer from poor selectivity. In order to solve this selectivity issue and identify unknown reducing gas species (CO, CH 4 , and CH 8 ) and concentrations, a high temperature resistive sensor array data set was built in this study based on 5 reported sensors. As each sensor showed specific responses towards different types of reducing gas with certain concentrations, based on which calibration curves were fitted, providing benchmark sensor array response database, then Bayesian inference framework was utilized to process themore » sensor array data and build a sample selection program to simultaneously identify gas species and concentration, by formulating proper likelihood between input measured sensor array response pattern of an unknown gas and each sampled sensor array response pattern in benchmark database. This algorithm shows good robustness which can accurately identify gas species and predict gas concentration with a small error of less than 10% based on limited amount of experiment data. These features indicate that Bayesian probabilistic approach is a simple and efficient way to process sensor array data, which can significantly reduce the required computational overhead and training data.« less

Total Observed Organic Carbon (TOOC): A Synthesis of North American Observations

NASA Technical Reports Server (NTRS)

Heald, C. L.; Goldstein, A. H.; Allan, J. D.; Aiken, A. C.; Apel, E.; Atlas, E. L.; Baker, A. K.; Bates, T. S.; Beyersdorf, A. J.; Blake, D. R.;

The spatial variability of water chemistry and DOC in bog pools: the importance of slope position, diurnal turnover and pool type

NASA Astrophysics Data System (ADS)

Holden, Joseph; Turner, Ed; Baird, Andy; Beadle, Jeannie; Billett, Mike; Brown, Lee; Chapman, Pippa; Dinsmore, Kerry; Dooling, Gemma; Grayson, Richard; Moody, Catherine; Gee, Clare

2017-04-01

We have previously shown that marine influence is an important factor controlling regional variability of pool water chemistry in blanket peatlands. Here we examine within-site controls on pool water chemistry. We surveyed natural and artificial (restoration sites) bog pools at blanket peatland sites in northern Scotland and Sweden. DOC, pH, conductivity, dissolved oxygen, temperature, cations, anions and absorbance spectra from 220-750nm were sampled. We sampled changes over time but also conducted intensive spatial surveys within individual pools and between pools on the same sampling days at individual study sites. Artificial pools had significantly greater DOC concentrations and different spectral absorbance characteristics when compared to natural pools at all sites studied. Within-pool variability in water chemistry tended to be small, even for very large pools ( 400 m2), except where pools had a layer of loose, mobile detritus on their beds. In these instances rapid changes took place between the overlying water column and the mobile sediment layer wherein dissolved oxygen concentrations dropped from values of around 12-10 mg/L to values less than 0.5 mg/L over just 2-3 cm of the depth profile. Such strong contrasts were not observed for pools which had a hard peat floor and which lacked a significant detritus layer. Strong diurnal turnover occurred within the pools on summer days, including within small, shallow pools (e.g. < 30 cm deep, 1 m2 area). For many pools on these summer days there was an evening spike in dissolved oxygen concentrations which originated at the surface and was then cycled downwards as the pool surface waters cooled. Slope location was a significant control on several pool water chemistry variables including pH and DOC concentration with accumulation (higher concentrations) in pools that were located further downslope in both natural and artificial pool systems. These processes have important implications for our interpretation of water chemistry and gas flux data from pool systems, how we design our sampling strategies and how we upscale results.

Gas hydrate concentration and characteristics within Hydrate Ridge inferred from multicomponent seismic reflection data

NASA Astrophysics Data System (ADS)

Kumar, Dhananjay; Sen, Mrinal K.; Bangs, Nathan L.

2007-12-01

A seismic experiment composed of streamer and ocean bottom seismometer (OBS) surveys was conducted in the summer of 2002 at southern Hydrate Ridge, offshore Oregon, to map the gas hydrate distribution within the hydrate stability zone. Gas hydrate concentrations within the reservoir can be estimated with P wave velocity (Vp); however, we can further constrain gas hydrate concentrations using S wave velocity (Vs), and use Vs through its relationship to Vp (Vp/Vs) to reveal additional details such as gas hydrate form within the matrix (i.e., hydrate cements the grains, becomes part of the matrix frame or floats in pore space). Both Vp and Vs can be derived simultaneously by inverting multicomponent seismic data. In this study, we use OBS data to estimate seismic velocities where both gas hydrate and free gas are present in the shallow sediments. Once Vp and Vs are estimated, they are simultaneously matched with modeled velocities to estimate the gas hydrate concentration. We model Vp using an equation based on a modification of Wood's equation that incorporates an appropriate rock physics model and Vs using an empirical relation. The gas hydrate concentration is estimated to be up to 7% of the rock volume, or 12% of the pore space. However, Vp and Vs do not always fit the model simultaneously. Vp can vary substantially more than Vs. Thus we conclude that a model, in which higher concentrations of hydrate do not affect shear stiffness, is more appropriate. Results suggest gas hydrates form within the pore space of the sediments and become part of the rock framework in our survey area.

Experimental simulation of air quality in street canyon under changes of building orientation and aspect ratio.

PubMed

Yassin, Mohamed F; Ohba, Masaake

2012-09-01

To assist validation of numerical simulations of urban pollution, air quality in a street canyon was investigated using a wind tunnel as a research tool under neutral atmospheric conditions. We used tracer gas techniques from a line source without buoyancy. Ethylene (C(2)H(4)) was used as the tracer gas. The street canyon model was formed of six parallel building rows of the same length. The flow and dispersion field was analyzed and measured using a hot-wire anemometer with split fiber probe and fast flame ionization detector. The diffusion flow field in the boundary layer within the street canyon was examined at different locations, with varying building orientations (θ=90°, 112.5°, 135° and 157.5°) and street canyon aspect ratios (W/H=1/2, 3/4 and 1) downwind of the leeward side of the street canyon model. Results show that velocity increases with aspect ratio, and with θ>90°. Pollutant concentration increases as aspect ratio decreases. This concentration decreases exponentially in the vertical direction, and decreases as θ increases from 90°. Measured pollutant concentration distributions indicate that variability of building orientation and aspect ratio in the street canyon are important for estimating air quality in the canyon. The data presented here can be used as a comprehensive database for validation of numerical models.

Prediction of operating parameters range for ammonia removal unit in coke making by-products

NASA Astrophysics Data System (ADS)

Tiwari, Hari Prakash; Kumar, Rajesh; Bhattacharjee, Arunabh; Lingam, Ravi Kumar; Roy, Abhijit; Tiwary, Shambhu

2018-02-01

Coke oven gas treatment plants are well equipped with distributed control systems (DCS) and therefore recording the vast amount of operational data efficiently. Analyzing the stored information manually from historians is practically impossible. In this study, data mining technique was examined for lowering the ammonia concentration in clean coke oven gas. Results confirm that concentration of ammonia in clean coke oven gas depends on the average PCDC temperature; gas scrubber temperatures stripped liquor flow, stripped liquor concentration and stripped liquor temperature. The optimum operating ranges of the above dependent parameters using data mining technique for lowering the concentration of ammonia is described in this paper.

[Research on the method of interference correction for nondispersive infrared multi-component gas analysis].

PubMed

Sun, You-Wen; Liu, Wen-Qing; Wang, Shi-Mei; Huang, Shu-Hua; Yu, Xiao-Man

2011-10-01

A method of interference correction for nondispersive infrared multi-component gas analysis was described. According to the successive integral gas absorption models and methods, the influence of temperature and air pressure on the integral line strengths and linetype was considered, and based on Lorentz detuning linetypes, the absorption cross sections and response coefficients of H2O, CO2, CO, and NO on each filter channel were obtained. The four dimension linear regression equations for interference correction were established by response coefficients, the absorption cross interference was corrected by solving the multi-dimensional linear regression equations, and after interference correction, the pure absorbance signal on each filter channel was only controlled by the corresponding target gas concentration. When the sample cell was filled with gas mixture with a certain concentration proportion of CO, NO and CO2, the pure absorbance after interference correction was used for concentration inversion, the inversion concentration error for CO2 is 2.0%, the inversion concentration error for CO is 1.6%, and the inversion concentration error for NO is 1.7%. Both the theory and experiment prove that the interference correction method proposed for NDIR multi-component gas analysis is feasible.

Augmented switching linear dynamical system model for gas concentration estimation with MOX sensors in an open sampling system.

PubMed

Di Lello, Enrico; Trincavelli, Marco; Bruyninckx, Herman; De Laet, Tinne

2014-07-11

In this paper, we introduce a Bayesian time series model approach for gas concentration estimation using Metal Oxide (MOX) sensors in Open Sampling System (OSS). Our approach focuses on the compensation of the slow response of MOX sensors, while concurrently solving the problem of estimating the gas concentration in OSS. The proposed Augmented Switching Linear System model allows to include all the sources of uncertainty arising at each step of the problem in a single coherent probabilistic formulation. In particular, the problem of detecting on-line the current sensor dynamical regime and estimating the underlying gas concentration under environmental disturbances and noisy measurements is formulated and solved as a statistical inference problem. Our model improves, with respect to the state of the art, where system modeling approaches have been already introduced, but only provided an indirect relative measures proportional to the gas concentration and the problem of modeling uncertainty was ignored. Our approach is validated experimentally and the performances in terms of speed of and quality of the gas concentration estimation are compared with the ones obtained using a photo-ionization detector.

Augmented Switching Linear Dynamical System Model for Gas Concentration Estimation with MOX Sensors in an Open Sampling System

PubMed Central

Di Lello, Enrico; Trincavelli, Marco; Bruyninckx, Herman; De Laet, Tinne

2014-01-01

In this paper, we introduce a Bayesian time series model approach for gas concentration estimation using Metal Oxide (MOX) sensors in Open Sampling System (OSS). Our approach focuses on the compensation of the slow response of MOX sensors, while concurrently solving the problem of estimating the gas concentration in OSS. The proposed Augmented Switching Linear System model allows to include all the sources of uncertainty arising at each step of the problem in a single coherent probabilistic formulation. In particular, the problem of detecting on-line the current sensor dynamical regime and estimating the underlying gas concentration under environmental disturbances and noisy measurements is formulated and solved as a statistical inference problem. Our model improves, with respect to the state of the art, where system modeling approaches have been already introduced, but only provided an indirect relative measures proportional to the gas concentration and the problem of modeling uncertainty was ignored. Our approach is validated experimentally and the performances in terms of speed of and quality of the gas concentration estimation are compared with the ones obtained using a photo-ionization detector. PMID:25019637

Carbon cycling in the mantled karst of the Ozark Plateaus, central United States

USGS Publications Warehouse

Knierim, Katherine J.; Pollock, Erik D.; Covington, Matthew D.; Hays, Phillip D.; Brye, Kristofor R.

2017-01-01

The nature of carbon (C) cycling in the unsaturated zone where groundwater is in contact with abundant gas-filled voids is poorly understood. The objective of this study was to trace inorganic-C cycling in a karst landscape using stable-C isotopes, with emphasis on a shallow groundwater flow path through the soil, to an underlying cave, and to the spring outlet of a cave stream in the Ozark Plateaus of northwestern Arkansas. Carbon dioxide (CO2) concentration and isotopic composition (δ13C-CO2) in gas and dissolved inorganic carbon (DIC) concentration and isotopic composition (δ13C-DIC) in water were measured in samples collected from two suction-cup soil samplers above the cave, three sites in the cave, and at the spring outlet of the cave stream. Soil-gas CO2 concentration (median 2,578 ppm) and δ13C-CO2 (median − 21.5‰) were seasonally variable, reflecting the effects of surface temperature changes on soil-CO2 production via respiration and organic-matter decomposition. Cave-air CO2 (median 1,026 ppm) was sourced from the soil zone and the surface atmosphere, with seasonally changing proportions of each source controlled by surface temperature-driven air density gradients. Soil-DIC concentration (median 1.7 mg L− 1) was lower and soil-δ13C-DIC (median − 19.5‰) was lighter compared to the cave (median 23.3 mg L− 1 and − 14.3‰, respectively) because carbonate-bedrock dissolution provided an inorganic source of C to the cave. Carbon species in the soil had a unique, light stable-C isotopic signature compared to the cave. Discrimination of soil-C sources to karst groundwater was achieved, which is critical for developing hydrologic budgets using environmental tracers such as C.

Environmental Benign Process for Production of Molybdenum Metal from Sulphide Based Minerals

NASA Astrophysics Data System (ADS)

Rajput, Priyanka; Janakiram, Vangada; Jayasankar, Kalidoss; Angadi, Shivakumar; Bhoi, Bhagyadhar; Mukherjee, Partha Sarathi

2017-10-01

Molybdenum is a strategic and high temperature refractory metal which is not found in nature in free state, it is predominantly found in earth's crust in the form of MoO3/MoS2. The main disadvantage of the industrial treatment of Mo concentrate is that the process contains many stages and requires very high temperature. Almost in every step many gaseous, liquid, solid chemical substances are formed which require further treatment. To overcome the above drawback, a new alternative one step novel process is developed for the treatment of sulphide and trioxide molybdenum concentrates. This paper presents the results of the investigations on molybdenite dissociation (MoS2) using microwave assisted plasma unit as well as transferred arc thermal plasma torch. It is a single step process for the preparation of pure molybdenum metal from MoS2 by hydrogen reduction in thermal plasma. Process variable such as H2 gas, Ar gas, input current, voltage and time have been examined to prepare molybdenum metal. Molybdenum recovery of the order of 95% was achieved. The XRD results confirm the phases of molybdenum metal and the chemical analysis of the end product indicate the formation of metallic molybdenum (Mo 98%).

Field Measurements of Respiratory Del13CO2 and Photodegradation

NASA Astrophysics Data System (ADS)

van Asperen, H.; Sabbatini, S.; Nicolini, G.; Warneke, T.; Papale, D.; Notholt, J.

2014-12-01

Carbon decomposition dynamics have been studied in a variety of ecosystems and its variation can mostly be explained in terms of environmental variables (e.g. temperature and precipitation). However, carbon dynamics in arid, water limited regions have shown to be very different and are still largely unknown. Several studies have indicated the importance of photodegradation, the direct breakdown of organic matter by sunlight, in these arid regions. A FTIR (Fourier Transform Infrared Spectrometer) was set up to continuously measure concentrations of CO2, CH4, N2O, CO as well as del13C in CO2. The FTIR was connected to 2 different flux measurement systems: a Flux Gradient system and 2 flux chambers, providing a continuous data set of gas concentrations and biosphere-atmosphere gas fluxes at different heights and scales. Field measurements showed photodegradation induced carbon fluxes. Also, respiratory del13CO2 was determined by use of Keeling plots, and was determined to vary between -25‰ and -21‰. A clear diurnal pattern in respiratory del13CO2 was found, suggesting either different (dominant) respiratory processes between day and night or the effect of diffusive fractionation.

Avian mortality associated with a volcanic gas seep at Kiska Island, Aleutian Islands, Alaska

USGS Publications Warehouse

Bond, Alexander L.; Evans, William C.; Jones, Ian L.

2012-01-01

We identified natural pits associated with avian mortality at the base of Kiska Volcano in the western Aleutian Islands, Alaska in 2007. Living, moribund, and dead birds were regularly found at low spots in a canyon between two lava flows during 2001–2006, but the phenomenon was attributed to natural trapping and starvation of fledgling seabirds (mostly Least Auklets, Aethia pusilla) at a colony site with >1 million birds present. However, 302 birds of eight species, including passerines, were found dead at the site during 2007–2010, suggesting additional factors were involved. Most carcasses showed no signs of injury and concentrations of dead birds had accumulated in a few distinctive low pits in the canyon. Gas samples from these locations showed elevated CO2 concentrations in late 2010. Analysis of carcasses indicated no evidence of blunt trauma or internal bleeding. Volcanic gases accumulating at these poorly ventilated sites may have caused the observed mortality, but are temporally variable. Most auklets breeding in the Aleutian Islands do so in recent lava flows that provide breeding habitat; our study documents a cost of this unusual habitat selection.

Long-term Internal Variability of the Tropical Pacific Atmosphere-Ocean System

NASA Astrophysics Data System (ADS)

Hadi Bordbar, Mohammad; Martin, Thomas; Park, Wonsun; Latif, Mojib

2016-04-01

The tropical Pacific has featured some remarkable trends during the recent decades such as an unprecedented strengthening of the Trade Winds, a strong cooling of sea surface temperatures (SST) in the eastern and central part, thereby slowing global warming and strengthening the zonal SST gradient, and highly asymmetric sea level trends with an accelerated rise relative to the global average in the western and a drop in the eastern part. These trends have been linked to an anomalously strong Pacific Walker Circulation, the major zonal atmospheric overturning cell in the tropical Pacific sector, but the origin of the strengthening is controversial. Here we address the question as to whether the recent decadal trends in the tropical Pacific atmosphere-ocean system are within the range of internal variability, as simulated in long unforced integrations of global climate models. We show that the recent trends are still within the range of long-term internal decadal variability. Further, such variability strengthens in response to enhanced greenhouse gas concentrations, which may further hinder detection of anthropogenic climate signals in that region.

A method for direct, semi-quantitative analysis of gas phase samples using gas chromatography-inductively coupled plasma-mass spectrometry

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

Carter, Kimberly E; Gerdes, Kirk

2013-07-01

A new and complete GC–ICP-MS method is described for direct analysis of trace metals in a gas phase process stream. The proposed method is derived from standard analytical procedures developed for ICP-MS, which are regularly exercised in standard ICP-MS laboratories. In order to implement the method, a series of empirical factors were generated to calibrate detector response with respect to a known concentration of an internal standard analyte. Calibrated responses are ultimately used to determine the concentration of metal analytes in a gas stream using a semi-quantitative algorithm. The method was verified using a traditional gas injection from a GCmore » sampling valve and a standard gas mixture containing either a 1 ppm Xe + Kr mix with helium balance or 100 ppm Xe with helium balance. Data collected for Xe and Kr gas analytes revealed that agreement of 6–20% with the actual concentration can be expected for various experimental conditions. To demonstrate the method using a relevant “unknown” gas mixture, experiments were performed for continuous 4 and 7 hour periods using a Hg-containing sample gas that was co-introduced into the GC sample loop with the xenon gas standard. System performance and detector response to the dilute concentration of the internal standard were pre-determined, which allowed semi-quantitative evaluation of the analyte. The calculated analyte concentrations varied during the course of the 4 hour experiment, particularly during the first hour of the analysis where the actual Hg concentration was under predicted by up to 72%. Calculated concentration improved to within 30–60% for data collected after the first hour of the experiment. Similar results were seen during the 7 hour test with the deviation from the actual concentration being 11–81% during the first hour and then decreasing for the remaining period. The method detection limit (MDL) was determined for the mercury by injecting the sample gas into the system following a period of equilibration. The MDL for Hg was calculated as 6.8 μg · m -3. This work describes the first complete GC–ICP-MS method to directly analyze gas phase samples, and detailed sample calculations and comparisons to conventional ICP-MS methods are provided.« less

A Novel Method for Determining the Gas Transfer Velocity of Carbon Dioxide in Streams

NASA Astrophysics Data System (ADS)

McDowell, M. J.; Johnson, M. S.

2016-12-01

Characterization of the global carbon cycle relies on the accurate quantification of carbon fluxes into and out of natural and human-dominated ecosystems. Among these fluxes, carbon dioxide (CO2) evasion from surface water has received increasing attention in recent years. However, limitations of current methods, including determination of the gas transfer velocity (k), compromise our ability to evaluate the significance of CO2 fluxes between freshwater systems and the atmosphere. We developed an automated method to determine gas transfer velocities of CO2 (kCO2), and tested it under a range of flow conditions for a first-order stream of a headwater catchment in southwestern British Columbia, Canada. Our method uses continuous in situ measurements of CO2 concentrations using two non-dispersive infrared (NDIR) sensors enclosed in water impermeable, gas permeable membranes (Johnson et al., 2010) downstream from a gas diffuser. CO2 was injected into the stream at regular intervals via a compressed gas tank connected to the diffuser. CO2 injections were controlled by a datalogger at fixed time intervals and in response to storm-induced changes in streamflow. Following the injection, differences in CO2 concentrations at known distances downstream from the diffuser relative to pre-injection baseline levels allowed us to calculate kCO2. Here we present relationships between kCO2 and hydro-geomorphologic (flow velocity, streambed slope, stream width, stream depth), atmospheric (wind speed and direction), and water quality (stream temperature, pH, electrical conductivity) variables. This method has advantages of being automatable and field-deployable, and it does not require supplemental gas chromatography, as is the case for propane injections typically used to determine k. The dataset presented suggests the potential role of this method to further elucidate the role that CO2 fluxes from headwater streams play in the global carbon cycle. Johnson, M. S., Billett, M. F., Dinsmore, K. J., Wallin, M., Dyson, K. E., & Jassal, R. S. (2010). Direct and continuous measurement of dissolved carbon dioxide in freshwater aquatic systems—method and applications. Ecohydrology, 3(1), 68-78. http://doi.org/10.1002/eco.95

Seasonal and geothermal production variations in concentrations of He and CO2 in soil gases, Roosevelt Hot Springs Known Geothermal Resource Area, Utah, U.S.A.

USGS Publications Warehouse

Hinkle, M.E.

1991-01-01

To increase understanding of natural variations in soil gas concentrations, CO2, He, O2 and N2 were measured in soil gases collected regularly for several months from four sites at the Roosevelt Hot Springs Known Geothermal Resource Area, Utah. Soil temperature, air temperature, per cent relative humidity, barometric pressure and amounts of rain and snowfall were also monitored to determine the effect of meteorological parameters on concentrations of the measured gases. Considerable seasonal variation existed in concentrations of CO2 and He. The parameters that most affected the soil-gas concentrations were soil and air temperatures. Moisture from rain and snow probably affected the soil-gas concentrations also. However, annual variations in meteorological parameters did not appear to affect measurements of anomalous concentrations in samples collected within a time period of a few days. Production from some of the geothermal wells probably affected the soil-gas concentrations. ?? 1990.

Effect of corona discharge on the gas composition of the sample flow in a Gas Particle Partitioner.

PubMed

Asbach, Christof; Kuhlbusch, Thomas A J; Fissan, Heinz

2005-09-01

A Gas Particle Partitioner (GPP) that allows highly efficient separation of gas and particles with no effect on the thermodynamic conditions and substantially no change of the gas composition has been developed. The GPP is a coaxial arrangement with inner and outer electrodes and utilizes a corona discharge to electrically charge the particles and a strong electric field to remove them from the sample flow. Several measures were taken to avoid an influence of the corona discharge on the gas composition. The GPP can be applied for various applications. This paper focuses on the use of the GPP as a pre-filter for gas analyzers, where zero pressure drop and a minimization of the influence of the corona discharge on the gas composition are the main objective. Due to its design, the GPP introduces no changes to the thermodynamic conditions. However, corona discharge is known to produce significant amounts of ozone and oxides of nitrogen. The effect of the corona on the gas composition of the sample flow was determined under various conditions. The gas concentrations strongly depended on several aspects, such as material and diameter of the corona wire and polarity of the corona voltage. Due to the measures taken to minimize an effect on the gas composition, the concentrations of these gases could effectively be reduced. Along with the maximum gas-particle separation efficiency of near 100%, the additional O3 concentration was 42 ppbV and the additional NO2 concentration 15 ppbV. If an efficiency of 95% is acceptable, the added concentrations can be as low as 2.5 ppbV (O3) and 0.5 ppbV (NO2), respectively.

Spatially-Scanned Dual Comb Spectroscopy for Atmospheric Measurements

NASA Astrophysics Data System (ADS)

Cossel, K.; Waxman, E.; Giorgetta, F.; Cermak, M.; Coddington, I.; Hesselius, D.; Ruben, S.; Swann, W.; Rieker, G. B.; Newbury, N.

2017-12-01

Measuring trace gas emissions from sources that are spatially complex and temporally variable, such as leaking natural gas infrastructure, is challenging with current measurement systems. Here, we present a new technique that provides the path-integrated concentrations of multiple gas species between a ground station and a retroreflector mounted on a small quadcopter. Such a system could provide the ability to quantify small area emissions sources as well measure vertical mixing within the boundary layer. The system is based on a near-infrared dual frequency-comb spectroscopy system (DCS) covering 1.58-1.7 microns, which enables rapid, accurate measurements of CO2, CH4, H2O, and HDO. The eye-safe laser light is launched from a telescope on a fast azimuth, elevation gimbal to a small quadcopter carrying a lightweight retroreflector as well as a high-precision real-time kinematic GPS receiver (for real-time cm-level path length measurements) and pressure, temperature and humidity sensors. Here, we show the results of test measurements from controlled releases of CH4 as well as from test vertical profiles.

Characterization of solid-phase microextraction and gas chromatography for the analysis of gasoline tracers in different microenvironments.

PubMed

Ceballos, Diana; Zielinska, Barbara; Fujita, Eric; Sagebiel, John

2007-03-01

Gasoline tracers were collected on solid-phase microextraction (SPME) fibers and analyzed by capillary gas chromatography with photoionization detector (GC/PID). This was part of a larger study to quantify personal exposure to motor vehicle gasoline evaporative and combustive emissions in high-end exposure microenvironments (MEs). The SPME fiber selected for this application was a 75-microm carboxen/polydimethylsiloxane. Sequential 10-min samples were collected for measurement of benzene, toluene, ethylbenzene, and ortho-, meta-, and para-xylene in different MEs in Atlanta, GA, in summer 2002 and Reno, NV, in spring 2003. Field calibrations were performed with certified gas standards in 1-L Tedlar bags for varying concentrations and exposure times. SPME detection limits were approximately 0.2 ppbv with a precision of 3-17% and accuracy of 30%. A dynamic system was designed for temperature and relative humidity calibrations, with corrections for the effects of these variables performed when necessary. SPME data compared satisfactorily with integrated canister samples, continuous PID, and field portable mass spectrometer data.

Characterization of Swirl-Venturi Lean Direct Injection Designs for Aviation Gas-Turbine Combustion

NASA Technical Reports Server (NTRS)

Heath, Christopher M.

2013-01-01

Injector geometry, physical mixing, chemical processes, and engine cycle conditions together govern performance, operability and emission characteristics of aviation gas-turbine combustion systems. The present investigation explores swirl-venturi lean direct injection combustor fundamentals, characterizing the influence of key geometric injector parameters on reacting flow physics and emission production trends. In this computational study, a design space exploration was performed using a parameterized swirl-venturi lean direct injector model. From the parametric geometry, 20 three-element lean direct injection combustor sectors were produced and simulated using steady-state, Reynolds-averaged Navier-Stokes reacting computations. Species concentrations were solved directly using a reduced 18-step reaction mechanism for Jet-A. Turbulence closure was obtained using a nonlinear ?-e model. Results demonstrate sensitivities of the geometric perturbations on axially averaged flow field responses. Output variables include axial velocity, turbulent kinetic energy, static temperature, fuel patternation and minor species mass fractions. Significant trends have been reduced to surrogate model approximations, intended to guide future injector design trade studies and advance aviation gas-turbine combustion research.

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

PubMed

Suzuki, Taku T; Sakaguchi, Isao

2016-01-01

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

Application of a support vector machine algorithm to the safety precaution technique of medium-low pressure gas regulators

NASA Astrophysics Data System (ADS)

Hao, Xuejun; An, Xaioran; Wu, Bo; He, Shaoping

2018-02-01

In the gas pipeline system, safe operation of a gas regulator determines the stability of the fuel gas supply, and the medium-low pressure gas regulator of the safety precaution system is not perfect at the present stage in the Beijing Gas Group; therefore, safety precaution technique optimization has important social and economic significance. In this paper, according to the running status of the medium-low pressure gas regulator in the SCADA system, a new method for gas regulator safety precaution based on the support vector machine (SVM) is presented. This method takes the gas regulator outlet pressure data as input variables of the SVM model, the fault categories and degree as output variables, which will effectively enhance the precaution accuracy as well as save significant manpower and material resources.

Southern Hemisphere climate variability forced by Northern Hemisphere ice-sheet topography

NASA Astrophysics Data System (ADS)

Jones, T. R.; Roberts, W. H. G.; Steig, E. J.; Cuffey, K. M.; Markle, B. R.; White, J. W. C.

2018-02-01

The presence of large Northern Hemisphere ice sheets and reduced greenhouse gas concentrations during the Last Glacial Maximum fundamentally altered global ocean-atmosphere climate dynamics. Model simulations and palaeoclimate records suggest that glacial boundary conditions affected the El Niño-Southern Oscillation, a dominant source of short-term global climate variability. Yet little is known about changes in short-term climate variability at mid- to high latitudes. Here we use a high-resolution water isotope record from West Antarctica to demonstrate that interannual to decadal climate variability at high southern latitudes was almost twice as large at the Last Glacial Maximum as during the ensuing Holocene epoch (the past 11,700 years). Climate model simulations indicate that this increased variability reflects an increase in the teleconnection strength between the tropical Pacific and West Antarctica, owing to a shift in the mean location of tropical convection. This shift, in turn, can be attributed to the influence of topography and albedo of the North American ice sheets on atmospheric circulation. As the planet deglaciated, the largest and most abrupt decline in teleconnection strength occurred between approximately 16,000 years and 15,000 years ago, followed by a slower decline into the early Holocene.

Decadal Variation's Offset of Global Warming in Recent Tropical Pacific Climate

NASA Astrophysics Data System (ADS)

Yeo, S. R.; Yeh, S. W.; Kim, K. Y.; Kim, W.

2015-12-01

Despite the increasing greenhouse gas concentration, there is no significant warming in the sea surface temperature (SST) over the tropical eastern Pacific since about 2000. This counterintuitive observation has generated substantial interest in the role of low-frequency variation over the Pacific Ocean such as Pacific Decadal Oscillation (PDO) or Interdecadal Pacific Oscillation (IPO). Therefore, it is necessary to appropriately separate low-frequency variability and global warming from SST records. Here we present three primary modes of global SST as a secular warming trend, a low-frequency variability, and a biennial oscillation through the use of novel statistical method. By analyzing temporal behavior of the three-mode, it is found that the opposite contributions of secular warming trend and cold phase of low-frequency variability since 1999 account for the warming hiatus in the tropical eastern Pacific. This result implies that the low-frequency variability modulates the manifestation of global warming signal in the tropical Pacific SST. Furthermore, if the low-frequency variability turns to a positive phase, warming in the tropical eastern Pacific will be amplified and also strong El Niño events will occur more frequently in the near future.

Radioiodine detector based on laser induced fluorescence

DOEpatents

McDonald, Jimmie R.; Baronavski, Andrew P.

1980-01-01

The invention involves the measurement of the concentration of the radioisotope .sup.129 I.sub.2 in the presence of a gas. The invention uses a laser to excite a sample of the .sup.129 I.sub.2 in a sample gas chamber and a reference sample of a known concentration of .sup.129 I.sub.2 in a reference gas chamber. The .sup.129 I.sub.2 in the sample and reference gas chamber each gives off fluorescence emissions which are received by photomultipliers which provide signals to a detector. The detector uses a ratioing technique to determine the concentration of .sup.129 I.sub.2 in the sample gas chamber.

High density Polyethylene plastic waste treatment with microwave heating pyrolysis method using coconut-shell activated carbon to produce alternative fuels

NASA Astrophysics Data System (ADS)

Juliastuti, S. R.; Hisbullah, M. I.; Abdillah, M.

2018-03-01

Pyrolysis is a technology that could crack polimer such as plastic waste into alternative fuels. This research uses microwave heating methode, which more efficient than conventional heating methode. The plastic waste used is 200 grams of HDPE, with feed to catalyst weight ratio are 1:1, 0.6:1, 0.4:1. Pyrolysis was run at temperatures of 250, 300, 350, & 400 °C for 15, 30 and 45 min. From the experimental result, the best variable of pyrolysis process with microwave method is at 45 minutes, at 400°C, and 1:1 feed to catalyst weight ratio. Result shows that yield of liquid and gas product is 99.22%; yield of residue is 0.78%; value of liquid product’s composition (cycloparaffin and n-paraffin) is 54.09% and concentration of methane gas is 10.2%.

Factors controlling sulfur gas exchange in Sphagnum-dominated wetlands

NASA Technical Reports Server (NTRS)

Demello, William Zamboni; Hines, Mark E.; Bayley, Suzanne E.

1992-01-01

Atmosphere-peatland exchange of reduced sulfur gases was determined seasonally in fen in NH, and in an artificially-acidified fen at the Experimental Lakes Area (ELA) in Canada. Dimethyl sulfide (DMS) dominated gas fluxes at rates as high as 400 nmol/m(sup -2)hr(sup -1). DMS fluxes measured using enclosures were much higher than those calculated using a stagnant-film model, suggesting that Sphagnum regulated efflux. Temperature controlled diel and seasonal variability in DMS emissions. Use of differing enclosure techniques indicated that vegetated peatlands consume atmospheric carbonyl sulfide. Sulfate amendments caused DMS and methane thiol concentrations in near-surface pore waters to increase rapidly, but fluxes of these gases to the atmosphere were not affected. However, emission data from sites experiencing large differences in rates of sulfate deposition from the atmosphere suggested that chronic elevated sulfate inputs enhance DMS emissions from northern wetlands.

Analysis of blood gases, serum fat and serum protein: a new approach to estimate survival chances of stranded Harbor seal (Phoca vitulina) pups from the German North Sea

PubMed Central

2014-01-01

Background Facing numerous challenges, such as illness, storms or human disturbance, some harbor seal (Phoca vitulina) pups lose contact to their dams and are found abandoned along the North Sea coast. In Schleswig-Holstein, pups with the prospect of surviving rehabilitation are admitted to the Seal Center Friedrichskoog. Despite elaborate clinical health assessments on admission, including differential hematology, in 2010, 17% of 108 admitted pups did not survive the first 20 days. The death rate during the years 2006 and 2009 varied between 9 and 19%. To broaden the spectrum of variables which could be predictive for survival, blood gas and serum analyses were performed for 99 pups using venous blood. Variables included total CO2, pH, partial CO2, HCO3–, base excess and anion gap as well as glucose, urea nitrogen, sodium, potassium and chloride. Moreover, total serum protein and fat (triglyceride) concentrations were measured for all pups on admission. Results Repeated measurements of 12 randomly selected individuals revealed a significant (p = 0.002) positive influence of time in rehabilitation on triglyceride concentrations. This trend probably shows the improvement of the pups’ nutritional status as a consequence of the shift from milk replacer formula to fish. No such positive influence was detected for total protein concentrations though. Hematologic values, including blood gases, were not predictive for survival. Conclusions For the first time blood gas values are reported in this study for a large sample size (N = 99) of seal pups (regardless of their health status). The ranges and medians calculated from the data can serve as a stepping stone towards the establishment of reference values for neonate harbor seals. However, future investigations on the development of blood gases in harbor seals with different health conditions and ages over time are necessary to allow for a better understanding of acid–base regulation in harbor seals. PMID:24490584

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

NASA Astrophysics Data System (ADS)

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

2012-07-01

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

Analysis of blood gases, serum fat and serum protein: a new approach to estimate survival chances of stranded Harbor seal (Phoca vitulina) pups from the German North Sea.

PubMed

Witte, Katharina A; Driver, Jörg; Rosenberger, Tanja; Adler, Sven; Siebert, Ursula

2014-02-04

Facing numerous challenges, such as illness, storms or human disturbance, some harbor seal (Phoca vitulina) pups lose contact to their dams and are found abandoned along the North Sea coast. In Schleswig-Holstein, pups with the prospect of surviving rehabilitation are admitted to the Seal Center Friedrichskoog. Despite elaborate clinical health assessments on admission, including differential hematology, in 2010, 17% of 108 admitted pups did not survive the first 20 days. The death rate during the years 2006 and 2009 varied between 9 and 19%. To broaden the spectrum of variables which could be predictive for survival, blood gas and serum analyses were performed for 99 pups using venous blood. Variables included total CO2, pH, partial CO2, HCO3-, base excess and anion gap as well as glucose, urea nitrogen, sodium, potassium and chloride. Moreover, total serum protein and fat (triglyceride) concentrations were measured for all pups on admission. Repeated measurements of 12 randomly selected individuals revealed a significant (p = 0.002) positive influence of time in rehabilitation on triglyceride concentrations. This trend probably shows the improvement of the pups' nutritional status as a consequence of the shift from milk replacer formula to fish. No such positive influence was detected for total protein concentrations though. Hematologic values, including blood gases, were not predictive for survival. For the first time blood gas values are reported in this study for a large sample size (N = 99) of seal pups (regardless of their health status). The ranges and medians calculated from the data can serve as a stepping stone towards the establishment of reference values for neonate harbor seals. However, future investigations on the development of blood gases in harbor seals with different health conditions and ages over time are necessary to allow for a better understanding of acid-base regulation in harbor seals.

Photoacoustic Effect of Ethene: Sound Generation due to Plant Hormone Gases.

NASA Astrophysics Data System (ADS)

Park, Han Jung; Ide, David; University of Tennessee at Chattanooga Team

2017-01-01

Ethene, which is produced in plants as they mature, was used to study its photoacoustic properties using photoacoustic spectroscopy. Detection of trace amounts, with N2 gas, of the ethylene gas were also applied. The gas was tested in various conditions: temperature, concentration of the gas, gas cell length, and power of the laser, were varied to determine their effect on the photoacoustic signal, the ideal conditions to detect trace gas amounts, and concentration of ethylene produced by an avocado and banana. A detection limit of 10 ppm was determined for pure C2H4. A detection of 5% and 13% (by volume) concentration of ethylene were produced for a ripening avocado and banana, respectively, in closed space.

Detecting small holes in packages

DOEpatents

Kronberg, J.W.; Cadieux, J.R.

1996-03-19

A package containing a tracer gas, and a method for determining the presence of a hole in the package by sensing the presence of the gas outside the package are disclosed. The preferred tracer gas, especially for food packaging, is sulfur hexafluoride. A quantity of the gas is added to the package and the package is closed. The concentration of the gas in the atmosphere outside the package is measured and compared to a predetermined value of the concentration of the gas in the absence of the package. A measured concentration greater than the predetermined value indicates the presence of a hole in the package. Measuring may be done in a chamber having a lower pressure than that in the package. 3 figs.

Oxidation of naturally reduced uranium in aquifer sediments by dissolved oxygen and its potential significance to uranium plume persistence

NASA Astrophysics Data System (ADS)

Davis, J. A.; Smith, R. L.; Bohlke, J. K.; Jemison, N.; Xiang, H.; Repert, D. A.; Yuan, X.; Williams, K. H.

2015-12-01

The occurrence of naturally reduced zones is common in alluvial aquifers in the western U.S.A. due to the burial of woody debris in flood plains. Such reduced zones are usually heterogeneously dispersed in these aquifers and characterized by high concentrations of organic carbon, reduced mineral phases, and reduced forms of metals, including uranium(IV). The persistence of high concentrations of dissolved uranium(VI) at uranium-contaminated aquifers on the Colorado Plateau has been attributed to slow oxidation of insoluble uranium(IV) mineral phases found in association with these reducing zones, although there is little understanding of the relative importance of various potential oxidants. Four field experiments were conducted within an alluvial aquifer adjacent to the Colorado River near Rifle, CO, wherein groundwater associated with the naturally reduced zones was pumped into a gas-impermeable tank, mixed with a conservative tracer (Br-), bubbled with a gas phase composed of 97% O2 and 3% CO2, and then returned to the subsurface in the same well from which it was withdrawn. Within minutes of re-injection of the oxygenated groundwater, dissolved uranium(VI) concentrations increased from less than 1 μM to greater than 2.5 μM, demonstrating that oxygen can be an important oxidant for uranium in such field systems if supplied to the naturally reduced zones. Dissolved Fe(II) concentrations decreased to the detection limit, but increases in sulfate could not be detected due to high background concentrations. Changes in nitrogen species concentrations were variable. The results contrast with other laboratory and field results in which oxygen was introduced to systems containing high concentrations of mackinawite (FeS), rather than the more crystalline iron sulfides found in aged, naturally reduced zones. The flux of oxygen to the naturally reduced zones in the alluvial aquifers occurs mainly through interactions between groundwater and gas phases at the water table. Seasonal variations of the water table at the Rifle, CO site may play an important role in introducing oxygen into the system. Although oxygen was introduced directly to the naturally reduced zones in these experiments, delivery of oxidants to the system may also be controlled by other oxidative pathways in which oxygen plays an indirect role.

A Gas Chromatographic System for the Detection of Ethylene Gas Using Ambient Air as a Carrier Gas.

PubMed

Zaidi, Nayyer Abbas; Tahir, Muhammad Waseem; Vellekoop, Michael J; Lang, Walter

2017-10-07

Ethylene gas is a naturally occurring gas that has an influence on the shelf life of fruit during their transportation in cargo ships. An unintentional exposure of ethylene gas during transportation results in a loss of fruit. A gas chromatographic system is presented here for the detection of ethylene gas. The gas chromatographic system was assembled using a preconcentrator, a printed 3D printed gas chromatographic column, a humidity sensor, solenoid valves, and an electrochemical ethylene gas sensor. Ambient air was used as a carrier gas in the gas chromatographic system. The flow rate was fixed to 10 sccm. It was generated through a mini-pump connected in series with a mass flow controller. The metal oxide gas sensor is discussed with its limitation in ambient air. The results show the chromatogram obtained from metal oxide gas sensor has low stability, drifts, and has uncertain peaks, while the chromatogram from the electrochemical sensor is stable and precise. Furthermore, ethylene gas measurements at higher ppb concentration and at lower ppb concentration were demonstrated with the electrochemical ethylene gas sensor. The system separates ethylene gas and humidity. The chromatograms obtained from the system are stable, and the results are 1.2% repeatable in five similar measurements. The statistical calculation of the gas chromatographic system shows that a concentration of 2.3 ppb of ethylene gas can be detected through this system.

The effect of dry and wet deposition of condensable vapors on secondary organic aerosols concentrations over the continental US

NASA Astrophysics Data System (ADS)

Knote, C.; Hodzic, A.; Jimenez, J. L.

2015-01-01

The effect of dry and wet deposition of semi-volatile organic compounds (SVOCs) in the gas phase on the concentrations of secondary organic aerosol (SOA) is reassessed using recently derived water solubility information. The water solubility of SVOCs was implemented as a function of their volatility distribution within the WRF-Chem regional chemistry transport model, and simulations were carried out over the continental United States for the year 2010. Results show that including dry and wet removal of gas-phase SVOCs reduces annual average surface concentrations of anthropogenic and biogenic SOA by 48 and 63% respectively over the continental US. Dry deposition of gas-phase SVOCs is found to be more effective than wet deposition in reducing SOA concentrations (-40 vs. -8% for anthropogenics, and -52 vs. -11% for biogenics). Reductions for biogenic SOA are found to be higher due to the higher water solubility of biogenic SVOCs. The majority of the total mass of SVOC + SOA is actually deposited via the gas phase (61% for anthropogenics and 76% for biogenics). Results are sensitive to assumptions made in the dry deposition scheme, but gas-phase deposition of SVOCs remains crucial even under conservative estimates. Considering reactivity of gas-phase SVOCs in the dry deposition scheme was found to be negligible. Further sensitivity studies where we reduce the volatility of organic matter show that consideration of gas-phase SVOC removal still reduces average SOA concentrations by 31% on average. We consider this a lower bound for the effect of gas-phase SVOC removal on SOA concentrations. A saturation effect is observed for Henry's law constants above 108 M atm-1, suggesting an upper bound of reductions in surface level SOA concentrations by 60% through removal of gas-phase SVOCs. Other models that do not consider dry and wet removal of gas-phase SVOCs would hence overestimate SOA concentrations by roughly 50%. Assumptions about the water solubility of SVOCs made in some current modeling systems (H* = H* (CH3COOH); H* = 105 M atm-1; H* = H* (HNO3)) still lead to an overestimation of 35%/25%/10% compared to our best estimate.

Kinetic bottlenecks to chemical exchange rates for deep-sea animals II: Carbon dioxide

NASA Astrophysics Data System (ADS)

Hofmann, A. F.; Peltzer, E. T.; Brewer, P. G.

2012-11-01

Increased ocean acidification from fossil fuel CO2 invasion, from temperature-driven changes in respiration, and from possible leakage from sub-seabed geologic CO2 disposal has aroused concern over the impacts of elevated CO2 concentrations on marine life. Discussion of these impacts has so far focused only on changes in the oceanic bulk fluid properties (ΔpH, Δ[∑CO2] etc.) as the critical variable and with a major focus on carbonate shell dissolution. Here we describe the rate problem for animals that must export CO2 at about the same rate at which O2 is consumed. We analyze the basic properties controlling CO2 export within the diffusive boundary layer around marine animals in an ocean changing in temperature (T) and CO2 concentration in order to compare the challenges posed by O2 uptake under stress with the equivalent problem of CO2 expulsion. The problem is more complex than that for a non-reactive gas since, as with gas exchange of CO2 at the air-sea interface, the influence of the ensemble of reactions within the CO2-HCO3--CO32- acid-base system needs to be considered. These reactions significantly facilitate CO2 efflux compared to O2 intake at equal temperature, pressure and flow rate under typical oceanic concentrations.The effect of these reactions can be described by an enhancement factor. For organisms, this means mechanically increasing flow over their surface to thin the boundary layer as is required to alleviate O2 stress seems not necessary to facilitate CO2 efflux. Nevertheless the elevated pCO2 cost most likely is non-zero. Regionally as with O2 the combination of T, P, and pH/pCO2 creates a zone of maximum CO2 stress at around 1000 m depth. But the net result is that, for the problem of gas exchange with the bulk ocean, the combination of an increasing T combined with declining O2 poses a greater challenge to marine life than does increasing CO2. The relationships developed here allow a more accurate prediction of the impacts on marine life from the combined effects of changing T, O2, and CO2 than can be estimated from single variable studies.

Characterization of gas hydrate distribution using conventional 3D seismic data in the Pearl River Mouth Basin, South China Sea

USGS Publications Warehouse

Wang, Xiujuan; Qiang, Jin; Collett, Timothy S.; Shi, Hesheng; Yang, Shengxiong; Yan, Chengzhi; Li, Yuanping; Wang, Zhenzhen; Chen, Duanxin

2016-01-01

A new 3D seismic reflection data volume acquired in 2012 has allowed for the detailed mapping and characterization of gas hydrate distribution in the Pearl River Mouth Basin in the South China Sea. Previous studies of core and logging data showed that gas hydrate occurrence at high concentrations is controlled by the presence of relatively coarse-grained sediment and the upward migration of thermogenic gas from the deeper sediment section into the overlying gas hydrate stability zone (BGHSZ); however, the spatial distribution of the gas hydrate remains poorly defined. We used a constrained sparse spike inversion technique to generate acoustic-impedance images of the hydrate-bearing sedimentary section from the newly acquired 3D seismic data volume. High-amplitude reflections just above the bottom-simulating reflectors (BSRs) were interpreted to be associated with the accumulation of gas hydrate with elevated saturations. Enhanced seismic reflections below the BSRs were interpreted to indicate the presence of free gas. The base of the BGHSZ was established using the occurrence of BSRs. In areas absent of well-developed BSRs, the BGHSZ was calculated from a model using the inverted P-wave velocity and subsurface temperature data. Seismic attributes were also extracted along the BGHSZ that indicate variations reservoir properties and inferred hydrocarbon accumulations at each site. Gas hydrate saturations estimated from the inversion of acoustic impedance of conventional 3D seismic data, along with well-log-derived rock-physics models were also used to estimate gas hydrate saturations. Our analysis determined that the gas hydrate petroleum system varies significantly across the Pearl River Mouth Basin and that variability in sedimentary properties as a product of depositional processes and the upward migration of gas from deeper thermogenic sources control the distribution of gas hydrates in this basin.

A Fast and Easily-Realized Concentration Sensor for Binary Gas Mixtures and Its Design Analysis.

PubMed

Guan, Yu; Lu, Song; Zhang, Dan; Hu, Yang; Yuan, Wei

2018-04-19

A low-cost and easily-realized sensing device used for the detection of gas mixtures at different concentrations is presented. Its sensing part includes a small critical nozzle, a laminar structure, and a differential pressure sensor. When gas flows through the laminar structure, there is a pressure drop between both ends of it, and for different components of gas, the pressure drop is different. Based on this feature, the concentration detection is achieved. Concentration tests for two types of fire extinguishing agents CBrF₃ and C₃HF₇ are presented. The results show the characteristics of fast response/recovery time, high accuracy, and good repeatability. Based on the theoretical analysis, the effects of the design parameters on the sensing performance to concentration detection are discussed in detail.

Mapping the geogenic radon potential: methodology and spatial analysis for central Hungary.

PubMed

Szabó, Katalin Zsuzsanna; Jordan, Gyozo; Horváth, Ákos; Szabó, Csaba

2014-03-01

A detailed geogenic radon potential (GRP) mapping based on field soil gas radon and soil gas permeability measurements was carried out in this study. A conventional continuous variable approach was used in this study for GRP determination and to test its applicability to the selected area of Hungary. Spatial pattern of soil gas radon concentration, soil permeability and GRP and the relationship between geological formations and these parameters were studied by performing detailed spatial analysis. Exploratory data analysis revealed that higher soil gas radon activity concentration and GRP characterizes the mountains and hills than the plains. The highest values were found in the proluvial-deluvial sediments, rock debris on the downhill slopes eroded from hills. Among the Quaternary sediments, which characterize the study area, the fluvial sediment has the highest values, which are also located in the hilly areas. The lowest values were found in the plain areas covered by drift sand, fluvioeolic sand, fluvial sand and loess. As a conclusion, radon is related to the sediment cycle in the study area. A geogenic radon risk map was created, which assists human health risk assessment and risk reduction since it indicates the potential of the source of indoor radon. The map shows that low and medium geogenic radon potential characterizes the study area in central Hungary. High risk occurs only locally. The results reveal that Quaternary sediments are inhomogeneous from a radon point of view, fluvial sediment has medium GRP, whereas the other rock formations such as drift sand, fluioeolic sand, fluvial sand and loess, found in the study area, have low GRP. Copyright © 2013 Elsevier Ltd. All rights reserved.

Modeling of electron cyclotron resonance discharges

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

Meyyappan, M.; Govindan, T.R.

The current trend in plasma processing is the development of high density plasma sources to achieve high deposition and etch rates, uniformity over large ares, and low wafer damage. Here, is a simple model to predict the spatially-averaged plasma characteristics of electron cyclotron resonance (ECR) reactors is presented. The model consists of global conservation equations for species concentration, electron density and energy. A gas energy balance is used to predict the neutral temperature self-consistently. The model is demonstrated for an ECR argon discharge. The predicted behavior of the discharge as a function of system variables agrees well with experimental observations.

Ultrafine particles and nitrogen oxides generated by gas and electric cooking.

PubMed

Dennekamp, M; Howarth, S; Dick, C A; Cherrie, J W; Donaldson, K; Seaton, A

2001-08-01

To measure the concentrations of particles less than 100 nm diameter and of oxides of nitrogen generated by cooking with gas and electricity, to comment on possible hazards to health in poorly ventilated kitchens. Experiments with gas and electric rings, grills, and ovens were used to compare different cooking procedures. Nitrogen oxides (NO(x)) were measured by a chemiluminescent ML9841A NO(x) analyser. A TSI 3934 scanning mobility particle sizer was used to measure average number concentration and size distribution of aerosols in the size range 10-500 nm. High concentrations of particles are generated by gas combustion, by frying, and by cooking of fatty foods. Electric rings and grills may also generate particles from their surfaces. In experiments where gas burning was the most important source of particles, most particles were in the size range 15-40 nm. When bacon was fried on the gas or electric rings the particles were of larger diameter, in the size range 50-100 nm. The smaller particles generated during experiments grew in size with time because of coagulation. Substantial concentrations of NO(X) were generated during cooking on gas; four rings for 15 minutes produced 5 minute peaks of about 1000 ppb nitrogen dioxide and about 2000 ppb nitric oxide. Cooking in a poorly ventilated kitchen may give rise to potentially toxic concentrations of numbers of particles. Very high concentrations of oxides of nitrogen may also be generated by gas cooking, and with no extraction and poor ventilation, may reach concentrations at which adverse health effects may be expected. Although respiratory effects of exposure to NO(x) might be anticipated, recent epidemiology suggests that cardiac effects cannot be excluded, and further investigation of this is desirable.

Tackling the mortality from long-term exposure to outdoor air pollution in megacities: Lessons from the Greater Cairo case study.

PubMed

Wheida, Ali; Nasser, Amira; El Nazer, Mostafa; Borbon, Agnes; Abo El Ata, Gehad A; Abdel Wahab, Magdy; Alfaro, Stephane C

2018-01-01

The poor outdoor air quality in megacities of the developing world and its impact on health is a matter of concern for both the local populations and the decision-makers. The objective of this work is to quantify the mortality attributable to long-term exposure to PM2.5, NO 2 , and O 3 in Greater Cairo (Egypt). We analyze the temporal and spatial variability of the three pollutants concentrations measured at 18 stations of the area. Then, we apply the method recommended by the WHO to estimate the excess mortality. In this assessment, three different shapes (log-linear, linear, and log-log) of the concentration-response functions (CRF) are used. With PM2.5 concentrations varying from 50 to more than 100µg/m 3 in the different sectors of the megacity, the spatial variability of this pollutant is found to be one important cause of uncertainty on the excess mortality associated with it. Also important is the choice of the CRF. With the average (75µg/m 3 ) PM2.5 concentration and the most favorable log-log shape of the CRF, 11% (CI, 9-14%) of the non-accidental mortality in the population older than 30 years can still be attributed to PM2.5, which corresponds to 12520 (CI, 10240-15930) yearly premature deaths. Should the Egyptian legal 70µg/m 3 PM10 limit (corresponding to approximately 37.5µg/m 3 for PM2.5) be met, this number would be reduced to 7970, meaning that 4550 premature deaths could be avoided each year. Except around some industrial or traffic hot spots, NO 2 concentration is found to be below the 40µg/m 3 air quality guideline of the WHO. However, the average concentration (34µg/m 3 ) of this gas exceeds the stricter 10µg/m 3 recommendation of the HRAPIE project and it is thus estimated that from 7850 to 10470 yearly deaths can be attributed to NO 2 . Finally, with the ozone concentration measured at one station only, it is found that, depending on the choice of the CRF, between 2.4% and 8.8% of the mortality due to respiratory diseases can be attributed to this gas. In Greater Cairo, PM2.5 and NO 2 constitute major health risks. The best estimate is that in the population older than 30 years, 11% and 8% of the non-accidental mortality can be attributed to these two pollutants, respectively. Copyright © 2017 Elsevier Inc. All rights reserved.

Variables controlling the recovery of ignitable liquid residues from simulated fire debris samples using solid-phase microextraction/gas chromatography

NASA Astrophysics Data System (ADS)

Furton, Kenneth G.; Almirall, Jose R.; Wang, Jing

1999-02-01

In this paper, we present data comparing a variety of different conditions for extracting ignitable liquid residues from simulated fire debris samples in order to optimize the conditions for using Solid Phase Microextraction. A simulated accelerant mixture containing 30 components, including those from light petroleum distillates, medium petroleum distillates and heavy petroleum distillates were used to study the important variables controlling Solid Phase Microextraction (SPME) recoveries. SPME is an inexpensive, rapid and sensitive method for the analysis of volatile residues from the headspace over solid debris samples in a container or directly from aqueous samples followed by GC. The relative effects of controllable variables, including fiber chemistry, adsorption and desorption temperature, extraction time, and desorption time, have been optimized. The addition of water and ethanol to simulated debris samples in a can was shown to increase the sensitivity when using headspace SPME extraction. The relative enhancement of sensitivity has been compared as a function of the hydrocarbon chain length, sample temperature, time, and added ethanol concentrations. The technique has also been optimized to the extraction of accelerants directly from water added to the fire debris samples. The optimum adsorption time for the low molecular weight components was found to be approximately 25 minutes. The high molecular weight components were found at a higher concentration the longer the fiber was exposed to the headspace (up to 1 hr). The higher molecular weight components were also found in higher concentrations in the headspace when water and/or ethanol was added to the debris.

A new numerical formulation of gas leakage and spread into a residential space in terms of hazard analysis.

PubMed

Nagaosa, Ryuichi S

2014-04-30

This study proposes a new numerical formulation of the spread of a flammable gas leakage. A new numerical approach has been applied to establish fundamental data for a hazard assessment of flammable gas spread in an enclosed residential space. The approach employs an extended version of a two-compartment concept, and determines the leakage concentration of gas using a mass-balance based formulation. The study also introduces a computational fluid dynamics (CFD) technique for calculating three-dimensional details of the gas spread by resolving all the essential scales of fluid motions without a turbulent model. The present numerical technique promises numerical solutions with fewer uncertainties produced by the model equations while maintaining high accuracy. The study examines the effect of gas density on the concentration profiles of flammable gas spread. It also discusses the effect of gas leakage rate on gas concentration profiles. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

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 measured during the period of tracer injection.

Determination of time-of-travel, dispersion characteristics, and oxygen reaeration coefficients during low streamflows--Lower Tacony/Frankford Creek, Philadelphia, Pennsylvania

USGS Publications Warehouse

Senior, Lisa A.; Gyves, Matthew C.

2010-01-01

Time-of-travel, dispersion characteristics, and oxygen reaeration coefficients were determined by use of dye and gas tracing for a 2-mile reach of Tacony/Frankford Creek in Philadelphia, southeastern Pennsylvania. The reach frequently has concentrations of dissolved oxygen (DO) below the water-quality standard of 4 milligrams per liter during warm months. Several large combined sewer overflows (CSOs), including one of the largest in Philadelphia (former Wingohocking Creek), discharge to the study reach in this urbanized watershed, affecting water quality and the timing and magnitude of storm peaks. In addition, a dam that commonly results in backwater conditions and reduced natural reaeration is present a few hundred feet from the end of the study reach. Time-of-travel and reaeration data were collected under base-flow conditions in August and September 2009 for three sub-reaches from Roosevelt Boulevard (U.S. Route 1) to Castor Avenue. Determination of traveltimes to the centroid of the dye cloud were needed for calculation of the reaeration coefficients. Results of the dye study in Tacony/Frankford Creek indicate that traveltimes were affected by the presence of man-made structures, such as the large scour hole and pool developed at the outfall of the T14 CSO and the dam, both of which reduce stream velocities. Mean stream velocities during the dye-tracer tests ranged from a maximum of 0.44 to 0.04 foot per second through a large pool. The dispersion efficiency of the stream was determined from relations between normalized unit concentrations to time to peak for use in water-quality modeling. Oxygen reaeration coefficients determined by a constant rate-injection method using propane as the tracer gas were as low as 0.04 unit per hour in a long pool affected by backwater conditions behind a dam. The highest reaeration coefficient was 2.29 units per hour for a steep-gradient reach with multiple winding channels through gravel deposits, just downstream of a large scour pool developed at the outlet of the T14 CSO. Reaeration coefficients determined from the field tracer-gas method were compared to values calculated by two other methods, one that is based on theoretical equations using physical properties of the stream as variables and the other that is based on equations using the timing of measured daily maximum DO concentrations in the stream. Reaeration coefficients from the two alternate methods were most similar to values determined from the field tracer-gas method for the upstream portion of the study reach, characterized by free-flowing riffle and pools. Values of reaeration coefficients determined by the tracer-gas method were 2 to 10 times higher than values determined by 2 alternate methods for most subreaches hydraulically affected by man-made structures. In addition to the tracer gas, propane, the gas analysis also included methane, ethane, and ethene, of which only methane was measured in concentrations above a few micrograms per liter. Methane, thought to occur naturally or because of ongoing processes in the stream, was measured in concentrations ranging from 6.6 to 78 micrograms per liter; the concentrations were greatest in sub-reaches dominated by pools.

Three field tests of a gas filter correlation radiometer

NASA Technical Reports Server (NTRS)

Campbell, S. A.; Casas, J. C.; Condon, E. P.

1977-01-01

Test flights to remotely measure nonurban carbon monoxide (CO) concentrations by gas filter correlation radiometry are discussed. The inferred CO concentrations obtained through use of the Gas Filter Correlation Radiometer (GFCR) agreed with independent measurements obtained by gas chromatography air sample bottle analysis to within 20 percent. The equipment flown on board the aircraft, the flight test procedure, the gas chromatograph direct air sampling procedure, and the GFCR data analysis procedure are reported.

Conversion of iodide to hypoiodous acid and iodine in aqueous microdroplets exposed to ozone.

PubMed

Pillar, Elizabeth A; Guzman, Marcelo I; Rodriguez, Jose M

2013-10-01

Halides are incorporated into aerosol sea spray, where they start the catalytic destruction of ozone (O3) over the oceans and affect the global troposphere. Two intriguing environmental problems undergoing continuous research are (1) to understand how reactive gas phase molecular halogens are directly produced from inorganic halides exposed to O3 and (2) to constrain the environmental factors that control this interfacial process. This paper presents a laboratory study of the reaction of O3 at variable iodide (I(-)) concentration (0.010-100 μM) for solutions aerosolized at 25 °C, which reveal remarkable differences in the reaction intermediates and products expected in sea spray for low tropospheric [O3]. The ultrafast oxidation of I(-) by O3 at the air-water interface of microdroplets is evidenced by the appearance of hypoiodous acid (HIO), iodite (IO2(-)), iodate (IO3(-)), triiodide (I3(-)), and molecular iodine (I2). Mass spectrometry measurements reveal an enhancement (up to 28%) in the dissolution of gaseous O3 at the gas-liquid interface when increasing the concentration of NaI or NaBr from 0.010 to 100 μM. The production of iodine species such as HIO and I2 from NaI aerosolized solutions exposed to 50 ppbv O3 can occur at the air-water interface of sea spray, followed by their transfer to the gas-phase, where they contribute to the loss of tropospheric ozone.

Atmospheric Gas Concentrations in the pre- and post-production Phases of an Unconventional Oil and Gas Recovery Operation at the MSEEL Test Site, West Virginia

NASA Astrophysics Data System (ADS)

Williams, J. P.; Reeder, M.; Pekney, N.; Osborne, J.; Risk, D. A.; McCawley, M.

2016-12-01

The Marcellus Shale Energy and Environment Laboratory (MSEEL) in West Virginia provides a unique opportunity in the field of unconventional energy research. By studying near-surface atmospheric chemistry over several phases of a hydraulic fracturing event, the project will help evaluate the impact of current practices, as well as new techniques and mitigation technologies. A total of 10 mobile surveys were conducted around the MSEEL site that contains 3 test wells (1 science well and 2 natural gas producing wells) and over several miles of nearby regional routes. Our surveying technique involved using a vehicle-mounted Los Gatos Research Ultraportable Methane/Acetylene Analyzer that provided geo-located measurements of methane (CH4) and carbon dioxide (CO2). The ratios of super-ambient concentrations of CO2 and CH4 were used to separate drilling- and fracturing-related observations from the natural background concentrations over the various well pad developmental stages. We found that regional background methane concentrations were elevated in all surveys, with a mean concentration of 3.21ppm (n = 99376), which simply reflected the mix of anthropogenic and natural CH4 sources in this riverine urban location. Over time and through successive stages of well development, we noted a progressive rise in the occurrence of enriched methane in the vicinity of the developed wells. While there was a moderate degree of variability over time, we did observe a higher occurrence of CH4-enriched observations during and after production began at the test site ( 25% of measurements within 500 meters of the test wells) compared to the baseline surveys (>10% of measurements). This change was expected, as we anticipated some level of increased emissions from the well pads as production began. However, we did not expect the rise to be so noticeable. The results of this study show that there is a statistically significant increase in the occurrence of enriched methane values in the vicinity of the well locations when we compare pre-production to post-production surveys, and that pre-existing methane sources in the immediate vicinity must be accounted for when assessing environmental impacts.

A review on disaster risk mitigation in the oil and gas project

NASA Astrophysics Data System (ADS)

Rodhi, N. N.; Anwar, N.; Wiguna, I. P. A.

2018-01-01

In addition to the very complex risks, hazards potentially lead to disasters in the oil and gas projects. These risks can certainly be anticipated with the application of risk management, but an unsystematic and ineffective implementation of risk management will still bring adverse impacts. According to the eleven risk management principles in ISO 31000:2009, the application of risk management must pay attention to all aspects, both internal and external factors. Thus, this paper aims to identify variables that could affect the disaster mitigation efforts of oil and gas projects. This research began with literature study to determine the problems of risk management in oil and gas projects, so the affecting variables as the study objectives can be specified subsequently based on the literature review as well. The variables that must be considered in the efforts of disaster risk mitigation of oil and gas project are the risk factors and sustainability aspect.

[Explore objective clinical variables for detecting delirium in ICU patients: a prospective case-control study].

PubMed

Liu, Xiaojiang; Lyu, Jie; An, Youzhong

2017-04-01

The aim of this case-control study is to explore clinical objective variables for diagnosing delirium of intensive care unit (ICU) patients. According to the method of prospective case-control study, critical adult postoperative patients who were transferred to ICU of Peking University People's Hospital from October 2015 to May 2016 and needed mechanical ventilation were included. After evaluating the Richmond agitation sedation scale score (RASS), the patients whose score were -2 or greater were sorted into two groups, delirium and non-delirium, according to the confusion assessment method for the ICU (CAM-ICU). Then these patients were observed by domestic multifunctional detector for electroencephalographic (EEG) variables such as brain lateralization, brain introvert, brain activity, brain energy consumption, focus inward, focus outward, cerebral inhibition, fatigue, sleep severity, sedation index, pain index, anxiety index, fidgety index, stress index and the cerebral blood flow (CBF) index which was named of perfusion index. Other variables including indexes of ICU blood gas analysis, which was consisted of variables of blood gas analysis, routine blood test and biochemistry, previous history and prognostic outcome was recorded. Binary logistic regression was used for multivariate analysis. Forty-three postoperative patients, who needed intensive care, were included. Eighteen were in delirium group and twenty-five in control group. Excluding the trauma, variables like gender, age, temperature, heart rate, respiratory rate, mean arterial pressure, acute physiology and chronic health evaluationII(APACHEII) score, organ failure, dementia and emergency surgery didn't show any statistical significance between two groups. The trauma in delirious patients increased obviously compared with the control group (33.3% vs. 4.0%, P = 0.031). Except for the brain activity [122.47 (88.62, 154.21) vs. 89.40 (86.27, 115.97), P = 0.034], there were no statistical differences in any other EEG and CBF variables. In ICU blood gas analysis, only pH value (7.43±0.42 vs. 7.47±0.31, P = 0.003), chloride concentration [Cl- (mmol/L): 114.66±4.32 vs. 111.90±3.08, P = 0.019], magnesium concentration [Mg2 + (mmol/L): 0.60±0.10 vs. 0.54±0.06, P = 0.035] and blood osmolality [mmol/L: 290.10 (284.15, 306.35) vs. 282.70 (280.20, 286.75), P = 0.014] were statistically significant. Compared with control group, the prognostic variables in delirium group such as duration of mechanical ventilation [days: 125.0 (49.0, 293.0) vs. 149.5 (32.0, 251.3)], length of stay in ICU [days: 216.5 (50.5, 360.8) vs. 190.0 (72.0, 330.5)] and mortality rate (22.2% vs. 24.0%) didn't appear to be statistically significant either (all P > 0.05). It was shown by multivariate logistic regression analysis that pH [odds ratio (OR) = 1.446, 95% confidence interval (95%CI) = 1.116-1.875, P = 0.005] and Cl - (OR = 0.708, 95%CI = 0.531-0.945, P = 0.019) were potential risk factors of delirium. The brain activity of HXD_I may contribute to the clinical diagnose of delirium, but it still remained to be proved further. The pH and Cl - are potential risk factors of delirium.

Absolute and relative emissions analysis in practical combustion systems—effect of water vapor condensation

NASA Astrophysics Data System (ADS)

Richter, J. P.; Mollendorf, J. C.; DesJardin, P. E.

2016-11-01

Accurate knowledge of the absolute combustion gas composition is necessary in the automotive, aircraft, processing, heating and air conditioning industries where emissions reduction is a major concern. Those industries use a variety of sensor technologies. Many of these sensors are used to analyze the gas by pumping a sample through a system of tubes to reach a remote sensor location. An inherent characteristic with this type of sampling strategy is that the mixture state changes as the sample is drawn towards the sensor. Specifically, temperature and humidity changes can be significant, resulting in a very different gas mixture at the sensor interface compared with the in situ location (water vapor dilution effect). Consequently, the gas concentrations obtained from remotely sampled gas analyzers can be significantly different than in situ values. In this study, inherent errors associated with sampled combustion gas concentration measurements are explored, and a correction methodology is presented to determine the absolute gas composition from remotely measured gas species concentrations. For in situ (wet) measurements a heated zirconium dioxide (ZrO2) oxygen sensor (Bosch LSU 4.9) is used to measure the absolute oxygen concentration. This is used to correct the remotely sampled (dry) measurements taken with an electrochemical sensor within the remote analyzer (Testo 330-2LL). In this study, such a correction is experimentally validated for a specified concentration of carbon monoxide (5020 ppmv).

Toward refined estimates of ambient PM2.5 exposure: Evaluation of a physical outdoor-to-indoor transport model

PubMed Central

Hodas, Natasha; Meng, Qingyu; Lunden, Melissa M.; Turpin, Barbara J.

2014-01-01

Because people spend the majority of their time indoors, the variable efficiency with which ambient PM2.5 penetrates and persists indoors is a source of error in epidemiologic studies that use PM2.5 concentrations measured at central-site monitors as surrogates for ambient PM2.5 exposure. To reduce this error, practical methods to model indoor concentrations of ambient PM2.5 are needed. Toward this goal, we evaluated and refined an outdoor-to-indoor transport model using measured indoor and outdoor PM2.5 species concentrations and air exchange rates from the Relationships of Indoor, Outdoor, and Personal Air Study. Herein, we present model evaluation results, discuss what data are most critical to prediction of residential exposures at the individual-subject and populations levels, and make recommendations for the application of the model in epidemiologic studies. This paper demonstrates that not accounting for certain human activities (air conditioning and heating use, opening windows) leads to bias in predicted residential PM2.5 exposures at the individual-subject level, but not the population level. The analyses presented also provide quantitative evidence that shifts in the gas-particle partitioning of ambient organics with outdoor-to-indoor transport contribute significantly to variability in indoor ambient organic carbon concentrations and suggest that methods to account for these shifts will further improve the accuracy of outdoor-to-indoor transport models. PMID:25798047

Seismic reflections identify finite differences in gas hydrate resources

USGS Publications Warehouse

Dillon, William P.; Max, M.

1999-01-01

Gas hydrate is a gas-bearing, ice-like crystalline solid. The substance's build ing blocks consist of a gas molecule (generally methane) sur-rounded by a cage of water molecules. The total amount of methane in hydrate in the world is immense - the most recent speculative estimate centers on values of 21x1015 cu meters. Thus, it may represent a future energy resource. This estimate was presented by Keith Kvenvolden at the International Symposium on Methane Hydrates, Resources in the Near Future, sponsor ed by Japanese National Oil Company (Tokyo, October, 1998).But, as with any natural resource, there is a need to find naturally occurring concentrations in order to effectively extract gas. We need to answer four basic questions:Do methane hydrate concentrations suitable for methane extraction exist?How can we recognize these concentrations?Where are concentrations located?What processes control methane hydrate concentrations?Gas hydrate occurs naturally at the pressure/ temperature/chemical conditions that are present within ocean floor sediments at water depths greater than about 500 meters. The gas hydrate stability zone (GHSZ) extends from the sea bottom downward to a depth where the natural increase in temperature causes the hydrate to melt (dissociate), even though the downward pressure increase is working to increase gas hydrate stability.Thus, the base of the GHSZ tends to parallel the seafloor at any given water depth (pressure), because the sub-seafloor isotherms (depths of constant temperature) generally parallel the seafloor. The layer at which gas hydrate is stable commonly extends from the sea floor to several hundred meters below it. The gas in most gas hydrates is methane, generated by bacteria in the sediments. In some cases, it can be higher carbon-number, thermogenic hydrocarbon gases that rise from greater depths.

Using noble gases measured in spring discharge to trace hydrothermal processes in the Norris Geyser Basin, Yellowstone National Park, U.S.A.

USGS Publications Warehouse

Gardner, W.P.; Susong, D.D.; Solomon, D.K.; Heasler, H.P.

2010-01-01

Dissolved noble gas concentrations in springs are used to investigate boiling of hydrothermal water and mixing of hydrothermal and shallow cool water in the Norris Geyser Basin area. Noble gas concentrations in water are modeled for single stage and continuous steam removal. Limitations on boiling using noble gas concentrations are then used to estimate the isotopic effect of boiling on hydrothermal water, allowing the isotopic composition of the parent hydrothermal water to be determined from that measured in spring. In neutral chloride springs of the Norris Geyser Basin, steam loss since the last addition of noble gas charged water is less than 30% of the total hydrothermal discharge, which results in an isotopic shift due to boiling of ?? 2.5% ??D. Noble gas concentrations in water rapidly and predictably change in dual phase systems, making them invaluable tracers of gas-liquid interaction in hydrothermal systems. By combining traditional tracers of hydrothermal flow such as deuterium with dissolved noble gas measurements, more complex hydrothermal processes can be interpreted. ?? 2010 Elsevier B.V.

RESULTS FROM EPA FUNDED RESEARCH PROGRAMS ON THE IMPORTANCE OF PURGE VOLUME, SAMPLE VOLUME, SAMPLE FLOW RATE AND TEMPORAL VARIATIONS ON SOIL GAS CONCENTRATIONS

EPA Science Inventory

Two research studies funded and overseen by EPA have been conducted since October 2006 on soil gas sampling methods and variations in shallow soil gas concentrations with the purpose of improving our understanding of soil gas methods and data for vapor intrusion applications. Al...

Polyaniline-ZnO nanocomposites as ethanol gas sensors

NASA Astrophysics Data System (ADS)

Talegaonkar, Janhavi; Patil, Y. B.; Patil, D. R.

2018-05-01

Polyaniline and it`s nanocomposites with ZnO were successfully synthesized by photo-induced polymerization method with various concentrations of ZnO, followed by characterizations viz. SEM, EDAX, XRD, FTIR and UV-Vis. Thick films of synthesized powders were fabricated by screen printing technique for monitoring various gases at different operating temperatures and at various gas concentrations. CuO activated polyaniline-ZnO nano-composite exhibits maximum response of ethanol gas at room temperature. The sensor exhibits high sensitivity, highest selectivity, quick response, fast recovery, long term stability, etc. An exceptional sensitivity was found to low concentrations of ethanol gas at room temperature and no cross sensitivity was observed even to high concentrations of other hazardous and polluting gases. The efforts have been made to develop the ethanol sensor based on PANI and its nanocomposites. The effects of microstructure and surfactant concentration on the ethanol response, selectivity, response and recovery of the sensor in the presence of ethanol gas were studied and discussed.

Measurement of gas species, temperatures, coal burnout, and wall heat fluxes in a 200 MWe lignite-fired boiler with different overfire air damper openings

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

Jianping Jing; Zhengqi Li; Guangkui Liu

Measurements were performed on a 200 MWe, wall-fired, lignite utility boiler. For different overfire air (OFA) damper openings, the gas temperature, gas species concentration, coal burnout, release rates of components (C, H, and N), furnace temperature, and heat flux and boiler efficiency were measured. Cold air experiments for a single burner were conducted in the laboratory. The double-swirl flow pulverized-coal burner has two ring recirculation zones starting in the secondary air region in the burner. As the secondary air flow increases, the axial velocity of air flow increases, the maxima of radial velocity, tangential velocity and turbulence intensity all increase,more » and the swirl intensity of air flow and the size of recirculation zones increase slightly. In the central region of the burner, as the OFA damper opening widens, the gas temperature and CO concentration increase, while the O{sub 2} concentration, NOx concentration, coal burnout, and release rates of components (C, H, and N) decrease, and coal particles ignite earlier. In the secondary air region of the burner, the O{sub 2} concentration, NOx concentration, coal burnout, and release rates of components (C, H, and N) decrease, and the gas temperature and CO concentration vary slightly. In the sidewall region, the gas temperature, O{sub 2} concentration, and NOx concentration decrease, while the CO concentration increases and the gas temperature varies slightly. The furnace temperature and heat flux in the main burning region decrease appreciably, but increase slightly in the burnout region. The NOx emission decreases from 1203.6 mg/m{sup 3} (6% O{sub 2}) for a damper opening of 0% to 511.7 mg/m{sup 3} (6% O{sub 2}) for a damper opening of 80% and the boiler efficiency decreases from 92.59 to 91.9%. 15 refs., 17 figs., 3 tabs.« less

The role of temperature in the variability and extremes of electricity and gas demand in Great Britain

NASA Astrophysics Data System (ADS)

Thornton, H. E.; Hoskins, B. J.; Scaife, A. A.

2016-11-01

The daily relationship of electricity and gas demand with temperature in Great Britain is analysed from 1975 to 2013 and 1996 to 2013 respectively. The annual mean and annual cycle amplitude of electricity demand exhibit low frequency variability. This low frequency variability is thought to be predominantly driven by socio-economic changes rather than temperature variation. Once this variability is removed, both daily electricity and gas demand have a strong anti-correlation with temperature (r elec = -0.90 , r gas = -0.94). However these correlations are inflated by the changing demand-temperature relationship during spring and autumn. Once the annual cycles of temperature and demand are removed, the correlations are {r}{{elec}}=-0.60 and {r}{{gas}}=-0.83. Winter then has the strongest demand-temperature relationship, during which a 1 °C reduction in daily temperature typically gives a ˜1% increase in daily electricity demand and a 3%-4% increase in gas demand. Extreme demand periods are assessed using detrended daily temperature observations from 1772. The 1 in 20 year peak day electricity and gas demand estimates are, respectively, 15% (range 14%-16%) and 46% (range 44%-49%) above their average winter day demand during the last decade. The risk of demand exceeding recent extreme events, such as during the winter of 2009/2010, is also quantified.

Influence of infrastructure on water quality and greenhouse gas dynamics in urban streams

NASA Astrophysics Data System (ADS)

Smith, Rose M.; Kaushal, Sujay S.; Beaulieu, Jake J.; Pennino, Michael J.; Welty, Claire

2017-06-01

Streams and rivers are significant sources of nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) globally, and watershed management can alter greenhouse gas (GHG) emissions from streams. We hypothesized that urban infrastructure significantly alters downstream water quality and contributes to variability in GHG saturation and emissions. We measured gas saturation and estimated emission rates in headwaters of two urban stream networks (Red Run and Dead Run) of the Baltimore Ecosystem Study Long-Term Ecological Research project. We identified four combinations of stormwater and sanitary infrastructure present in these watersheds, including: (1) stream burial, (2) inline stormwater wetlands, (3) riparian/floodplain preservation, and (4) septic systems. We selected two first-order catchments in each of these categories and measured GHG concentrations, emissions, and dissolved inorganic and organic carbon (DIC and DOC) and nutrient concentrations biweekly for 1 year. From a water quality perspective, the DOC : NO3- ratio of streamwater was significantly different across infrastructure categories. Multiple linear regressions including DOC : NO3- and other variables (dissolved oxygen, DO; total dissolved nitrogen, TDN; and temperature) explained much of the statistical variation in nitrous oxide (N2O, r2 = 0.78), carbon dioxide (CO2, r2 = 0.78), and methane (CH4, r2 = 0.50) saturation in stream water. We measured N2O saturation ratios, which were among the highest reported in the literature for streams, ranging from 1.1 to 47 across all sites and dates. N2O saturation ratios were highest in streams draining watersheds with septic systems and strongly correlated with TDN. The CO2 saturation ratio was highly correlated with the N2O saturation ratio across all sites and dates, and the CO2 saturation ratio ranged from 1.1 to 73. CH4 was always supersaturated, with saturation ratios ranging from 3.0 to 2157. Longitudinal surveys extending form headwaters to third-order outlets of Red Run and Dead Run took place in spring and fall. Linear regressions of these data yielded significant negative relationships between each gas with increasing watershed size as well as consistent relationships between solutes (TDN or DOC, and DOC : TDN ratio) and gas saturation. Despite a decline in gas saturation between the headwaters and stream outlet, streams remained saturated with GHGs throughout the drainage network, suggesting that urban streams are continuous sources of CO2, CH4, and N2O. Our results suggest that infrastructure decisions can have significant effects on downstream water quality and greenhouse gases, and watershed management strategies may need to consider coupled impacts on urban water and air quality.

``Smoking From The Same Pipe": Developement of an 40Ar/39Ar Datting Intercalibration PIpette System (Invited)

NASA Astrophysics Data System (ADS)

Turrin, B. D.; Swisher, C. C.; Deino, A.; Hemming, S. R.; Hodges, K.; Renne, P. R.

2010-12-01

The precision and accuracy of Ar isotope ratio measurements is one of the main limiting factors in the uncertainties of an 40Ar/39Ar age. Currently, it is relatively common to measure Ar isotopic ratios to a precision of 1-2‰ or better on an intralaboratory basis. This level of analytical precision equates to a comparable level of precision (1-3‰) in the calculated age, depending on the extent of atmospheric Ar contamination, importance of nucleogenic interference corrections, and other factors. However, it has become clear that improving the precision of mass spectrometry is not the only bottleneck towards improving the accuracy and precision of 40Ar/39Ar dating in general. Rather, the most urgent issue is interlaboratory reproducibility. This became obvious in a recent EARTHTIME initiative undertaken to intercalibrate two commonly used 40Ar/39Ar standards [the Fish Canyon sanidine (FCs) and the Alder Creek sanidine (ACs)]. This effort revealed variations amongst laboratories (at the 1-2% level), an order of magnitude greater than the internal analytical precisions. To address these issues, we have proposed (to NSF) to construct two identical pipette systems loaded to identical starting pressures and with identical isotopic compositions. One pipette system will travel between participating 40Ar/39Ar labs and the second system will not travel and serve as the “Master” system to test for any fractionation or undocumented depletion of the traveling pipette system. In order to ensure delivery of uniform amounts of homogenous gas, the pipette system will be computer-controlled with preprogrammed routines and lockouts to prevent compromising the reservoirs. The pipette systems will deliver three gas samples with different isotopic ratios at two different pressures/concentrations. One pipette bulb will be of atmospheric isotopic composition, and the other two pipette bulbs will have 40Ar*/39ArK ratios corresponding to co-irradiated ACs and FCs fixed by their relative ages at ~1:23.6. A pipette system will permit the participating labs to measure gas samples with exactly the same isotopic composition(s) and similar gas volumes. Measuring the same gas controls the variables such as 1) sample heterogeneity or experimental artifacts arising from neutron dosage; 2) incomplete degassing and the possibility of isotopic fractionation of Ar; and 3) problems related to isobaric interferences from e.g. hydrocarbons or HCl. By fixing these variables, the influence of different data reduction protocols can be assessed. In addition, measuring gas samples with fixed isotopic ratios at different pressures/concentrations will also test the pressure effects on ion source and/or detector linearity.

Denitrification and inference of nitrogen sources in the karstic Floridan Aquifer

USGS Publications Warehouse

Heffernan, J.B.; Albertin, A.R.; Fork, M.L.; Katz, B.G.; Cohen, M.J.

2011-01-01

Aquifer denitrification is among the most poorly constrained fluxes in global and regional nitrogen budgets. The few direct measurements of denitrification in groundwaters provide limited information about its spatial and temporal variability, particularly at the scale of whole aquifers. Uncertainty in estimates of denitrification may also lead to underestimates of its effect on isotopic signatures of inorganic N, and thereby confound the inference of N source from these data. In this study, our objectives are to quantify the magnitude and variability of denitrification in the Upper Floridan Aquifer (UFA) and evaluate its effect on N isotopic signatures at the regional scale. Using dual noble gas tracers (Ne, Ar) to generate physical predictions of N2 gas concentrations for 112 observations from 61 UFA springs, we show that excess (i.e. denitrification-derived) N2 is highly variable in space and inversely correlated with dissolved oxygen (O2). Negative relationship between O2 and ??15NNO 3 across a larger dataset of 113 springs, well-constrained isotopic fractionation coefficients, and strong 15N: 18O covariation further support inferences of denitrification in this uniquely organic-matter-poor system. Despite relatively low average rates, denitrification accounted for 32% of estimated aquifer N inputs across all sampled UFA springs. Back-calculations of source ??15NNO 3 based on denitrification progression suggest that isotopically-enriched nitrate (NO3-) in many springs of the UFA reflects groundwater denitrification rather than urban- or animal-derived inputs. ?? Author(s) 2011.

Variable Temperature Blackbodies via Variable Conductance: Thermal Design, Modelling and Testing

NASA Astrophysics Data System (ADS)

Melzack, N.; Jones, E.; Peters, D. M.; Hurley, J. G.; Watkins, R. E. J.; Fok, S.; Sawyer, C.; Marchetaux, G.; Acreman, A.; Winkler, R.; Lowe, D.; Theocharous, T.; Montag, V.; Gibbs, D.; Pearce, A. B.; Bishop, G.; Newman, E.; Keen, S.; Stokes, J.; Pearce, A.; Stamper, R.; Cantell-Hynes, A.

2017-02-01

This paper presents the overall design for large (˜ 400 mm aperture) reference blackbody cavities currently under development at the Science and Technology Facilities Council Rutherford Appleton Laboratory Space Department (STFC RAL Space), in collaboration with the National Physical Laboratory (NPL). These blackbodies are designed to operate in vacuum over a temperature range from 160 K to 370 K, with an additional capability to operate at ˜ 100 K as a point of near-zero radiance. This is a challenging problem for a single blackbody. The novel thermal design presented in this paper enables one target that can physically achieve and operate successfully at both thermal extremes, whilst also meeting stringent temperature gradient requirements. The overall blackbody design is based upon a helium gas-gap heat switch and modified to allow for variable thermal conductance. The blackbody design consists of three main concentric cylinder components—an inner cavity (aluminium alloy), a radiation shield (aluminium) and an outer liquid nitrogen (LN2) jacket (stainless steel). The internal surface of the cavity is the effective radiating surface. There is a helium gas interspace surrounding the radiation shield and enclosed by the LN2 jacket and the inner cavity. The blackbodies are now at a mature stage of development. In this paper, the overall design, focusing upon the thermal design solution, is detailed. This paper will also concern the full-scale prototype breadboard model, for which results on thermal stability, spatial gradients and other sensitivities will be presented.

Nitro-polycyclic aromatic hydrocarbon concentrations and sources in urban and suburban atmospheres of the Mid-Atlantic region

NASA Astrophysics Data System (ADS)

Bamford, Holly A.; Baker, Joel E.

Gas and particle phase concentrations of 26 nitro-PAHs were quantified in ambient air collected in downtown Baltimore, MD, an urban region, and in Fort Meade, MD, a suburban area 20 km south-southeast of Baltimore, during January and July 2001. Total (gas+particle) concentrations for individual nitro-PAH compounds varied by as much as five times from sample to sample within each month. 2-Nitrofluoranthene and 9-nitroanthracene were the most abundant of the nitro-PAHs quantitatively analyzed in the air at both sites, accounting for approximately half of the total nitro-PAH concentrations during January and July. Concentrations at Baltimore were on average two to three times higher than those measured at the Fort Meade site. Concentrations for most nitro-PAHs were higher in January than in July, suggesting a reduction in photodecay of nitro-PAHs during January promoted the accumulation of nitro-PAHs. Concentrations of nitro-PAHs produced from gas-phase reactions were significantly correlated with concentrations of oxides of nitrogen (NO x) measured simultaneously at the Fort Meade site. 3-Nitrophenanthrene and 4-nitrophenanthrene were negatively correlated with NO x and were the only nitro-PAHs correlated with O 3, suggesting a different formation mechanism for these compounds compared to the other nitro-PAHs found in this study. The relative contribution of gas-phase reactions and primary emission sources of nitro-PAHs were evaluated using source specific concentration ratios of 2-nitrofluoranthene and 1-nitropyrene (2-NF/1-NP). The mean ratios of 2-NF/1-NP at both sites were statistically higher in July than January, indicating gas-phase reactions were an important source of 2-nitrofluoranthene in the summer. However, in January, gas-phase reactions were reduced, the NO 3-initiated reaction in particular, and primary emissions may significantly contribute to ambient nitro-PAH levels. The two dominant gas-phase production pathways of nitro-PAHs from the OH and NO 3-initiated reactions were investigated using concentration ratios of 2-nitrofluoranthene and 2-nitropyrene (2-NF/2-NP). At both sites, 2-NF/2-NP ratios indicated that the daytime OH-initiated reaction was the dominant gas-phase formation pathway. The estimated contributions of nitro-PAHs produced through gas-phase reactions via the OH pathway during July were >45% and during January were >83% at both Fort Meade and Baltimore.

Gas chemistry of Icelandic thermal fluids

NASA Astrophysics Data System (ADS)

Stefánsson, Andri

2017-10-01

The chemistry of gases in thermal fluids from Iceland was studied in order to evaluate the sources and processes affecting volatile concentrations in volcanic geothermal systems at divergent plate boundaries. The fluids included vapor fumaroles and two-phase well discharges with temperatures of 100-340 °C. The vapor was dominated by H2O accounting for 62-100 mol% and generally for > 99 mol%, with CO2, H2S and H2 being the dominant gases followed by N2, CH4, and Ar. Overall mineral-gas and gas-gas equilibria were not observed for the major gases, including CO2, H2S, H2 and CH4 within the geothermal reservoirs. Instead the system proved to be controlled by source(s) and their ratios and various metastable equilibria along a fluid-rock reaction progress with gas concentrations controlled by such metastable equilibria varying at particular temperatures as a functional extent of reaction. The concentrations of H2S and H2 closely reflect mineral-fluid metastable equilibria, whereas CO2 concentrations are controlled by the input of magma gas corresponding to > 0.1 to < 5% mass input. With fluid ascent to the surface, boiling and condensation may occur, further changing the gas concentrations and hence surface fumaroles may not reflect the reservoir fluid characteristics but rather secondary processes.

Formation and coalescence of nanobubbles under controlled gas concentration and species

NASA Astrophysics Data System (ADS)

Li, Chenliang; Zhang, A.-Man; Wang, Shiping; Cui, Pu

2018-01-01

Using molecular dynamics simulations, the effects of gas concentration and species on the coalescence and growth of nanobubbles were systematically investigated. With increasing gas concentration, not only surface nanobubbles but also bulk nanobubbles are formed. The bulk nanobubble in water is less explored so far. Here, its coalescence, stability, movement trajectory and velocity are discussed. A comparison of the motion and coalescence of the bulk nanobubble to the surface nanobubble, directly demonstrates that the three-phase contact line plays a crucial role for surface nanobubble stability. Compared with the bubble size, the distance between surface nanobubbles is a more important factor to decide the merging order among three nanobubbles. The study also shows that three factors including the oversaturated gas concentration, the distance between surface nanobubbles, and the stronger solid-gas interactions influence the formation of the gas-enrichment layer at the solid-liquid interface. The result has an important significance to enhancing the boundary slip due to the presence of nanobubbles.

Development of a new measurement system to detect selectively volatile organic compounds derived from the human body.

PubMed

Kanou, S; Nagaoka, T; Kobayashi, N; Kurahashi, M; Takeda, S; Aoki, T; Tsuji, T; Urano, T; Abe, T; Magatani, K

2013-01-01

A new concept expired gas measurement system used double cold-trap method was developed. The system could detect selectively volatile organic compound (VOC) derived from the human body. The gas chromatography (GC) profiles of healthy volunteer's expired gas collected by our system were analyzed. As a result, 60 VOCs were detected from the healthy volunteer's expired gas. We examined 14 VOCs among them further, which could be converted to the concentration from the GC profiles. The concentration of almost VOCs decreased when the subjects inspired purified air compared with the atmosphere. On the other hand, isoprene was almost the same. It was strongly suggested that these VOCs were derived from the human body because the concentration of these VOCs in the atmosphere were nearly zero. Expired gas of two sleep apnea syndrome (SAS) patients were analyzed as preliminary study. As a result of the study, the concentration of some VOCs contained in the expired gas of the SAS patients showed higher value than a healthy controls.

Gas1 extends the range of Hedgehog action by facilitating its signaling

PubMed Central

Martinelli, David C.; Fan, Chen-Ming

2007-01-01

Cellular signaling initiated by Hedgehog binding to Patched1 has profound importance in mammalian embryogenesis, genetic disease, and cancer. Hedgehog acts as a morphogen to specify distinctive cell fates using different concentration thresholds, but our knowledge of how the concentration gradient is interpreted into the activity gradient is incomplete. The membrane protein Growth Arrest-Specific Gene 1 (GAS1) was thought to be a negative regulator of the Hedgehog concentration gradient. Here, we report unexpected genetic evidence that Gas1 positively regulates Hedgehog signaling in multiple developmental contexts, an effect particularly noticeable at regions where Hedgehog acts at low concentration. Using a combination of in vitro cell culture and in ovo electroporation assays, we demonstrate that GAS1 acts cooperatively with Patched1 for Hedgehog binding and enhances signaling activity in a cell-autonomous manner. Our data support a model in which GAS1 helps transform the Hedgehog protein gradient into the observed activity gradient. We propose that Gas1 is an evolutionarily novel, vertebrate-specific Hedgehog pathway regulator. PMID:17504940

Application of gas cyclone-liquid jet absorption separator for purification of tail gas containing ammonia.

PubMed

Ma, Liang; Zhao, Zhi-Huang; Peng, Lv; Yang, Xue-Jing; Fu, Peng-Bo; Liu, Yi; Huang, Yuan

2018-05-31

In this experiment, with stainless steel gas cyclone-liquid jet absorption separator as carrier, NH 3 as experimental gas, and water and H 3 PO 4 solution as absorbents, corresponding NH 3 absorption rate change is obtained through the adjustment of experimental parameters, such as NH 3 inlet concentration, inlet velocity of mixed gas, injection flow rate of absorbent, temperature of absorbent, and H 3 PO 4 absorbent concentration. The NH 3 absorption rate decreases with the increase in NH 3 inlet concentration and inlet gas velocity. The NH 3 absorption rate will increase first and then tends to remain unchanged after reaching a certain degree with the increase in liquid injection flow rate and absorbent concentration. The NH 3 absorption rate will increase first and then decrease with the increase in the absorbent temperature. The maximum NH 3 removal efficiencies of water and H 3 PO 4 were 96% and 99%, respectively.

multiUQ: An intrusive uncertainty quantification tool for gas-liquid multiphase flows

NASA Astrophysics Data System (ADS)

Turnquist, Brian; Owkes, Mark

2017-11-01

Uncertainty quantification (UQ) can improve our understanding of the sensitivity of gas-liquid multiphase flows to variability about inflow conditions and fluid properties, creating a valuable tool for engineers. While non-intrusive UQ methods (e.g., Monte Carlo) are simple and robust, the cost associated with these techniques can render them unrealistic. In contrast, intrusive UQ techniques modify the governing equations by replacing deterministic variables with stochastic variables, adding complexity, but making UQ cost effective. Our numerical framework, called multiUQ, introduces an intrusive UQ approach for gas-liquid flows, leveraging a polynomial chaos expansion of the stochastic variables: density, momentum, pressure, viscosity, and surface tension. The gas-liquid interface is captured using a conservative level set approach, including a modified reinitialization equation which is robust and quadrature free. A least-squares method is leveraged to compute the stochastic interface normal and curvature needed in the continuum surface force method for surface tension. The solver is tested by applying uncertainty to one or two variables and verifying results against the Monte Carlo approach. NSF Grant #1511325.

Noble gas signatures in the Island of Maui, Hawaii: Characterizing groundwater sources in fractured systems

USGS Publications Warehouse

Niu, Yi; Castro, M. Clara; Hall, Chris M.; Gingerich, Stephen B.; Scholl, Martha A.; Warrier, Rohit B.

2017-01-01

Uneven distribution of rainfall and freshwater scarcity in populated areas in the Island of Maui, Hawaii, renders water resources management a challenge in this complex and ill-defined hydrological system. A previous study in the Galapagos Islands suggests that noble gas temperatures (NGTs) record seasonality in that fractured, rapid infiltration groundwater system rather than the commonly observed mean annual air temperature (MAAT) in sedimentary systems where infiltration is slower thus, providing information on recharge sources and potential flow paths. Here we report noble gas results from the basal aquifer, springs, and rainwater in Maui to explore the potential for noble gases in characterizing this type of complex fractured hydrologic systems. Most samples display a mass-dependent depletion pattern with respect to surface conditions consistent with previous observations both in the Galapagos Islands and Michigan rainwater. Basal aquifer and rainwater noble gas patterns are similar and suggest direct, fast recharge from precipitation to the basal aquifer. In contrast, multiple springs, representative of perched aquifers, display highly variable noble gas concentrations suggesting recharge from a variety of sources. The distinct noble gas patterns for the basal aquifer and springs suggest that basal and perched aquifers are separate entities. Maui rainwater displays high apparent NGTs, incompatible with surface conditions, pointing either to an origin at high altitudes with the presence of ice or an ice-like source of undetermined origin. Overall, noble gas signatures in Maui reflect the source of recharge rather than the expected altitude/temperature relationship commonly observed in sedimentary systems.

The Performance of CO2 Laser Photoacoustic Spectrometer In Concentration Acetone Detection As Biomarker For Diabetes Mellitus Type 2

NASA Astrophysics Data System (ADS)

Tyas, F. H.; Nikita, J. G.; Apriyanto, D. K.; Mitrayana; Amin, M. N.

2018-04-01

Breath analysis is useful for the diagnosis of human diseases and monitoring of metabolic status. However, because of the low concentrations and the large numbers of compounds in the breath, the breath analysis requires highly sensitive and highly selective instruments to identify and determine the concentrations of certain biomarkers [1]. Various methods developed over the past 20 years to detect biomarker gases [2]. CO2 laser photoacoustic spectroscopy offers a sensitive technique for the detection and monitoring of gas footprints at low concentrations [3]. The performance of photoacoustic spectrometer (PAS) examined with intracavity configuration. In this research, the highest observed intracavity power was (49,96 ± 0,02) W for active medium gas composition He: N2: CO2 at 30:50:50. The highest laser absorption line for standard acetone gas set at 10P20, and the lowest detection limit set at (30 ± 4) ppb. For application purposes, the photoacoustic spectrometer was used to measure the concentration of acetone gas in exhaled gases from a group of patients with type 2 diabetes mellitus and a group of healthy volunteers. Exhaled gas sampling method took manually, and the measurement result was examined using multicomponent analysis. The measurement showed that the highest acetone gas concentration for type 2 diabetes mellitus patients was (162 ± 3) × 10 ppb and the lowest one was (101 ± 3) × 10 ppb. Furthermore, for healthy volunteers, the highest acetone gas concentration was (85 ± 3) × 10 ppb and the lowest one was (15 ± 3) × 10 ppb.

Novel Apparatus for the Real-Time Quantification of Dissolved Gas Concentrations and Isotope Ratios

NASA Astrophysics Data System (ADS)

Gupta, M.; Leen, J.; Baer, D. S.; Owano, T. G.; Liem, J.

2013-12-01

Measurements of dissolved gases and their isotopic composition are critical in studying a variety of phenomena, including underwater greenhouse gas generation, air-surface exchange, and pollution migration. These studies typically involve obtaining water samples from streams, lakes, or ocean water and transporting them to a laboratory, where they are degased. The gases obtained are then generally measured using gas chromatography and isotope ratio mass spectrometry for concentrations and isotope ratios, respectively. This conventional, off-line methodology is time consuming, significantly limits the number of the samples that can be measured and thus severely inhibits detailed spatial and temporal mapping of gas concentrations and isotope ratios. In this work, we describe the development of a new membrane-based degassing device that interfaces directly to Los Gatos Research (cavity enhanced laser absorption or Off-Axis ICOS) gas analyzers (cavity enhanced laser absorption or Off-Axis ICOS analyzers) to create an autonomous system that can continuously and quickly measure concentrations and isotope ratios of dissolved gases in real time in the field. By accurately controlling the water flow rate through the membrane degasser, gas pressure on the outside of the membrane, and water pressure on the inside of the membrane, the system is able to generate precise and highly reproducible results. Moreover, by accurately measuring the gas flow rates in and out of the degasser, the gas-phase concentrations (ppm) could be converted into dissolved gas concentrations (nM). We will present detailed laboratory test data that quantifies the linearity, precision, and dynamic range of the system for the concentrations and isotope ratios of dissolved methane, carbon dioxide, and nitrous oxide. By interfacing the degassing device to a novel cavity-enhanced spectrometer (developed by LGR), preliminary data will also be presented for dissolved volatile organics (VOC) and other pollutants. Finally, the system was deployed shipboard, and field deployment data will also be presented.

Compact air scrubber

DOEpatents

Bentley, Bill F.; Jett, James H.; Martin, John C.; Saunders, George C.

1992-01-01

Method and apparatus for removing material from a gas. A mist created by a piezoelectric ultrasonic transducer is contacted with the gas and both gas and mist are passed through baffled separators. Liquid effluent from the separators contains solid material removed from the gas and gaseous material which reacted with the liquid or was absorbed by the liquid. The invention is useful for collecting a sample of material in a gas, such as a vapor in the atmosphere, and in cleaning a gas. A relatively concentrated solution of a material present in a gas in a very small concentration can be obtained.

Integrated vacuum absorption steam cycle gas separation

DOEpatents

Chen, Shiaguo [Champaign, IL; Lu, Yonggi [Urbana, IL; Rostam-Abadi, Massoud [Champaign, IL

2011-11-22

Methods and systems for separating a targeted gas from a gas stream emitted from a power plant. The gas stream is brought into contact with an absorption solution to preferentially absorb the targeted gas to be separated from the gas stream so that an absorbed gas is present within the absorption solution. This provides a gas-rich solution, which is introduced into a stripper. Low pressure exhaust steam from a low pressure steam turbine of the power plant is injected into the stripper with the gas-rich solution. The absorbed gas from the gas-rich solution is stripped in the stripper using the injected low pressure steam to provide a gas stream containing the targeted gas. The stripper is at or near vacuum. Water vapor in a gas stream from the stripper is condensed in a condenser operating at a pressure lower than the stripper to concentrate the targeted gas. Condensed water is separated from the concentrated targeted gas.

Gravimetric Measurements of Filtering Facepiece Respirators Challenged With Diesel Exhaust.

PubMed

Satish, Swathi; Swanson, Jacob J; Xiao, Kai; Viner, Andrew S; Kittelson, David B; Pui, David Y H

2017-07-01

Elevated concentrations of diesel exhaust have been linked to adverse health effects. Filtering facepiece respirators (FFRs) are widely used as a form of respiratory protection against diesel particulate matter (DPM) in occupational settings. Previous results (Penconek A, Drążyk P, Moskal A. (2013) Penetration of diesel exhaust particles through commercially available dust half masks. Ann Occup Hyg; 57: 360-73.) have suggested that common FFRs are less efficient than would be expected for this purpose based on their certification approvals. The objective of this study was to measure the penetration of DPM through NIOSH-certified R95 and P95 electret respirators to verify this result. Gravimetric-based penetration measurements conducted using polytetrafluoroethylene (PTFE) and polypropylene (PP) filters were compared with penetration measurements made with a Scanning Mobility Particle Sizer (SMPS, TSI Inc.), which measures the particle size distribution. Gravimetric measurements using PP filters were variable compared to SMPS measurements and biased high due to adsorption of gas phase organic material. Relatively inert PTFE filters adsorbed less gas phase organic material resulting in measurements that were more accurate. To attempt to correct for artifacts associated with adsorption of gas phase organic material, primary and secondary filters were used in series upstream and downstream of the FFR. Correcting for adsorption by subtracting the secondary mass from the primary mass improved the result for both PTFE and PP filters but this correction is subject to 'equilibrium' conditions that depend on sampling time and the concentration of particles and gas phase hydrocarbons. Overall, the results demonstrate that the use of filters to determine filtration efficiency of FFRs challenged with diesel exhaust produces erroneous results due to the presence of gas phase hydrocarbons in diesel exhaust and the tendency of filters to adsorb organic material. Published by Oxford University Press on behalf of the British Occupational Hygiene Society 2017.

Environmental baselines: preparing for shale gas in the UK

NASA Astrophysics Data System (ADS)

Bloomfield, John; Manamsa, Katya; Bell, Rachel; Darling, George; Dochartaigh, Brighid O.; Stuart, Marianne; Ward, Rob

2014-05-01

Groundwater is a vital source of freshwater in the UK. It provides almost 30% of public water supply on average, but locally, for example in south-east England, it is constitutes nearly 90% of public supply. In addition to public supply, groundwater has a number of other uses including agriculture, industry, and food and drink production. It is also vital for maintaining river flows especially during dry periods and so is essential for maintaining ecosystem health. Recently, there have been concerns expressed about the potential impacts of shale gas development on groundwater. The UK has abundant shales and clays which are currently the focus of considerable interest and there is active research into their characterisation, resource evaluation and exploitation risks. The British Geological Survey (BGS) is undertaking research to provide information to address some of the environmental concerns related to the potential impacts of shale gas development on groundwater resources and quality. The aim of much of this initial work is to establish environmental baselines, such as a baseline survey of methane occurrence in groundwater (National methane baseline study) and the spatial relationships between potential sources and groundwater receptors (iHydrogeology project), prior to any shale gas exploration and development. The poster describes these two baseline studies and presents preliminary findings. BGS are currently undertaking a national survey of baseline methane concentrations in groundwater across the UK. This work will enable any potential future changes in methane in groundwater associated with shale gas development to be assessed. Measurements of methane in potable water from the Cretaceous, Jurassic and Triassic carbonate and sandstone aquifers are variable and reveal methane concentrations of up to 500 micrograms per litre, but the mean value is relatively low at < 10 micrograms per litre. These values compare with much higher levels of methane in aquicludes and thermal waters, for example from the Carboniferous and Triassic which have concentrations in excess of 1500 micrograms per litre. It is important to understand the spatial relationships between potential shale gas source rocks and overlying aquifers if shale gas is to be developed in a safe and sustainable manner. The BGS and the Environment Agency have undertaken a national-scale study of the UK to assess the vertical separation between potential shale gas source rocks and major aquifers (iHydrogeology project). Aquifer - shale separations have been documented in the range <200m to >2km. The geological modelling process will be presented and discussed along with maps combining the results of the methane baseline study, the distribution of Principal Aquifers and shale/clay units, and aquifer - shale separation maps for the UK.

Evolution of vehicle exhaust particles in the atmosphere.

PubMed

Canagaratna, Manjula R; Onasch, Timothy B; Wood, Ezra C; Herndon, Scott C; Jayne, John T; Cross, Eben S; Miake-Lye, Richard C; Kolb, Charles E; Worsnop, Douglas R

2010-10-01

Aerosol mass spectrometer (AMS) measurements are used to characterize the evolution of exhaust particulate matter (PM) properties near and downwind of vehicle sources. The AMS provides time-resolved chemically speciated mass loadings and mass-weighted size distributions of nonrefractory PM smaller than 1 microm (NRPM1). Source measurements of aircraft PM show that black carbon particles inhibit nucleation by serving as condensation sinks for the volatile and semi-volatile exhaust gases. Real-world source measurements of ground vehicle PM are obtained by deploying an AMS aboard a mobile laboratory. Characteristic features of the exhaust PM chemical composition and size distribution are discussed. PM mass and number concentrations are used with above-background gas-phase carbon dioxide (CO2) concentrations to calculate on-road emission factors for individual vehicles. Highly variable ratios between particle number and mass concentrations are observed for individual vehicles. NRPM1 mass emission factors measured for on-road diesel vehicles are approximately 50% lower than those from dynamometer studies. Factor analysis of AMS data (FA-AMS) is applied for the first time to map variations in exhaust PM mass downwind of a highway. In this study, above-background vehicle PM concentrations are highest close to the highway and decrease by a factor of 2 by 200 m away from the highway. Comparison with the gas-phase CO2 concentrations indicates that these vehicle PM mass gradients are largely driven by dilution. Secondary aerosol species do not show a similar gradient in absolute mass concentrations; thus, their relative contribution to total ambient PM mass concentrations increases as a function of distance from the highway. FA-AMS of single particle and ensemble data at an urban receptor site shows that condensation of these secondary aerosol species onto vehicle exhaust particles results in spatial and temporal evolution of the size and composition of vehicle exhaust PM on urban and regional scales.

Surface greenhouse gas fluxes downwind of a penguin colony in the maritime sub-Antarctic

NASA Astrophysics Data System (ADS)

Drewer, Julia; Braban, Christine F.; Tang, Y. Sim; Anderson, Margaret; Skiba, Ute M.; Dragosits, Ulrike; Trathan, Phil

2015-12-01

The relationship between ammonia (NH3) concentrations downwind from a penguin colony and local surface greenhouse gas (GHG) fluxes was investigated on the remote sub-Antarctic Bird Island (54°00‧S, 38°03‧W) during summer 2010 (November and December). A Macaroni penguin (Eudyptes chrysolophus) colony (40,000 pairs) at Goldcrest Point is a large point source of NH3 on the island and a measurement transect of 23 m, 36 m, 70 m, 143 m and 338 m was set up downwind from the colony. Atmospheric NH3 concentrations measured by passive diffusion samplers declined from 23 μg m-3 close to the colony to less than 1 μg m-3 338 m downwind. As increased nitrogen (N) deposition can affect soil carbon (C) and N cycling, it can therefore potentially influence GHG and nitric oxide (NO) emission rates. However, in this study, a clear correlation between surface GHG fluxes and atmospheric NH3 concentrations could not be established. Average fluxes for nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) over the entire transect and the eight week study period ranged from 7 to 23 μg N2O-N m-2 h-1, -5.5-245 μg CH4 m-2 h-1, and CO2 respiration rates averaged 2.2 μmol m-2 s-1. Laboratory studies using intact soil cores from the transect also did not show any significant correlation between atmospheric NH3 concentrations and N2O, NO, CH4 emissions or CO2 respiration rates. Overall, fluxes measured in the laboratory study reflected the high variability measured in the field. Large changes in soil depth along the transect, due to the topography of the island, possibly influenced fluxes more than NH3 concentration and seabirds appeared to have a more localised input (e.g. ground nesting birds). However, warmer temperatures might have a large potential to increase GHG fluxes in this ecosystem. This study confirms that GHG fluxes do occur in these ornithogenic ecosystems, however, the scale of the impact remains largely unquantified due to high uncertainties and high spatial variability.

On studies of 3He and isobutane mixture as neutron proportional counter gas

NASA Astrophysics Data System (ADS)

Desai, S. S.; Shaikh, A. M.

2006-02-01

The performance of neutron detectors filled with 3He+iC 4H 10 (isobutane) gas mixtures has been studied and compared with the performance of detectors filled with 3He+Kr gas mixtures. The investigations are made to determine suitable concentration of isobutane in the gas mixture to design neutron proportional counters and linear position sensitive neutron detectors (1-D PSDs). Energy resolution, range of proportionality, plateau and gas gain characteristics are studied for various gas mixtures of 3He and isobutane. The values for various gas constants are determined by fitting the gas gains to Diethorn and Bateman's equations and their variation with isobutane concentration in the fill gas mixture is studied.

Factors controlling the concentration of methane and other volatiles in groundwater and soil-gas around a waste site

NASA Astrophysics Data System (ADS)

Barber, C.; Davis, G. B.; Briegel, D.; Ward, J. K.

1990-01-01

The concentration of methane in groundwater and soil-gas in the vicinity of a waste landfill on an unconfined sand aquifer has been investigated in detail. These data have been used to evaluate techniques which use volatile organic compounds in soil-gas as indicators of groundwater contamination. Simple one-dimensional models of gas advection and diffusion have been adapted for use in the study. Lateral advection of gas in the unsaturated sand was found to be seasonal and was most noticeable in winter when the profile was wet; a mean velocity of 1 m d - was measured from breakthrough of a helium tracer in an injection test. The effects of advection on trace concentrations of methane in soil-gas were limited to within 150-200m from the waste site and resulted from pressure gradients brought about by positive gas pressures in the landfill, and also as a result of ebullition (gas bubbling) from contaminated groundwater. The distribution of methane in soil-gas at shallow (2m) depth gave a general indication of the direction of movement of contaminants with groundwater in close proximity to the landfill. Outside this zone, diffusional transport of methane from groundwater to soil-gas occurred and methane in soil-gas sampled close to the water table was found to be a useful indicator of contaminated groundwater. Modelling the exchange of volatiles between aqueous and gas phases indicates that a wide range of organic compounds, particularly those with Henry's Law constants greater than 2.5 × 10 t-2 kPam 3mol -1, would have potential for use as indicators of pollution, if these were present in groundwater and they behaved relatively conservatively. In general, the principal factors controlling the concentration of these volatiles in soil-gas were the concentration gradient at the water table and capillary fringe and the ratio of diffusion coefficients in the saturated and unsaturated zones.

Spatial and Temporal Variability in Biogenic Gas Accumulation and Release in The Greater Everglades at Multiple Scales of Measurement

NASA Astrophysics Data System (ADS)

McClellan, M. D.; Cornett, C.; Schaffer, L.; Comas, X.

2017-12-01

Wetlands play a critical role in the carbon (C) cycle by producing and releasing significant amounts of greenhouse biogenic gasses (CO2, CH4) into the atmosphere. Wetlands in tropical and subtropical climates (such as the Florida Everglades) have become of great interest in the past two decades as they account for more than 20% of the global peatland C stock and are located in climates that favor year-round C emissions. Despite the increase in research involving C emission from these types of wetlands, the spatial and temporal variability involving C production, accumulation and release is still highly uncertain, and is the focus of this research at multiple scales of measurement (i.e. lab, field and landscape). Spatial variability in biogenic gas content, build up and release, at both the lab and field scales, was estimated using a series of ground penetrating radar (GPR) surveys constrained with gas traps fitted with time-lapse cameras. Variability in gas content was estimated at the sub-meter scale (lab scale) within two extracted monoliths from different wetland ecosystems at the Disney wilderness Preserve (DWP) and the Blue Cypress Preserve (BCP) using high frequency GPR (1.2 GHz) transects across the monoliths. At the field scale (> 10m) changes in biogenic gas content were estimated using 160 MHz GPR surveys collected within 4 different emergent wetlands at the DWP. Additionally, biogenic gas content from the extracted monoliths was used to developed a landscape comparison of C accumulation and emissions for each different wetland ecosystem. Changes in gas content over time were estimated at the lab scale at high temporal resolution (i.e. sub-hourly) in monoliths from the BCP and Water Conservation Area 1-A. An autonomous rail system was constructed to estimate biogenic gas content variability within the wetland soil matrix using a series of continuous, uninterrupted 1.2 GHz GPR transects along the samples. Measurements were again constrained with an array of gas traps fitted with time-lapse cameras. This research seeks to better understand the spatial and temporal variability of biogenic gas content within wetlands from the Greater Everglades Watershed. Such understanding may help to identify potential hotspots (both in space and time) and their implication for the flux estimates used as input in climate models.

Effect of cage vs. floor litter environments on the pulmonary hypertensive response to intravenous endotoxin and on blood-gas values in broilers.

PubMed

Wang, W; Erf, G F; Wideman, R F

2002-11-01

Intravenous endotoxin has been shown to trigger a delayed pulmonary hypertensive response that varies widely in magnitude and duration among individual broilers. It was proposed that this individual variability may reflect immunological differences acquired during previous respiratory challenges that might have subsequently altered the endotoxin-initiated biochemical cascade. In Experiment 1, we tested the hypothesis that, when compared with broilers reared in clean stainless steel cages (Cage group), broilers reared on floor litter (Floor group) should experience a greater respiratory challenge and therefore may consistently exhibit a more enhanced pulmonary hypertensive response to intravenous endotoxin. Birds in the Cage group were grown in stainless steel cages at a low density (72 birds/8 m2 chamber), and fecal and dander materials were removed daily. Birds in the Floor group were reared on wood-shavings litter at a higher density (110 birds/8 m2 chamber). Pulmonary and systemic mean arterial pressures and blood-gas values were evaluated prior to and following the intravenous administration of 1 mg Salmonella typhimurium endotoxin. Broilers in the Floor and Cage groups exhibited pulmonary hypertensive responses to endotoxin that were very similar in terms of time of onset, duration, and magnitude, as well as variability in the response among individuals. Systemic hypotension also developed similarly in both groups following endotoxin injection. Blood-gas values indicated that the partial pressure of CO2 and the HCO3- concentration in arterial blood were higher (P < 0.05) in the Floor group than in the Cage group prior to and subsequent to the endotoxin injection. In Experiment 2, we reevaluated the effect of a dirty vs. a clean environment on blood-gas values using a different strain of broilers, and confirmed the negative impact of floor rearing on blood-gas values. We conclude that broilers reared on the floor inhaled litter dust and noxious fumes, which impaired pulmonary gas exchange and increased the arterial partial pressure of CO2 when compared with broilers reared in clean stainless steel cages. Nevertheless, the pulmonary hypertensive response to endotoxin did not differ between broilers reared on the floor and those in cages.

Hydrogen gas concentration measurement in small area using raman lidar measurement technnology

NASA Astrophysics Data System (ADS)

Sugimoto, Sachiyo; Asahi, Ippei; Shiina, Tatuso

2018-04-01

When change of hydrogen(H2) gas concentration in a certain point is measured, non-contact measurement technology with high temporal and spatial resolution is necessary. In this study, H2 concentration in the small area of <1cm2 under the gas flow was measured by using a Raman lidar. Raman scattering light at the measurement point of 750mm ahead was detected by the Raman lidar. As a result, it was proved that the H2 concentration of more than 100ppm could be successfully measured.

A Gas Chromatographic System for the Detection of Ethylene Gas Using Ambient Air as a Carrier Gas

PubMed Central

Zaidi, Nayyer Abbas; Tahir, Muhammad Waseem; Vellekoop, Michael J.; Lang, Walter

2017-01-01

Ethylene gas is a naturally occurring gas that has an influence on the shelf life of fruit during their transportation in cargo ships. An unintentional exposure of ethylene gas during transportation results in a loss of fruit. A gas chromatographic system is presented here for the detection of ethylene gas. The gas chromatographic system was assembled using a preconcentrator, a printed 3D printed gas chromatographic column, a humidity sensor, solenoid valves, and an electrochemical ethylene gas sensor. Ambient air was used as a carrier gas in the gas chromatographic system. The flow rate was fixed to 10 sccm. It was generated through a mini-pump connected in series with a mass flow controller. The metal oxide gas sensor is discussed with its limitation in ambient air. The results show the chromatogram obtained from metal oxide gas sensor has low stability, drifts, and has uncertain peaks, while the chromatogram from the electrochemical sensor is stable and precise. Furthermore, ethylene gas measurements at higher ppb concentration and at lower ppb concentration were demonstrated with the electrochemical ethylene gas sensor. The system separates ethylene gas and humidity. The chromatograms obtained from the system are stable, and the results are 1.2% repeatable in five similar measurements. The statistical calculation of the gas chromatographic system shows that a concentration of 2.3 ppb of ethylene gas can be detected through this system. PMID:28991173

Noble gases solubility models of hydrocarbon charge mechanism in the Sleipner Vest gas field

NASA Astrophysics Data System (ADS)

Barry, P. H.; Lawson, M.; Meurer, W. P.; Warr, O.; Mabry, J. C.; Byrne, D. J.; Ballentine, C. J.

2016-12-01

Noble gases are chemically inert and variably soluble in crustal fluids. They are primarily introduced into hydrocarbon reservoirs through exchange with formation waters, and can be used to assess migration pathways and mechanisms, as well as reservoir storage conditions. Of particular interest is the role groundwater plays in hydrocarbon transport, which is reflected in hydrocarbon-water volume ratios. Here, we present compositional, stable isotope and noble gas isotope and abundance data from the Sleipner Vest field, in the Norwegian North Sea. Sleipner Vest gases are generated from primary cracking of kerogen and the thermal cracking of oil. Gas was emplaced into the Sleipner Vest from the south and subsequently migrated to the east, filling and spilling into the Sleipner Ost fields. Gases principally consist of hydrocarbons (83-93%), CO2 (5.4-15.3%) and N2 (0.6-0.9%), as well as trace concentrations of noble gases. Helium isotopes (3He/4He) are predominantly radiogenic and range from 0.065 to 0.116 RA; reported relative to air (RA = 1.4 × 10-6; Clarke et al., 1976; Sano et al., 1988), showing predominantly (>98%) crustal contributions, consistent with Ne (20Ne/22Ne from 9.70 to 9.91; 21Ne/22Ne from 0.0290 to 0.0344) and Ar isotopes (40Ar/36Ar from 315 to 489). Air-derived noble gas isotopes (20Ne, 36Ar, 84Kr, 132Xe) are introduced into the hydrocarbon system by direct exchange with air-saturated water (ASW). The distribution of air-derived noble gas species are controlled by phase partitioning processes; in that they preferentially partition into the gas (i.e., methane) phase, due to their low solubilities in fluids. Therefore, the extent of exchange between hydrocarbon phases and formation waters - that have previously equilibrated with the atmosphere - can be determined by investigating air-derived noble gas species. We utilize both elemental ratios to address process (i.e., open vs. closed system) and concentrations to quantify the extent of hydrocarbon-water exchange (i.e., volumetric gas-water ratios). These data are discussed within the framework of several conceptual models: (i) total gas-stripping model, which assumes all noble gases have been stripped from the water phase, thus defining the minimum volume of water to have interacted with the hydrocarbon phase; (ii) equilibrium model, which assumes equilibration between groundwater and hydrocarbon phase at reservoir P, T and salinity; and (iii) open and closed system gas-stripping models, using concentrations and elemental ratios. By applying these models to Ne-Ar data from Sleipner, we estimate volumetric gas-water ratios (Vg/Vw) between 0.02 and 0.07, which are lower than standard geologic gas-water estimates of ∼0.24, estimated by combining gas-in-place estimates with groundwater porosity estimates. Sleipner Vest data can be best approximated by an open system model, which predicts more than an order of magnitude more groundwater interaction during migration than geologic estimates, indicating a dynamic aquifer system and/or a hydrous migration pathway. In an open system, the extent of gas loss can be estimated to be between 8 and 10 reservoir volumes, which have passed through the system and been lost (i.e., filled and spilled).

Special aspects of pharmacokinetics of inhalation anesthesia.

PubMed

Hendrickx, J F A; De Wolf, A

2008-01-01

Recent interest in the use of low-flow or closed circuit anesthesia has rekindled interest in the pharmacokinetics of inhaled anesthetics. The kinetic properties of inhaled anesthetics are most often modeled by physiologic models because of the abundant information that is available on tissue solubilities and organ perfusion. These models are intuitively attractive because they can be easily understood in terms of the underlying anatomy and physiology. The use of classical compartment modeling, on the other hand, allows modeling of data that are routinely available to the anesthesiologist, and eliminates the need to account for every possible confounding factor at each step of the partial pressure cascade of potent inhaled agents. Concepts used to describe IV kinetics can readily be applied to inhaled agents (e.g., context-sensitive half-time and effect site concentrations). The interpretation of the F(A)/F(I) vs time curve is expanded by reintroducing the concept of the general anesthetic equation-the focus is shifted from "how F(A) approaches F(I)" to "what combination of delivered concentration and fresh gas flow (FGF) can be used to attain the desired F(A)." When the desired F(A) is maintained with a FGF that is lower than minute ventilation, rebreathing causes a discrepancy between the concentration delivered by the anesthesia machine (=selected by the anesthesiologist on the vaporizer, F(D)) and that inspired by the patient. This F(D)-F(I) discrepancy may be perceived as "lack of control" and has been the rationale to use a high FGF to ensure the delivered matched the inspired concentration. Also, with low FGF there is larger variability in F(D) because of interpatient variability in uptake. The F(D)-F(I) discrepancy increases with lower FGF because of more rebreathing, and as a consequence the uptake pattern seems to be more reflected in the F(D) required to keep F(A) constant. The clinical implication for the anesthesiologist is that with high FGF few F(D) adjustments have to be made, while with a low FGF F(D) has to be adjusted according to a pattern that follows the decreasing uptake pattern in the body. The ability to model and predict the uptake pattern of the individual patient and the resulting kinetics in a circle system could therefore help guide the anesthesiologist in the use of low-flow anesthesia with conventional anesthesia machines. Several authors have developed model-based low FGF administration schedules, but biologic variability limits the performance of any model, and therefore end-expired gas analysis is obligatory. Because some fine-tuning based on end-expired gas analysis will always be needed, some clinicians may not be inclined to use very low FGF in a busy operating room, considering the perceived increase in complexity. This practice may be facilitated by the development of anesthesia machines that use closed circuit anesthesia (CCA) with end-expired feedback control--they "black box" these issues (see Chapter 21). In this chapter, we first explore how and why the kinetic properties of intravenous and inhaled anesthetics have been modeled differently. Next, we will review the method most commonly used to describe the kinetics of inhaled agents, the F(A)/F(I) vs time curve that describes how the alveolar (F(A)) approaches the inspired (F(I)) fraction (in the gas phase, either "fraction," "concentration," or "partial pressure" can be used). Finally, we will reintroduce the concept of the general anesthetic equation to explain why the use of low-flow or closed circuit anesthesia has rekindled interest in the modeling of pharmacokinetics of inhaled anesthetics. Clinical applications of some of these models are reviewed. A basic understanding of the circle system is required, and will be provided in the introduction.

Decreased 2,3-diphosphoglycerate concentration in low cardiac output patients and its influence on the determination of in vivo p50.

PubMed

Piccioni, Marilde A; Cestari, Idágene A; Strunz, Célia M C; Auler, José O

2003-08-01

We investigated whether 2,3-diphosphoglycerate (2,3-DPG) is altered in patients with low cardiac output and the influence of its concentration on the calculation of in vivo P(50). Biochemical and blood gas analysis were performed along with the measurement of cardiac output and body temperature in 13 patients submitted to cardiopulmonary bypass surgeries without the use of donor blood. In vivo P(50) was calculated using the measured (P(50m)) and the estimated 2,3-DPG (P(50e)). 2,3-DPG concentration was lower in these patients when compared to the values obtained in normal volunteers (6.9 +/- 2.2 vs. 11.9 +/- 2.4 microm/gHb). P(50m) was lower than P(50e) (21.6 +/- 1.1 vs. 30.1 +/- 1.2 mm Hg) at all time points. Our data show that in patients with low cardiac output, 2,3-DPG concentration is reduced. Therefore, in these patients, the use of standard values for this variable may introduce an error in the calculation of in vivo P(50).

Temporal variability of benzene concentration in the ambient air of Delhi: a comparative assessment of pre- and post-CNG periods.

PubMed

Khillare, P S; Hoque, Raza Rafiqul; Shridhar, Vijay; Agarwal, Tripti; Balachandran, S

2008-06-15

CNG (compressed natural gas) was fully implemented in public transport system in Delhi in December 2002. The study assesses the benzene concentration trends at two busy traffic intersections and a background site in Delhi, India. Monitoring was done for two different time periods viz; in the year 2001-2002 (pre-CNG) and two winter months (January and February) of the year 2007 (post-CNG) to assess the impact of various policy measures adopted by the government of Delhi to improve the air quality in the city. Annual average benzene concentration for the pre-CNG period was found to be 86.47+/-53.24 microg m(-3). Average benzene concentrations for the winter months (January-February) of pre- and post-CNG periods were 116.32+/-51.65 microg m(-3) and 187.49+/-22.50 microg m(-3), respectively. Enhanced values could be solely attributed to the increase in the vehicular population from 3.5 million in the year 2001-2002 to approximately 5.1 millions in the year 2007.

Use of the Keele injector for sample introduction for gas chromatographic analysis of vinclozolin in lettuces.

PubMed

Shim, J H; Lee, Y S; Kim, M R; Lee, C J; Kim, I S

2003-10-10

We examined a Keele injector for sample introduction for gas chromatographic analysis of vinclozolin treated in lettuces. Samples in milligram quantity were introduced into a glass tube in a Keele injector at a gas chromatograph injection port. The glass tube was then crushed to allow the sample to carry onto a capillary column in a normal manner. The standard calibration curve for quantitative detection of vinclozolin was obtained by determining vinclozolin spiked in samples at variable concentrations. The calibration curve showed a linear response to vinclozolin ranging from 0.05 to 1.0 microg/g, giving a slope value of 174.8, the y-intercept value of -2.8146 and the mean r2-value of 0.9994. Limit of quantification for vinclozolin was 0.05 microg/g by this method, comparable to 0.01 microg/g by a normal injector. When samples treated previously with vinclozolin were determined by the Keele injector, vinclozolin was found to be about 30% lower as compared to a normal method, suggesting about 70% recovery of the spiked vinclozolin by the Keele injector. From these results, the Keele injector was suggested to be potential for sample introduction in gas chromatographic analysis of vinclozolin in lettuce samples.

[Radon risk in healthcare facilities: environmental monitoring and effective dose].

PubMed

Cammarota, B; Cascone, Maria Teresa; De Paola, L; Schillirò, F; Del Prete, U

2009-01-01

Radon, the second cause of lung cancer after smoking (WHO- IARC), is a natural, radioactive gas, which originates from the soil and pollutes indoor air, especially in closed or underground spaces. The purpose of this study was to determine the concentration of radon gas, its effective dose, and the measurement of microclimatic degrees C; U.R. % and air velocity in non-academic intensive care units of public hospitals in the Naples area. The annual average concentrations of radon gas were detected with EIC type ionization electret chambers, type LLT with exposure over four 3-month periods. The concentrations varied for all health facilities between 186 and 1191 Bq/m3. Overall, the effective dose of exposure to radon gas of 3mSv/a recommended by Italian legislation was never exceeded. The concentration of radon gas showed a decreasing trend starting from the areas below ground level to those on higher floors; such concentrations were also influenced by natural and artificial ventilation of the rooms, building materials used for walls, and by the state of maintenance and improvements of the building (insulation of floors and walls). The data obtained confirmed the increased concentration of radionuclides in the yellow tuff of volcanic origin in the Campania Region and the resulting rate of release of radon gas, whereas the reinforced concrete structure (a hospital located on the hillside), which had the lowest values, proved to provide good insulation against penetration and accumulation of radon gas.

Toward Adequate Operation of Amorphous Oxide Thin-Film Transistors for Low-Concentration Gas Detection.

PubMed

Kim, Kyung Su; Ahn, Cheol Hyoun; Jung, Sung Hyeon; Cho, Sung Woon; Cho, Hyung Koun

2018-03-28

We suggest the use of a thin-film transistor (TFT) composed of amorphous InGaZnO (a-IGZO) as a channel and a sensing layer for low-concentration NO 2 gas detection. Although amorphous oxide layers have a restricted surface area when reacting with NO 2 gas, such TFT sensors have incomparable advantages in the aspects of electrical stability, large-scale uniformity, and the possibility of miniaturization. The a-IGZO thin films do not possess typical reactive sites and grain boundaries, so that the variation in drain current of the TFTs strictly originates from oxidation reaction between channel surface and NO 2 gas. Especially, the sensing data obtained from the variation rate of drain current makes it possible to monitor efficiently and quickly the variation of the NO 2 concentration. Interestingly, we found that enhancement-mode TFT (EM-TFT) allows discrimination of the drain current variation rate at NO 2 concentrations ≤10 ppm, whereas a depletion-mode TFT is adequate for discriminating NO 2 concentrations ≥10 ppm. This discrepancy is attributed to the ratio of charge carriers contributing to gas capture with respect to total carriers. This capacity for the excellent detection of low-concentration NO 2 gas can be realized through (i) three-terminal TFT gas sensors using amorphous oxide, (ii) measurement of the drain current variation rate for high selectivity, and (iii) an EM mode driven by tuning the electrical conductivity of channel layers.

Particle dispersing system and method for testing semiconductor manufacturing equipment

DOEpatents

Chandrachood, Madhavi; Ghanayem, Steve G.; Cantwell, Nancy; Rader, Daniel J.; Geller, Anthony S.

1998-01-01

The system and method prepare a gas stream comprising particles at a known concentration using a particle disperser for moving particles from a reservoir of particles into a stream of flowing carrier gas. The electrostatic charges on the particles entrained in the carrier gas are then neutralized or otherwise altered, and the resulting particle-laden gas stream is then diluted to provide an acceptable particle concentration. The diluted gas stream is then split into a calibration stream and the desired output stream. The particles in the calibration stream are detected to provide an indication of the actual size distribution and concentration of particles in the output stream that is supplied to a process chamber being analyzed. Particles flowing out of the process chamber within a vacuum pumping system are detected, and the output particle size distribution and concentration are compared with the particle size distribution and concentration of the calibration stream in order to determine the particle transport characteristics of a process chamber, or to determine the number of particles lodged in the process chamber as a function of manufacturing process parameters such as pressure, flowrate, temperature, process chamber geometry, particle size, particle charge, and gas composition.

Home interventions are effective at decreasing indoor nitrogen dioxide concentrations.

PubMed

Paulin, L M; Diette, G B; Scott, M; McCormack, M C; Matsui, E C; Curtin-Brosnan, J; Williams, D L; Kidd-Taylor, A; Shea, M; Breysse, P N; Hansel, N N

2014-08-01

Nitrogen dioxide (NO2 ), a by-product of combustion produced by indoor gas appliances such as cooking stoves, is associated with respiratory symptoms in those with obstructive airways disease. We conducted a three-armed randomized trial to evaluate the efficacy of interventions aimed at reducing indoor NO2 concentrations in homes with unvented gas stoves: (i) replacement of existing gas stove with electric stove; (ii) installation of ventilation hood over existing gas stove; and (iii) placement of air purifiers with high-efficiency particulate air (HEPA) and carbon filters. Home inspection and NO2 monitoring were conducted at 1 week pre-intervention and at 1 week and 3 months post-intervention. Stove replacement resulted in a 51% and 42% decrease in median NO2 concentration at 3 months of follow-up in the kitchen and bedroom, respectively (P = 0.01, P = 0.01); air purifier placement resulted in an immediate decrease in median NO2 concentration in the kitchen (27%, P < 0.01) and bedroom (22%, P = 0.02), but at 3 months, a significant reduction was seen only in the kitchen (20%, P = 0.05). NO2 concentrations in the kitchen and bedroom did not significantly change following ventilation hood installation. Replacing unvented gas stoves with electric stoves or placement of air purifiers with HEPA and carbon filters can decrease indoor NO2 concentrations in urban homes. Several combustion sources unique to the residential indoor environment, including gas stoves, produce nitrogen dioxide (NO2), and higher NO2 concentrations, are associated with worse respiratory morbidity in people with obstructive lung disease. A handful of studies have modified the indoor environment by replacing unvented gas heaters; this study, to our knowledge, is the first randomized study to target unvented gas stoves. The results of this study show that simple home interventions, including replacement of an unvented gas stove with an electric stove or placement of HEPA air purifiers with carbon filters, can significantly decrease indoor NO2 concentrations. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Fabrication of Graded Porous and Skin-Core Structure RDX-Based Propellants via Supercritical CO2 Concentration Profile

NASA Astrophysics Data System (ADS)

Yang, Weitao; Li, Yuxiang; Ying, Sanjiu

2015-04-01

A fabrication process to produce graded porous and skin-core structure propellants via supercritical CO2 concentration profile is reported in this article. It utilizes a partial gas saturation technique to obtain nonequilibrium gas concentration profiles in propellants. Once foamed, the propellant obtains a graded porous or skin-pore structure. This fabrication method was studied with RDX(Hexogen)-based propellant under an SC-CO2 saturation condition. The principle was analyzed and the one-dimensional diffusion model was employed to estimate the gas diffusion coefficient and to predict the gas concentration profiles inside the propellant. Scanning electron microscopy images were used to analyze the effects of partial saturation on the inner structure. The results also suggested that the sorption time and desorption time played an important role in gas profile generation and controlled the inner structure of propellants.

Low-cost photonic sensors for carbon dioxide exchange rate measurement

NASA Astrophysics Data System (ADS)

Bieda, Marcin S.; Sobotka, Piotr; Lesiak, Piotr; Woliński, Tomasz R.

2017-10-01

Carbon dioxide (CO2) measurement has an important role in atmosphere monitoring. Usually, two types of measurements are carried out. The first one is based on gas concentration measurement while the second involves gas exchange rate measurement between earth surface and atmosphere [1]. There are several methods which allow gas concentration measurement. However, most of them require expensive instrumentation or large devices (i.e. gas chambers). In order to precisely measure either CO2 concentration or CO2 exchange rate, preferably a sensors network should be used. These sensors must have small dimensions, low power consumption, and they should be cost-effective. Therefore, this creates a great demand for a robust low-power and low-cost CO2 sensor [2,3]. As a solution, we propose a photonic sensor that can measure CO2 concentration and also can be used to measure gas exchange by using the Eddy covariance method [1].

Correlation Between Geological Stuctures and Gas Hydrate amount Offshore the South Shetland Island — Preliminary Results

NASA Astrophysics Data System (ADS)

Loreto, M. F.; Tinivella, U.; Accaino, F.; Giustiniani, M.

2010-05-01

Sediments of the accretionary prism, present along the continental margin of the Peninsula Antarctica SW of Elephant Island, are filled by gas hydrates as evidenced by a strong BSR. A multidisciplinary geophysical dataset, represented by seismic data, multibeam, chirp profiles, CTD and core samples, was acquired during three oceanographic cruises. The estimation of gas hydrate and free gas concentrations is based on the P-wave velocity analysis. In order to extract a detailed and reliable velocity field, we have developed and optimized a procedure that includes the pre-stack depth migration to determine, iteratively and with a layer stripping approach method, the velocity field and the depth-migrated seismic section. The final velocity field is then translated in terms of gas hydrate and free gas amounts by using theoretical approaches. Several seismic sections have been processed in the investigated area. The final 2D velocity sections have been translated in gas-phase concentration sections, considering the gas distribution within sediments both uniformly and patchly distributed. The free gas layer is locally present and, consequently, the base of the free gas reflector was identified only in some lines or part of them. The hydrate layer shows important lateral variations of hydrate concentration in correspondence of geological features, such as faults and folds. The intense fluid migration along faults and different fluid accumulation in correspondence of geological structures can control the gas hydrate concentration and modify the geothermal field in the surrounding area.

Hydrolysis optimization and characterization study of preparing fatty acids from Jatropha curcas seed oil.

PubMed

Salimon, Jumat; Abdullah, Bashar Mudhaffar; Salih, Nadia

2011-11-01

Fatty acids (FAs) are important as raw materials for the biotechnology industry. Existing methods of FAs production are based on chemical methods. In this study potassium hydroxide (KOH)-catalyzed reactions were utilized to hydrolysis Jatropha curcas seed oil. The parameters effect of ethanolic KOH concentration, reaction temperature, and reaction time to free fatty acid (FFA%) were investigated using D-Optimal Design. Characterization of the product has been studied using Fourier transforms infrared spectroscopy (FTIR), gas chromatography (GC) and high performance liquid chromatography (HPLC). The optimum conditions for maximum FFA% were achieved at 1.75M of ethanolic KOH concentration, 65°C of reaction temperature and 2.0 h of reaction time. This study showed that ethanolic KOH concentration was significant variable for J. curcas seed oil hydrolysis. In a 18-point experimental design, FFA% of hydrolyzed J. curcas seed oil can be raised from 1.89% to 102.2%, which proved by FTIR and HPLC.

Separation of sodium chloride from the evaporated residue of the reverse osmosis reject generated in the leather industry--optimization by response surface methodology.

PubMed

Boopathy, R; Sekaran, G

2014-08-01

Reverse osmosis (RO) concentrate is being evaporated by solar/thermal evaporators to meet zero liquid discharge standards. The resulted evaporated residue (ER) is contaminated with both organic and inorganic mixture of salts. The generation of ER is exceedingly huge in the leather industry, which is being collected and stored under the shelter to avoid groundwater contamination by the leachate. In the present investigation, a novel process for the separation of sodium chloride from ER was developed, to reduce the environmental impact on RO concentrate discharge. The sodium chloride was selectively separated by the reactive precipitation method using hydrogen chloride gas. The selected process variables were optimized for maximum yield ofNaCl from the ER (optimum conditions were pH, 8.0; temperature, 35 degrees C; concentration of ER, 600 g/L and HCl purging time, 3 min). The recovered NaCl purity was verified using a cyclic voltagramm.

Redox Control For Hanford HLW Feeds VSL-12R2530-1, REV 0

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

Kruger, A. A.; Matlack, Keith S.; Pegg, Ian L.

2012-12-13

The principal objectives of this work were to investigate the effects of processing simulated Hanford HLW at the estimated maximum concentrations of nitrates and oxalates and to identify strategies to mitigate any processing issues resulting from high concentrations of nitrates and oxalates. This report provides results for a series of tests that were performed on the DM10 melter system with simulated C-106/AY-102 HLW. The tests employed simulated HLW feeds containing variable amounts of nitrates and waste organic compounds corresponding to maximum concentrations proj ected for Hanford HLW streams in order to determine their effects on glass production rate, processing characteristics,more » glass redox conditions, melt pool foaming, and the tendency to form secondary phases. Such melter tests provide information on key process factors such as feed processing behavior, dynamic effects during processing, processing rates, off-gas amounts and compositions, foaming control, etc., that cannot be reliably obtained from crucible melts.« less

Mercury species in dab (Limanda limanda) from the North Sea, Baltic Sea and Icelandic waters in relation to host-specific variables.

PubMed

Lang, Thomas; Kruse, Reinhard; Haarich, Michael; Wosniok, Werner

2017-03-01

In the framework of the ICON project (Integrated Assessment of Contaminant Impacts on the North Sea), muscle tissue from a total of 135 common dab (Limanda limanda) (20-28 cm total length) was collected in seven offshore sampling areas in the North Sea, at Iceland and in the Baltic Sea during Aug/Sept and December 2008 for a chemical mercury speciation analysis by means of gas chromatography and detection by cold vapour atomic fluorescence spectroscopy (GC-CVAFS). There was a highly significant correlation between concentrations of methylmercury (MeHg + ) and inorganic mercury (Hg 2+ ) in individual fish, and the mean ratio of MeHg + compared to Σ Hg (MeHg +  + Hg 2+ ) was 94.0%. The results revealed statistically significant differences in concentrations of MeHg + and Hg 2+ , respectively, between sampling areas. Mean concentrations in the German Bight (North Sea), in Icelandic waters and in Mecklenburg Bight (Baltic Sea) were low (MeHg + : 0.023-0.036; Hg 2+ : 0.001-0.002 mg/kg wet weight), while concentrations in dab from the Dogger Bank, Firth of Forth and the vicinity of the Ekofisk oil field (all North Sea) were significantly higher (MeHg + : 0.059-0.101; Hg 2+ : 0.003-0.004 mg/kg wet weight). Statistical correlation analysis on effects of host-specific factors revealed that neither length, weight, age, sex nor condition factor showed a significant relationship with Hg concentrations. However, Hg concentrations were significantly correlated with the Fish Disease Index (FDI), indicating a relationship between Hg concentrations and the health status of dab. Multiple linear regression analysis aiming to find factors affecting Hg concentrations revealed that only the sampling area had a highly significant main effect on Hg concentrations, and in some cases, additionally the condition factor contributed significantly to the final model. From the results, it cannot be excluded that elevated Hg concentration recorded in dab were linked to discharges from offshore oil and gas installations and that Hg affected the health status of dab. Copyright © 2016 Elsevier Ltd. All rights reserved.

Seismic character of gas hydrates on the Southeastern U.S. continental margin

USGS Publications Warehouse

Lee, M.W.; Hutchinson, D.R.; Agena, W.F.; Dillon, William P.; Miller, J.J.; Swift, B.A.

1994-01-01

Gas hydrates are stable at relatively low temperature and high pressure conditions; thus large amounts of hydrates can exist in sediments within the upper several hundred meters below the sea floor. The existence of gas hydrates has been recognized and mapped mostly on the basis of high amplitude Bottom Simulating Reflections (BSRs) which indicate only that an acoustic contrast exists at the lower boundary of the region of gas hydrate stability. Other factors such as amplitude blanking and change in reflection characteristics in sediments where a BSR would be expected, which have not been investigated in detail, are also associated with hydrated sediments and potentially disclose more information about the nature of hydratecemented sediments and the amount of hydrate present. Our research effort has focused on a detailed analysis of multichannel seismic profiles in terms of reflection character, inferred distribution of free gas underneath the BSR, estimation of elastic parameters, and spatial variation of blanking. This study indicates that continuous-looking BSRs in seismic profiles are highly segmented in detail and that the free gas underneath the hydrated sediment probably occurs as patches of gas-filled sediment having variable thickness. We also present an elastic model for various types of sediments based on seismic inversion results. The BSR from sediments of high ratio of shear to compressional velocity, estimated as about 0.52, encased in sediments whose ratios are less than 0.35 is consistent with the interpretation of gasfilled sediments underneath hydrated sediments. This model contrasts with recent results in which the BSR is explained by increased concentrations of hydrate near the base of the hydrate stability field and no underlying free gas is required. 

Effect of water injection and off scheduling of variable inlet guide vanes, gas generator speed and power turbine nozzle angle on the performance of an automotive gas turbine engine

NASA Technical Reports Server (NTRS)

Warren, E. L.

1980-01-01

The Chrysler/ERDA baseline automotive gas turbine engine was used to experimentally determine the power augmentation and emissions reductions achieved by the effect of variable compressor and power engine geometry, water injection downstream of the compressor, and increases in gas generator speed. Results were dependent on the mode of variable geometry utilization. Over 20 percent increase in power was accompanied by over 5 percent reduction in SFC. A fuel economy improvement of at least 6 percent was estimated for a vehicle with a 75 kW (100 hp) engine which could be augmented to 89 kW (120 hp) relative to an 89 Kw (120 hp) unaugmented engine.

Purging of a multilayer insulation with dacron tuft spacer by gas diffusion

NASA Technical Reports Server (NTRS)

Sumner, I. E.; Fisk, W. J.

1976-01-01

The time and purge gas usage required to purge a multilayer insulation (MLI) panel with gaseous helium by means of gas diffusion to obtain a condensable gas (nitrogen) concentration of less than 1 percent within the panel are stipulated. Two different, flat, rectangular MLI panels, one incorporating a butt joint, were constructed of of 11 double-aluminized Mylar (DAM) radiation shields separated by Dacron tuft spacers. The DAM/Dacron tuft concept is known commercially as Superfloc. The nitrogen gas concentration as a function of time within the MLI panel could be adequately predicted by using a simple, one dimensional gas diffusion model in which the boundary conditions at the edge of the MLI panel were time dependent. The time and purge gas usage required to achieve 1 percent nitrogen gas concentration within the MLI panel varied from 208 to 86 minutes and 34.1 to 56.5 MLI panel purge volumes, respectively, for gaseous helium purge rates from 10 to 40 MLI panel volumes per hour.

Gas Dispersion Coefficients in Variably Saturated and Differently Textured Porous Media Muhammad Naveed (1), Shoichiro Hamamoto (1), Ken Kawamoto (1,2), Toshihiro Sakaki (3), Per Moldrup (4), and Toshiko Komatsu (1,2) (1) Graduate School of Science and Engineering, Saitama University, Saitama, Japan (2) Institute of Environmental Science and Technology, Saitama University, Saitama, Japan (3) Center for Experimental Study of Subsurface Environmental Processes, Colorado School of Mines, Golden, CO, USA (4) Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Aalborg, Denmark

NASA Astrophysics Data System (ADS)

Naveed, M.; Kawamoto, K.; Hamamoto, S.; Sakaki, T.; Moldrup, P.; Komatsu, T.

2010-12-01

The transport and fate of gases in the soil are governed by gas advection, diffusion and dispersion phenomena. Among three gas transport phenomena, gas dispersion is least understood. Main objective of this study is to investigate the gas dispersion phenomena, emphasising on the effect of moisture content, sand particle shape, particle size, particle size distribution, and scale dependency on gas dispersion. One dimensional laboratory column experiments, in an apparatus consisting of an acrylic column attached to inlet and outlet chambers (Hamamoto et al., SSAJ, 2009), were conducted for the measurements of gas dispersion coefficient (DH). Various types of sands (Narita and Toyoura sands from Japan, and Granusils and Accusands from United States) and glass beads with variable moisture contents were used as porous media. Shape of the sand particles were characterized in terms of sphericity and roundness. The changes in the oxygen concentration within the soil column and in the inlet and outlet chambers were monitored. In addition the air pressure at inlet and middle of the soil column was also monitored to ensure the uniform density of porous media along the column. The measured breakthrough curves were fitted with the analytical solution of the advection dispersion equation to determine dispersion coefficients. The measured dispersion coefficient (DH) showed linear increase with pore velocity (u0). Measured dispersivity (λ= DH/u0) increases with decrease in air filled porosity induced by adding moisture contents in sands. Its values varies from 0 to 3 cm on decreasing air filled porosity from 0.50 (air dry) to 0.25 (field capacity). Shape of the sand particles has no significant effect on gas dispersion. When gas dispersion phenomena was studied on different shape of the sand particles at various air filled porosities, it was found that for angular sand particles initially gas dispersivity increases more rapidly as compared to rounded sand particles and finally both attains nearly same values at field capacity. Particle size has no significant effect on gas dispersion but particle size distribution has considerable effect on it. For the same sand when a coefficient of uniformity (Uc) increases from 1 to 4, gas dispersivity increases by 1.5 times. Gas dispersion coefficient was measured with two different sized columns and it was found that there is no effect of diameter and length of the column on gas dispersion for sandy soils. Therefore it can be concluded that only air filled porosity and particle size distribution should be considered for modeling the gas dispersivity in porous media.

A study of gas flow pattern, undercutting and torch modification in variable polarity plasma arc welding

NASA Technical Reports Server (NTRS)

Mcclure, John C.; Hou, Haihui Ron

1994-01-01

A study on the plasma and shield gas flow patterns in variable polarity plasma arc (VPPA) welding was undertaken by shadowgraph techniques. Visualization of gas flow under different welding conditions was obtained. Undercutting is often present with aluminum welds. The effects of torch alignment, shield gas flow rate and gas contamination on undercutting were investigated and suggestions made to minimize the defect. A modified shield cup for the welding torch was fabricated which consumes much less shield gas while maintaining the weld quality. The current torch was modified with a trailer flow for Al-Li welding, in which hot cracking is a critical problem. The modification shows improved weldablility on these alloys.

Multi-period natural gas market modeling Applications, stochastic extensions and solution approaches

NASA Astrophysics Data System (ADS)

Egging, Rudolf Gerardus

This dissertation develops deterministic and stochastic multi-period mixed complementarity problems (MCP) for the global natural gas market, as well as solution approaches for large-scale stochastic MCP. The deterministic model is unique in the combination of the level of detail of the actors in the natural gas markets and the transport options, the detailed regional and global coverage, the multi-period approach with endogenous capacity expansions for transportation and storage infrastructure, the seasonal variation in demand and the representation of market power according to Nash-Cournot theory. The model is applied to several scenarios for the natural gas market that cover the formation of a cartel by the members of the Gas Exporting Countries Forum, a low availability of unconventional gas in the United States, and cost reductions in long-distance gas transportation. 1 The results provide insights in how different regions are affected by various developments, in terms of production, consumption, traded volumes, prices and profits of market participants. The stochastic MCP is developed and applied to a global natural gas market problem with four scenarios for a time horizon until 2050 with nineteen regions and containing 78,768 variables. The scenarios vary in the possibility of a gas market cartel formation and varying depletion rates of gas reserves in the major gas importing regions. Outcomes for hedging decisions of market participants show some significant shifts in the timing and location of infrastructure investments, thereby affecting local market situations. A first application of Benders decomposition (BD) is presented to solve a large-scale stochastic MCP for the global gas market with many hundreds of first-stage capacity expansion variables and market players exerting various levels of market power. The largest problem solved successfully using BD contained 47,373 variables of which 763 first-stage variables, however using BD did not result in shorter solution times relative to solving the extensive-forms. Larger problems, up to 117,481 variables, were solved in extensive-form, but not when applying BD due to numerical issues. It is discussed how BD could significantly reduce the solution time of large-scale stochastic models, but various challenges remain and more research is needed to assess the potential of Benders decomposition for solving large-scale stochastic MCP. 1 www.gecforum.org

Optimal sensor locations for the backward Lagrangian stochastic technique in measuring lagoon gas emission

USDA-ARS?s Scientific Manuscript database

This study evaluated the impact of gas concentration and wind sensor locations on the accuracy of the backward Lagrangian stochastic inverse-dispersion technique (bLS) for measuring gas emission rates from a typical lagoon environment. Path-integrated concentrations (PICs) and 3-dimensional (3D) wi...

Laboratory investigation of the factors impact on bubble size, pore blocking and enhanced oil recovery with aqueous Colloidal Gas Aphron.

PubMed

Shi, Shenglong; Wang, Yefei; Li, Zhongpeng; Chen, Qingguo; Zhao, Zenghao

Colloidal Gas Aphron as a mobility control in enhanced oil recovery is becoming attractive; it is also designed to block porous media with micro-bubbles. In this paper, the effects of surfactant concentration, polymer concentration, temperature and salinity on the bubble size of the Colloidal Gas Aphron were studied. Effects of injection rates, Colloidal Gas Aphron fluid composition, heterogeneity of reservoir on the resistance to the flow of Colloidal Gas Aphron fluid through porous media were investigated. Effects of Colloidal Gas Aphron fluid composition and temperature on residual oil recovery were also studied. The results showed that bubble growth rate decreased with increasing surfactant concentration, polymer concentration, and decreasing temperature, while it decreased and then increased slightly with increasing salinity. The obvious increase of injection pressure was observed as more Colloidal Gas Aphron fluid was injected, indicating that Colloidal Gas Aphron could block the pore media effectively. The effectiveness of the best blend obtained through homogeneous sandpack flood tests was modestly improved in the heterogeneous sandpack. The tertiary oil recovery increased 26.8 % by Colloidal Gas Aphron fluid as compared to 20.3 % by XG solution when chemical solution of 1 PV was injected into the sandpack. The maximum injected pressure of Colloidal Gas Aphron fluid was about three times that of the XG solution. As the temperature increased, the Colloidal Gas Aphron fluid became less stable; the maximum injection pressure and tertiary oil recovery of Colloidal Gas Aphron fluid decreased.

Kinetics of binary nucleation of vapors in size and composition space.

PubMed

Fisenko, Sergey P; Wilemski, Gerald

2004-11-01

We reformulate the kinetic description of binary nucleation in the gas phase using two natural independent variables: the total number of molecules g and the molar composition x of the cluster. The resulting kinetic equation can be viewed as a two-dimensional Fokker-Planck equation describing the simultaneous Brownian motion of the clusters in size and composition space. Explicit expressions for the Brownian diffusion coefficients in cluster size and composition space are obtained. For characterization of binary nucleation in gases three criteria are established. These criteria establish the relative importance of the rate processes in cluster size and composition space for different gas phase conditions and types of liquid mixtures. The equilibrium distribution function of the clusters is determined in terms of the variables g and x. We obtain an approximate analytical solution for the steady-state binary nucleation rate that has the correct limit in the transition to unary nucleation. To further illustrate our description, the nonequilibrium steady-state cluster concentrations are found by numerically solving the reformulated kinetic equation. For the reformulated transient problem, the relaxation or induction time for binary nucleation was calculated using Galerkin's method. This relaxation time is affected by processes in both size and composition space, but the contributions from each process can be separated only approximately.

Dispersion in deep polar firn driven by synoptic-scale surface pressure variability

NASA Astrophysics Data System (ADS)

Buizert, Christo; Severinghaus, Jeffrey P.

2016-09-01

Commonly, three mechanisms of firn air transport are distinguished: molecular diffusion, advection, and near-surface convective mixing. Here we identify and describe a fourth mechanism, namely dispersion driven by synoptic-scale surface pressure variability (or barometric pumping). We use published gas chromatography experiments on firn samples to derive the along-flow dispersivity of firn, and combine this dispersivity with a dynamical air pressure propagation model forced by surface air pressure time series to estimate the magnitude of dispersive mixing in the firn. We show that dispersion dominates mixing within the firn lock-in zone. Trace gas concentrations measured in firn air samples from various polar sites confirm that dispersive mixing occurs. Including dispersive mixing in a firn air transport model suggests that our theoretical estimates have the correct order of magnitude, yet may overestimate the true dispersion. We further show that strong barometric pumping, such as at the Law Dome site, may reduce the gravitational enrichment of δ15N-N2 and other tracers below gravitational equilibrium, questioning the traditional definition of the lock-in depth as the depth where δ15N enrichment ceases. Last, we propose that 86Kr excess may act as a proxy for past synoptic activity (or paleo-storminess) at the site.

Gas hydrate in seafloor sediments: Impact on future resources and drilling safety

USGS Publications Warehouse

Dillon, William P.; Max, Michael D.

2001-01-01

Gas hydrate concentrates methane and sometimes other gases in its crystal lattice and this gas can be released intentionally creating a resource or escape accidentally forming a hazard. The densest accumulations of gas hydrate tend to occur at sites where the base of the gas hydrate stability zone (commonly the upper several hundred m of the sedimentary section) is configured to trap gas, often as a broad arch. The gas may rise from below or form by bacterial activity at shallow depth, but gas commonly is concentrated near the base of the gas hydrate stability zone by recycling. This gas accumulates in presumably leaky traps, then enriches the hydrate above as it migrates upward by diffusion, fluid movement through sedimentary pores, or flow along fracture channelways. Analysis of seismic reflection profiles is beginning to identify such concentrations and the circumstances that create them. The first attempt to explore for gas hydrate off Japan by the Japanese National Oil Corporation produced quite favorable results, showing high gas hydrate contents in permeable sediments. Gas hydrate dissociation can be a safety concern in drilling and production. The volume of water and gas released in dissociation is often greater than the volume of the hydrate, so overpressures can be created. Furthermore, the gas hydrate can provide shallow seals, so the possibility of high-pressure flows or generation of slides is apparent. 

The effect of dry and wet deposition of condensable vapors on secondary organic aerosols concentrations over the continental US

DOE PAGES

Knote, C.; Hodzic, A.; Jimenez, J. L.

2015-01-06

The effect of dry and wet deposition of semi-volatile organic compounds (SVOCs) in the gas phase on the concentrations of secondary organic aerosol (SOA) is reassessed using recently derived water solubility information. The water solubility of SVOCs was implemented as a function of their volatility distribution within the WRF-Chem regional chemistry transport model, and simulations were carried out over the continental United States for the year 2010. Results show that including dry and wet removal of gas-phase SVOCs reduces annual average surface concentrations of anthropogenic and biogenic SOA by 48 and 63% respectively over the continental US. Dry deposition ofmore » gas-phase SVOCs is found to be more effective than wet deposition in reducing SOA concentrations (−40 vs. −8% for anthropogenics, and −52 vs. −11% for biogenics). Reductions for biogenic SOA are found to be higher due to the higher water solubility of biogenic SVOCs. The majority of the total mass of SVOC + SOA is actually deposited via the gas phase (61% for anthropogenics and 76% for biogenics). Results are sensitive to assumptions made in the dry deposition scheme, but gas-phase deposition of SVOCs remains crucial even under conservative estimates. Considering reactivity of gas-phase SVOCs in the dry deposition scheme was found to be negligible. Further sensitivity studies where we reduce the volatility of organic matter show that consideration of gas-phase SVOC removal still reduces average SOA concentrations by 31% on average. We consider this a lower bound for the effect of gas-phase SVOC removal on SOA concentrations. A saturation effect is observed for Henry's law constants above 10 8 M atm −1, suggesting an upper bound of reductions in surface level SOA concentrations by 60% through removal of gas-phase SVOCs. Other models that do not consider dry and wet removal of gas-phase SVOCs would hence overestimate SOA concentrations by roughly 50%. Assumptions about the water solubility of SVOCs made in some current modeling systems ( H * = H * (CH 3COOH); H * = 10 5 M atm −1; H * = H * (HNO 3)) still lead to an overestimation of 35%/25%/10% compared to our best estimate.« less

Hydrogen peroxide ingestion associated with portal venous gas and treatment with hyperbaric oxygen: a case series and review of the literature.

PubMed

French, Loren Keith; Horowitz, B Zane; McKeown, Nathanael J

2010-07-01

Ingestion of concentrated hydrogen peroxide (H(2)O(2)) has been associated with venous and arterial gas embolic events, hemorrhagic gastritis, gastrointestinal bleeding, shock, and death. Although H(2)O(2) is generally considered a benign ingestion in low concentrations, case reports have described serious toxicity following high concentration exposures. Hyperbaric oxygen (HBO) has been used with success in managing patients suffering from gas embolism with and without manifestations of ischemia. Poison center records were searched from July 1999 to January 2010 for patients with H(2)O(2) exposure and HBO treatment. Cases were reviewed for the concentration of H(2)O(2), symptoms, CT scan findings of portal gas embolism, HBO treatment, and outcome. RESULTS; Eleven cases of portal gas embolism were found. Ages ranged from 4 to 89 years. All but one ingestion was accidental in nature. In 10 cases 35% H(2)O(2) was ingested and in 1 case 12% H(2)O(2) was ingested. All abdominal CT scans demonstrated portal venous gas embolism in all cases. Hyperbaric treatment was successful in completely resolving all portal venous gas bubbles in nine patients (80%) and nearly resolving them in two others. Ten patients were able to be discharged home within 1 day, and one patient had a 3.5-day length of stay. HBO was successful in resolving portal venous gas embolism from accidental concentrated H(2)O(2) ingestions.

Evaluation of software sensors for on-line estimation of culture conditions in an Escherichia coli cultivation expressing a recombinant protein.

PubMed

Warth, Benedikt; Rajkai, György; Mandenius, Carl-Fredrik

2010-05-03

Software sensors for monitoring and on-line estimation of critical bioprocess variables have mainly been used with standard bioreactor sensors, such as electrodes and gas analyzers, where algorithms in the software model have generated the desired state variables. In this article we propose that other on-line instruments, such as NIR probes and on-line HPLC, should be used to make more reliable and flexible software sensors. Five software sensor architectures were compared and evaluated: (1) biomass concentration from an on-line NIR probe, (2) biomass concentration from titrant addition, (3) specific growth rate from titrant addition, (4) specific growth rate from the NIR probe, and (5) specific substrate uptake rate and by-product rate from on-line HPLC and NIR probe signals. The software sensors were demonstrated on an Escherichia coli cultivation expressing a recombinant protein, green fluorescent protein (GFP), but the results could be extrapolated to other production organisms and product proteins. We conclude that well-maintained on-line instrumentation (hardware sensors) can increase the potential of software sensors. This would also strongly support the intentions with process analytical technology and quality-by-design concepts. 2010 Elsevier B.V. All rights reserved.

Geologic implications of gas hydrates in the offshore of India: results of the National Gas Hydrate Program Expedition 01

USGS Publications Warehouse

Collett, Timothy S.; Boswell, Ray; Cochran, J.R.; Kumar, Pushpendra; Lall, Malcolm; Mazumdar, Aninda; Ramana, Mangipudi Venkata; Ramprasad, Tammisetti; Riedel, Michael; Sain, Kalachand; Sathe, Arun Vasant; Vishwanath, Krishna

2014-01-01

One of the specific objectives of this expedition was to test gas hydrate formation models and constrain model parameters, especially those that account for the formation of concentrated gas hydrate accumulations. The necessary data for characterizing the occurrence of in situ gas hydrate, such as interstitial water chlorinities, core-derived gas chemistry, physical and sedimentological properties, thermal images of the recovered cores, and downhole measured logging data (LWD and/or conventional wireline log data), were obtained from most of the drill sites established during NGHP-01. Almost all of the drill sites yielded evidence for the occurrence of gas hydrate; however, the inferred in situ concentration of gas hydrate varied substantially from site to site. For the most part, the interpretation of downhole logging data, core thermal images, interstitial water analyses, and pressure core images from the sites drilled during NGHP-01 indicate that the occurrence of concentrated gas hydrate is mostly associated with the presence of fractures in the sediments, and in some limited cases, by coarser grained (mostly sand-rich) sediments.

Models for Gas Hydrate-Bearing Sediments Inferred from Hydraulic Permeability and Elastic Velocities

USGS Publications Warehouse

Lee, Myung W.

2008-01-01

Elastic velocities and hydraulic permeability of gas hydrate-bearing sediments strongly depend on how gas hydrate accumulates in pore spaces and various gas hydrate accumulation models are proposed to predict physical property changes due to gas hydrate concentrations. Elastic velocities and permeability predicted from a cementation model differ noticeably from those from a pore-filling model. A nuclear magnetic resonance (NMR) log provides in-situ water-filled porosity and hydraulic permeability of gas hydrate-bearing sediments. To test the two competing models, the NMR log along with conventional logs such as velocity and resistivity logs acquired at the Mallik 5L-38 well, Mackenzie Delta, Canada, were analyzed. When the clay content is less than about 12 percent, the NMR porosity is 'accurate' and the gas hydrate concentrations from the NMR log are comparable to those estimated from an electrical resistivity log. The variation of elastic velocities and relative permeability with respect to the gas hydrate concentration indicates that the dominant effect of gas hydrate in the pore space is the pore-filling characteristic.

Membrane loop process for separating carbon dioxide for use in gaseous form from flue gas

DOEpatents

Wijmans, Johannes G; Baker, Richard W; Merkel, Timothy C

2014-10-07

The invention is a process involving membrane-based gas separation for separating and recovering carbon dioxide emissions from combustion processes in partially concentrated form, and then transporting the carbon dioxide and using or storing it in a confined manner without concentrating it to high purity. The process of the invention involves building up the concentration of carbon dioxide in a gas flow loop between the combustion step and a membrane separation step. A portion of the carbon dioxide-enriched gas can then be withdrawn from this loop and transported, without the need to liquefy the gas or otherwise create a high-purity stream, to a destination where it is used or confined, preferably in an environmentally benign manner.

Process for hydrogen isotope concentration between liquid water and hydrogen gas

DOEpatents

Stevens, William H.

1976-09-21

A process for hydrogen isotope exchange and concentration between liquid water and hydrogen gas, wherein liquid water and hydrogen gas are contacted, in an exchange section, with one another and with at least one catalyst body comprising at least one metal selected from Group VIII of the Periodic Table and preferably a support therefor, the catalyst body has a liquid-water-repellent, gas permeable polymer or organic resin coating, preferably a fluorinated olefin polymer or silicone coating, so that the isotope concentration takes place by two simultaneously occurring steps, namely, ##EQU1## WHILE THE HYDROGEN GAS FED TO THE EXCHANGE SECTION IS DERIVED IN A REACTOR VESSEL FROM LIQUID WATER THAT HAS PASSED THROUGH THE EXCHANGE SECTION.

Volumetric direct nuclear pumped laser

NASA Technical Reports Server (NTRS)

Jalufka, N. W.; Hohl, F.; Deyoung, R. J.; Williams, M. D. (Inventor)

1978-01-01

A volumetric direct nuclear pumped laser was developed in which the gas is a mixture of He-3 and a minority gas from the group of argon, krypton, xenon, chlorine and fluorine. The mixture of He-3 and the minority gas produces lasing with a minority gas concentration of from 0.01 to 10 percent argon, 1 percent krypton, 0.01 to 5 percent xenon and small concentrations of chlorine or fluorine.

Impact of radon gas concentration in the aerosoles profile

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

Lukaj, Edmond, E-mail: mondilukaj@yahoo.com; Vila, Floran, E-mail: floranvila@yahoo.com; Mandija, Florian, E-mail: fmandija@yahoo.com

Radon gases relased from building materials and from earth surface are the major responsibility of air ionization. Radon nuclear decay can produce an alpha particle with high energy and Radon progeny. This particle and gamma rays can deliver particles in the air and produce ions with different polarities. This ions, because of induced electric charge, can attach with air aerosols and charge them with their electric charge. The charged aerosols can interact with the other aerosols and ions. Because of this exchange, the air conductivity and the aerosol profiles will change dependently by Radon gas concentration and gamma radiation. Observationsmore » show an increase in concentration of Radon during the night, and a decrease during the daylight time. The Radon gas concentration changed hour by hour can induce aerosol profile to change. This dependency between the aerosol profiles and the Radon gas concentrations is discussed.« less

An inverse radiation model for optical determination of temperature and species concentration: Development and validation

NASA Astrophysics Data System (ADS)

Ren, Tao; Modest, Michael F.; Fateev, Alexander; Clausen, Sønnik

2015-01-01

In this study, we present an inverse calculation model based on the Levenberg-Marquardt optimization method to reconstruct temperature and species concentration from measured line-of-sight spectral transmissivity data for homogeneous gaseous media. The high temperature gas property database HITEMP 2010 (Rothman et al. (2010) [1]), which contains line-by-line (LBL) information for several combustion gas species, such as CO2 and H2O, was used to predict gas spectral transmissivities. The model was validated by retrieving temperatures and species concentrations from experimental CO2 and H2O transmissivity measurements. Optimal wavenumber ranges for CO2 and H2O transmissivity measured across a wide range of temperatures and concentrations were determined according to the performance of inverse calculations. Results indicate that the inverse radiation model shows good feasibility for measurements of temperature and gas concentration.

Semipermeable membrane devices used to estimate bioconcentration of polychlorinated biphenyls

USGS Publications Warehouse

Chambers, D.B.

1999-01-01

Aquatic organisms passively accumulate hydrophobic organic compounds, such as polychlorinated biphenyls, even when ambient water concentrations of the contaminant are below analytical detection limits. However, contaminant concentrations in tissue samples are subject to an inherently high level of variability due to differences in species, life stage, and gender bioconcentration potentials. Semipermeable membrane devices (SPMDs) were used to sample Aroclor 1254, a mixture of readily bioconcentrated polychlorinated biphenyls (PCBs), in a contaminated wetland near Flat Top, WV. The devices consisted of triolein, a lipid found in fish, enclosed in a polyethylene membrane. SPMDs were deployed in the water column and in direct contact with wetland sediments along a previously identified concentration gradient of PCBs. The devices were retrieved after a 25-day exposure period. Analytes were recovered by dialyzing the devices in nanograde hexane. Hexane dialysates were condensed and analyzed by gas chromatography. All deployed devices sequestered quantifiable amounts of Aroclor 1254. Water-column SPMDs accumulated PCBs far in excess of ambient water concentrations. The devices contacting sediments accumulated PCBs at all sites, though accumulated concentrations did not exceed concentrations in sediment. Patterns of PCB concentration in the devices corresponded to the identified gradient at the site. Results from the water-column SPMDs were used to estimate the concentration of the dissolved, bioavailable fraction of PCBs present in the water column. These concentrations ranged from 0.01 to 0.09 ??g/L of bioavailable Aroclor 1254.

A novel approach to scavenging anesthetic gases in rodent surgery.

PubMed

Nesbitt, Jeffrey C; Krageschmidt, Dale A; Blanco, Michael C

2013-01-01

Laboratory animal procedures using gas anesthetics may amass elevated waste gas concentrations in operating rooms if controls are not implemented for capturing and removing the vapors. Area sampling using an infrared analyzer indicated isoflurane concentrations likely to exceed occupational exposure guidelines. Our study showed environmental concentrations of oxygen as high as 40% and isoflurane concentrations >100 ppm when no controls or merely passive controls were utilized. These extraneous isoflurane emissions were determined to be originating from the pre-procedural induction process as well as the gas delivery nose cone. A novel waste gas collection cylinder was designed to enclose the gas delivery nose cone and animal head during the administration of anesthetic gases. The vented cylinder utilized a house vacuum to remove the waste anesthetic gases from the surgical field. A commercially available induction chamber designed to be actively and externally exhausted was used to lower concentrations during the induction process. With implementation of local exhaust ventilation controls, waste anesthetic gas concentrations decreased to below recommended occupational exposure levels. In vitro (sham) testing compared favorably to in vivo measurements validating the reduction capability of active ventilation during rodent anesthetic administration. In vivo isoflurane reductions for the induction chamber emissions, the operating room, and the surgeon's breathing zone were 95%, 60%, and 53%, respectively. The same measurements for an in vitro procedure were 98%, 84%, and 87%, respectively.

Techno-economic Analysis of Acid Gas Removal and Liquefaction for Pressurized LNG

NASA Astrophysics Data System (ADS)

Lee, S. H.; Seo, Y. K.; Chang, D. J.

2018-05-01

This study estimated the life cycle cost (LCC) of an acid gas removal and a liquefaction processes for Pressurized LNG (PLNG) production and compared the results with the cost of normal LNG production. PLNG is pressurized LNG that is liquefied at a higher pressure and temperature than normal LNG. Due to the high temperature, the energy for liquefaction is reduced. The allowable CO2 concentration in PLNG is increased up to 3 mol% when the product pressure 25 bar. An amine process with 35 wt% of diethanolamine (DEA) aqueous solution and a nitrogen expansion cycle were selected for the acid gas removal and the liquefaction processes, respectively. Two types of CO2 concentration in the feed gas were investigated to analyze their impacts on the acid gas removal unit. When the CO2 concentration was 5 mol%, the acid gas removal unit was required for both LNG and PLNG production. However, the acid gas removal unit was not necessary in PLNG when the concentration was 0.5 mol% and the pressure was higher than 15 bar. The results showed that the LCC of PLNG was reduced by almost 35% relative to that of LNG when the PLNG pressure was higher than 15 bar.

FIELD TEST PROGRAM TO DEVELOP COMPREHENSIVE DESIGN, OPERATING, AND COST DATA FOR MERCURY CONTROL SYSTEMS

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

Michael D. Durham

PG&E NEG Salem Harbor Station Unit 1 was successfully tested for applicability of activated carbon injection as a mercury control technology. Test results from this site have enabled a thorough evaluation of mercury control at Salem Harbor Unit 1, including performance, estimated cost, and operation data. This unit has very high native mercury removal, thus it was important to understand the impacts of process variables on native mercury capture. The team responsible for executing this program included plant and PG&E headquarters personnel, EPRI and several of its member companies, DOE, ADA, Norit Americas, Inc., Hamon Research-Cottrell, Apogee Scientific, TRC Environmentalmore » Corporation, Reaction Engineering, as well as other laboratories. The technical support of all of these entities came together to make this program achieve its goals. Overall the objectives of this field test program were to determine the mercury control and balance-of-plant impacts resulting from activated carbon injection into a full-scale ESP on Salem Harbor Unit 1, a low sulfur bituminous-coal-fired 86 MW unit. It was also important to understand the impacts of process variables on native mercury removal (>85%). One half of the gas stream was used for these tests, or 43 MWe. Activated carbon, DARCO FGD supplied by NORIT Americas, was injected upstream of the cold side ESP, just downstream of the air preheater. This allowed for approximately 1.5 seconds residence time in the duct before entering the ESP. Conditions tested in this field evaluation included the impacts of the Selective Non-Catalytic Reduction (SNCR) system on mercury capture, of unburned carbon in the fly ash, of adjusting ESP inlet flue gas temperatures, and of boiler load on mercury control. The field evaluation conducted at Salem Harbor looked at several sorbent injection concentrations at several flue gas temperatures. It was noted that at the mid temperature range of 322-327 F, the LOI (unburned carbon) lost some of its ability to capture vapor phase Hg, however activated carbon performed relatively well. At the normal operating temperatures of 298-306 F, mercury emissions from the ESP were so low that both particulate and elemental mercury were ''not detected'' at the detection limits of the Ontario Hydro method for both baseline and injection tests. The oxidized mercury however, was 95% lower at a sorbent injection concentration of 10 lbs/MMacf compared with baseline emissions. When the flue gas temperatures were increased to a range of 343-347 F, mercury removal efficiencies were limited to <25%, even at the same sorbent injection concentration. Other tests examined the impacts of fly ash LOI, operation of the SNCR system, and flue gas temperature on the native mercury capture without sorbent injection. Listed below are the main conclusions from this program: (1) SNCR on/off test showed no beneficial effect on mercury removal caused by the SNCR system. (2) At standard operating temperatures ({approx} 300 F), reducing LOI from 30-35% to 15-20% had minimal impact on Hg removal. (3) Increasing flue gas temperatures reduced Hg removal regardless of LOI concentrations at Salem Harbor (minimum LOI was 15%). Native mercury removal started to fall off at temperatures above 320 F. ACI effectiveness for mercury removal fell off at temperatures above 340 F. (4) Test method detection limits play an important role at Salem Harbor due to the low residual emissions. Examining the proposed MA rule, both the removal efficiency and the emission concentrations will be difficult to demonstrate on an ongoing basis. (5) Under tested conditions the baseline emissions met the proposed removal efficiency for 2006, but not the proposed emission concentration. ACI can meet the more-stringent 2012 emission limits, as long as measurement detection limits are lower than the Ontario Hydro method. SCEM testing was able to verify the low emissions. For ACI to perform at this level, process conditions need to match those obtained during testing.« less

Use of a turbine in a breath-by-breath computer-based respiratory measurement system.

PubMed

Venkateswaran, R S; Gallagher, R R

1997-01-01

The Computer-Based Respiratory Measurement System (CBRMS) is capable of analyzing individual breaths to monitor the kinetics of oxygen uptake, carbon dioxide production, tidal volumes, pulmonary ventilation, and other respiratory parameters during rest, exercise, and recovery. Respiratory gas volumes are measured by a calibrated turbine transducer while the respiratory gas concentrations are measured by a calibrated, fast-responding medical gas analyzer. To improve accuracy of the results, the inspiratory volumes and gas concentrations are measured and not assumed to be equal to expiratory volumes or ambient concentrations respectively. The respiratory gas volumes and concentration signals are digitized and stored in arrays. The gas volumes are converted to flow signals by software differentiation. These digitized data arrays are stored as files in a personal computer. Time alignment of the flow and gas concentration signals is performed at each breath for maximum accuracy in analysis. For system verification, data were obtained under resting conditions and under constant load exercises at 50 W, 100 W, and 150 W. These workloads were performed by a healthy, male subject on a bicycle ergometer. A strong correlation existed between the CBRMS steady-state results and the standard end-expirate bag collection technique. Thus, there is reason to believe that the CBRMS is capable of calculating respiratory transient responses accurately, a significant contribution to an understanding of total respiratory system function.

40 CFR 86.004-28 - Compliance with emission standards.

Code of Federal Regulations, 2010 CFR

2010-07-01

... factor may not be appropriate in cases where testing variability is significantly greater than engine-to-engine variability. Multiplicative deterioration factors must be specified to one more significant figure... regenerations are increasing exhaust gas temperature to remove sulfur from an adsorber or increasing exhaust gas...

Fouling of microfiltration membranes by flowback and produced waters from the Marcellus shale gas play.

PubMed

Xiong, Boya; Zydney, Andrew L; Kumar, Manish

2016-08-01

There is growing interest in possible options for treatment or reuse of flowback and produced waters from natural gas processing. Here we investigated the fouling characteristics during microfiltration of different flowback and produced waters from hydraulic fracturing sites in the Marcellus shale. All samples caused severe and highly variable fouling, although there was no direct correlation between the fouling rate and total suspended solids, turbidity, or total organic carbon. Furthermore, the fouling of water after prefiltration through a 0.2 μm membrane was also highly variable. Low fouling seen with prefiltered water was mainly due to removal of submicron particles 0.4-0.8 μm during prefiltration. High fouling seen with prefiltered water was mainly caused by a combination of hydrophobic organics and colloidal particles <100 nm in size (quantified by transmission electron microscopy) that passed through the prefiltration membranes. The small colloidal particles were highly stable, likely due to the surfactants and other organics present in the fracking fluids. The colloid concentration was as high as 10(11) colloids/ml, which is more than 100 times greater than that in typical seawater. Furthermore, these colloids were only partially removed by MF, causing substantial fouling during a subsequent ultrafiltration. These results clearly show the importance of organics and colloidal material in membrane fouling caused by flowback and produced waters, which is of critical importance in the development of more sustainable treatment strategies in natural gas processing. Copyright © 2016 Elsevier Ltd. All rights reserved.

Geography and the costs of urban energy infrastructure: The case of electricity and natural gas capital investments

NASA Astrophysics Data System (ADS)

Senyel, Muzeyyen Anil

Investments in the urban energy infrastructure for distributing electricity and natural gas are analyzed using (1) property data measuring distribution plant value at the local/tax district level, and (2) system outputs such as sectoral numbers of customers and energy sales, input prices, company-specific characteristics such as average wages and load factor. Socio-economic and site-specific urban and geographic variables, however, often been neglected in past studies. The purpose of this research is to incorporate these site-specific characteristics of electricity and natural gas distribution into investment cost model estimations. These local characteristics include (1) socio-economic variables, such as income and wealth; (2) urban-related variables, such as density, land-use, street pattern, housing pattern; (3) geographic and environmental variables, such as soil, topography, and weather, and (4) company-specific characteristics such as average wages, and load factor. The classical output variables include residential and commercial-industrial customers and sales. In contrast to most previous research, only capital investments at the local level are considered. In addition to aggregate cost modeling, the analysis focuses on the investment costs for the system components: overhead conductors, underground conductors, conduits, poles, transformers, services, street lighting, and station equipment for electricity distribution; and mains, services, regular and industrial measurement and regulation stations for natural gas distribution. The Box-Cox, log-log and additive models are compared to determine the best fitting cost functions. The Box-Cox form turns out to be superior to the other forms at the aggregate level and for network components. However, a linear additive form provides a better fit for end-user related components. The results show that, in addition to output variables and company-specific variables, various site-specific variables are statistically significant at the aggregate and disaggregate levels. Local electricity and natural gas distribution networks are characterized by a natural monopoly cost structure and economies of scale and density. The results provide evidence for the economies of scale and density for the aggregate electricity and natural gas distribution systems. However, distribution components have varying economic characteristics. The backbones of the networks (overhead conductors for electricity, and mains for natural gas) display economies of scale and density, but services in both systems and street lighting display diseconomies of scale and diseconomies of density. Finally multi-utility network cost analyses are presented for aggregate and disaggregate electricity and natural gas capital investments. Economies of scope analyses investigate whether providing electricity and natural gas jointly is economically advantageous, as compared to providing these products separately. Significant economies of scope are observed for both the total network and the underground capital investments.

UV Spectroscopy of Star-Grazing Comets Within the 49 Ceti Debris Disk

NASA Technical Reports Server (NTRS)

Miles, Brittany E.; Roberge, Aki; Welsh, Barry

2016-01-01

We present the analysis of time-variable Doppler-shifted absorption features in far-UV spectra of the unusual 49 Ceti debris disk. This nearly edge-on disk is one of the brightest known and is one of the very few containing detectable amounts of circumstellar (CS) gas as well as dust. In our two visits of Hubble Space Telescope STIS spectra, variable absorption features are seen on the wings of lines arising from CII and CIV but not for any of the other CS absorption lines. Similar variable features have long been seen in spectra of the well-studied Beta Pictoris debris disk and attributed to the transits of star-grazing comets. We calculated the velocity ranges and apparent column densities of the 49 Cet variable gas, which appears to have been moving at velocities of tens to hundreds of kms(-1) relative to the central star. The velocities in the redshifted variable event seen in the second visit show that the maximum distances of the in falling gas at the time of transit were about 0.050.2 au from the central star. A preliminary attempt at a composition analysis of the redshifted event suggests that the C/O ratio in the in falling gas is super-solar, as it is in the bulk of the stable disk gas.

Enhancement of organic matter degradation and methane gas production of anaerobic granular sludge by degasification of dissolved hydrogen gas.

PubMed

Satoh, Hisashi; Bandara, Wasala M K R T W; Sasakawa, Manabu; Nakahara, Yoshihito; Takahashi, Masahiro; Okabe, Satoshi

2017-11-01

A hollow fiber degassing membrane (DM) was applied to enhance organic matter degradation and methane gas production of anaerobic granular sludge process by reducing the dissolved hydrogen gas (D-H 2 ) concentration in the liquid phase. DM was installed in the bench-scale anaerobic granular sludge reactors and D-H 2 was removed through DM using a vacuum pump. Degasification improved the organic matter degradation efficiency to 79% while the efficiency was 62% without degasification at 12,000mgL -1 of the influent T-COD concentration. Measurement of D-H 2 concentrations in the liquid phase confirmed that D-H 2 was removed by degasification. Furthermore, the effect of acetate concentrations on the organic matter degradation efficiency was investigated. At acetate concentrations above 3gL -1 , organic matter degradation deteriorated. Degasification enhanced the propionate and acetate degradation. These results suggest that degasification reduced D-H 2 concentration and volatile fatty acids concentrations, prevented pH drop, and subsequent enhanced organic matter degradation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Argon concentration time-series as a tool to study gas dynamics in the hyporheic zone.

PubMed

Mächler, Lars; Brennwald, Matthias S; Kipfer, Rolf

2013-07-02

The oxygen dynamics in the hyporheic zone of a peri-alpine river (Thur, Switzerland), were studied through recording and analyzing the concentration time-series of dissolved argon, oxygen, carbon dioxide, and temperature during low flow conditions, for a period of one week. The argon concentration time-series was used to investigate the physical gas dynamics in the hyporheic zone. Differences in the transport behavior of heat and gas were determined by comparing the diel temperature evolution of groundwater to the measured concentration of dissolved argon. These differences were most likely caused by vertical heat transport which influenced the local groundwater temperature. The argon concentration time-series were also used to estimate travel times by cross correlating argon concentrations in the groundwater with argon concentrations in the river. The information gained from quantifying the physical gas transport was used to estimate the oxygen turnover in groundwater after water recharge. The resulting oxygen turnover showed strong diel variations, which correlated with the water temperature during groundwater recharge. Hence, the variation in the consumption rate was most likely caused by the temperature dependence of microbial activity.