Science.gov

Sample records for gas tracer studies

  1. Multiple-tracer gas analyzer

    SciTech Connect

    Uhl, J.E.

    1982-01-01

    A multi-gas tracer system has been designed, built, and used on an explosively fractured oil shale rubble bed. This paper deals exclusively with the hardware, software, and overall operation of the tracer system. This system is a field portable, self-contained unit, which utilizes a mass spectrometer for gas analysis. The unit has a 20 channel sample port capability and is controlled by a desk top computer. The system is configured to provide a dynamic sensitivity range of up to six orders of magnitude. A roots blower is manifolded to the unit to provide continuous flow in all sample lines. The continuous flow process allows representative samples as well as decreasing the time between each measurement. Typical multiplex cycle time to evaluate four unique gases is approximately 12 seconds.

  2. PERFLUOROCARBON GAS TRACER STUDIES TO SUPPORT RISK ASSESSMENT MODELING OF CRITICAL INFRASTRUCTURE SUBJECTED TO TERRORIST ATTACKS.

    SciTech Connect

    SULLIVAN, T.M.; HEISER, J.; WATSON, T.; ALLWINE, K.J.; FLAHERTY, J.E.

    2006-05-06

    Development of real-time predictive modeling to identify the dispersion and/or source(s) of airborne weapons of mass destruction including chemical, biological, radiological, and nuclear material in urban environments is needed to improve response to potential releases of these materials via either terrorist or accidental means. These models will also prove useful in defining airborne pollution dispersion in urban environments for pollution management/abatement programs. Predicting gas flow in an urban setting on a scale of less than a few kilometers is a complicated and challenging task due to the irregular flow paths that occur along streets and alleys and around buildings of different sizes and shapes, i.e., ''urban canyons''. In addition, air exchange between the outside and buildings and subway areas further complicate the situation. Transport models that are used to predict dispersion of WMD/CBRN materials or to back track the source of the release require high-density data and need defensible parameterizations of urban processes. Errors in the data or any of the parameter inputs or assumptions will lead to misidentification of the airborne spread or source release location(s). The need for these models to provide output in a real-time fashion if they are to be useful for emergency response provides another challenge. To improve the ability of New York City's (NYC's) emergency management teams and first response personnel to protect the public during releases of hazardous materials, the New York City Urban Dispersion Program (UDP) has been initiated. This is a four year research program being conducted from 2004 through 2007. This paper will discuss ground level and subway Perfluorocarbon tracer (PFT) release studies conducted in New York City. The studies released multiple tracers to study ground level and vertical transport of contaminants. This paper will discuss the results from these tests and how these results can be used for improving transport models

  3. A pilot study of the behavior of gas- and particle-phase ETS tracers in residences

    SciTech Connect

    Apte, Michael; Gundel, Lara; Dod, Raymond; Chang, Gee-Min; Sextro, Richard

    2002-02-01

    Our previous study of environmental tobacco smoke (ETS) in a three-room environmental chamber showed that smoking history significantly influenced inter-room ETS transport, particularly of gas-phase nicotine. We conducted a three-home pilot study where smoking was limited to one room. Single-smoker residences were monitored during five one-week periods while the smoker participated in a smoking cessation program. Nicotine traced ETS particles were detected reliably in the smoking rooms (SRs) and unreliably in the non-smoking rooms (NSRs). On average, the ventilation- and volume-normalized smoking rate, 0.1 Cigarette-h{sup -1} m{sup -3}, added about 17 and 4 {micro}g m{sup -3} of ETS particles into the SR and NSR, while average nicotine concentration increases were 2 and 0.06 {micro}g m{sup -3}, respectively. Thus, nicotine tracers may underestimate ETS particle exposure in a NSR (e.g., a child's bedroom) by a factor of 2 to 8. In other words, ETS exposure predicted from nicotine concentrations could be almost an order of magnitude lower than actual exposure.

  4. Quantifying capture efficiency of gas collection wells with gas tracers.

    PubMed

    Yazdani, Ramin; Imhoff, Paul; Han, Byunghyun; Mei, Changen; Augenstein, Don

    2015-09-01

    A new in situ method for directly measuring the gas collection efficiency in the region around a gas extraction well was developed. Thirteen tests were conducted by injecting a small volume of gas tracer sequentially at different locations in the landfill cell, and the gas tracer mass collected from each test was used to assess the collection efficiency at each injection point. For 11 tests the gas collection was excellent, always exceeding 70% with seven tests showing a collection efficiency exceeding 90%. For one test the gas collection efficiency was 8±6%. Here, the poor efficiency was associated with a water-laden refuse or remnant daily cover soil located between the point of tracer injection and the extraction well. The utility of in situ gas tracer tests for quantifying landfill gas capture at particular locations within a landfill cell was demonstrated. While there are certainly limitations to this technology, this method may be a valuable tool to help answer questions related to landfill gas collection efficiency and gas flow within landfills. Quantitative data from tracer tests may help assess the utility and cost-effectiveness of alternative cover systems, well designs and landfill gas collection management practices.

  5. Novel tracer method to measure isotopic labeled gas-phase nitrous acid (HO15NO) in biogeochemical studies.

    PubMed

    Wu, Dianming; Kampf, Christopher J; Pöschl, Ulrich; Oswald, Robert; Cui, Junfang; Ermel, Michael; Hu, Chunsheng; Trebs, Ivonne; Sörgel, Matthias

    2014-07-15

    Gaseous nitrous acid (HONO), the protonated form of nitrite, contributes up to ∼60% to the primary formation of hydroxyl radical (OH), which is a key oxidant in the degradation of most air pollutants. Field measurements and modeling studies indicate a large unknown source of HONO during daytime. Here, we developed a new tracer method based on gas-phase stripping-derivatization coupled to liquid chromatography-mass spectrometry (LC-MS) to measure the 15N relative exceedance, ψ(15N), of HONO in the gas-phase. Gaseous HONO is quantitatively collected and transferred to an azo dye, purified by solid phase extraction (SPE), and analyzed using high performance liquid chromatography coupled to mass spectrometry (HPLC-MS). In the optimal working range of ψ(15N)=0.2-0.5, the relative standard deviation of ψ(15N) is <4%. The optimum pH and solvents for extraction by SPE and potential interferences are discussed. The method was applied to measure HO15NO emissions from soil in a dynamic chamber with and without spiking 15) labeled urea. The identification of HO15NO from soil with 15N urea addition confirmed biogenic emissions of HONO from soil. The method enables a new approach of studying the formation pathways of HONO and its role for atmospheric chemistry (e.g., ozone formation) and environmental tracer studies on the formation and conversion of gaseous HONO or aqueous NO2- as part of the biogeochemical nitrogen cycle, e.g., in the investigation of fertilization effects on soil HONO emissions and microbiological conversion of NO2- in the hydrosphere.

  6. Exotic tracers for atmospheric studies

    NASA Astrophysics Data System (ADS)

    Lovelock, James E.; Ferber, Gilbert J.

    Tracer materials can be injected into the atmosphere to study transport and dispersion processes and to validate air pollution model calculations. Tracers should be inert, non-toxic and harmless to the environment. Tracers for long-range experiments, where dilution is very great, must be measurable at extremely low concentrations, well below the parts per trillion level. Compounds suitable for long-range tracer work are rare and efforts should be made to reserve them for meteorological studies, barring them from commercial uses which would increase atmospheric background concentrations. The use of these exotic tracers, including certain perfluorocarbons and isotopically labelled methanes, should be coordinated within the meteorological community to minimize interferences and maximize research benefits.

  7. Tracer Simulation Study.

    DTIC Science & Technology

    1972-04-01

    32 3. Measurement of Ignition Time ......... . . ... 34 4. Relative Reflectance Measurement .... ............ . 36 5. Laser...most reflective. Conversely, the same anomaly that was true for the laser ignition performance and for ignition energy was also true for the reflectance ... measurement ; the best weapon performance lot was not the least reflective. The use of the laser for igniting spinning tracer bullets is a practical

  8. Applied gas tracers for subsurface and surface hydrology

    NASA Astrophysics Data System (ADS)

    Elliot, T.; Kalin, R. M.; MacKinnon, P. A.; McNeill, G. W.; Murphy, J. L.

    2003-04-01

    Tracer methods can be broadly taken to be techniques for obtaining information about an environmental and/or engineering system or some part of a system (eg transit times in media, permeability, dispersivity, internal structure, subsurface activities, etc.) by observing the behaviour of a specific substance (natural or anthropogenic) either injected into or inherently added within that system. Recent studies at QUB have focussed on applied tracer methods using dissolved inert gases both as geochemically conservative tracers in groundwater systems (providing structural information, flow-paths, transit times, physical transport properties) and also as non-conservative, bulk partitioning agents to determine re-aeration coefficients (K_2 values) in surface stream systems or for characterising the presence and extent of nonaqueous phases in subsurface groundwater systems (eg NAPLs at contaminated land sites). Noble gas applications as applied tracers particularly are being investigated because of their low natural background levels and high sensitivity of determination (by GC-MS), and lack of any taste, odour, colour and toxicity problems -- these latter properties suggesting a more "environmentally-friendly" type of tracer either to protect potable water (eg public) supplies under investigation or so as not to impact intrinsic reactive processes in the system being traced. Both laboratory column investigations and field studies are presented, emphasising the utility of applied gas tracing for hydrological investigations. Mackinnon, P.A., Elliot, T., Zhao, Y.Q., Murphy, J.L. &Kalin, R.M. (2002) Evaluation of a novel technique for measuring reaeration in rivers. In C.A. Brebbia, P. Zanetti (Eds.) Development and Application of Computer Techniques to Environmental Studies IX. WIT Press, Southampton, UK. pp.531--540. McNeill, G.W., Yang, Y.S., Elliot, T., Kalin, R.M. (2001) Krypton gas as a novel applied tracer of groundwater flow in a fissured sandstone aquifer. In K

  9. A case study of the Weather Research and Forecasting model applied to the Joint Urban 2003 tracer field experiment. Part 2: Gas tracer dispersion

    SciTech Connect

    Nelson, Matthew A.; Brown, Michael J.; Halverson, Scot A.; Bieringer, Paul E.; Annunzio, Andrew; Bieberbach, George; Meech, Scott

    2016-07-28

    Here, the Quick Urban & Industrial Complex (QUIC) atmospheric transport, and dispersion modelling, system was evaluated against the Joint Urban 2003 tracer-gas measurements. This was done using the wind and turbulence fields computed by the Weather Research and Forecasting (WRF) model. We compare the simulated and observed plume transport when using WRF-model-simulated wind fields, and local on-site wind measurements. Degradation of the WRF-model-based plume simulations was cased by errors in the simulated wind direction, and limitations in reproducing the small-scale wind-field variability. We explore two methods for importing turbulence from the WRF model simulations into the QUIC system. The first method uses parametrized turbulence profiles computed from WRF-model-computed boundary-layer similarity parameters; and the second method directly imports turbulent kinetic energy from the WRF model. Using the WRF model’s Mellor-Yamada-Janjic boundary-layer scheme, the parametrized turbulence profiles and the direct import of turbulent kinetic energy were found to overpredict and underpredict the observed turbulence quantities, respectively. Near-source building effects were found to propagate several km downwind. These building effects and the temporal/spatial variations in the observed wind field were often found to have a stronger influence over the lateral and vertical plume spread than the intensity of turbulence. Correcting the WRF model wind directions using a single observational location improved the performance of the WRF-model-based simulations, but using the spatially-varying flow fields generated from multiple observation profiles generally provided the best performance.

  10. A case study of the Weather Research and Forecasting model applied to the Joint Urban 2003 tracer field experiment. Part 2: Gas tracer dispersion

    DOE PAGES

    Nelson, Matthew A.; Brown, Michael J.; Halverson, Scot A.; ...

    2016-07-28

    Here, the Quick Urban & Industrial Complex (QUIC) atmospheric transport, and dispersion modelling, system was evaluated against the Joint Urban 2003 tracer-gas measurements. This was done using the wind and turbulence fields computed by the Weather Research and Forecasting (WRF) model. We compare the simulated and observed plume transport when using WRF-model-simulated wind fields, and local on-site wind measurements. Degradation of the WRF-model-based plume simulations was cased by errors in the simulated wind direction, and limitations in reproducing the small-scale wind-field variability. We explore two methods for importing turbulence from the WRF model simulations into the QUIC system. The firstmore » method uses parametrized turbulence profiles computed from WRF-model-computed boundary-layer similarity parameters; and the second method directly imports turbulent kinetic energy from the WRF model. Using the WRF model’s Mellor-Yamada-Janjic boundary-layer scheme, the parametrized turbulence profiles and the direct import of turbulent kinetic energy were found to overpredict and underpredict the observed turbulence quantities, respectively. Near-source building effects were found to propagate several km downwind. These building effects and the temporal/spatial variations in the observed wind field were often found to have a stronger influence over the lateral and vertical plume spread than the intensity of turbulence. Correcting the WRF model wind directions using a single observational location improved the performance of the WRF-model-based simulations, but using the spatially-varying flow fields generated from multiple observation profiles generally provided the best performance.« less

  11. A Case Study of the Weather Research and Forecasting Model Applied to the Joint Urban 2003 Tracer Field Experiment. Part 2: Gas Tracer Dispersion

    NASA Astrophysics Data System (ADS)

    Nelson, Matthew A.; Brown, Michael J.; Halverson, Scot A.; Bieringer, Paul E.; Annunzio, Andrew; Bieberbach, George; Meech, Scott

    2016-12-01

    The Quick Urban & Industrial Complex (QUIC) atmospheric transport, and dispersion modelling, system was evaluated against the Joint Urban 2003 tracer-gas measurements. This was done using the wind and turbulence fields computed by the Weather Research and Forecasting (WRF) model. We compare the simulated and observed plume transport when using WRF-model-simulated wind fields, and local on-site wind measurements. Degradation of the WRF-model-based plume simulations was cased by errors in the simulated wind direction, and limitations in reproducing the small-scale wind-field variability. We explore two methods for importing turbulence from the WRF model simulations into the QUIC system. The first method uses parametrized turbulence profiles computed from WRF-model-computed boundary-layer similarity parameters; and the second method directly imports turbulent kinetic energy from the WRF model. Using the WRF model's Mellor-Yamada-Janjic boundary-layer scheme, the parametrized turbulence profiles and the direct import of turbulent kinetic energy were found to overpredict and underpredict the observed turbulence quantities, respectively. Near-source building effects were found to propagate several km downwind. These building effects and the temporal/spatial variations in the observed wind field were often found to have a stronger influence over the lateral and vertical plume spread than the intensity of turbulence. Correcting the WRF model wind directions using a single observational location improved the performance of the WRF-model-based simulations, but using the spatially-varying flow fields generated from multiple observation profiles generally provided the best performance.

  12. Following Footsteps: ECD Tracer Studies.

    ERIC Educational Resources Information Center

    Smale, Jim, Editor

    2002-01-01

    This document consists of the single 2002 issue of The Bernard van Leer Foundation's "Early Childhood Matters," a periodical addressed to practitioners in the field of early childhood education and including information on projects funded by the Foundation. Articles in this issue focus on early childhood development tracer studies of…

  13. Field measurements of tracer gas transport by barometric pumping

    SciTech Connect

    Lagus, P.L.; McKinnis, W.B.; Hearst, J.R.; Burkhard, N.R.; Smith, C.F.

    1994-07-28

    Vertical gas motions induced by barometric pressure variations can carry radioactive gases out of the rubblized region produced by an underground nuclear explosion, through overburden rock, into the atmosphere. To better quantify transit time and amount of transport, field experiments were conducted at two sites on Pahute Mesa, Kapelli and Tierra, where radioactive gases had been earlier detected in surface cracks. At each site, two tracer gases were injected into the rubblized chimney 300-400 m beneath the surface and their arrival was monitored by concentration measurements in gas samples extracted from shallow collection holes. The first ``active`` tracer was driven by a large quantity of injected air; the second ``passive`` tracer was introduced with minimal gas drive to observe the natural transport by barometric pumping. Kapelli was injected in the fall of 1990, followed by Tierra in the fall of 1991. Data was collected at both sites through the summer of 1993. At both sites, no surface arrival of tracer was observed during the active phase of the experiment despite the injection of several million cubic feet of air, suggesting that cavity pressurization is likely to induce horizontal transport along high permeability layers rather than vertical transport to the surface. In contrast, the vertical pressure gradients associated with barometric pumping brought both tracers to the surface in comparable concentrations within three months at Kapelli, whereas 15 months elapsed before surface arrival at Tierra. At Kapelli, a quasisteady pumping regime was established, with tracer concentrations in effluent gases 1000 times smaller than concentrations thought to exist in the chimney. Tracer concentrations observed at Tierra were typically an order of magnitude smaller. Comparisons with theoretical calculations suggest that the gases are traveling through {approximately}1 millimeter vertical fractures spaced 2 to 4 meters apart. 6 refs., 18 figs., 3 tabs.

  14. Partitioning Gas Tracer Technology for Measuring Water in Landfills

    NASA Astrophysics Data System (ADS)

    Briening, M. L.; Jakubowitch, A.; Imhoff, P. T.; Chiu, P. C.; Tittlebaum, M. E.

    2002-12-01

    Unstable landfills can result in significant environmental contamination and can become a risk to public health. To reduce this risk, water may be added to landfills to ensure that enough moisture exists for biodegradation of organic wastes. In this case risks associated with future breaks in the landfill cap are significantly reduced because organic material is degraded more rapidly. To modify moisture conditions and enhance biodegradation, leachate is typically collected from the bottom of the landfill and then recirculated near the top. It is difficult, though, to know how much leachate to add and where to add it to achieve uniform moisture conditions. This situation is exacerbated by the heterogeneous nature of landfill materials, which is known to cause short circuiting of infiltrating water, a process that has been virtually impossible to measure or model. Accurate methods for measuring the amount of water in landfills would be valuable aids for implementing leachate recirculation systems. Current methods for measuring water are inadequate, though, since they provide point measurements and are frequently affected by heterogeneity of the solid waste composition and solid waste compaction. The value of point measurements is significantly reduced in systems where water flows preferentially, such as in landfills. Here, spatially integrated measurements might be of greater value. In this research we are evaluating a promising technology, the partitioning gas tracer test, to measure the water saturation within landfills, the amount of free water in solid waste divided by the volume of the voids. The partitioning gas tracer test was recently developed by researchers working in the vadose zone. In this methodology two gas tracers are injected into a landfill. One tracer is non-reactive with landfill materials, while the second partitions into and out of free water trapped within the pore space of the solid waste. Chromatographic separation of the tracers occurs

  15. Measuring Greenhouse-Gas Emissions from a Synthetic Tracer Source

    NASA Astrophysics Data System (ADS)

    Wang, W.; Liu, W.; Zhang, T.; Lu, Y.

    2014-05-01

    This paper describes a controlled tracer-release experiment in which methane was released from a synthetic source at known rates. An open-path Fourier transform infrared (OP-FTIR) spectroscopy system was used to measure line-averaged methane concentrations downwind of the source. A Lagrangian stochastic (LS) dispersion model was employed to infer emission rates from downwind gas concentrations. The main purpose of our study was to investigate the ability of our open-path FTIR system combined with the LS dispersion model to accurately measure greenhouse gas emissions. In our study, the average ratio of the estimated emissions to actual release rates QLS/Q for CH4 was about 0.86 (σQLS/Q = 0.2, n = 6) and 0.84 (σQLS/Q = 0.22, n = 3) after data fi ltering for a 15- and a 30- min period, respectively. Although there is a limited amount of data in this experiment, the results demonstrate the potential of the measurement system for accurate quantifi cation of greenhouse gas emissions.

  16. Impact of Salinity on the Air-Water Partition Coefficient of Gas Tracers

    SciTech Connect

    Zhong, Lirong; Pope, Gary A.; Evans, John C.; Cameron, Richard J.

    2005-09-01

    The use of a gas partitioning interwell tracer test (PITT) has been proposed as a standard approach to the measurement of field-scale vadose zone water saturation fractions. The accuracy of the saturation measurement is largely dependent on the determination of the air-water partitioning coefficient, K, of the tracers; however, in practice, K is also strongly influenced by the physical and chemical properties of the water. In this study, column tests were conducted to investigate the impact of salinity on tracer partitioning coefficients for two promising gas phase candidate tracers, dibromomethane and dimethylether. Sodium thiosulfate was used as a salinity surrogate. The dynamic K values of the two partitioning tracers were measured for sodium thiosulfate concentrations between 0% and 36% by weight. Methane was used as the non-partitioning tracer for all experiments. K values were found to decrease significantly with increasing sodium thiosulfate concentration. Similar correlations between K values and sodium thiosulfate concentration were found for both of the partitioning tracers tested.

  17. Unit vent airflow measurements using a tracer gas technique

    SciTech Connect

    Adams, D.G.; Lagus, P.L.; Fleming, K.M.

    1997-08-01

    An alternative method for assessing flowrates that does not depend on point measurements of air flow velocity is the constant tracer injection technique. In this method one injects a tracer gas at a constant rate into a duct and measures the resulting concentration downstream of the injection point. A simple equation derived from the conservation of mass allows calculation of the flowrate at the point of injection. Flowrate data obtained using both a pitot tube and a flow measuring station were compared with tracer gas flowrate measurements in the unit vent duct at the Callaway Nuclear Station during late 1995 and early 1996. These data are presented and discussed with an eye toward obtaining precise flowrate data for release rate calculations. The advantages and disadvantages of the technique are also described. In those test situations for which many flowrate combinations are required, or in large area ducts, a tracer flowrate determination requires fewer man-hours than does a conventional traverse-based technique and does not require knowledge of the duct area. 6 refs., 10 figs., 6 tabs.

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

    SciTech Connect

    Lunden, Melissa; Faulkner, David; Heredia, Elizabeth; Cohn, Sebastian; Dickerhoff, Darryl; Noris, Federico; Logue, Jennifer; Hotchi, Toshifumi; Singer, Brett; Sherman, Max H.

    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 between different gas sampling methods, and the effect of different ventilation conditions.

  19. Evaluating Gas-Phase Transport And Detection Of Noble Gas Signals From Underground Nuclear Explosions Using Chemical Tracers

    NASA Astrophysics Data System (ADS)

    Carrigan, C. R.; Hunter, S. L.; Sun, Y.; Wagoner, J. L.; Ruddle, D.; Anderson, G.; Felske, D.; Myers, K.; Zucca, J. J.; Emer, D. F.; Townsend, M.; Drellack, S.; Chipman, V.; Snelson, C. M.

    2013-12-01

    The 1993 Non-Proliferation Experiment (NPE) involved detonating 1 kiloton of chemical explosive in a subsurface cavity which also contained bottles of tracer gases (ref 1). That experiment provided an improved understanding of transport processes relevant to the detection of noble gas signals at the surface emanating from a clandestine underground nuclear explosion (UNE). As an alternative to performing large chemical detonations to simulate gas transport from UNEs, we have developed a test bed for subsurface gas transport, sampling and detection studies using a former UNE cavity. The test bed site allows for the opportunity to evaluate pathways to the surface created by the UNE as well as possible transport mechanisms including barometric pumping and cavity pressurization (ref 2). With the test bed we have monitored long-term chemical tracers as well as newly injected tracers. In order to perform high temporal resolution tracer gas monitoring, we have also developed a Subsurface Gas Smart Sampler (SGSS) which has application during an actual On Site Inspection (OSI) and is available for deployment in OSI field exercises planned for 2014. Deployment of five SGSS at the remote test bed has provided unparalleled detail concerning relationships involving tracer gas transport to the surface, barometric fluctuations and temporal variations in the natural radon concentration. We anticipate that the results of our tracer experiments will continue to support the development of improved noble gas detection technology for both OSI and International Monitoring System applications. 1. C.R. Carrigan et al., 1996, Nature, 382, p. 528. 2. Y. Sun and C.R. Carrigan, 2012, Pure Appl. Geophys., DOI 10.1007/s00024-012-0514-4.

  20. Estimating fracture spacing from natural tracers in shale-gas production

    NASA Astrophysics Data System (ADS)

    Bauer, S. J.; McKenna, S. A.; Heath, J. E.; Gardner, P.

    2012-12-01

    Resource appraisal and long-term recovery potential of shale gas relies on the characteristics of the fracture networks created within the formation. Both well testing and analysis of micro-seismic data can provide information on fracture characteristics, but approaches that directly utilize observations of gas transport through the fractures are not well-developed. We examine transport of natural tracers and analyze the breakthrough curves (BTC's) of these tracers with a multi-rate mass transfer (MMT) model to elucidate fracture characteristics. The focus here is on numerical simulation studies to determine constraints on the ability to accurately estimate fracture network characteristics as a function of the diffusion coefficients of the natural tracers, the number and timing of observations, the flow rates from the well, and the noise in the observations. Traditional tracer testing approaches for dual-porosity systems analyze the BTC of an injected tracer to obtain fracture spacing considering a single spacing value. An alternative model is the MMT model where diffusive mass transfer occurs simultaneously over a range of matrix block sizes defined by a statistical distribution (e.g., log-normal, gamma, or power-law). The goal of the estimation is defining the parameters of the fracture spacing distribution. The MMT model has not yet been applied to analysis of natural in situ natural tracers. Natural tracers are omnipresent in the subsurface, potentially obviating the needed for introduced tracers, and could be used to improve upon fracture characteristics estimated from pressure transient and decline curve production analysis. Results of this study provide guidance for data collection and analysis of natural tracers in fractured shale formations. Parameter estimation on simulated BTC's will provide guidance on the necessary timing of BTC sampling in field experiments. The MMT model can result in non-unique or nonphysical parameter estimates. We address this

  1. Multimodel analysis of anisotropic diffusive tracer-gas transport in a deep arid unsaturated zone

    USGS Publications Warehouse

    Green, Christopher T.; Walvoord, Michelle Ann; Andraski, Brian J.; Striegl, Robert G.; Stonestrom, David A.

    2015-01-01

    Gas transport in the unsaturated zone affects contaminant flux and remediation, interpretation of groundwater travel times from atmospheric tracers, and mass budgets of environmentally important gases. Although unsaturated zone transport of gases is commonly treated as dominated by diffusion, the characteristics of transport in deep layered sediments remain uncertain. In this study, we use a multimodel approach to analyze results of a gas-tracer (SF6) test to clarify characteristics of gas transport in deep unsaturated alluvium. Thirty-five separate models with distinct diffusivity structures were calibrated to the tracer-test data and were compared on the basis of Akaike Information Criteria estimates of posterior model probability. Models included analytical and numerical solutions. Analytical models provided estimates of bulk-scale apparent diffusivities at the scale of tens of meters. Numerical models provided information on local-scale diffusivities and feasible lithological features producing the observed tracer breakthrough curves. The combined approaches indicate significant anisotropy of bulk-scale diffusivity, likely associated with high-diffusivity layers. Both approaches indicated that diffusivities in some intervals were greater than expected from standard models relating porosity to diffusivity. High apparent diffusivities and anisotropic diffusivity structures were consistent with previous observations at the study site of rapid lateral transport and limited vertical spreading of gas-phase contaminants. Additional processes such as advective oscillations may be involved. These results indicate that gases in deep, layered unsaturated zone sediments can spread laterally more quickly, and produce higher peak concentrations, than predicted by homogeneous, isotropic diffusion models.

  2. Isotopologues of dense gas tracers in NGC 1068

    SciTech Connect

    Wang, Junzhi; Qiu, Jianjie; Zhang, Zhi-Yu; Shi, Yong; Zhang, Jiangshui; Fang, Min

    2014-11-20

    We present observations of isotopic lines of dense gas tracers toward the nuclear region of nearby Seyfert 2 galaxy NGC 1068 with the IRAM 30 m telescope and the Atacama Pathfinder Experiment (APEX) 12 m telescope. We detected four isotopic lines (H{sup 13}CN 1-0, H{sup 13}CO{sup +} 1-0, HN{sup 13}C 1-0, and HC{sup 18}O{sup +} 1-0) at the 3 mm band with the IRAM 30 m telescope and obtained upper limits of other lines. We calculated optical depths of dense gas tracers with the detected isotopic lines of HCN 1-0, HCO{sup +} 1-0, and HNC 1-0. We find that the {sup 14}N/{sup 15}N abundance ratio is greater than 420 if we adopt the upper limit of HC{sup 15}N(1-0) emission. Combining this with fluxes of 1-0 lines from IRAM 30 m observations and the upper limit of 3-2 lines from APEX 12 m observations, we also estimated the excitation condition of molecular gas in the nuclear region of NGC 1068, which is less dense than that in the extreme starburst regions of galaxies.

  3. Analysis of volatile phase transport in soils using natural radon gas as a tracer

    SciTech Connect

    Chen, C.; Thomas, D.M.

    1992-12-31

    We have conducted a field study of soil gas transport processes using radon gas as a naturally occurring tracer. The .experiment monitored soil gas radon activity, soil moisture, and soil temperature at three depths in the shallow soil column; barometric pressure, rainfall and wind speed were monitored at the soil surface. Linear and multiple regression analysis of the data sets has shown that the gas phase radon activities under natural environmental conditions are influenced by soil moisture content, barometric pressure variations, soil temperature and soil structure. The effect of wind speed on subsurface radon activities under our field conditions has not been demonstrated.

  4. Analysis of volatile phase transport in soils using natural radon gas as a tracer

    SciTech Connect

    Chen, C.; Thomas, D.M.

    1992-01-01

    We have conducted a field study of soil gas transport processes using radon gas as a naturally occurring tracer. The .experiment monitored soil gas radon activity, soil moisture, and soil temperature at three depths in the shallow soil column; barometric pressure, rainfall and wind speed were monitored at the soil surface. Linear and multiple regression analysis of the data sets has shown that the gas phase radon activities under natural environmental conditions are influenced by soil moisture content, barometric pressure variations, soil temperature and soil structure. The effect of wind speed on subsurface radon activities under our field conditions has not been demonstrated.

  5. Analysis of volatile-phase transport in soils using natural radon gas as a tracer

    SciTech Connect

    Chen, C.; Thomas, D.M.

    1994-01-01

    We have conducted a field study of soil gas transport processes using radon gas as a naturally occurring tracer. The experiment monitored soil gas radon activity, soil moisture, and soil temperature at depth; barometric pressure, rainfall, and wind speed were monitored at the soil surface. Linear and multiple regression analysis under natural environmental conditions are influenced by soil moisture content, barometric pressure variations, soil temperature, and soil structure. The effect of wind speed on subsurface radon activities under our field conditions has not been observed. 25 refs., 12 figs., 1 tab.

  6. New Tracers of Gas Migration in the Continental Crust

    SciTech Connect

    Kurz, Mark D.

    2015-11-01

    Noble gases are exceptional tracers in continental settings due to the remarkable isotopic variability between the mantle, crust, and atmosphere, and because they are inert. Due to systematic variability in physical properties, such as diffusion, solubility, and production rates, the combination of helium, neon, and argon provides unique but under-utilized indices of gas migration. Existing noble gas data sets are dominated by measurements of gas and fluid phases from gas wells, ground waters and hot springs. There are very few noble gas measurements from the solid continental crust itself, which means that this important reservoir is poorly characterized. The central goal of this project was to enhance understanding of gas distribution and migration in the continental crust using new measurements of noble gases in whole rocks and minerals from existing continental drill cores, with an emphasis on helium, neon, argon. We carried out whole-rock and mineral-separate noble gas measurements on Precambrian basement samples from the Texas Panhandle. The Texas Panhandle gas field is the southern limb of the giant Hugoton-Panhandle oil and gas field; it has high helium contents (up to ~ 2 %) and 3He/4He of 0.21 (± 0.03) Ra. Because the total amount of helium in the Panhandle gas field is relatively well known, crustal isotopic data and mass balance calculations can be used to constrain the ultimate source rocks, and hence the helium migration paths. The new 3He/4He data range from 0.03 to 0.11 Ra (total), all of which are lower than the gas field values. There is internal isotopic heterogeneity in helium, neon, and argon, within all the samples; crushing extractions yield less radiogenic values than melting, demonstrating that fluid inclusions preserve less radiogenic gases. The new data suggest that the Precambrian basement has lost significant amounts of helium, and shows the importance of measuring helium with neon and argon. The 4He/40Ar values are particularly useful

  7. Dissolved gas dynamics in wetland soils: Root-mediated gas transfer kinetics determined via push-pull tracer tests

    NASA Astrophysics Data System (ADS)

    Reid, Matthew C.; Pal, David S.; Jaffé, Peter R.

    2015-09-01

    Gas transfer processes are fundamental to the biogeochemical and water quality functions of wetlands, yet there is limited knowledge of the rates and pathways of soil-atmosphere exchange for gases other than oxygen and methane (CH4). In this study, we use a novel push-pull technique with sulfur hexafluoride (SF6) and helium (He) as dissolved gas tracers to quantify the kinetics of root-mediated gas transfer, which is a critical efflux pathway for gases from wetland soils. This tracer approach disentangles the effects of physical transport from simultaneous reaction in saturated, vegetated wetland soils. We measured significant seasonal variation in first-order gas exchange rate constants, with smaller spatial variations between different soil depths and vegetation zones in a New Jersey tidal marsh. Gas transfer rates for most biogeochemical trace gases are expected to be bracketed by the rate constants for SF6 and He, which ranged from ˜10-2 to 2 × 10-1 h-1 at our site. A modified Damköhler number analysis is used to evaluate the balance between biochemical reaction and root-driven gas exchange in governing the fate of environmental trace gases in rooted, anaerobic soils. This approach confirmed the importance of plant gas transport for CH4, and showed that root-driven transport may affect nitrous oxide (N2O) balances in settings where N2O reduction rates are slow.

  8. Plan for radionuclide tracer studies of the residence time distribution in the Wilsonville dissolver and preheater

    SciTech Connect

    Jolley, R.L.; Begovich, J.M.; Brashear, H.R.; Case, N.; Clark, T.G.; Emery, J.F.; Patton, B.D.; Rodgers, B.R.; Villiers-Fisher, J.F.; Watson, J.S.

    1983-12-01

    Stimulus-response measurements using radiotracers to measure residence time distribution (RTD) and hydrodynamic parameters for the preheaters and dissolvers at the Ft. Lewis Solvent Refined Coal (SRC) and the Exxon Donor Solvent (EDS) coal conversion pilot plants are reviewed. A plan is also presented for a series of radioactive tracer studies proposed for the Advanced Coal Liquefaction Facility at Wilsonville, Alabama, to measure the RTD for the preheater and dissolvers in the SRC-I mode. The tracer for the gas phase will be /sup 133/Xe, and /sup 198/Au (on carbonized resin or as an aqueous colloidal suspension) will be used as the slurry tracer. Four experimental phases are recommended for the RTD tracer studies: (1) preheater; (2) dissolver with 100% takeoff; (3) dissolver with 100% takeoff and solids withdrawal; and (4) dissolver with 50% takeoff. Eighteen gas-tracer and 22 liquid-tracer injections are projected to accomplish the four experimental phases. Two to four tracer injections are projected for preliminary tests to ensure the capability of safe injection of the radiotracers and the collection of statistically significant data. A complete projected cost and time schedule is provided, including procurement of necessary components, preparation of the radiotracers, assembly and testing of tracer injection apparatus and detection systems, onsite work and tracer injections, laboratory experimentation, data analysis, and report writing.

  9. Photoacoustic infrared spectroscopy for conducting gas tracer tests and measuring water saturations in landfills

    SciTech Connect

    Jung, Yoojin; Han, Byunghyun; Mostafid, M. Erfan; Chiu, Pei; Yazdani, Ramin; Imhoff, Paul T.

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Photoacoustic infrared spectroscopy tested for measuring tracer gas in landfills. Black-Right-Pointing-Pointer Measurement errors for tracer gases were 1-3% in landfill gas. Black-Right-Pointing-Pointer Background signals from landfill gas result in elevated limits of detection. Black-Right-Pointing-Pointer Technique is much less expensive and easier to use than GC. - Abstract: Gas tracer tests can be used to determine gas flow patterns within landfills, quantify volatile contaminant residence time, and measure water within refuse. While gas chromatography (GC) has been traditionally used to analyze gas tracers in refuse, photoacoustic spectroscopy (PAS) might allow real-time measurements with reduced personnel costs and greater mobility and ease of use. Laboratory and field experiments were conducted to evaluate the efficacy of PAS for conducting gas tracer tests in landfills. Two tracer gases, difluoromethane (DFM) and sulfur hexafluoride (SF{sub 6}), were measured with a commercial PAS instrument. Relative measurement errors were invariant with tracer concentration but influenced by background gas: errors were 1-3% in landfill gas but 4-5% in air. Two partitioning gas tracer tests were conducted in an aerobic landfill, and limits of detection (LODs) were 3-4 times larger for DFM with PAS versus GC due to temporal changes in background signals. While higher LODs can be compensated by injecting larger tracer mass, changes in background signals increased the uncertainty in measured water saturations by up to 25% over comparable GC methods. PAS has distinct advantages over GC with respect to personnel costs and ease of use, although for field applications GC analyses of select samples are recommended to quantify instrument interferences.

  10. Generation of ethylene tracer by noncatalytic pyrolysis of natural gas at elevated pressure

    USGS Publications Warehouse

    Lu, Y.; Chen, S.; Rostam-Abadi, M.; Ruch, R.; Coleman, D.; Benson, L.J.

    2005-01-01

    There is a critical need within the pipeline gas industry for an inexpensive and reliable technology to generate an identification tag or tracer that can be added to pipeline gas to identify gas that may escape and improve the deliverability and management of gas in underground storage fields. Ethylene is an ideal tracer, because it does not exist naturally in the pipeline gas, and because its physical properties are similar to the pipeline gas components. A pyrolysis process, known as the Tragen process, has been developed to continuously convert the ???2%-4% ethane component present in pipeline gas into ethylene at common pipeline pressures of 800 psi. In our studies of the Tragen process, pyrolysis without steam addition achieved a maximum ethylene yield of 28%-35% at a temperature range of 700-775 ??C, corresponding to an ethylene concentration of 4600-5800 ppm in the product gas. Coke deposition was determined to occur at a significant rate in the pyrolysis reactor without steam addition. The ?? 13C isotopic analysis of gas components showed a ?? 13C value of ethylene similar to ethane in the pipeline gas, indicating that most of the ethylene was generated from decomposition of the ethane in the raw gas. However, ?? 13C isotopic analysis of the deposited coke showed that coke was primarily produced from methane, rather than from ethane or other heavier hydrocarbons. No coke deposition was observed with the addition of steam at concentrations of > 20% by volume. The dilution with steam also improved the ethylene yield. ?? 2005 American Chemical Society.

  11. Application of the gas tracer method for measuring oxygen transfer rates in subsurface flow constructed wetlands.

    PubMed

    Tyroller, Lina; Rousseau, Diederik P L; Santa, Santa; García, Joan

    2010-07-01

    The oxygen transfer rate (OTR) has a significant impact on the design, optimal operation and modelling of constructed wetlands treating wastewater. Oxygen consumption is very fast in wetlands and the OTR cannot be determined using an oxygen mass balance. This problem is circumvented in this study by applying the gas tracer method. Experiments were conducted in an unplanted gravel bed (dimensions L x W x d 125 x 50 x 35 cm filled with a 30-cm layer of 10-11-mm gravel) and a planted horizontal subsurface flow constructed wetland (HSSFCW) (L x W x d 110 x 70 x 38 cm filled with a 30-cm layer of 3.5-mm gravel with Phragmites australis). Tap water saturated with propane as gas tracer (pure or commercial cooking gas, depending on the test) was used. The mass transfer ratio between oxygen and commercial propane gas was quite constant and averaged R = 1.03, which is slightly lower than the value of R = 1.39 that is usually reported for pure propane. The OTR ranged from 0.31 to 5.04 g O(2) m(-2) d(-1) in the unplanted gravel bed and from 0.3 to 3.2 g O(2) m(-2) d(-1) in the HSSFCW, depending on the hydraulic retention time (HRT). The results of this study suggest that the OTR in HSSFCW is very low for the oxygen demand of standard wastewater and the OTR calculations based on mass balances and theoretical stoichiometric considerations overestimate OTR values by a factor that ranges from 10 to 100. The gas tracer method is a promising tool for determining OTR in constructed wetlands, with commercial gas proving to be a viable low-cost alternative for determining OTR.

  12. ANALYSIS OF A GAS-PHASE PARTITIONING TRACER TEST CONDUCTED THROUGH FRACTURED MEDIA

    EPA Science Inventory

    The gas-phase partitioning tracer method was used to estimate non-aqueous phase liquid (NAPL), water, and air saturations in the vadose zone at a chlorinated-solvent contaminated field site in Tucson, AZ. The tracer test was conducted in a fractured clay system that is the confin...

  13. 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

  14. Gas-partitioning tracer test to qualify trapped gas during recharge

    USGS Publications Warehouse

    Heilweil, Victor M.; Kip, Solomon D.; Perkins, Kim S.; Ellett, Kevin M.

    2004-01-01

    Dissolved helium and bromide tracers were used to evaluate trapped gas during an infiltration pond experiment. Dissolved helium preferentially partitioned into trapped gas bubbles, or other pore air, because of its low solubility in water. This produced observed helium retardation factors of as much as 12 relative to bromide. Numerical simulations of helium breakthrough with both equilibrium and kinetically limited advection/dispersion/retardation did not match observed helium concentrations. However, better fits were obtained by including a decay term representing the diffusive loss of helium through interconnected, gas-filled pores. Calculations indicate that 7% to more than 26% of the porosity beneath the pond was filled with gas. Measurements of laboratory hydraulic properties indicate that a 10% decrease in saturation would reduce the hydraulic conductivity by at least one order of magnitude in the well-sorted sandstone, but less in the overlying soils. This is consistent with in situ measurements during the experiment, which show steeper hydraulic gradients in sandstone than in soil. Intrinsic permeability of the soil doubled during the first six months of the experiment, likely caused by a combination of dissolution and thermal contraction of trapped gas. Managers of artificial recharge basins may consider minimizing the amount of trapped gas by using wet, rather than dry, tilling to optimize infiltration rates, particularly in well-sorted porous media in which reintroduced trapped gas may cause substantial reductions in permeability. Trapped gas may also inhibit the amount of focused infiltration that occurs naturally during ephemeral flood events along washes and playas.

  15. Gas-partitioning tracer test to quantify trapped gas during recharge

    USGS Publications Warehouse

    Heilweil, V.M.; Solomon, D.K.; Perkins, K.S.; Ellett, K.M.

    2004-01-01

    Dissolved helium and bromide tracers were used to evaluate trapped gas during an infiltration pond experiment. Dissolved helium preferentially partitioned into trapped gas bubbles, or other pore air, because of its low solubility in water. This produced observed helium retardation factors of as much as 12 relative to bromide. Numerical simulations of helium breakthrough with both equilibrium and kinetically limited advection/dispersion/retardation did not match observed helium concentrations. However, better fits were obtained by including a decay term representing the diffusive loss of helium through interconnected, gas-filled pores. Calculations indicate that 7% to more than 26% of the porosity beneath the pond was filled with gas. Measurements of laboratory hydraulic properties indicate that a 10% decrease in saturation would reduce the hydraulic conductivity by at least one order of magnitude in the well-sorted sandstone, but less in the overlying soils. This is consistent with in situ measurements during the experiment, which show steeper hydraulic gradients in sandstone than in soil. Intrinsic permeability of the soil doubled during the first six months of the experiment, likely caused by a combination of dissolution and thermal contraction of trapped gas. Managers of artificial recharge basins may consider minimizing the amount of trapped gas by using wet, rather than dry, tilling to optimize infiltration rates, particularly in well-sorted porous media in which reintroduced trapped gas may cause substantial reductions in permeability. Trapped gas may also inhibit the amount of focused infiltration that occurs naturally during ephemeral flood events along washes and playas.

  16. Tracer studies of nitrogen assimilation in yeast.

    PubMed

    ABRAMS, R; HAMMARSTEN, E

    1949-01-01

    By using N(15) as a tracer the assimilation of ammonia by the yeast, Torulopsis utilis, has been studied. It has been shown that: 1. There was no measurable incorporation of N in the protein or polynucleotide purine of carbon-starved yeast. 2. When ammonia is added to nitrogen-starved yeast there is a long lag period before division begins during which the yeast rapidly synthesizes protein, this process being accompanied by a turnover of polynucleotide purine. There was no significant dilution of the N(15)H(4) (+) of the medium by ordinary NH(4) (+). 3. When yeast containing N(15) is allowed to divide and grow in ordinary ammonia, the total amount of N(15) in the yeast remains constant. The dicarboxylic amino acids are most diluted, while arginine and nucleic acid guanine are not diluted at all.

  17. RE-ENTRAINMENT AND DISPERSION OF EXHAUSTS FROM INDOOR RADON REDUCTION SYSTEMS: ANALYSIS OF TRACER GAS DATA

    EPA Science Inventory

    Tracer gas studies were conducted around four model houses in a wind tunnel, and around one house in the field, to quantify re-entrainment and dispersion of exhaust gases released from residential indoor radon reduction systems. Re-entrainment tests in the field suggest that acti...

  18. Field-scale sulfur hexafluoride tracer experiment to understand long distance gas transport in the deep unsaturated zone

    USGS Publications Warehouse

    Walvoord, Michelle Ann; Andraski, Brian; Green, Christopher T.; Stonestrom, David A.; Striegl, Robert G.

    2014-01-01

    A natural gradient SF6 tracer experiment provided an unprecedented evaluation of long distance gas transport in the deep unsaturated zone (UZ) under controlled (known) conditions. The field-scale gas tracer test in the 110-m-thick UZ was conducted at the U.S. Geological Survey’s Amargosa Desert Research Site (ADRS) in southwestern Nevada. A history of anomalous (theoretically unexpected) contaminant gas transport observed at the ADRS, next to the first commercial low-level radioactive waste disposal facility in the United States, provided motivation for the SF6 tracer study. Tracer was injected into a deep UZ borehole at depths of 15 and 48 m, and plume migration was observed in a monitoring borehole 9 m away at various depths (0.5–109 m) over the course of 1 yr. Tracer results yielded useful information about gas transport as applicable to the spatial scales of interest for off-site contaminant transport in arid unsaturated zones. Modeling gas diffusion with standard empirical expressions reasonably explained SF6 plume migration, but tended to underpredict peak concentrations for the field-scale experiment given previously determined porosity information. Despite some discrepancies between observations and model results, rapid SF6 gas transport commensurate with previous contaminant migration was not observed. The results provide ancillary support for the concept that apparent anomalies in historic transport behavior at the ADRS are the result of factors other than nonreactive gas transport properties or processes currently in effect in the undisturbed UZ.

  19. Tracer Developments: Results of Experimental Studies

    SciTech Connect

    Adams, M.C.; Ahn, J.H.; Bentley, H.; Moore, J.N.; Veggeberg, S.

    1986-01-21

    Tracers can be used to monitor the movement of groundwaters and geothermal fluids and they can be used as a reference to quantify changes in fluid chemistry as a result of injection. Despite their potential importance to the geothermal operator, very few tracers are presently available and of those that are, little is known about their stability or behavior at the elevated temperatures that typify resources capable of electric power generation. During the past two years the University of Utah Research Institute has been involved in tracer research and testing, largely through the DOE Injection Research Program. The purpose of this paper is to summarize the results of these laboratory and field investigations.

  20. Ambient Gas-Particle Partitioning of Tracers for Biogenic Oxidation

    SciTech Connect

    Isaacman-VanWertz, Gabriel; Yee, Lindsay D.; Kreisberg, Nathan M.; Wernis, Rebecca; Moss, Joshua A.; Hering, Susanne V.; de Sa, Suzanne; Martin, Scot T.; Alexander, Mikaela L.; Palm, Brett B.; Hu, Weiwei; Campuzano-Jost, Pedro; Day, Douglas; Jimenez, Jose L.; Riva, Matthieu; Surratt, Jason D.; Viegas, Juarez; Manzi, Antonio; Edgerton, Eric S.; Baumann, K.; Souza, Rodrigo A.; Artaxo, Paulo; Goldstein, Allen H.

    2016-08-23

    Exchange of atmospheric organic compounds between gas and particle phases is important in the production and chemistry of particle-phase mass but is poorly understood due to a lack of simultaneous measurements in both phases of individual compounds. Measurements of particle- and gas phase organic compounds are reported here for the southeastern United States and central Amazonia. Polyols formed from isoprene oxidation contribute 8% and 15% on average to particle-phase organic mass at these sites but are also observed to have substantial gas-phase concentrations contrary to many models that treat these compounds as nonvolatile. The results of the present study show that the gas-particle partitioning of approximately 100 known and newly observed oxidation products is not well explained by environmental factors (e.g., temperature). Compounds having high vapor pressures have higher particle fractions than expected from absorptive equilibrium partitioning models. These observations support the conclusion that many commonly measured biogenic oxidation products may be bound in low-volatility mass (e.g., accretion products, inorganic organic adducts) that decomposes to individual compounds on analysis. However, the nature and extent of any such bonding remains uncertain. Similar conclusions are reach for both study locations, and average particle fractions for a given compound are consistent within similar to 25% across measurement sites.

  1. 10 CFR 39.45 - Subsurface tracer studies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 1 2010-01-01 2010-01-01 false Subsurface tracer studies. 39.45 Section 39.45 Energy NUCLEAR REGULATORY COMMISSION LICENSES AND RADIATION SAFETY REQUIREMENTS FOR WELL LOGGING Equipment § 39.45 Subsurface tracer studies. (a) The licensee shall require all personnel handling...

  2. 10 CFR 39.45 - Subsurface tracer studies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 1 2014-01-01 2014-01-01 false Subsurface tracer studies. 39.45 Section 39.45 Energy NUCLEAR REGULATORY COMMISSION LICENSES AND RADIATION SAFETY REQUIREMENTS FOR WELL LOGGING Equipment § 39.45 Subsurface tracer studies. (a) The licensee shall require all personnel handling...

  3. 10 CFR 39.45 - Subsurface tracer studies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 1 2012-01-01 2012-01-01 false Subsurface tracer studies. 39.45 Section 39.45 Energy NUCLEAR REGULATORY COMMISSION LICENSES AND RADIATION SAFETY REQUIREMENTS FOR WELL LOGGING Equipment § 39.45 Subsurface tracer studies. (a) The licensee shall require all personnel handling...

  4. 10 CFR 39.45 - Subsurface tracer studies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 1 2011-01-01 2011-01-01 false Subsurface tracer studies. 39.45 Section 39.45 Energy NUCLEAR REGULATORY COMMISSION LICENSES AND RADIATION SAFETY REQUIREMENTS FOR WELL LOGGING Equipment § 39.45 Subsurface tracer studies. (a) The licensee shall require all personnel handling...

  5. 10 CFR 39.45 - Subsurface tracer studies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 1 2013-01-01 2013-01-01 false Subsurface tracer studies. 39.45 Section 39.45 Energy NUCLEAR REGULATORY COMMISSION LICENSES AND RADIATION SAFETY REQUIREMENTS FOR WELL LOGGING Equipment § 39.45 Subsurface tracer studies. (a) The licensee shall require all personnel handling...

  6. [Determination of tracer gas contents in sediment pore water of gas hydrate area by two-dimensional gas chromatography].

    PubMed

    Wang, Hu; Yang, Qunhui; Ji, Fuwu; Zhou, Huaiyang; Xue, Xiang

    2011-01-01

    A two-dimensional gas chromatographic instrument was established by the capillary flow technology (Deans Switch) and two columns (PoraPLOT Q and Molsieve 5A) and three detectors (pulsed discharge helium ionization detector, flame photometric detector and thermal conductivity detector). The instrument can be used to measure tracer gases simultaneously including hydrogen, methane, carbon dioxide and hydrogen sulfide. The detection limits of the hydrogen, methane, carbon dioxide and hydrogen sulfide were 0.51, 0.17, 82 and 0.08 micromol/mol, and the calibration curves presented good linear relationships in the range of 2-1030, 0.6-501, 120-10500 and 0.2- 49.1 micromol/mol, respectively. The relative standard deviations were less than 10% for the measurements of ten standard gases. By this method, the tracer gases in the sediment pore water of gas hydrate area in South China Sea had been detected. This method is simple, sensitive, and suitable for on-board detection. Compared with the usual methods for measuring tracer gases, the amount of a sample necessary is reduced greatly. It is useful for the survey of gas hydrate and hydrothermal resources below sea floor and for the research of dissolved gases in the ocean.

  7. Tracer study of San Vicente reservoir

    SciTech Connect

    Williams, R.T.

    1996-11-01

    The City of San Diego remains on the cutting edge of water conservation. With an unwavering commitment to maintain an adequate water supply for the future, water repurification is now being considered. The City of San Diego and San Diego Water Authority (CWA) have proposed to recycle repurified water through San Vicente Reservoir. A key component of assessing the feasibility of such a project is to calculate the retention time of repurified water in the reservoir. Working with engineering consultant team (Montgomery-Watson Engineers and Flow Science, Incorporated) two tracer studies were conducted to model the circulation and mixing of repurified water introduced into the reservoir. The goal was to determine whether repurified water recycled through San Vicente will meet the retention time criteria established by the Department of Health Services. This presentation however, will not attempt to interpret the results of the study, that aspect will be evaluated by the Flow Scientist. The objective here is to explain how the project was carried out and to focus mostly on the analytical work performed on the samples by the chemist in the City of San Diego Water Quality Laboratory.

  8. Leak testing of bubble-tight dampers using tracer gas techniques

    SciTech Connect

    Lagus, P.L.; DuBois, L.J.; Fleming, K.M.

    1995-02-01

    Recently tracer gas techniques have been applied to the problem of measuring the leakage across an installed bubble-tight damper. A significant advantage of using a tracer gas technique is that quantitative leakage data are obtained under actual operating differential pressure conditions. Another advantage is that leakage data can be obtained using relatively simple test setups that utilize inexpensive materials without the need to tear ducts apart, fabricate expensive blank-off plates, and install test connections. Also, a tracer gas technique can be used to provide an accurate field evaluation of the performance of installed bubble-tight dampers on a periodic basis. Actual leakage flowrates were obtained at Zion Generating Station on four installed bubble-tight dampers using a tracer gas technique. Measured leakage rates ranged from 0.01 CFM to 21 CFM. After adjustment and subsequent retesting, the 21 CFM damper leakage was reduced to a leakage of 3.8 CFM. In light of the current regulatory climate and the interest in Control Room Habitability issues, imprecise estimates of critical air boundary leakage rates--such as through bubble-tight dampers--are not acceptable. These imprecise estimates can skew radioactive dose assessments as well as chemical contaminant exposure calculations. Using a tracer gas technique, the actual leakage rate can be determined. This knowledge eliminates a significant source of uncertainty in both radioactive dose and/or chemical exposure assessments.

  9. National Biomedical Tracer Facility: Project definition study

    SciTech Connect

    Heaton, R.; Peterson, E.; Smith, P.

    1995-05-31

    The Los Alamos National Laboratory is an ideal institution and New Mexico is an ideal location for siting the National Biomedical Tracer Facility (NBTF). The essence of the Los Alamos proposal is the development of two complementary irradiation facilities that combined with our existing radiochemical processing hot cell facilities and waste handling and disposal facilities provide a low cost alternative to other proposals that seek to satisfy the objectives of the NBTF. We propose the construction of a 30 MeV cyclotron facility at the site of the radiochemical facilities, and the construction of a 100 MeV target station at LAMPF to satisfy the requirements and objectives of the NBTF. We do not require any modifications to our existing radiochemical processing hot cell facilities or our waste treatment and disposal facilities to accomplish the objectives of the NBTF. The total capital cost for the facility defined by the project definition study is $15.2 M. This cost estimate includes $9.9 M for the cyclotron and associated facility, $2.0 M for the 100 MeV target station at LAMPF, and $3.3 M for design.

  10. 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)

  11. Dispersion in the Surfzone: Tracer Dispersion Studies

    DTIC Science & Technology

    2011-09-30

    objective is to improve understanding and modeling of dispersion of tracers (pol­ lution, fecal indicator bacteria, fine sediments) within the...discussed further here. Stochastic Particle Simulation for Surfzone Dispersion Drifter-derived diffusivities are time-dependent. In an unbounded...diffusion. Here HB06 particle trajectories are stochastically simulated with the Langevin equations with a shoreline boundary to explain the observed

  12. Olive Oil Tracer Particle Size Analysis for Optical Flow Investigations in a Gas Medium

    NASA Astrophysics Data System (ADS)

    Harris, Shaun; Smith, Barton

    2014-11-01

    Seed tracer particles must be large enough to scatter sufficient light while being sufficiently small to follow the flow. These requirements motivate a desire for control over the particle size. For gas measurements, it is common to use atomized oil droplets as tracer particles. A Laskin nozzle is a device for generating oil droplets in air by directing high-pressure air through small holes under an oil surface. The droplet diameter frequency distribution can be varied by altering the hole diameter, the number of holes, or the inlet pressure. We will present a systematic study of the effect of these three parameters on the resultant particle distribution as it leaves the Laskin nozzle. The study was repeated for cases where the particles moved through a typical jet facility before their size was measured. While the jet facility resulted in an elimination of larger particles, the average particle diameter could be varied by a factor of two at both the seeder exit and downstream of the jet facility.

  13. CH as a Molecular Gas Tracer and C-shock Tracer Across a Molecular Cloud Boundary in Taurus

    NASA Astrophysics Data System (ADS)

    Xu, Duo; Li, Di

    2016-12-01

    We present new observations of all three ground-state transitions of the methylidyne (CH) radical and all four ground-state transitions of the hydroxyl (OH) radical toward a sharp boundary region of the Taurus molecular cloud. These data were analyzed in conjunction with existing CO and dust images. The derived CH abundance is consistent with previous observations of translucent clouds (0.8 ≤ A v ≤ 2.1 mag). The X(CH)-factor is nearly a constant (1.0 ± 0.06) × 1022 cm-2 K-1 km-1 s in this extinction range, with less dispersion than that of the more widely used molecular tracers CO and OH. CH turns out be a better tracer of total column density in such an intermediate extinction range than CO or OH. Compared with previous observations, CH is overabundant below 1 mag extinction. Such an overabundance of CH is consistent with the presence of a C-shock. CH has two kinematic components, one of which shifts from 5.3 to 6 km s-1, while the other stays at 6.8 km s-1 when moving from outside toward inside of the cloud. These velocity behaviors exactly match previous OH observation. The shifting of the two kinematic components indicates colliding streams or gas flow at the boundary region, which could be the cause of the C-shock.

  14. Estimation of Fracture Porosity in an Unsaturated Fractured Welded Tuff Using Gas Tracer Testing

    SciTech Connect

    B.M. Freifeild

    2001-10-18

    Kinematic fracture porosity is an important hydrologic transport parameter for predicting the potential of rapid contaminant migration through fractured rock. The transport velocity of a solute moving within a fracture network is inversely related to the fracture porosity. Since fracture porosity is often one or two orders of magnitude smaller than matrix porosity, and fracture permeability is often orders of magnitude greater than matrix permeability, solutes may travel significantly faster in the fracture network than in the surrounding matrix. This dissertation introduces a new methodology for conducting gas tracer tests using a field portable mass spectrometer along with analytical tools for estimating fracture porosity using the measured tracer concentration breakthrough curves. Field experiments were conducted at Yucca Mountain, Nevada, consisting of air-permeability transient testing and gas-tracer-transport tests. The experiments were conducted from boreholes drilled within an underground tunnel as part of an investigation of rock mass hydrological behavior. Air-permeability pressure transients, recorded during constant mass flux injections, have been analyzed using a numerical inversion procedure to identify fracture permeability and porosity. Dipole gas tracer tests have also been conducted from the same boreholes used for air-permeability testing. Mass breakthrough data has been analyzed using a random walk particle-tracking model, with a dispersivity that is a function of the advective velocity. The estimated fracture porosity using the tracer test and air-injection test data ranges from .001 to .015. These values are an order of magnitude greater than the values estimated by others using hydraulically estimated fracture apertures. The estimates of porosity made using air-permeability test data are shown to be highly sensitive to formation heterogeneity. Uncertainty analyses performed on the gas tracer test results show high confidence in the parameter

  15. Estimation of fracture porosity in an unsaturated fractured welded tuff using gas tracer testing

    SciTech Connect

    Freifeld, Barry Mark

    2001-12-01

    Kinematic fracture porosity is an important hydrologic transport parameter for predicting the potential of rapid contaminant migration through fractured rock. The transport velocity of a solute moving within a fracture network is inversely related to the fracture porosity. Since fracture porosity is often one or two orders of magnitude smaller than matrix porosity, and fracture permeability is often orders of magnitude greater than matrix permeability, solutes may travel significantly faster in the fracture network than in the surrounding matrix. This dissertation introduces a new methodology for conducting gas tracer tests using a field portable mass spectrometer along with analytical tools for estimating fracture porosity using the measured tracer concentration breakthrough curves. Field experiments were conducted at Yucca Mountain, Nevada, consisting of air-permeability transient testing and gas-tracer-transport tests. The experiments were conducted from boreholes drilled within an underground tunnel as part of an investigation of rock mass hydrological behavior. Air-permeability pressure transients, recorded during constant mass flux injections, have been analyzed using a numerical inversion procedure to identify fracture permeability and porosity. Dipole gas tracer tests have also been conducted from the same boreholes used for air-permeability testing. Mass breakthrough data has been analyzed using a random walk particle-tracking model, with a dispersivity that is a function of the advective velocity. The estimated fracture porosity using the tracer test and air-injection test data ranges from .001 to .015. These values are an order of magnitude greater than the values estimated by others using hydraulically estimated fracture apertures. The estimates of porosity made using air-permeability test data are shown to be highly sensitive to formation heterogeneity. Uncertainty analyses performed on the gas tracer test results show high confidence in the parameter

  16. Optimization and evaluation of fluorescent tracers for flare removal in gas-phase particle image velocimetry

    NASA Astrophysics Data System (ADS)

    Chennaoui, M.; Angarita-Jaimes, D.; Ormsby, M. P.; Angarita-Jaimes, N.; McGhee, E.; Towers, C. E.; Jones, A. C.; Towers, D. P.

    2008-11-01

    We report the development of optimized fluorescent dye-doped tracer particles for gas-phase particle image velocimetry (PIV) and their use to eliminate 'flare' from the images obtained. In such applications, micron-sized tracer particles are normally required to accurately follow the flow. However, as the tracer size is reduced the amount of light incident on the particle diminishes and consequently the intensity of emitted light (fluorescence). Hence, there is a requirement to identify dyes with high quantum yield that can be dissolved in conventional tracer media at high concentrations. We describe the selection and characterization of a highly fluorescent blue-emitting dye, Bis-MSB, using a novel method, employing stabilized micro-emulsions, to emulate the fluorescence properties of tracer particles. We present the results of PIV experiments, using 1 µm tracer particles of o-xylene doped with Bis-MSB, in which elastically scattered 'flare' has been successfully removed from the images using an appropriate optical filter.

  17. Constraining cloud parameters using high density gas tracers in galaxies

    NASA Astrophysics Data System (ADS)

    Kazandjian, M. V.; Pelupessy, I.; Meijerink, R.; Israel, F. P.; Coppola, C. M.; Rosenberg, M. J. F.; Spaans, M.

    2016-11-01

    Far-infrared molecular emission is an important tool used to understand the excitation mechanisms of the gas in the interstellar medium (ISM) of star-forming galaxies. In the present work, we model the emission from rotational transitions with critical densities n ≳ 104 cm-3. We include 4-3 < J ≤ 15-14 transitions of CO and 13CO , in addition to J ≤ 7-6 transitions of HCN, HNC, and HCO+ on galactic scales. We do this by re-sampling high density gas in a hydrodynamic model of a gas-rich disk galaxy, assuming that the density field of the ISM of the model galaxy follows the probability density function (PDF) inferred from the resolved low density scales. We find that in a narrow gas density PDF, with a mean density of 10 cm-3 and a dispersion σ = 2.1 in the log of the density, most of the emission of molecular lines, even of gas with critical densities >104 cm-3, emanates from the 10-1000 cm-3 part of the PDF. We construct synthetic emission maps for the central 2 kpc of the galaxy and fit the line ratios of CO and 13CO up to J = 15-14, as well as HCN, HNC, and HCO+ up to J = 7-6, using one photo-dissociation region (PDR) model. We attribute the goodness of the one component fits for our model galaxy to the fact that the distribution of the luminosity, as a function of density, is peaked at gas densities between 10 and 1000 cm-3, with negligible contribution from denser gas. Specifically, the Mach number, ℳ, of the model galaxy is 10. We explore the impact of different log-normal density PDFs on the distribution of the line-luminosity as a function of density, and we show that it is necessary to have a broad dispersion, corresponding to Mach numbers ≳30 in order to obtain significant (>10%) emission from n> 104 cm-3 gas. Such Mach numbers are expected in star-forming galaxies, luminous infrared galaxies (LIRGS), and ultra-luminous infrared galaxies (ULIRGS). This method provides a way to constrain the global PDF of the ISM of galaxies from observations of

  18. Radon as a natural tracer for gas transport within uranium waste rock piles.

    PubMed

    Silva, N C; Chagas, E G L; Abreu, C B; Dias, D C S; Lopez, D; Guerreiro, E T Z; Alberti, H L C; Braz, M L; Branco, O; Fleming, P

    2014-07-01

    Acid mine drainage (AMD) has been identified as the main cause for outflow of acid water and radioactive/non-radioactive contaminants. AMD encompasses pyrites oxidation when water and oxygen are available. AMD was identified in uranium waste rock piles (WRPs) of Indústrias Nucleares do Brasil-Caldas facility (Brazilian uranium mine), resulting in high costs for water treatment. AMD reduction is the main challenge, and scientific investigation has been conducted to understand oxygen and water transportation within WRPs, where 222Rn is used as natural tracer for oxygen transportation. The study consists of soil radon gas mapping in the top layer of WRP4 using active soil gas pumping, radon adsorption in active charcoal and 222Rn determination using high-resolution gamma-ray spectrometry. A sampling network of 71 points was built where samples were collected at a depth of 40 cm. Soil radon gas concentration ranged from 33.7 to 1484.2 kBq m(-3) with mean concentration of 320.7±263.3 kBq m(-3).

  19. New Isotopic Tracers for Shale Gas and Hydraulic Fracturing Fluids

    EPA Pesticide Factsheets

    The combined application of geochemistry, stable isotopes (δ18O, δ2H), strontium isotopes (87Sr/86Sr), boron isotopes (δ11B), and radium isotopes (228Ra/226Ra) provides a unique methodology for tracing and monitoring shale gas and fracking fluids in the environment.

  20. National Biomedical Tracer Facility. Project definition study

    SciTech Connect

    Schafer, R.

    1995-02-14

    We request a $25 million government-guaranteed, interest-free loan to be repaid over a 30-year period for construction and initial operations of a cyclotron-based National Biomedical Tracer Facility (NBTF) in North Central Texas. The NBTF will be co-located with a linear accelerator-based commercial radioisotope production facility, funded by the private sector at approximately $28 million. In addition, research radioisotope production by the NBTF will be coordinated through an association with an existing U.S. nuclear reactor center that will produce research and commercial radioisotopes through neutron reactions. The combined facilities will provide the full range of technology for radioisotope production and research: fast neutrons, thermal neutrons, and particle beams (H{sup -}, H{sup +}, and D{sup +}). The proposed NBTF facility includes an 80 MeV, 1 mA H{sup -} cyclotron that will produce proton-induced (neutron deficient) research isotopes.

  1. Evaluation of Partitioning Gas Tracer Tests for Measuring Water in Landfills

    NASA Astrophysics Data System (ADS)

    Imhoff, P. T.; Han, B.; Jafarpour, Y.; Gallagher, V. N.; Chiu, P. C.; Fluman, D. A.; Vasuki, N. C.; Yazdani, R.; Augenstein, D.; Cohen, K. K.

    2003-12-01

    Methane is an important greenhouse gas, and landfills are the largest anthropogenic source in many developed countries. Bioreactor landfills have been proposed as one means of abating greenhouse gas emissions from landfills. Here, the decomposition of organic wastes is enhanced by the controlled addition of water or leachate to maintain optimal conditions for waste decomposition. Greenhouse gas abatement is accomplished by sequestration of photosynthetically derived carbon in wastes, CO2 offsets from energy use of waste derived gas, and mitigation of methane emission from the wastes. An important issue in the operation of bioreactor landfills is knowing how much water to add and where to add it. Accurate methods for measuring the amount of water in landfills would be valuable aids for implementing leachate recirculation systems. Current methods for measuring water are inadequate, though, since they provide point measurements and are frequently affected by heterogeneity of the solid waste composition and solid waste compaction. The value of point measurements is significantly reduced in systems where water flows preferentially, such as in landfills. Here, spatially integrated measurements might be of greater value. We are evaluating a promising technology, the partitioning gas tracer test, to measure the water saturation within landfills, the amount of free water in solid waste divided by the volume of the voids. The partitioning gas tracer test was recently developed by researchers working in the vadose zone. We report the results from laboratory and field tests designed to evaluate the partitioning gas tracer test within an anaerobic landfill operated by the Delaware Solid Waste Authority. Vertical wells were installed within the landfill to inject and extract tracer gases. Gas flow and tracer gas movement in the solid waste were controlled by the landfill's existing gas collection system, which included vertical wells installed throughout the landfill through

  2. Appraisal of transport and deformation in shale reservoirs using natural noble gas tracers

    SciTech Connect

    Heath, Jason E.; Kuhlman, Kristopher L.; Robinson, David G.; Bauer, Stephen J.; Gardner, William Payton

    2015-09-01

    This report presents efforts to develop the use of in situ naturally-occurring noble gas tracers to evaluate transport mechanisms and deformation in shale hydrocarbon reservoirs. Noble gases are promising as shale reservoir diagnostic tools due to their sensitivity of transport to: shale pore structure; phase partitioning between groundwater, liquid, and gaseous hydrocarbons; and deformation from hydraulic fracturing. Approximately 1.5-year time-series of wellhead fluid samples were collected from two hydraulically-fractured wells. The noble gas compositions and isotopes suggest a strong signature of atmospheric contribution to the noble gases that mix with deep, old reservoir fluids. Complex mixing and transport of fracturing fluid and reservoir fluids occurs during production. Real-time laboratory measurements were performed on triaxially-deforming shale samples to link deformation behavior, transport, and gas tracer signatures. Finally, we present improved methods for production forecasts that borrow statistical strength from production data of nearby wells to reduce uncertainty in the forecasts.

  3. Delineation of Fast Flow Paths in Porous Media Using Noble Gas Tracers

    SciTech Connect

    Hudson, G B; Moran, J E

    2002-03-21

    Isotopically enriched xenon isotopes are ideal for tracking the flow of relatively large volumes of groundwater. Dissolved noble gas tracers behave conservatively in the saturated zone, pose no health risk to drinking water supplies, and can be used with a large dynamic range. Different Xe isotopes can be used simultaneously at multiple recharge sources in a single experiment. Results from a tracer experiment at a California water district suggests that a small fraction of tracer moved from the recharge ponds through the thick, unconfined, coarse-grained alluvial aquifer to high capacity production wells at a horizontal velocity of 6 m/day. In contrast, mean water residence times indicate that the average rate of transport is 0.5 to 1 m/day.

  4. Dense Molecular Gas Tracers in the Outflow of the Starburst Galaxy NGC 253

    NASA Astrophysics Data System (ADS)

    Walter, Fabian; Bolatto, Alberto D.; Leroy, Adam K.; Veilleux, Sylvain; Warren, Steven R.; Hodge, Jacqueline; Levy, Rebecca C.; Meier, David S.; Ostriker, Eve C.; Ott, Jürgen; Rosolowsky, Erik; Scoville, Nick; Weiss, Axel; Zschaechner, Laura; Zwaan, Martin

    2017-02-01

    We present a detailed study of a molecular outflow feature in the nearby starburst galaxy NGC 253 using ALMA. We find that this feature is clearly associated with the edge of NGC 253's prominent ionized outflow, has a projected length of ∼300 pc, with a width of ∼50 pc, and a velocity dispersion of ∼40 km s‑1, which is consistent with an ejection from the disk about 1 Myr ago. The kinematics of the molecular gas in this feature can be interpreted (albeit not uniquely) as accelerating at a rate of 1 km s‑1 pc‑1. In this scenario, the gas is approaching an escape velocity at the last measured point. Strikingly, bright tracers of dense molecular gas (HCN, CN, HCO+, CS) are also detected in the molecular outflow: we measure an HCN(1–0)/CO(1–0) line ratio of ∼ 1/10 in the outflow, similar to that in the central starburst region of NGC 253 and other starburst galaxies. By contrast, the HCN/CO line ratio in the NGC 253 disk is significantly lower (∼ 1/30), similar to other nearby galaxy disks. This strongly suggests that the streamer gas originates from the starburst, and that its physical state does not change significantly over timescales of ∼1 Myr during its entrainment in the outflow. Simple calculations indicate that radiation pressure is not the main mechanism for driving the outflow. The presence of such dense material in molecular outflows needs to be accounted for in simulations of galactic outflows.

  5. ANALYSIS OF A GAS-PHASE PARTITIONING TRACER TEST CONDUCTED IN AN UNSATURATED FRACTURED-CLAY FORMATION

    EPA Science Inventory

    The gas-phase partitioning tracer method was used to estimate non-aqueous phase liquid (NAPL), water, and air saturations in the vadose zone at a chlorinated-solvent contaminated field site in Tucson, AZ. The tracer test was conducted in a fractured-clay system that is the confin...

  6. Tracer Studies In A Laboratory Beach Subjected To Waves

    EPA Science Inventory

    This work investigated the washout of dissolved nutrients from beaches due to waves by conducting tracer studies in a laboratory beach facility. The effects of waves were studied in the case where the beach was subjected to the tide, and that in which no tidal action was present...

  7. The Tracer Gas Method of Determining the Charging Efficiency of Two-stroke-cycle Diesel Engines

    NASA Technical Reports Server (NTRS)

    Schweitzer, P H; Deluca, Frank, Jr

    1942-01-01

    A convenient method has been developed for determining the scavenging efficiency or the charging efficiency of two-stroke-cycle engines. The method consists of introducing a suitable tracer gas into the inlet air of the running engine and measuring chemically its concentration both in the inlet and exhaust gas. Monomethylamine CH(sub 3)NH(sub 2) was found suitable for the purpose as it burns almost completely during combustion, whereas the "short-circuited" portion does not burn at all and can be determined quantitatively in the exhaust. The method was tested both on four-stroke and on two-stroke engines and is considered accurate within 1 percent.

  8. A Tracer Study of Lebanese Upper Secondary School Students

    ERIC Educational Resources Information Center

    Vlaardingerbroek, Barend; Dallal, Kamel; Rizkallah, George; Rabah, Jihan

    2007-01-01

    This paper presents data arising from a tracer study of 90 terminating Beirut upper secondary school students. Nearly all the students intended to transit to university, about half of them to science and technology programmes, and subsequently did so. Median anticipated earnings upon graduation were realistic, but a lack of information or guidance…

  9. Studies of thunderstorm transport processes with aircraft using tracer techniques

    SciTech Connect

    Detwiler, A.G.; Smith, P.L.; Stith, J.L.

    1996-10-01

    Instrumented aircraft can provide in situ measurements of winds and turbulence useful for studying transport and dispersion in clouds. Using inert artificial gases as tracers, and fast response analyzers on aircraft, time-resolved observations of transport and dispersion have been obtained. Examples are shown of these types of observations in and around cumulus and cumulonimbus clouds. 23 refs., 6 figs.

  10. Sediment tracers in water erosion studies: Current approaches and challenges

    NASA Astrophysics Data System (ADS)

    Guzmán, Gema; Quinton, John N.; Nearing, Mark A.; Mabit, Lionel; Giráldez, Juan V.; Gómez, José A.

    2013-04-01

    The quest for alternative methods of soil losses assessment, due to water erosion to complement and enhance existing methods has directed attention to the use of tracing approaches because of the additional information they provide, such as sediment source identification, tracking of sediment movement across the landscape at various temporal and spatial scales and soil erosion rates. For these reasons, the utility and robustness of sediment tracing approaches using a wide range of substances and soil properties have been evaluated in numerous studies. A comprehensive literature review on tracing approaches used in water erosion studies was carried out in June 2011 using the Web of Science database and as search terms in the title or as keywords: "erosion AND tracer" OR "sediment AND tracer" OR "sediment AND tracking". The search excluded reviews and tillage and/or wind erosion studies. Only studies that used tracers to make a determination of water erosion or sedimentation rates, or in some cases relative erosion contribution, were considered in this study, and were further refined by manually checking that the articles corresponded to experiments involving sediment studies using tracers, as defined within the context of this review. Five distinct groups of tracing approaches were identified: fallout radionuclides, rare earth elements, soil magnetism and magnetic substances, other tracers, and sediment fingerprinting techniques. This abstract presents a synthesis of the current approaches of each of the tracing techniques identified in assessing soil erosion and sediment redistribution and a summary with the commonalities and differences between the approaches and identifying research gaps and future trends.

  11. Using Noble Gas Tracers to Estimate CO2 Saturation in the Field: Results from the 2014 CO2CRC Otway Repeat Residual Saturation Test

    NASA Astrophysics Data System (ADS)

    LaForce, T.; Ennis-King, J.; Boreham, C.; Serno, S.; Cook, P. J.; Freifeld, B. M.; Gilfillan, S.; Jarrett, A.; Johnson, G.; Myers, M.; Paterson, L.

    2015-12-01

    Residual trapping efficiency is a critical parameter in the design of secure subsurface CO2 storage. Residual saturation is also a key parameter in oil and gas production when a field is under consideration for enhanced oil recovery. Tracers are an important tool that can be used to estimate saturation in field tests. A series of measurements of CO2 saturation in an aquifer were undertaken as part of the Otway stage 2B extension field project in Dec. 2014. These tests were a repeat of similar tests in the same well in 2011 with improvements to the data collection and handling method. Two single-well tracer tests using noble gas tracers were conducted. In the first test krypton and xenon are injected into the water-saturated formation to establish dispersivity of the tracers in single-phase flow. Near-residual CO2 saturation is then established near the well. In the second test krypton and xenon are injected with CO2-saturated water to measure the final CO2 saturation. The recovery rate of the tracers is similar to predicted rates using recently published partitioning coefficients. Due to technical difficulties, there was mobile CO2 in the reservoir throughout the second tracer test in 2014. As a consequence, it is necessary to use a variation of the previous simulation procedure to interpret the second tracer test. One-dimensional, radial simulations are used to estimate average saturation of CO2 near the well. Estimates of final average CO2 saturation are computed using two relative permeability models, thermal and isothermal simulations, and three sets of coefficients for the partitioning of the tracers between phases. Four of the partitioning coefficients used were not previously available in the literature. The noble gas tracer field test and analysis of the 2011 and 2014 data both give an average CO2 saturation that is consistent with other field measurements. This study has demonstrated the repeatability of the methodology for noble gas tracer tests in the

  12. Tracer test for the measurement of gas diffusion and non-aqueous phase liquid (NAPL) saturation in soil.

    PubMed

    Van De Steene, Joke; Höhener, Patrick

    2009-01-01

    During soil bioremediation, the diffusion of oxygen into the soil is an important prerequisite for aerobic biodegradation, and the decrease of petroleum products is the ultimate goal. Both processes need to be monitored. The aim of this work was to develop a gas tracer test that yields information on both, gas diffusion and residual saturation with non-aqueous phase liquids (NAPLs) in unsaturated soil heaps. One conservative tracer (methane) and 4 partitioning gas tracers (diethylether, methyl tert-butyl ether, chloroform and n-heptane) were injected as vapors into laboratory columns filled with unsaturated sand with increasing NAPL saturation. Breakthrough curves of gaseous compounds were measured at two points and compared to analytical solutions of an analytical diffusive-reactive transport equation. By fitting of methane data, robust results for effective diffusivity (tortuosity) were obtained. NAPL saturation was most accurately measured by the moderately water soluble tracers (ethers and chloroform). The hydrophobic tracer n-heptane did not partition into water-immersed NAPL. An easy and accurate way to assess air-NAPL partitioning constants from gas chromatography retention times is furthermore reported. It is concluded that gas tracer tests have the potential for measuring two important properties in soil bioremediation systems easily and quickly.

  13. Interpretation of tracer surface diffusion experiments on UO2 — roles of gas and solid transport processes

    SciTech Connect

    Olander, D. R.

    1981-02-01

    In this paper, the spreading of a tracer from an enriched needle source which contacts the surface of a depleted pellet sink is analyzed rigorously. It is shown that volume diffusion in both the needle and the pellet need to be considered because only by this process is sufficient radioactivity accumulated for measurement after the anneal. Parasitic gas phase processes are of two types: evaporative loss of solid if a flowing gas is used, or molecular diffusion from enriched portions of the surface to depleted zones if the couple is in a closed vessel with a stagnant gas. A complete numerical solution including surface diffusion, solid diffusion, evaporative loss and contact resistance is applied to the UO2 tracer study of Marlowe and Kazanoff at 1915°C. Based upon UO2 evaporation experiments, the analysis shows that the evaporative loss effect is not important in these experiments. Finally, the UO2 surface diffusion coefficient deduced from analysis of these data is 0.2 ± 0.1 cm2/s at 1915°C, which is 104 times larger than that predicted by extrapolation of values obtained by mass transfer techniques.

  14. The Horsehead Nebula: a template for extragalactic high density tracers studies?

    NASA Astrophysics Data System (ADS)

    Gratier, P.; Pety, J.; Gerin, M.; Montillaud, J.; Guzman, V.; Goicoechea, J. R.

    2011-05-01

    The Horsehead Nebula, thanks to its proximity (1'' = 0.002 pc) and simple geometry is a perfect benchmark case to study the interplay between structure and chemistry in PDRs (Photon Dominated Regions). Our past studies of many tracers enabled us to obtain a clear picture of the density and temperature structure of the region. The presence of a steep density gradient (from less than 10^3 cm-3 to 10^5 cm-3 in less than 10'' = 0.02 pc) allows to probe different environments, from far-UV photon-dominated regions to shielded cold gas, in less than 50''. With the increased sensitivity available, extragalactic observations of gas tracers other than CO such as HCN, HNC, HCO^+ become more common. These observations are used in the extragalactic context to probe the density of the interstellar medium, to identify the heating mechanisms : FUV photons --- related to starburst phenomena, whose interaction with the ISM can be understood using PDR models ) or X rays --- related to AGN, using XDR models ---, and to probe star formation using specific molecular lines as tracers of embedded star forming regions. Nevertheless these observations are of low linear resolution and the details of the physics and chemistry of the interstellar medium are smeared by averaging over different environments. We will study how the understanding of these tracers in well known Galactic environments, such as the Horsehead PDR, can help the interpretation of extragalactic observations. We present high resolution multiline observations of HCN, HNC, CN and HCO^+ by the IRAM PdBI and 30m telescope instruments. We study the emission line ratios of these different molecules with the objective of comparing these high resolution observations of a well characterized Galactic region to extragalactic observations of the same tracers. Among the questions raised are : What is the importance of hyperfine anomalies in understanding the HCN and HNC observations? Can HCN be used as a tracer of star formation at

  15. DISSOCIATION OF SULFUR HEXAFLUORIDE TRACER GAS IN THE PRESENCE OF AN INDOOR COMBUSTION SOURCE

    EPA Science Inventory

    As an odorless, non-toxic, and inert compound, sulfur hexafluoride (SF6) is one of the most widely used tracer gases in indoor air quality studies in both controlled and uncontrolled environments. This compound may be subject to hydrolysis under elevated temperature to form acidi...

  16. Lighting the Dark Molecular Gas: H2 as a Direct Tracer

    NASA Astrophysics Data System (ADS)

    Togi, Aditya; Smith, J. D. T.

    2016-10-01

    Robust knowledge of molecular gas mass is critical for understanding star formation in galaxies. The {{{H}}}2 molecule does not emit efficiently in the cold interstellar medium, hence the molecular gas content of galaxies is typically inferred using indirect tracers. At low metallicity and in other extreme environments, these tracers can be subject to substantial biases. We present a new method of estimating total molecular gas mass in galaxies directly from pure mid-infrared rotational {{{H}}}2 emission. By assuming a power-law distribution of {{{H}}}2 rotational temperatures, we can accurately model {{{H}}}2 excitation and reliably obtain warm (T ≳ 100 K) {{{H}}}2 gas masses by varying only the power law’s slope. With sensitivities typical of Spitzer/IRS, we are able to directly probe the {{{H}}}2 content via rotational emission down to ∼80 K, accounting for ∼15% of the total molecular gas mass in a galaxy. By extrapolating the fitted power-law temperature distributions to a calibrated single lower cutoff temperature, the model also recovers the total molecular content within a factor of ∼2.2 in a diverse sample of galaxies, and a subset of broken power-law models performs similarly well. In ULIRGs, the fraction of warm {{{H}}}2 gas rises with dust temperature, with some dependency on α CO. In a sample of five low-metallicity galaxies ranging down to 12+{log}[{{O}}/{{H}}]=7.8, the model yields molecular masses up to ∼100× larger than implied by CO, in good agreement with other methods based on dust mass and star formation depletion timescale. This technique offers real promise for assessing molecular content in the early universe where CO and dust-based methods may fail.

  17. Gas exchange across the air - water interface determined with man-made and natural tracers

    SciTech Connect

    Wanninkhof, R.H.

    1986-01-01

    Gas exchange coefficients were determined on Rockland Lake, NY; Crowley Lake, CA; and Mono Lake, CA which have surface areas of 1 km/sup 2/, 20 km/sup 2/, and 190 km/sup 2/, respectively, by injecting a small amount of man made tracer gas, sulfur hexafluoride (SF/sub 6/) into the lake and measuring the rate of concentration decrease in the water column with time. The dependency of gas exchange on wind speed is similar for the three lakes indicating that wind fetch is not a critical parameter for the gas exchange coefficient for lakes with sizes greater than 1 km/sup 2/. Little gas exchange occurs for wind speeds less than 2.5 m/s and gas exchange increases linearly with wind speed from 2.5 to 6 m/s. The relationship of gas exchange and wind speed for the lakes agrees well with a compilation of earlier single wind speed - exchange coefficient measurements on lakes and oceans but they are lower than most results obtained in wind tunnels.

  18. Hanford facilities tracer study report (315 Water Treatment Facility)

    SciTech Connect

    Ambalam, T.

    1995-04-14

    This report presents the results and findings of a tracer study to determine contact time for the disinfection process of 315 Water Treatment Facility that supplies sanitary water for the 300 Area. The study utilized fluoride as the tracer and contact times were determined for two flow rates. Interpolation of data and short circuiting effects are also discussed. The 315 Water Treatment Facility supplies sanitary water for the 300 Area to various process and domestic users. The Surface Water Treatment Rule (SWTR), outlined in the 1986 Safe Drinking Water Act Amendments enacted by the EPA in 1989 and regulated by the Washington State Department of Health (DOH) in Section 246-290-600 of the Washington Administrative Code (WAC), stipulates filtration and disinfection requirements for public water systems under the direct influence of surface water. The SWTR disinfection guidelines require that each treatment system achieves predetermined inactivation ratios. The inactivation by disinfection is approximated with a measure called CxT, where C is the disinfectant residual concentration and T is the effective contact time of the water with the disinfectant. The CxT calculations for the Hanford water treatment plants were derived from the total volume of the contact basin(s). In the absence of empirical data to support CxT calculations, the DOH determined that the CxT values used in the monthly reports for the water treatment plants on the Hanford site were invalid and required the performance of a tracer study at each plant. In response to that determination, a tracer study will be performed to determine the actual contact times of the facilities for the CxT calculations.

  19. 13C Tracer Studies of Metabolism in Mouse Tumor Xenografts

    PubMed Central

    Lane, Andrew N.; Yan, Jun; Fan, Teresa W-M.

    2015-01-01

    Mice are widely used for human tumor xenograft studies of cancer development and drug efficacy and toxicity. Stable isotope tracing coupled with metabolomic analysis is an emerging approach for assaying metabolic network activity. In mouse models there are several routes of tracer introduction, which have particular advantages and disadvantages that depend on the model and the questions addressed. This protocol describes the bolus i.v. route via repeated tail vein injections of solutions of stable isotope enriched tracers including 13C6-glucose and 13C5,15N2-glutamine. Repeated injections give higher enrichments and over longer labeling periods than a single bolus. Multiple injections of glutamine are necessary to achieve adequate enrichment in engrafted tumors. PMID:26693168

  20. Atmospheric noble gases as tracers of biogenic gas dynamics in a shallow unconfined aquifer

    NASA Astrophysics Data System (ADS)

    Jones, Katherine L.; Lindsay, Matthew B. J.; Kipfer, Rolf; Mayer, K. Ulrich

    2014-03-01

    Atmospheric noble gases (NGs) were used to investigate biogenic gas dynamics in a shallow unconfined aquifer impacted by a crude oil spill, near Bemidji, MN. Concentrations of 3,4He, 20,22Ne, 36,40Ar, Kr, and Xe were determined for gas- and aqueous-phase samples collected from the vadose and saturated zones, respectively. Systematic elemental fractionation of Ne, Ar, Kr, and Xe with respect to air was observed in both of these hydrogeologic zones. Within the vadose zone, relative ratios of Ne and Ar to Kr and Xe revealed distinct process-related trends when compared to corresponding ratios for air. The degree of NG deviation from atmospheric concentrations generally increased with greater atomic mass (i.e., ΔXe > ΔKr > ΔAr > ΔNe), indicating that Kr and Xe are the most sensitive NG tracers in the vadose zone. Reactive transport modeling of the gas data confirms that elemental fractionation can be explained by mass-dependent variations in diffusive fluxes of NGs opposite to a total pressure gradient established between different biogeochemical process zones. Depletion of atmospheric NGs was also observed within a methanogenic zone of petroleum hydrocarbon degradation located below the water table. Solubility normalized NG abundances followed the order Xe > Kr > Ar > Ne, which is indicative of dissolved NG partitioning into the gas phase in response to bubble formation and possibly ebullition. Observed elemental NG ratios of Ne/Kr, Ne/Xe, Ar/Xe, and Kr/Xe and a modeling analysis provide strong evidence that CH4 generation below the water table caused gas exsolution and possibly ebullition and carbon transfer from groundwater to the vadose zone. These results suggest that noble gases provide sensitive tracers in biologically active unconfined aquifers and can assist in identifying carbon cycling and transfer within the vadose zone, the capillary fringe, and below the water table.

  1. A Rapid, Low-Cost Method to Determine Travel Times at Managed Aquifer Recharge Operations Using Noble Gas Tracers

    NASA Astrophysics Data System (ADS)

    Moran, J. E.; Visser, A.; Singleton, M. J.; Esser, B. K.; Halliwell, M.; Hillegonds, D. J.

    2012-12-01

    Managed aquifer recharge is a key component for the sustainable use of surface water and groundwater in the arid western U.S. When recycled water is a recharge water source, subsurface residence time, required for bacteria and virus deactivation, is best verified by application of an extrinsic tracer. Desirable tracer properties include: no real or perceived health risk, inexpensive even for a large volume of tagged water, large dynamic range, efficient introduction, convenient sampling methods, and rapid, low-cost analysis. We have developed and tested a dissolved noble gas tracer technique ideally suited for tracing large water volumes at managed aquifer recharge facilities. In an application of the method at a water district's facilities in the San Francisco Bay area, Xenon was introduced into a 106 m3 pond over a period of 7 days using a 300 m length of gas-permeable silicone tubing. Samples from the pond, near-field shallow monitoring wells, and production wells about 400 m from the recharge pond were analyzed for dissolved Xe by noble gas membrane inlet mass spectrometry (NGMIMS). The NGMIMS uses a syringe pump, gas-permeable membrane inlet, and quadrupole residual gas analyzer for measurement of noble gas concentrations. Samples are collected in VOA vials, and analysis can be carried out in real-time, with a measurement uncertainty of about 5% for Xe. Tracer first appeared in a production well 136 days after starting the tracer introduction at 0.7% (C/C0) of the peak pond xenon concentration. The cost of the tracer is about US650/106 m3 water, and the NGMIMS was assembled with parts totaling approximately US50,000, making application of the tracer method feasible for most managed aquifer recharge projects. This project is part of the California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment (GAMA) Program.

  2. Radioisotope tracer study in a sludge hygienization research irradiator (SHRI).

    PubMed

    Pant, H J; Thýn, J; Zitný, R; Bhatt, B C

    2001-01-01

    A radioisotope tracer study has been carried out in a batch type sludge hygienization research irradiator with flow from top to bottom, the objective being to measure flow rate, circulation and mixing times and to investigate the hydrodynamic behaviour of the irradiator for identifying the cause(s) of malfunction. A stimulus-response technique with NH4(82)Br as a tracer was used to measure the above parameters. Experiments were carried out at three different flow rates, i.e 1.0, 0.64 and 0.33 m3/min. Three combined models based on a set of differential equations are proposed and used to simulate the measured tracer concentration curves. The obtained parameters were used to estimate dead volume and analyse hydrodynamic behaviour of the irradiator. The nonlinear regression problem of model parameter estimation was solved using the Marquardt-Levenberg method. The measured flow rate was found to be in good agreement with the values shown by the flow meter. The circulation times were found to be half of the mixing times. A simple approach for estimation of dose based on a known vertical dose-rate profile inside the irradiator is presented. About one-fourth of the volume of the irradiator was found to be dead at lower flow rates and this decreased with increase in flow rate. At higher flow rates, a semi stagnant volume was found with slow exchange of flow between the active and dead volumes.

  3. The role of soil air composition for noble gas tracer applications in tropical groundwater

    NASA Astrophysics Data System (ADS)

    Mayer, Simon; Jenner, Florian; Aeschbach, Werner; Weissbach, Therese; Peregovich, Bernhard; Machado, Carlos

    2016-04-01

    Dissolved noble gases (NGs) in groundwater provide a well-established tool for paleo temperature reconstruction. However, reliable noble gas temperature (NGT) determination needs appropriate assumptions or rather an exact knowledge of soil air composition. Deviations of soil air NG partial pressures from atmospheric values have already been found in mid latitudes during summer time as a consequence of subsurface oxygen depletion. This effect depends on ambient temperature and humidity and is thus expected to be especially strong in humid tropical soils, which was not investigated so far. We therefore studied NGs in soil air and shallow groundwater near Santarém (Pará, Brazil) at the end of the rainy and dry seasons, respectively. Soil air data confirms a correlation between NG partial pressures, the sum value of O2+CO2 and soil moisture contents. During the rainy season, we find significant NG enhancements in soil air by up to 7% with respect to the atmosphere. This is twice as much as observed during the dry season. Groundwater samples show neon excess values between 15% and 120%. Nearly all wells show no seasonal variations of excess air, even though the local river level seasonally fluctuates by about 8 m. Assuming atmospheric NG contents in soil air, fitted NGTs underestimate the measured groundwater temperature by about 1-2° C. However, including enhanced soil air NG contents as observed during the rainy season, resulting NGTs are in good agreement with local groundwater temperatures. Our presented data allows for a better understanding of subsurface NG variations. This is essential with regard to NG tracer applications in humid tropical areas, for which reliable paleoclimate data is of major importance for modern climate research.

  4. Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain Site Characterization Study; Progress report, July 1, 1991--December 31, 1991

    SciTech Connect

    Dombrowski, T.; Stetzenbach, K.

    1991-12-31

    Studies continued on organic tracers for use as hydrologic tracers as part of the Yucca Mountain Site Characterization project. Tracers studied include benzoic acids, cinnamic acids, and salicylic acids. The main focus of the work performed during the time period from 07/01/91 to 12/31/91 has been the continuation of (1) LC-MS optimization for tracer identification, (2) batch sorption and degradation studies, (3) neoprene tubing evaluation studies, and (4) soil column evaluation of tracer compounds. All of these areas of research (except perhaps the neoprene tubing evaluation) are ongoing and will continue throughout the coming year.

  5. C I Emission in Ultraluminous Infrared Galaxies as a Molecular Gas Mass Tracer

    NASA Astrophysics Data System (ADS)

    Papadopoulos, Padeli P.; Greve, Thomas R.

    2004-11-01

    We present new sensitive wide-band measurements of the fine-structure line 3P1-->3P0 (J=1-0, 492 GHz) of neutral atomic carbon (C I) in the two typical ultraluminous infrared galaxies (ULIRGs) NGC 6240 and Arp 220. We then use them along with several other C I measurements in similar objects found in the literature to estimate their global molecular gas content under the assumption of a full C I-H2 concomitance. We find excellent agreement between the H2 gas mass estimated with this method and the standard methods using 12CO. This may provide a new way to measure H2 gas mass in galaxies and one that may be very valuable in ULIRGs since in such systems the bright 12CO emission is known to systematically overestimate the gas mass while their 13CO emission (an often-used alternative) is usually very weak. At redshifts z>=1 the C I J=1-0 line shifts to much more favorable atmospheric windows and can become a viable alternative tracer of the H2 gas, fueling starburst events in the distant universe.

  6. Effect of release rate of the SF(6) tracer on methane emission estimates based on ruminal and breath gas samples.

    PubMed

    Martin, C; Koolaard, J; Rochette, Y; Clark, H; Jouany, J P; Pinares-Patiño, C S

    2012-03-01

    The release rate (RR) of sulphur hexafluoride (SF(6)) gas from permeation tube in the rumen appears to be positively related with methane (CH(4)) emissions calculated using the SF(6) tracer technique. Gas samples of breath and ruminal headspace were collected simultaneously in order to evaluate the hypothesis that transactions of SF(6) in the rumen are the source for this relationship. Six non-lactating dairy cows fitted with rumen cannulae were subdivided into two groups and randomly assigned to a two-period crossover design to permeation tubes with low RR (LRR = 1.577 mg/day) or two-times higher RR (HRR = 3.147 mg/day) RR. The cows were fed limited amounts of maize silage (80% ad libitum) split into two meals (40% at 0800 h and 60% at 1600 h). Each period consisted of 3-day gas sampling. Immediately before the morning feed and then each hour over 8 h, ruminal gas samples (50 ml) were withdrawn through the cannula fitted with stoppers to prevent opening. Simultaneously, 8-h integrated breath gas samples were collected over the same period. Ratios of concentration of CH(4)/SF(6), CO(2)/SF(6) and CO(2)/CH(4) and emission estimates of CH(4) and CO(2) were calculated for each sample source using the SF(6) tracer technique principles. The LRR treatment yielded higher (P < 0.001) ruminal CH(4)/SF(6) (by 1.79 times) and CO(2)/SF(6) (by 1.90 times) ratios than the HRR treatment; however, these differences were lower than the 2.0 times difference expected from the RR between the LRR and HRR. Consequently, the LRR treatment was associated with lower (P < 0.01) ruminal emissions of CH(4) over the 8-h collection period than with the HRR treatment (+11%), a difference also confirmed by the breath samples (+11%). RR treatments did not differ (P = 0.53) in ruminal or breath CO(2) emissions; however, our results confirm that the SF(6) tracer seems inappropriate for CO(2) emissions estimation in ruminants. Irrespective of the RR treatment, breath samples yielded 8% to 9% higher CH

  7. Noble gas and hydrocarbon tracers in multiphase unconventional hydrocarbon systems: Toward integrated advanced reservoir simulators

    NASA Astrophysics Data System (ADS)

    Darrah, T.; Moortgat, J.; Poreda, R. J.; Muehlenbachs, K.; Whyte, C. J.

    2015-12-01

    Although hydrocarbon production from unconventional energy resources has increased dramatically in the last decade, total unconventional oil and gas recovery from black shales is still less than 25% and 9% of the totals in place, respectively. Further, the majority of increased hydrocarbon production results from increasing the lengths of laterals, the number of hydraulic fracturing stages, and the volume of consumptive water usage. These strategies all reduce the economic efficiency of hydrocarbon extraction. The poor recovery statistics result from an insufficient understanding of some of the key physical processes in complex, organic-rich, low porosity formations (e.g., phase behavior, fluid-rock interactions, and flow mechanisms at nano-scale confinement and the role of natural fractures and faults as conduits for flow). Noble gases and other hydrocarbon tracers are capably of recording subsurface fluid-rock interactions on a variety of geological scales (micro-, meso-, to macro-scale) and provide analogs for the movement of hydrocarbons in the subsurface. As such geochemical data enrich the input for the numerical modeling of multi-phase (e.g., oil, gas, and brine) fluid flow in highly heterogeneous, low permeability formations Herein we will present a combination of noble gas (He, Ne, Ar, Kr, and Xe abundances and isotope ratios) and molecular and isotopic hydrocarbon data from a geographically and geologically diverse set of unconventional hydrocarbon reservoirs in North America. Specifically, we will include data from the Marcellus, Utica, Barnett, Eagle Ford, formations and the Illinois basin. Our presentation will include geochemical and geological interpretation and our perspective on the first steps toward building an advanced reservoir simulator for tracer transport in multicomponent multiphase compositional flow (presented separately, in Moortgat et al., 2015).

  8. Radon entry rate analyses using in situ tracer gas method application.

    PubMed

    Froňka, A; Jílek, K

    2014-07-01

    Recently, the role of energy savings in indoor air quality deterioration has been extensively emphasised, predominantly in the context of significant air exchange rate reduction as a result of home energy retrofits. In case of refurbishment of existing buildings, the effect of energy-efficient technologies on indoor radon concentration is considerably complex and has to be carefully evaluated with respect to radon entry rate (RER) and air exchange rate alteration. For the purpose of detailed analysis of radon entry pathways, the unique infiltration experiment has been carried out using the tracer gas (N2O) method application in field conditions. Significant amount of experimental works has been done to provide an independent assessment of RER and air-exchange rate facilitating the analysis of fundamental factors influencing the indoor radon variations (e.g. indoor-outdoor pressure difference induced by wind, stack effect, heating, ventilation and operation of air-conditioning systems).

  9. Carbonyl sulfide as an inverse tracer for biogenic organic carbon in gas and aerosol phases

    NASA Astrophysics Data System (ADS)

    de Gouw, J. A.; Warneke, C.; Montzka, S. A.; Holloway, J. S.; Parrish, D. D.; Fehsenfeld, F. C.; Atlas, E. L.; Weber, R. J.; Flocke, F. M.

    2009-03-01

    Carbonyl sulfide (COS) is a long-lived trace gas in the atmosphere with an oceanic source and a surface sink through the uptake by vegetation and soils. We demonstrate the use of COS as an inverse tracer for the impact of biogenic emissions on an air mass including the formation of secondary organic aerosol (SOA). Using airborne data from the summer of 2004 over the northeastern U.S., we find that air masses with reduced COS in the continental boundary layer had on average higher mixing ratios of biogenic VOCs (isoprene, monoterpenes, methanol) and their photo-oxidation products (methacrolein, methyl vinyl ketone, methyl furan and MPAN, a peroxyacyl nitrate derived from isoprene). Measurements of water-soluble organic carbon were only weakly correlated with COS, indicating that SOA formation from biogenic precursors was a small contribution to the total.

  10. Noble gas tracers of ventilation during deep-water formation in the Weddell Sea

    NASA Astrophysics Data System (ADS)

    Nicholson, D. P.; Khatiwala, S.; Heimbach, P.

    2016-05-01

    To explore the dynamics and implications of incomplete air-sea equilibration during the formation of abyssal water masses, we simulated noble gases in the Estimating the Circulation & Climate of the Ocean (ECCO) global ocean state estimate. A novel computation approach utilizing a matrix-free Newton-Krylov (MFNK) scheme was applied to quickly compute the periodic seasonal solutions for noble gas tracers. MFNK allows for quick computation of a cyclo-stationary solution for tracers (i.e., a spun-up, repeating seasonal cycle), which would otherwise be computationally infeasible due to the long time scale of dynamic adjustment of the abyssal ocean (1000’s of years). A suite of experiments isolates individual processes, including atmospheric pressure effects, the solubility pump and air-sea bubble fluxes. In addition to these modeled processes, a volumetric contribution of 0.28 ± 0.07% of glacial melt water is required to reconcile deep-water observations in the Weddell Sea. Another primary finding of our work is that the saturation anomaly of heavy noble gases in model simulations is in excess of two-fold more negative than is suggested from Weddell Sea observations. This result suggests that model water masses are insufficiently ventilated prior to subduction and thus there is insufficient communication between atmosphere and ocean at high latitudes. The discrepancy between noble gas observations and ECCO simulations highlights that important inadequacies remain in how we model high-latitude ventilation with large implications for the oceanic uptake and storage of carbon.

  11. Study of stomach motility using the relaxation of magnetic tracers

    NASA Astrophysics Data System (ADS)

    Carneiro, A. A.; Baffa, O.; Oliveira, R. B.

    1999-07-01

    Magnetic tracers can be observed in the interior of the human body to give information about their quantity, position and state of order. With the aim of detecting and studying the degree of disorder of these tracers after they have been previously magnetized inside the stomach, a system composed of magnetization coils and magnetic detectors was developed. Helmholtz coils of diameter 84 cm were used to magnetize the sample and the remanent magnetization (RM) was detected with two first-order gradiometric fluxgate arrays each with a 15 cm base line, sensitivity of 0.5 nT and common mode rejection (CMR) of at least 10. The system allows simultaneous measurement in the anterior and posterior projections of the stomach. Measurements of the time evolution of the RM were performed in vitro and in normal subjects after the ingestion of a test meal labelled with magnetic particles. The data were fitted with an exponential curve and the relaxation time tau was obtained. Initial studies were performed to ascertain the action of a drug that is known to affect the gastric motility, showing that the decay of the remanent magnetization was indeed due to stomach contractions.

  12. The CII line in Draco as a tracer for CO-dark gas

    NASA Astrophysics Data System (ADS)

    Schneider, Nicola

    The Draco cloud can be considered as a template region for a colliding HI flow scenario in which H2 formation is partly triggered by the shock interaction between a high-velocity (HVC) and intermediate-velocity cloud (IVC). From Herschel dust maps, a double lognormal PDF is obtained, that we interprete as arising from the atomic and molecular hydrogen gas phase. Because the observed total hydrogen column densities are very low (<2 10^20 cm^-2), a large part of the H2 gas is CO-dark. Simulations predict that the CII 158 micron line is a good tracer for this gas phase, we thus propose to observe the CII emission towards two points in Draco with upGREAT. One point is located at the collision point of the HVC and IVC, the other one is found in a region without emission from the HVC. We will compare the intensities and kinematics of the CII with HI and CO and model predictions, and deduce how much CO-dark H2 is associated with the cloud. These observations will also allow us to refine theoretical models of molecular cloud formation and they will provide important constraints on numerical simulations of this process.

  13. Determination of the solubility of low volatility liquid organic compounds in water using volatile-tracer assisted headspace gas chromatography.

    PubMed

    Zhang, Shu-Xin; Chai, Xin-Sheng; Barnes, Donald G

    2016-02-26

    This study reports a new headspace gas chromatographic method (HS-GC) for the determination of water solubility of low volatility liquid organic compounds (LVLOs). The HS-GC analysis was performed on a set of aqueous solutions containing a range of concentrations of toluene-spiked (as a tracer) LVLOs, from under-saturation to over-saturation. A plot of the toluene tracer GC signal vs. the concentration of the LVLO results in two lines of different slopes that intersect at the concentration corresponding to the compound's solubility in water. The results showed that the HS-GC method has good precision (RSD <6.3%) and good accuracy, in which the relative deference between the data measured by the HS-GC method and the reference method were within 6.0%. The HS-GC method is simple and particularly suitable for measuring the solubility of LVLOs at elevated temperatures. This approach should be of special interest to those concerned about the impact of the presence of low-volatility organic liquids in waters of environmental and biological systems.

  14. Near-Road Mulltipollutant Profiles: Association between Volatile Organic Compounds and a Tracer Gas Surrogate Near a Busy Highway

    EPA Science Inventory

    This research characterizes associations between multiple pollutants in the near-road environment attributed to a roadway line source. It also examines the use of a tracer gas as a surrogate of mobile source pollutants. Air samples were collected in summa canisters along a 300 m ...

  15. Vertical Tracer Concentration Profiles Measured During the Joint Urban 2003 Dispersion Study

    SciTech Connect

    Flaherty, Julia E.; Lamb, Brian K.; Allwine, K Jerry; Allwine, Eugene J.

    2007-12-01

    An atmospheric tracer dispersion study known as Joint Urban 2003 was conducted in Oklahoma City, Oklahoma during the summer of 2003. As part of this field program, vertical concentration profiles were measured at approximately 1 km from downtown tracer gas release locations. These profiles indicated that the urban landscape was very effective in mixing the plume vertically. The height of the plume centerline (as determined by the maximum concentration over the depth of the measurements) for any specific 30 min period varied over the 65 m measurement range. Most of the variations in tracer concentration observed in the profile time series were related to changes in wind direction as opposed to changes in turbulence. As a simple analysis tool for emergency response, maximum normalized concentration curves were developed with 5-minute averaged measurements. These curves give the maximum concentration (normalized by the release rate) that would be observed as a function of downwind distance in an urban area. The 5-min data resulted in greater concentrations than predicted with a simple Gaussian plume model. However, the curve compared well with results from a computational fluid dynamics simulation. This dispersion dataset is a valuable asset not only for refining air quality models, but also for developing new tools for emergency response personnel in the event of a toxic release.

  16. Reintegration of child soldiers in Burundi: a tracer study

    PubMed Central

    2012-01-01

    Background Substantial attention and resources are aimed at the reintegration of child soldiers, yet rigorous evaluations are rare. Methods This tracer study was conducted among former child soldiers (N=452) and never-recruited peers (N=191) who participated in an economic support program in Burundi. Socio-economic outcome indicators were measured retrospectively for the period before receiving support (T1; 2005–06); immediately afterwards (T2; 2006–07); and at present (T3; 2010). Participants also rated present functional impairment and mental health indicators. Results Participants reported improvement on all indicators, especially economic opportunity and social integration. At present no difference existed between both groups on any of the outcome indicators. Socio-economic functioning was negatively related with depression- and, health complaints and positively with intervention satisfaction. Conclusion The present study demonstrates promising reintegration trajectories of former child soldiers after participating in a support program. PMID:23095403

  17. Groundwater surface water interaction study using natural isotopes tracer

    NASA Astrophysics Data System (ADS)

    Yoon, Yoon Yeol; Kim, Yong Chul; Cho, Soo Young; Lee, Kil Yong

    2015-04-01

    Tritium and stable isotopes are a component of the water molecule, they are the most conservative tracer for groundwater study. And also, radon is natural radioactive nuclide and well dissolved in groundwater. Therefore, these isotopes are used natural tracer for the study of surface water and groundwater interaction of water curtain greenhouse area. The study area used groundwater as a water curtain for warming tool of greenhouse during the winter, and is associated with issues of groundwater shortage while being subject to groundwater-river water interaction. During the winter time, these interactions were studied by using Rn-222, stable isotopes and H-3. These interaction was monitored in multi depth well and linear direction well of groundwater flow. And dam effect was also compared. Samples were collected monthly from October 2013 to April 2014. Radon and tritium were analyzed using Quantulus low background liquid scintillation counter and stable isotopes were analyzed using an IRIS (Isotope Ratio Infrared Spectroscopy ; L2120-i, Picarro). During the winter time, radon concentration was varied from 0.07 Bq/L to 8.9 Bq/L and different interaction was showed between dam. Surface water intrusion was severe at February and restored April when greenhouse warming was ended. The stable isotope results showed different trend with depth and ranged from -9.16 ‰ to -7.24 ‰ for δ 18O value, while the δD value was ranged from -57.86 ‰ to -50.98 ‰. The groundwater age as dated by H-3 was ranged 0.23 Bq/L - 0.59 Bq/L with an average value of 0.37 Bq/L.

  18. Using a Gas-Phase Tracer Test to Characterize the Impact of Landfill Gas Generation on Advective-Dispersive Transport of VOCs in the Vadose Zone

    PubMed Central

    Monger, Gregg R.; Duncan, Candice Morrison; Brusseau, Mark L.

    2015-01-01

    A gas-phase tracer test (GTT) was conducted at a landfill in Tucson, AZ, to help elucidate the impact of landfill gas generation on the transport and fate of chlorinated aliphatic volatile organic contaminants (VOCs). Sulfur hexafluoride (SF6) was used as the non-reactive gas tracer. Gas samples were collected from a multiport monitoring well located 15.2 m from the injection well, and analyzed for SF6, CH4, CO2, and VOCs. The travel times determined for SF6 from the tracer test are approximately two to ten times smaller than estimated travel times that incorporate transport by only gas-phase diffusion. In addition, significant concentrations of CH4 and CO2 were measured, indicating production of landfill gas. Based on these results, it is hypothesized that the enhanced rates of transport observed for SF6 are caused by advective transport associated with landfill gas generation. The rates of transport varied vertically, which is attributed to multiple factors including spatial variability of water content, refuse mass, refuse permeability, and gas generation. PMID:26380532

  19. Using a Gas-Phase Tracer Test to Characterize the Impact of Landfill Gas Generation on Advective-Dispersive Transport of VOCs in the Vadose Zone.

    PubMed

    Monger, Gregg R; Duncan, Candice Morrison; Brusseau, Mark L

    2014-12-01

    A gas-phase tracer test (GTT) was conducted at a landfill in Tucson, AZ, to help elucidate the impact of landfill gas generation on the transport and fate of chlorinated aliphatic volatile organic contaminants (VOCs). Sulfur hexafluoride (SF6) was used as the non-reactive gas tracer. Gas samples were collected from a multiport monitoring well located 15.2 m from the injection well, and analyzed for SF6, CH4, CO2, and VOCs. The travel times determined for SF6 from the tracer test are approximately two to ten times smaller than estimated travel times that incorporate transport by only gas-phase diffusion. In addition, significant concentrations of CH4 and CO2 were measured, indicating production of landfill gas. Based on these results, it is hypothesized that the enhanced rates of transport observed for SF6 are caused by advective transport associated with landfill gas generation. The rates of transport varied vertically, which is attributed to multiple factors including spatial variability of water content, refuse mass, refuse permeability, and gas generation.

  20. IMPURITY AND TRACER DIFFUSION STUDIES IN MAGNESIUM AND ITS ALLOYS

    SciTech Connect

    Brennan, Sarah; Sohn, Yong Ho; Warren, Andrew; Coffey, Kevin; Klimov, Mikhail; Kulkarni, Nagraj S; Todd, Peter J

    2010-01-01

    An Integrated Computational Materials Engineering (ICME) approach for optimizing processing routes for Mg-alloys requires reliable thermodynamic and diffusion databases. We are developing an impurity and tracer diffusion database using both stable and unstable isotopes for Mg and its alloys. In this study, Al impurity diffusion in pure polycrystalline Mg (99.9%) was examined using the thin film method. Approximately 500 nm thick Al films were deposited on in-situ RF plasma-cleaned polycrystalline Mg by DC magnetron sputtering from pure Al (99.9%) targets. Specimens were then diffusion annealed at 300, 350 and 400 C in quartz capsules that were evacuated to 10-8 Torr and backfilled with Ar-H2 mixtures. Concentration profile of Al diffusion profiles into single phase Mg was determined by depth-profiling technique using secondary ion mass spectroscopy. The Al impurity diffusion coefficients were determined as a function of temperature

  1. Tracer studies of SO{sub 2} oxidation in clouds

    SciTech Connect

    Burkhard, E.G.

    1994-12-31

    The quantitative determination of aqueous phase oxidation of S(IV) is critical to determining: (1) the relationship between regional SO{sub 2} emissions and acid deposition at distant receptors; and (2) the size distribution of anthropogenic sulphate aerosols which has consequences on global climate. Husain developed a tracer technique, based on the similarities in physical and chemical behavior of SO{sub 4} and Se aerosols to quantitatively determine SO{sub 2} oxidation in clouds. Extensive investigation of the technique including verification of the assumptions, extension to develop other tracers, its application to study S(IV) oxidation in clouds, comparison of the field data with calculations based on laboratory reaction rates and an assessment of the role of clouds on SO{sub 2} oxidation were the important goals of this dissertation. Field investigations were conducted at Whiteface Mountain, New York during the summers of 1990, 1991, and 1992. Three hundred seventy cloud water samples, usually of 15 min duration were collected from thirteen clouds. Aerosol in cloud free air were also collected for each cloud system. pH of the cloud water ranged between 2.85 and 4.7. Six clouds were selected, based on chemical and meteorological conditions for determination of in-cloud SO{sub 2} oxidation. The amount of SO{sub 4} formed in situ by aqueous phase oxidation (SO{sub 4in}) ranged from none to about 40%. In three clouds, in-cloud oxidation was quantified using Se, As, and Sb as tracers. The results were in good agreement when large amounts of SO{sub 4in} were produced. It is concluded that all three, Se, As, and Sb can be used to determine SO{sub 2} oxidation in clouds. Based on SO{sub 4in}, concentrations of SO{sub 2}, H{sub 2}O{sub 2}, and laboratory reaction rates, progression of the reaction was followed in time using a simple computer model.

  2. Isotope tracers in oceanographic studies: some sticky wickets

    NASA Astrophysics Data System (ADS)

    GROUSSET, F. E.

    2001-12-01

    Trace elements and isotopes have found widespread applications in oceanography. In most cases, their use has led to a better understanding of many oceanic processes (viz., chemical inputs to the ocean, chemical fluxes through the water column, particulate- dissolved-matter exchanges, watermass circulation, etc), permitting the application of reliable models. Anomalies have been observed, however, in the data on some tracers of particulates that should be given more attention in future. For example, it is widely recognized that the Sr isotopic composition of detrital particles is grain-size dependant (Dasch, 1969), whereas their Nd isotopic composition would not vary with grain-size (Goldstein et al., 1984). Recent sudies of detrital grain-size fractions, however, reveal that Sr, Nd and Pb isotopes can be strongly grain-size dependant. Some of these same isotopes can be used to study dissolved phases. The isotopic composition of Nd associated with iron oxides deposited on surface sediment planktic foraminifers has been used as a watermass tracer (Palmer et al., 1985). In the northern Atlantic surface sediments, however, the Nd isotope composition of the foraminifers is in fact mostly controled by the isotopic composition of the ambient detrital particles that are partially dissolved into the intertitial waters, subsequently contaminating the foraminifers (Grousset et al., 1986). The original watermass fingerprint is thus partly obscured. Another example is provided by iron-manganese nodules. In the Pacific ocean, the temporal evolution of the Pb-isotope composition of three nodules located at different latitudes has been explained by their plate-tectonic latitudinal shift through time (Meynadier, 2000). In the same ocean, another study still in progress of two nodules from a unique box-core reveals two totally different temporal behaviors of their trace elements and isotopes (Bernard et al., in prep.). Such anomalies will be reviewed and discussed.

  3. Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain Site Characterization Study; Progress report, June 1--December 31, 1990

    SciTech Connect

    Stetzenbach, K.J.

    1990-12-31

    Ground water tracers are solutes dissolved in or carried by ground water to delineate flow pathways. Tracers provide information on direction and speed of water movement and that of contaminants that might be conveyed by the water. Tracers can also be used to measure effective porosity, hydraulic conductivity, dispersivity and solute distribution coefficients. For most applications tracers should be conservative, that is, move at the same rate as the water and not sorb to aquifer materials. Tracers must have a number of properties to be functional. Regardless of the desired properties, the chemical and physical behavior of a tracer in ground water and the porous medium under study must be understood. Good estimates of tracer behavior can be obtained from laboratory studies. Studies in this proposal will address tracer properties with analytical method development, static sorption and degradation studies and column transport studies, Mutagenicity tests will be performed on promising candidates. The tracers that will be used for these experiments are fluorinated organic acids and other organic compounds that have the chemical and biological stability necessary to be effective in the Yucca Mountain environment. Special emphasis will be placed on compounds that fluoresce or have very large ultraviolet absorption coefficients for very high analytical sensitivity.

  4. Aligning Higher Education to Workforce Needs in Liberia: A Tracer Study of University Graduates in Liberia

    ERIC Educational Resources Information Center

    Flomo, John S., Jr.

    2013-01-01

    This study investigated the congruence between higher education and the labor market from the perspectives of college graduates in Liberia. It specifically examined the alignment of the skills college students acquire in college to Liberia's labor market. The study employed a Tracer Study quantitative research methodology. Tracer study as a…

  5. Enhancing the activation of silicon carbide tracer particles for PEPT applications using gas-phase deposition of alumina at room temperature and atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Valdesueiro, D.; Garcia-Triñanes, P.; Meesters, G. M. H.; Kreutzer, M. T.; Gargiuli, J.; Leadbeater, T. W.; Parker, D. J.; Seville, J. P. K.; van Ommen, J. R.

    2016-01-01

    We have enhanced the radio-activation efficiency of SiC (silicon carbide) particles, which by nature have a poor affinity towards 18F ions, to be employed as tracers in studies using PEPT (Positron Emission Particle Tracking). The resulting SiC-Al2O3 core-shell structure shows a good labelling efficiency, comparable to γ-Al2O3 tracer particles, which are commonly used in PEPT. The coating of the SiC particles was carried at 27±3 °C and 1 bar in a fluidized bed reactor, using trimethylaluminium and water as precursors, by a gas phase technique similar to atomic layer deposition. The thickness of the alumina films, which ranged from 5 to 500 nm, was measured by elemental analysis and confirmed with FIB-TEM (focused ion beam - transmission electron microscope), obtaining consistent results from both techniques. By depositing such a thin film of alumina, properties that influence the hydrodynamic behaviour of the SiC particles, such as size, shape and density, are hardly altered, ensuring that the tracer particle shows the same flow behaviour as the other particles. The paper describes a general method to improve the activation efficiency of materials, which can be applied for the production of tracer particles for many other applications too.

  6. Using noble gas tracers to constrain a groundwater flow model with recharge elevations: A novel approach for mountainous terrain

    NASA Astrophysics Data System (ADS)

    Doyle, Jessica M.; Gleeson, Tom; Manning, Andrew H.; Mayer, K. Ulrich

    2015-10-01

    Environmental tracers provide information on groundwater age, recharge conditions, and flow processes which can be helpful for evaluating groundwater sustainability and vulnerability. Dissolved noble gas data have proven particularly useful in mountainous terrain because they can be used to determine recharge elevation. However, tracer-derived recharge elevations have not been utilized as calibration targets for numerical groundwater flow models. Herein, we constrain and calibrate a regional groundwater flow model with noble-gas-derived recharge elevations for the first time. Tritium and noble gas tracer results improved the site conceptual model by identifying a previously uncertain contribution of mountain block recharge from the Coast Mountains to an alluvial coastal aquifer in humid southwestern British Columbia. The revised conceptual model was integrated into a three-dimensional numerical groundwater flow model and calibrated to hydraulic head data in addition to recharge elevations estimated from noble gas recharge temperatures. Recharge elevations proved to be imperative for constraining hydraulic conductivity, recharge location, and bedrock geometry, and thus minimizing model nonuniqueness. Results indicate that 45% of recharge to the aquifer is mountain block recharge. A similar match between measured and modeled heads was achieved in a second numerical model that excludes the mountain block (no mountain block recharge), demonstrating that hydraulic head data alone are incapable of quantifying mountain block recharge. This result has significant implications for understanding and managing source water protection in recharge areas, potential effects of climate change, the overall water budget, and ultimately ensuring groundwater sustainability.

  7. Using noble gas tracers to constrain a groundwater flow model with recharge elevations: A novel approach for mountainous terrain

    USGS Publications Warehouse

    Doyle, Jessica M.; Gleeson, Tom; Manning, Andrew H.; Mayer, K. Ulrich

    2015-01-01

    Environmental tracers provide information on groundwater age, recharge conditions, and flow processes which can be helpful for evaluating groundwater sustainability and vulnerability. Dissolved noble gas data have proven particularly useful in mountainous terrain because they can be used to determine recharge elevation. However, tracer-derived recharge elevations have not been utilized as calibration targets for numerical groundwater flow models. Herein, we constrain and calibrate a regional groundwater flow model with noble-gas-derived recharge elevations for the first time. Tritium and noble gas tracer results improved the site conceptual model by identifying a previously uncertain contribution of mountain block recharge from the Coast Mountains to an alluvial coastal aquifer in humid southwestern British Columbia. The revised conceptual model was integrated into a three-dimensional numerical groundwater flow model and calibrated to hydraulic head data in addition to recharge elevations estimated from noble gas recharge temperatures. Recharge elevations proved to be imperative for constraining hydraulic conductivity, recharge location, and bedrock geometry, and thus minimizing model nonuniqueness. Results indicate that 45% of recharge to the aquifer is mountain block recharge. A similar match between measured and modeled heads was achieved in a second numerical model that excludes the mountain block (no mountain block recharge), demonstrating that hydraulic head data alone are incapable of quantifying mountain block recharge. This result has significant implications for understanding and managing source water protection in recharge areas, potential effects of climate change, the overall water budget, and ultimately ensuring groundwater sustainability.

  8. The project MOHAVE tracer study: study design, data quality, and overview of results

    NASA Astrophysics Data System (ADS)

    Green, Mark C.

    In the winter and summer of 1992, atmospheric tracer studies were conducted in support of project MOHAVE, a visibility study in the southwestern United States. The primary goal of project MOHAVE is to determine the effects of the Mohave power plant and other sources upon visibility at Grand Canyon National Park. Perfluorocarbon tracers (PFTs) were released from the Mohave power plant and other locations and monitored at about 30 sites. The tracer data are being used for source attribution analysis and for evaluation of transport and dispersion models and receptor models. Collocated measurements showed the tracer data to be of high quality and suitable for source attribution analysis and model evaluation. The results showed strong influences of channeling by the Colorado River canyon during both winter and summer. Flow from the Mohave power plant was usually to the south, away from the Grand Canyon in winter and to the northeast, toward the Grand Canyon in summer. Tracer released at Lake Powell in winter was found to often travel downstream through the entire length of the Grand Canyon. Data from summer tracer releases in southern California demonstrated the existence of a convergence zone in the western Mohave Desert.

  9. Optimization of Sampling Positions for Measuring Ventilation Rates in Naturally Ventilated Buildings Using Tracer Gas

    PubMed Central

    Shen, Xiong; Zong, Chao; Zhang, Guoqiang

    2012-01-01

    Finding out the optimal sampling positions for measurement of ventilation rates in a naturally ventilated building using tracer gas is a challenge. Affected by the wind and the opening status, the representative positions inside the building may change dynamically at any time. An optimization procedure using the Response Surface Methodology (RSM) was conducted. In this method, the concentration field inside the building was estimated by a three-order RSM polynomial model. The experimental sampling positions to develop the model were chosen from the cross-section area of a pitched-roof building. The Optimal Design method which can decrease the bias of the model was adopted to select these sampling positions. Experiments with a scale model building were conducted in a wind tunnel to achieve observed values of those positions. Finally, the models in different cases of opening states and wind conditions were established and the optimum sampling position was obtained with a desirability level up to 92% inside the model building. The optimization was further confirmed by another round of experiments.

  10. A gas-tracer injection for evaluating the fate of methane in a coastal plain stream: Degassing versus in-stream oxidation

    USGS Publications Warehouse

    Heilweil, Victor M.; Solomon, D. Kip; Darrah, Thomas H.; Gilmore, Troy E.; Genereux, David P.

    2016-01-01

    Methane emissions from streams and rivers have recently been recognized as an important component of global greenhouse budgets. Stream methane is lost as evasion to the atmosphere or in-stream methane oxidation. Previous studies have quantified evasion and oxidation with point-scale measurements. In this study, dissolved gases (methane, krypton) were injected into a coastal plain stream in North Carolina to quantify stream CH4 losses at the watershed scale. Stream-reach modeling yielded gas transfer and oxidation rate constants of 3.2 ± 0.5 and 0.5 ± 1.5 d–1, respectively, indicating a ratio of about 6:1. The resulting evasion and oxidation rates of 2.9 mmol m–2 d–1 and 1,140 nmol L–1 d–1, respectively, lie within ranges of published values. Similarly, the gas transfer velocity (K600) of 2.1 m d–1 is consistent with other gas tracer studies. This study illustrates the utility of dissolved-gas tracers for evaluating stream methane fluxes. In contrast to point measurements, this approach provides a larger watershed-scale perspective. Further work is needed to quantify the magnitude of these fluxes under varying conditions (e.g., stream temperature, nutrient load, gradient, flow rate) at regional and global scales before reliable bottom-up estimates of methane evasion can be determined at global scales.

  11. Gas transport below artificial recharge ponds: insights from dissolved noble gases and a dual gas (SF6 and 3He) tracer experiment.

    PubMed

    Clark, Jordan F; Hudson, G Bryant; Avisar, Dror

    2005-06-01

    A dual gas tracer experiment using sulfur hexafluoride (SF6) and an isotope of helium (3He) and measurements of dissolved noble gases was performed at the El Rio spreading grounds to examine gas transport and trapped air below an artificial recharge pond with a very high recharge rate (approximately 4 m day(-1)). Noble gas concentrations in the groundwater were greater than in surface water due to excess air formation showing that trapped air exists below the pond. Breakthrough curves of SF6 and 3He at two nearby production wells were very similar and suggest that nonequilibrium gas transfer was occurring between the percolating water and the trapped air. At one well screened between 50 and 90 m below ground, both tracers were detected after 5 days and reached a maximum at approximately 24 days. Despite the potential dilution caused by mixing within the production well, the maximum concentration was approximately 25% of the mean pond concentration. More than 50% of the SF6 recharged was recovered by the production wells during the 18 month long experiment. Our results demonstrate that at artificial recharge sites with high infiltration rates and moderately deep water tables, transport times between recharge locations and wells determined with gas tracer experiments are reliable.

  12. Simultaneous Analyses and Applications of Multiple Fluorobenzoate and Halide Tracers in Hydrologic Studies

    SciTech Connect

    Hu, Q; Moran, J E

    2004-01-22

    An analytical method that employs ion chromatography has been developed to more fully exploit the use of fluorobenzoic acids (FBAs) and halides as hydrologic tracers. In a single run, this reliable, sensitive, and robust method can simultaneously separate and quantify halides (fluoride, chloride, bromide, and iodide) and up to seven FBAs from other common groundwater constituents (e.g., nitrate and sulfate). The usefulness of this ion chromatographic (IC) analytical method is demonstrated in both field and laboratory tracer experiments. Field experiments in unsaturated tuff featuring fractures or a fault show that this efficient and cost-effective method helps achieve the objectives of tracer studies that use multiple FBAs and/or diffusivity tracers (simultaneous use of one or more FBA and halide). The field study examines the hydrologic response of fractures and the matrix to different flow rates and the contribution of matrix diffusion in chemical transport. Laboratory tracer experiments with eight geologic media from across the United States--mostly from Department of Energy facilities where groundwater contamination is prevalent and where subsurface characterization employing tracers has been ongoing or is in need--reveal several insights about tracer transport behavior: (1) Bromide and FBAs are not always transported conservatively. (2) The delayed transport of these anionic tracers is likely related to geologic media characteristics, such as organic matter, pH, iron oxide content, and clay mineralogy. (3) Any use of iodine as a hydrologic tracer should take into account the different sorption behaviors of iodide and iodate and the possible conversion of iodine's initial chemical form. (4) The transport behavior of potential FBA and halide tracers under relevant geochemical conditions should be evaluated before beginning ambitious, large-scale field tracer experiments.

  13. Project definition study for the National Biomedical Tracer Facility

    SciTech Connect

    Roozen, K.

    1995-02-15

    The University of Alabama at Birmingham (UAB) has conducted a study of the proposed National Biomedical Tracer Facility (NBTF). In collaboration with General Atomics, RUST International, Coleman Research Corporation (CRC), IsoMed, Ernst and Young and the advisory committees, they have examined the issues relevant to the NBTF in terms of facility design, operating philosophy, and a business plan. They have utilized resources within UAB, CRC and Chem-Nuclear to develop recommendations on environmental, safety and health issues. The Institute of Medicine Panel`s Report on Isotopes for Medicine and the Life Sciences took the results of prior workshops further in developing recommendations for the mission of the NBTF. The IOM panel recommends that the NBTF accelerator have the capacity to accelerate protons to 80 MeV and a minimum of 750 microamperes of current. The panel declined to recommend a cyclotron or a linac. They emphasized a clear focus on research and development for isotope production including target design, separation chemistry and generator development. The facility needs to emphasize education and training in its mission. The facility must focus on radionuclide production for the research and clinical communities. The formation of a public-private partnership resembling the TRIUMF-Nordion model was encouraged. An advisory panel should assist with the NBTF operations and prioritization.

  14. Preliminary Results from Downhole Osmotic Samplers in a Gas Tracer Injection Experiment in the Upper Oceanic Crust on the Eastern Flank of the Juan de Fuca Ridge.

    NASA Astrophysics Data System (ADS)

    de Jong, M. T.; Clark, J. F.; Neira, N. M.; Fisher, A. T.; Wheat, C. G.

    2015-12-01

    We present results from a gas tracer injection experiment in the ocean crust on the eastern flank of the Juan de Fuca Ridge, in an area of hydrothermal circulation. Sulfur hexafluoride (SF6) tracer was injected in Hole 1362B in 2010, during IODP Expedition 327. Fluid samples were subsequently collected from a borehole observatory (CORK) installed in this hole and similar CORKs in three additional holes (1026B, 1362A, and 1301A), located 300 to 500 m away. This array of holes is located on 3.5 My old seafloor, as an array oriented subparallel to the Endeavor Segment of Juan de Fuca Ridge. Borehole fluid samples were collected in copper coils using osmotic pumps. In addition to pumps at seafloor wellheads, downhole sampling pumps were installed in the perforated casing in the upper ocean crust. These downhole samplers were intended to produce a high-resolution continuous record of tracer concentrations, including records from the first year after tracer injection in Holes 1362A and 1362B. In contrast, wellhead samplers were not installed on these CORKs holes until 2011, and wellhead records from all CORKs have a record gap of up to one year, because of a delayed expedition in 2012. The downhole samples were recovered with the submersible Alvin in August 2014. SF6 concentrations in downhole samples recovered in 2014 are generally consistent with data obtained from wellhead samples. Of particular interest are the results from Hole 1362B, where a seafloor valve was opened and closed during various recovery expeditions. High resolution tracer curves produced from the 1362B downhole samples confirm that these operations produced an SF6 breakthrough curve corresponding to a classic push-pull test used to evaluate contaminant field locations in terrestrial setting. Complete analyses of downhole samples from these CORKs are expected to produce high-resolution breakthrough curves that will allow more precise analysis and modeling of hydrothermal flow in the study area.

  15. Analysis techniques for tracer studies of oxidation. M. S. Thesis Final Report

    NASA Technical Reports Server (NTRS)

    Basu, S. N.

    1984-01-01

    Analysis techniques to obtain quantitative diffusion data from tracer concentration profiles were developed. Mass balance ideas were applied to determine the mechanism of oxide growth and to separate the fraction of inward and outward growth of oxide scales. The process of inward oxygen diffusion with exchange was theoretically modelled and the effect of lattice diffusivity, grain boundary diffusivity and grain size on the tracer concentration profile was studied. The development of the tracer concentration profile in a growing oxide scale was simulated. The double oxidation technique was applied to a FeCrAl-Zr alloy using 0-18 as a tracer. SIMS was used to obtain the tracer concentration profile. The formation of lacey oxide on the alloy was discussed. Careful consideration was given to the quality of data required to obtain quantitative information.

  16. Application of multitracer technology to petroleum reservoir studies. [Perfluorocarbon tracer technology

    SciTech Connect

    Senum, G.I.

    1992-09-01

    The objectives of this research program are to: Improve the assessment of the character of petroleum reservoirs using tracer technology for the monitoring and improvement of EOR techniques, specifically, (a) to apply the presently available multitracer perfluorocarbon tracer (PFI) technology to the study of petroleum reservoirs in characterizing reservoir bulk subsurface flow transport and dispersion rates; and (b) to demonstrate that PFTs with differing physical properties will interact with differing rates of adsorption and dispersion within such reservoirs, from which may be inferred difference in the character and/or extent of petroleum in those reservoirs. Develop additional tracers, and tracer injection, sampling and analyses methodologies for use in petroleum reservoir characterization experiments. Develop a data base of petroleum transport and dispersion properties from tracer experiments for use by modellers for developing, validating and extending petroleum reservoirs models used for characterizing petroleum reservoirs. Technical progress is discussed according to the three ongoing field experiments at the Naval Petroleum Reserve in California (NPRC).

  17. TRACER DISPERSION STUDIES FOR HYDRAULIC CHARACTERIZATION OF PIPES

    EPA Science Inventory

    A series of experiments were conducted at the U. S. Environmental Protection Agency (EPA) Test & Evaluation (T&E) Facility in Cincinnati, Ohio, to quantify longitudinal dispersion of a sodium fluoride tracer in polyvinyl chloride (PVC) pipe and ductile iron pipe under laminar, tr...

  18. Sediment tracers in water erosion studies: Current approaches and challenges

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The interest in the use of sediment tracers as a complementary tool to traditional water soil erosion or deposition measurements or assessment has increased due to the additional information they may provide such as sediment source identification and tracking of sediment movement over the landscape ...

  19. Study of North Atlantic ventilation using transient tracers. Doctoral Thesis

    SciTech Connect

    Doney, S.C.

    1991-08-01

    Tritium, (3)He, and chlorofluorocarbon distributions in the North Atlantic provide constraints on the ventilation time-scales for the thermocline and abyssal water. A new model function based on a factor analysis of the WMO/IAEA precipitation data set is developed for predicting the spatial and temporal patterns of bomb-tritium in precipitation. Model atmospheric and advective tritium inputs to the North Atlantic are compared with the observed bomb-tritium inventories calculated from the 1972 GEOSECS and 1981-1983 TTO data sets. The observed growth of bomb-tritium levels in the deep North Atlantic are used, along with the tracer gradients ((3)H and (3)He) in the Deep Western Boundary Current, to estimate abyssal ventilation rates and boundary current recirculation. The surface boundary conditions for different transient tracers are found to profoundly effect thermocline ventilation rates estimates. Tracers that equilibrate rapidly with the atmosphere, such as (3)He and the CFCs, have faster apparent ventilation rates and are more appropriate for estimating oxygen utilization rates than tracers that are reset slowly in the surface ocean (e.g. (3)H and (14)C). The chlorofluorocarbon data for a new section in the eastern North Atlantic are presented and used to illustrate the ventilation time-scales for the major water masses in the region. (Copyright (c) Scott C. Doney, 1991.)

  20. Artificial ultra-fine aerosol tracers for highway transect studies

    NASA Astrophysics Data System (ADS)

    Cahill, Thomas A.; Barnes, David E.; Wuest, Leann; Gribble, David; Buscho, David; Miller, Roger S.; De la Croix, Camille

    2016-07-01

    The persistent evidence of health impacts of roadway aerosols requires extensive information for urban planning to avoid putting populations at risk, especially in-fill projects. The required information must cover both highway aerosol sources as well as transport into residential areas under a variety of roadway configurations, traffic conditions, downwind vegetation, and meteorology. Such studies are difficult and expensive to do, but were easier in the past when there was a robust fine aerosol tracer uniquely tied to traffic - lead. In this report we propose and test a modern alternative, highway safety flare aerosols. Roadway safety flares on vehicles in traffic can provide very fine and ultra-fine aerosols of unique composition that can be detected quantitatively far downwind of roadways due to a lack of upwind interferences. The collection method uses inexpensive portable aerosol collection hardware and x-ray analysis protocols. The time required for each transect is typically 1 h. Side by side tests showed precision at ± 4%. We have evaluated this technique both by aerosol removal in vegetation in a wind tunnel and by tracking aerosols downwind of freeways as a function of season, highway configuration and vegetation coverage. The results show that sound walls for at-grade freeways cause freeway pollution to extend much farther downwind than standard models predict. The elevated or fill section freeway on a berm projected essentially undiluted roadway aerosols at distances well beyond 325 m, deep into residential neighborhoods. Canopy vegetation with roughly 70% cover reduced very fine and ultra-fine aerosols by up to a factor of 2 at distances up to 200 m downwind.

  1. Green River air quality model development: meteorological and tracer data, July/August 1982 field study in Brush Valley, Colorado

    SciTech Connect

    Whiteman, C.D.; Lee, R.N.; Orgill, M.M.; Zak, B.D.

    1984-06-01

    Meteorological and atmospheric tracer studies were conducted during a 3-week period in July and August of 1982 in the Brush Creek Valley of northwestern Colorado. The objective of the field experiments was to obtain data to evaluate a model, called VALMET, developed at PNL to predict dispersion of air pollutants released from an elevated stack located within a deep mountain valley in the post-sunrise temperature inversion breakup period. Three tracer experiments were conducted in the valley during the 2-week period. In these experiments, sulfur hexafluoride (SF/sub 6/) was released from a height of approximately 100 m, beginning before sunrise and continuing until the nocturnal down-valley winds reversed several hours after sunrise. Dispersion of the sulfur hexafluoride after release was evaluated by measuring SF/sub 6/ concentrations in ambient air samples taken from sampling devices operated within the valley up to about 8 km down valley from the source. An instrumented research aircraft was also used to measure concentrations in and above the valley. Tracer samples were collected using a network of radio-controlled bag sampling stations, two manually operated gas chromatographs, a continuous SF/sub 6/ monitor, and a vertical SF/sub 6/ profiler. In addition, basic meteorological data were collected during the tracer experiments. Frequent profiles of vertical wind and temperature structure were obtained with tethered balloons operated at the release site and at a site 7.7 km down the valley from the release site. 10 references, 63 figures, 50 tables.

  2. Air intake contamination by building exhausts: tracer gas investigation of atmospheric dispersion models in the urban environment.

    PubMed

    Lazure, Louis; Saathoff, Pat; Stathopoulos, Ted

    2002-02-01

    The establishment of a safe distance between sources of pollution and air intakes is based on a complex exercise that should take into account several wind, physical, and topographical factors. To estimate the maximum concentrations of the pollutants as a function of the distance from the emission source, some heating, ventilation, and air conditioning (HVAC) system designers use the atmospheric dispersion models suggested by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). Two of these models, the Halitsky and Wilson-Chui-Lamb models, have been developed and evaluated mainly with laboratory data. There have been relatively few evaluations with full-scale field data. The objective of this study, carried out on a building in downtown Montreal, Quebec, Canada, was to compare the measured concentrations of a tracer gas emitted by an exhaust stack with those predicted by these models. The results indicate that the Halitsky model gives lower than actual dilution, while the Wilson-Chui-Lamb model generally gives acceptable estimates, with occasional over-estimations of the dilution.

  3. DUST CONTINUUM EMISSION AS A TRACER OF GAS MASS IN GALAXIES

    SciTech Connect

    Groves, Brent A.; Schinnerer, Eva; Walter, Fabian; Leroy, Adam; Galametz, Maud; Bolatto, Alberto; Hunt, Leslie; Dale, Daniel; Calzetti, Daniela; Croxall, Kevin; Kennicutt, Robert Jr.

    2015-01-20

    We use a sample of 36 galaxies from the KINGFISH (Herschel IR), HERACLES (IRAM CO), and THINGS (Very Large Array H I) surveys to study empirical relations between Herschel infrared (IR) luminosities and the total mass of the interstellar gas (H{sub 2} + H I). Such a comparison provides a simple empirical relationship without introducing the uncertainty of dust model fitting. We find tight correlations, and provide fits to these relations, between Herschel luminosities and the total gas mass integrated over entire galaxies, with the tightest, almost linear, correlation found for the longest wavelength data (SPIRE 500). However, we find that accounting for the gas-phase metallicity (affecting the dust to gas ratio) is crucial when applying these relations to low-mass, and presumably high-redshift, galaxies. The molecular (H{sub 2}) gas mass is found to be better correlated with the peak of the IR emission (e.g., PACS160), driven mostly by the correlation of stellar mass and mean dust temperature. When examining these relations as a function of galactocentric radius, we find the same correlations, albeit with a larger scatter, up to a radius of r ∼ 0.7 r {sub 25} (containing most of a galaxy's baryonic mass). However, beyond that radius, the same correlations no longer hold, with increasing gas (predominantly H I) mass relative to the infrared emission. The tight relations found for the bulk of the galaxy's baryonic content suggest that total gas masses of disk-like (non-merging/ULIRG) galaxies can be inferred from far-infrared continuum measurements in situations where only the latter are available, e.g., in ALMA continuum observations of high-redshift galaxies.

  4. Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain Site characterization study. Progress report, January 1, 1995--March 31, 1995

    SciTech Connect

    Stetzenbach, K.; Farnham, I.

    1995-05-01

    Fluorinated organic acids were utilized in a test study as hydrologic tracers for the Yucca Mountain Project. Fluorinated acids included cinnamic acid; benzoic acid, and toluic acid. Results are discussed pertaining to retention time, elution time, and stability.

  5. THE NEW YORK CITY URBAN DISPERSION PROGRAM MARCH 2005 FIELD STUDY: TRACER METHODS AND RESULTS.

    SciTech Connect

    WATSON, T.B.; HEISER, J.; KALB, P.; DIETZ, R.N.; WILKE, R.; WIESER, R.; VIGNATO, G.

    2005-10-01

    The Urban Dispersion Program March 2005 Field Study tracer releases, sampling, and analytical methods are described in detail. There were two days where tracer releases and sampling were conducted. A total of 16.0 g of six tracers were released during the first test day or Intensive Observation Period (IOP) 1 and 15.7 g during IOP 2. Three types of sampling instruments were used in this study. Sequential air samplers, or SAS, collected six-minute samples, while Brookhaven atmospheric tracer samplers (BATS) and personal air samplers (PAS) collected thirty-minute samples. There were a total of 1300 samples resulting from the two IOPs. Confidence limits in the sampling and analysis method were 20% as determined from 100 duplicate samples. The sample recovery rate was 84%. The integrally averaged 6-minute samples were compared to the 30-minute samples. The agreement was found to be good in most cases. The validity of using a background tracer to calculate sample volumes was examined and also found to have a confidence level of 20%. Methods for improving sampling and analysis are discussed. The data described in this report are available as Excel files. An additional Excel file of quality assured tracer data for use in model validation efforts is also available. The file consists of extensively quality assured BATS tracer data with background concentrations subtracted.

  6. A new method for measuring concentration of a fluorescent tracer in bubbly gas-liquid flows

    NASA Astrophysics Data System (ADS)

    Moghaddas, J. S.; Trägårdh, C.; Kovacs, T.; Östergren, K.

    2002-06-01

    A new experimental model, the two-tracer method (TTM), based on the planar laser-induced fluorescence technique (PLIF), is presented for the measurement of the local concentration of a fluorescent tracer in the liquid phase of a bubbly two-phase system. Light scattering and shading effects due to the bubbles were compensated for using the new model. The TTM results were found to give more accurate predictions of the local concentration than the normal PLIF method in a bubbly two-phase system.

  7. Driven tracers in narrow channels

    NASA Astrophysics Data System (ADS)

    Cividini, J.; Mukamel, D.; Posch, H. A.

    2017-01-01

    Steady-state properties of a driven tracer moving in a narrow two-dimensional (2D) channel of quiescent medium are studied. The tracer drives the system out of equilibrium, perturbs the density and pressure fields, and gives the bath particles a nonzero average velocity, creating a current in the channel. Three models in which the confining effect of the channel is probed are analyzed and compared in this study: the first is the simple symmetric exclusion process (SSEP), for which the stationary density profile and the pressure on the walls in the frame of the tracer are computed. We show that the tracer acts like a dipolar source in an average velocity field. The spatial structure of this 2D strip is then simplified to a one-dimensional (1D) SSEP, in which exchanges of position between the tracer and the bath particles are allowed. Using a combination of mean-field theory and exact solution in the limit where no exchange is allowed gives good predictions of the velocity of the tracer and the density field. Finally, we show that results obtained for the 1D SSEP with exchanges also apply to a gas of overdamped hard disks in a narrow channel. The correspondence between the parameters of the SSEP and of the gas of hard disks is systematic and follows from simple intuitive arguments. Our analytical results are checked numerically.

  8. Ammonium transport and reaction in contaminated groundwater: Application of isotope tracers and isotope fractionation studies

    USGS Publications Warehouse

    Böhlke, J.K.; Smith, R.L.; Miller, D.N.

    2006-01-01

    Ammonium (NH4+) is a major constituent of many contaminated groundwaters, but its movement through aquifers is complex and poorly documented. In this study, processes affecting NH4+ movement in a treated wastewater plume were studied by a combination of techniques including large-scale monitoring of NH4+ distribution; isotopic analyses of coexisting aqueous NH4+, NO3-, N2, and sorbed NH 4+; and in situ natural gradient 15NH 4+ tracer tests with numerical simulations of 15NH4+, 15NO3-, and 15N2 breakthrough data. Combined results indicate that the main mass of NH4+ was moving downgradient at a rate about 0.25 times the groundwater velocity. Retardation factors and groundwater ages indicate that much of the NH4+ in the plume was recharged early in the history of the wastewater disposal. NO3- and excess N2 gas, which were related to each other by denitrification near the plume source, were moving downgradient more rapidly and were largely unrelated to coexisting NH 4+. The ??15N data indicate areas of the plume affected by nitrification (substantial isotope fractionation) and sorption (no isotope fractionation). There was no conclusive evidence for NH 4+-consuming reactions (nitrification or anammox) in the anoxic core of the plume. Nitrification occurred along the upper boundary of the plume but was limited by a low rate of transverse dispersive mixing of wastewater NH4+ and O2 from overlying uncontaminated groundwater. Without induced vertical mixing or displacement of plume water with oxic groundwater from upgradient sources, the main mass of NH4+ could reach a discharge area without substantial reaction long after the more mobile wastewater constituents are gone. Multiple approaches including in situ isotopic tracers and fractionation studies provided critical information about processes affecting NH4+ movement and N speciation.

  9. Optical depth estimates and effective critical densities of dense gas tracers in the inner parts of nearby galaxy discs

    NASA Astrophysics Data System (ADS)

    Jiménez-Donaire, M. J.; Bigiel, F.; Leroy, A. K.; Cormier, D.; Gallagher, M.; Usero, A.; Bolatto, A.; Colombo, D.; García-Burillo, S.; Hughes, A.; Kramer, C.; Krumholz, M. R.; Meier, D. S.; Murphy, E.; Pety, J.; Rosolowsky, E.; Schinnerer, E.; Schruba, A.; Tomičić, N.; Zschaechner, L.

    2017-04-01

    High critical density molecular lines like HCN (1-0) or HCO+ (1-0) represent our best tool to study currently star-forming, dense molecular gas at extragalactic distances. The optical depth of these lines is a key ingredient to estimate the effective density required to excite emission. However, constraints on this quantity are even scarcer in the literature than measurements of the high-density tracers themselves. Here, we combine new observations of HCN, HCO+ and HNC (1-0) and their optically thin isotopologues H13CN, H13CO+ and HN13C (1-0) to measure isotopologue line ratios. We use IRAM 30-m observations from the large programme EMPIRE and new Atacama Large Millimetre/submillimetre Array observations, which together target six nearby star-forming galaxies. Using spectral stacking techniques, we calculate or place strong upper limits on the HCN/H13CN, HCO+/H13CO+ and HNC/HN13C line ratios in the inner parts of these galaxies. Under simple assumptions, we use these to estimate the optical depths of HCN (1-0) and HCO+ (1-0) to be τ ∼ 2-11 in the active, inner regions of our targets. The critical densities are consequently lowered to values between 5 and 20 × 105 cm-3, 1 and 3 × 105 cm-3 and 9 × 104 cm-3 for HCN, HCO+ and HNC, respectively. We study the impact of having different beam-filling factors, η, on these estimates and find that the effective critical densities decrease by a factor of η _{12}/η _{13} τ_{12}. A comparison to existing work in NGC 5194 and NGC 253 shows the HCN/H13CN and HCO+/H13CO+ ratios in agreement with our measurements within the uncertainties. The same is true for studies in other environments such as the Galactic Centre or nuclear regions of active galactic nucleus dominated nearby galaxies.

  10. Measuring the emission rate of an aerosol source placed in a ventilated room using a tracer gas: influence of particle wall deposition.

    PubMed

    Bémer, D; Lecler, M T; Régnier, R; Hecht, G; Gerber, J M

    2002-04-01

    A method to measure the emission rate of an airborne pollutant source using a tracer gas was tested in the case of an aerosol source. The influence of particle deposition on the walls of a test room of 72 m3 was studied. The deposition rate of an aerosol of MgCl2 was determined by means of two methods: one based on measuring the aerosol concentration decay inside the ventilated room, the other based on calculation of the material mass balance. The concentration decay was monitored by optical counting and the aerosol mass concentration determined by means of sampling on a filter and analysis of the mass deposited by atomic absorption spectrometry. Four series of measurements were carried out. The curve giving the deposition rate according to the particle aerodynamic diameter (d(ae)) was established and shows deposition rates higher than those predicted using the model of Corner. The decay method gives the best results. The study carried out has shown that the phenomenon of deposition has little effect on the measurement of the aerosol source emission rate using a tracer gas for particles of aerodynamic diameter < 5 microm (underestimation < 25%). For particles of a greater diameter, wall deposition is an extremely limiting factor for the method, the influence of which can, however, be limited by using a test booth of small volume and keeping the sampling duration as short as possible.

  11. Urban Dispersion Program MSG05 Field Study: Summary of Tracer and Meteorological Measurements

    SciTech Connect

    Allwine, K Jerry; Flaherty, Julia E.

    2006-08-09

    The Urban Dispersion Program is a multi-year project, funded by the U.S. Department of Homeland Security, to better understand the flow and dispersion of airborne contaminants through and around the deep street canyons of New York City. The first tracer and meteorological field study was a limited study conducted during March 2005 near the Madison Square Garden in midtown Manhattan. Six safe, inert, gaseous perfluorocarbon tracers were released simultaneously at five street-level locations during two experimental days. In addition to collecting tracer data, meteorological data were also collected. Brookhaven National Laboratory conducted the bulk of the tracer and meteorological field efforts with Pacific Northwest National Laboratory and Stevens Institute of Technology assisting by measuring the vertical profile of winds. The Environmental Protection Agency worked with Brookhaven National Laboratory in accomplishing the personal exposure component of the study. This report presents some results from this analysis. In general, different release locations showed vastly different plume footprints for tracer materials, and the situation was made very complex with upwind and/or crosswind transport of tracer near street-level for the different release locations. Overall wind speeds and directions upwind and over the city were generally constant throughout each of the two experimental periods.

  12. Using biofuel tracers to study alternative combustion regimes

    NASA Astrophysics Data System (ADS)

    Mack, J. H.; Flowers, D. L.; Buchholz, B. A.; Dibble, R. W.

    2007-06-01

    Interest in the use of alternative fuels and engines is increasing as the price of petroleum climbs. The inherently higher efficiency of Diesel engines has led to increased adoption of Diesels in Europe, capturing approximately 40% of the new passenger car market. Unfortunately, lower CO2 emissions are countered with higher nitrogen oxides (NOx) and particulate matter (PM) emissions and higher noise. Adding oxygenated compounds to the fuel helps reduce PM emissions. However, relying on fuel alone to reduce PM is unrealistic due to economic constraints and difficult due to the emerging PM standards. Keeping peak combustion temperature below 1700 K inhibits NOx formation. Altering the combustion regime to burn at temperatures below the NOx threshold and accept a wide variety of fuels seems like a promising alternative for future engines. Homogeneous charge compression ignition (HCCI) is a possible solution. Fuel and air are well mixed prior to intake into a cylinder (homogeneous charge) and ignition occurs by compression of the fuel-air mixture by the piston. HCCI is rapid and relatively cool, producing little NOx and PM. Unfortunately, it is hard to control since HCCI is initiated by temperature and pressure instead of a spark or direct fuel injection. We investigate biofuel HCCI combustion, and use intrinsically labeled biofuels as tracers of HCCI combustion. Data from tracer experiments are used to improve our combustion modeling.

  13. Use of stable tracer studies to evaluate pesticide photolysis at elevated temperatures.

    PubMed

    Hebert, V R; Hoonhout, C; Miller, G C

    2000-05-01

    New methods were developed to determine photolysis rates of medium-weight pesticides in the gas phase using elevated air temperatures and solid-phase microextraction (SPME). A 57-L glass chamber was constructed that utilized collimated xenon arc irradiation that could heat chamber air to increase the amount of pesticide in the gas phase. Gas-phase photolysis rates were determined at various air temperatures by comparing the rate of loss of each of the tested pesticides to a photochemically stable tracer, hexachlorobenzene. Interval sampling of gas-phase constituents was performed using SPME immediately followed by GC-ECD or GC-MSD analysis. The two pesticides under examination were the dinitroaniline herbicide trifluralin and the organophosphorus insecticide chlorpyrifos. The gas-phase photolysis for trifluralin was found to be rapid with half-lives of 22-24 min corrected for sunlight. These results were comparable to photochemical lifetime estimates from other investigators under sunlight conditions. Elevating temperatures from 60 to 80 degrees C did not affect photolysis rates, and these rates could be extrapolated to environmental temperatures. From 60 to 80 degrees C, gas-phase chlorpyrifos photolysis lifetimes were observed to range from 1.4 to 2.2 h corrected for sunlight and will thus be important together with hydroxyl radical reactions for removing this substance from the atmosphere. At these elevated temperatures, pesticides and tracer compounds were found to be substantially in the gas phase, and possible effects on reaction rates from wall interactions were minimized.

  14. Uncertainties in Air Exchange using Continuous-Injection, Long-Term Sampling Tracer-Gas Methods

    SciTech Connect

    Sherman, Max H.; Walker, Iain S.; Lunden, Melissa M.

    2013-12-01

    The PerFluorocarbon Tracer (PFT) method is a low-cost approach commonly used for measuring air exchange in buildings using tracer gases. It is a specific application of the more general Continuous-Injection, Long-Term Sampling (CILTS) method. The technique is widely used but there has been little work on understanding the uncertainties (both precision and bias) associated with its use, particularly given that it is typically deployed by untrained or lightly trained people to minimize experimental costs. In this article we will conduct a first-principles error analysis to estimate the uncertainties and then compare that analysis to CILTS measurements that were over-sampled, through the use of multiple tracers and emitter and sampler distribution patterns, in three houses. We find that the CILTS method can have an overall uncertainty of 10-15percent in ideal circumstances, but that even in highly controlled field experiments done by trained experimenters expected uncertainties are about 20percent. In addition, there are many field conditions (such as open windows) where CILTS is not likely to provide any quantitative data. Even avoiding the worst situations of assumption violations CILTS should be considered as having a something like a ?factor of two? uncertainty for the broad field trials that it is typically used in. We provide guidance on how to deploy CILTS and design the experiment to minimize uncertainties.

  15. Using noble gas tracers to estimate residual CO2 saturation in the field: results from the CO2CRC Otway residual saturation and dissolution test

    NASA Astrophysics Data System (ADS)

    LaForce, T.; Ennis-King, J.; Paterson, L.

    2013-12-01

    Residual CO2 saturation is a critically important parameter in CO2 storage as it can have a large impact on the available secure storage volume and post-injection CO2 migration. A suite of single-well tests to measure residual trapping was conducted at the Otway test site in Victoria, Australia during 2011. One or more of these tests could be conducted at a prospective CO2 storage site before large-scale injection. The test involved injection of 150 tonnes of pure carbon dioxide followed by 454 tonnes of CO2-saturated formation water to drive the carbon dioxide to residual saturation. This work presents a brief overview of the full test sequence, followed by the analysis and interpretation of the tests using noble gas tracers. Prior to CO2 injection krypton (Kr) and xenon (Xe) tracers were injected and back-produced to characterise the aquifer under single-phase conditions. After CO2 had been driven to residual the two tracers were injected and produced again. The noble gases act as non-partitioning aqueous-phase tracers in the undisturbed aquifer and as partitioning tracers in the presence of residual CO2. To estimate residual saturation from the tracer test data a one-dimensional radial model of the near-well region is used. In the model there are only two independent parameters: the apparent dispersivity of each tracer and the residual CO2 saturation. Independent analysis of the Kr and Xe tracer production curves gives the same estimate of residual saturation to within the accuracy of the method. Furthermore the residual from the noble gas tracer tests is consistent with other measurements in the sequence of tests.

  16. Using Biofuel Tracers to Study Alternative Combustion Regimes

    SciTech Connect

    Mack, J H; Flowers, D L; Buchholz, B A; Dibble, R W

    2006-02-14

    Interest in the use of alternative fuels and combustion regimes is increasing as the price of petroleum climbs. The inherently higher efficiency of Diesel engines has led to increased adoption of Diesels in Europe, capturing approximately 40% of the new passenger car market. Unfortunately, lower CO{sub 2} emissions are countered with higher nitrogen oxides (NOx) and particulate matter (PM) emissions, and higher noise. Noise and PM have traditionally been the obstacles toward consumer acceptance of Diesel passenger cars in North America, while NOx (a key component in photochemical smog) has been more of an engineering challenge. Diesels are lean burning (combustion with excess oxygen) and reducing NOx to N2 in an oxygen rich environment is difficult. Adding oxygenated compounds to the fuel helps reduce PM emissions, but relying on fuel alone to reduce PM is unrealistic. Keeping peak combustion temperature below 1700 K prevents NOx formation. Altering the combustion regime to burn at temperatures below the NOx threshold and accept a wide variety of fuels seems like a promising alternative for future engines. Homogeneous Charge Compression Ignition (HCCI) is a possible solution. Fuel and air are well mixed prior to intake into a cylinder (homogeneous charge) and ignition occurs by compression of the fuel-air mixture by the piston. HCCI is rapid and relatively cool, producing little NOx and PM. Unfortunately, it is hard to control since HCCI is initiated by temperature and pressure instead of a spark or direct fuel injection. We investigate biofuel HCCI combustion, and use intrinsically labeled biofuels as tracers of HCCI combustion. Data from tracer experiments are used to validate combustion modeling.

  17. Insights into secondary organic aerosol formation mechanisms from measured gas/particle partitioning of specific organic tracer compounds.

    PubMed

    Zhao, Yunliang; Kreisberg, Nathan M; Worton, David R; Isaacman, Gabriel; Weber, Robin J; Liu, Shang; Day, Douglas A; Russell, Lynn M; Markovic, Milos Z; VandenBoer, Trevor C; Murphy, Jennifer G; Hering, Susanne V; Goldstein, Allen H

    2013-04-16

    In situ measurements of organic compounds in both gas and particle phases were made with a thermal desorption aerosol gas chromatography (TAG) instrument. The gas/particle partitioning of phthalic acid, pinonaldehyde, and 6,10,14-trimethyl-2-pentadecanone is discussed in detail to explore secondary organic aerosol (SOA) formation mechanisms. Measured fractions in the particle phase (f(part)) of 6,10,14-trimethyl-2-pentadecanone were similar to those expected from the absorptive gas/particle partitioning theory, suggesting that its partitioning is dominated by absorption processes. However, f(part) of phthalic acid and pinonaldehyde were substantially higher than predicted. The formation of low-volatility products from reactions of phthalic acid with ammonia is proposed as one possible mechanism to explain the high f(part) of phthalic acid. The observations of particle-phase pinonaldehyde when inorganic acids were fully neutralized indicate that inorganic acids are not required for the occurrence of reactive uptake of pinonaldehyde on particles. The observed relationship between f(part) of pinonaldehyde and relative humidity suggests that the aerosol water plays a significant role in the formation of particle-phase pinonaldehyde. Our results clearly show it is necessary to include multiple gas/particle partitioning pathways in models to predict SOA and multiple SOA tracers in source apportionment models to reconstruct SOA.

  18. Isotopic tracer studies of Fischer-Tropsch Synthesis over Ru/TiO sub 2 catalysts

    SciTech Connect

    Krishna, K.R.

    1992-01-01

    Fischer-Tropsch synthesis is a process in which CO and H{sub 2} react to give predominantly liquid hydrocarbons. The reaction can be considered a special type of polymerization in which the monomer is produced in situ, and chain growth occurs by a sequence of independently repeated additions of the monomer to the growing chain. A investigation has been conducted to study the CO hydrogenation reaction in order to better understand catalyst deactivation and the elementary surface processes involved in chain growth. Isotopic tracers are used in conjunction with transient-response techniques in this study of Fischer-Tropsch synthesis over Ru/TiO{sub 2} catalysts. Experiments are conducted at a total pressure of 1 atmosphere, reaction temperatures of 453--498 K and D{sub 2}/CO (or H{sub 2}/CO) ratios of 2--5. Synthesis products are analyzed by gas chromatography or isotope-ratio gas chromatography-mass spectrometry. Rate constants for chain initiation, propagation and termination are evaluated under steady-state reaction conditions by using transients in isotopic composition. The activation energy for chain termination is much higher than that for propagation, accounting for the observed decrease in the chain growth parameter are also estimated. Coverages by reaction intermediates are also estimated. When small amounts of {sup 12}C-labelled ethylene are added to {sup 13}CO/H{sub 2} synthesis gas, ethylene acts as the sole chain initiator. Ethylene-derived carbon also accounts for 45% of the C{sub 1} monomer pool. 102 refs., 29 figs., 11 tabs.

  19. Isotopic tracer studies of Fischer-Tropsch Synthesis over Ru/TiO{sub 2} catalysts

    SciTech Connect

    Krishna, K.R.

    1992-01-01

    Fischer-Tropsch synthesis is a process in which CO and H{sub 2} react to give predominantly liquid hydrocarbons. The reaction can be considered a special type of polymerization in which the monomer is produced in situ, and chain growth occurs by a sequence of independently repeated additions of the monomer to the growing chain. A investigation has been conducted to study the CO hydrogenation reaction in order to better understand catalyst deactivation and the elementary surface processes involved in chain growth. Isotopic tracers are used in conjunction with transient-response techniques in this study of Fischer-Tropsch synthesis over Ru/TiO{sub 2} catalysts. Experiments are conducted at a total pressure of 1 atmosphere, reaction temperatures of 453--498 K and D{sub 2}/CO (or H{sub 2}/CO) ratios of 2--5. Synthesis products are analyzed by gas chromatography or isotope-ratio gas chromatography-mass spectrometry. Rate constants for chain initiation, propagation and termination are evaluated under steady-state reaction conditions by using transients in isotopic composition. The activation energy for chain termination is much higher than that for propagation, accounting for the observed decrease in the chain growth parameter are also estimated. Coverages by reaction intermediates are also estimated. When small amounts of {sup 12}C-labelled ethylene are added to {sup 13}CO/H{sub 2} synthesis gas, ethylene acts as the sole chain initiator. Ethylene-derived carbon also accounts for 45% of the C{sub 1} monomer pool. 102 refs., 29 figs., 11 tabs.

  20. Tracer-based quantification of individual frac discharge in single-well multiple-frac backflow: sensitivity study

    NASA Astrophysics Data System (ADS)

    Ghergut, Julia; Behrens, Horst; Sauter, Martin

    2014-05-01

    Within the deep-geothermal research project at GroßSchönebeck in the NE German Basin, targeting volcanic rocks (Lower Rotliegend) and siliciclastics (Upper Rotliegend) in the Lower Permian by means of a well doublet with several screening intervals between 3815 and 4247 m b.s.l., several artificial fractures with different geometric and hydraulic characteristics were created at each well, aiming to increase reservoir performance [1], [2]. It could not be told a priori which of the various fracturing treatments was to prove as most promising in terms of future reservoir productivity. At the intended-production well (GS-4), one large-area waterfrac was created in the low-permeability volcanic rocks, and two gel-proppant fractures in selected sandstone layers. Each fracturing treatment was accompanied by the injection of a water-dissolved tracer slug, followed by a defined volume of tracer-free ('chaser') fluid [3]. Each frac received a different species of a sulfonated aromatic acid salt, as a conservative water tracer. During subsequent backflow tests (either gas-based lifting, or production by means of a downhole submersible pump), each frac can contribute a certain (more or less constant) amount to the measured total discharge (also depending on whether and when each frac 'starts' contributing, and which effective aperture and area it actually 'manifests' during the process). Since these individual-frac discharge amounts cannot be measured directly, it was endeavoured to indirectly determine ('resolve') them from tracer signals as detectable in the overall backflow discharge. Therefore, we need to examine how these tracer signals depend on local discharge values and on local hydrogeologic parameters (matrix porosity, permeability distribution; frac transmissivity, thickness, effective area and aperture), and to what extent hydrogeological uncertainty will impede the inversion of local discharge values. To this end, a parameter sensitivity study was conducted on

  1. Study of stability zone influences and tracer patterns from the 1987 ANATEX (Across North America Tracer Experiment) experiment

    SciTech Connect

    Porch, W.M.; Gifford, F.A.; Hoard, D.E.

    1988-01-01

    In this paper, we will show preliminary results which appear to connect much of the hit and miss behavior of the surface tracer samples to large scale stability zones 100 to 1000 km wide. With these wintertime stability effects in mind, we have done the best we can to characterize the observed overall tracer patterns as well as individual tracer releases. This type of survey information is important to numerical model development. Diagnostic models often have difficulty reproducing surface plume concentrations where transport over stable layers have occurred. Prognostic models can, in theory, model effects of strong stable layers. However, these models would have great difficulty predicting large scale stable regions such as those observed during ANATEX. Also, though these models have ways of budging in synoptic wind fields, temperature observations are presently ignored. This is because if both wind and temperature observations are forced too strongly into the model, conflicting results may be produced. 12 refs., 5 figs.

  2. Radon as a tracer of biogenic gas equilibration and transport from methane-saturated sediments

    NASA Technical Reports Server (NTRS)

    Martens, Christopher S.; Chanton, Jeffrey P.

    1989-01-01

    Data on Rn-222 activity in methane-rich gas bubbles from anoxic coastal sediments of Cape Lookout Bight, North Carolina, were used to determine gas equilibration with pore waters and the rates of ebullitive stripping and transport of gases to overlying waters and the atmosphere. Results showed that, during summer months, the bubble ebullition process strips and transports 1.9-4.8 percent/day of the standing crop of radon (and, by inference, other gases equilibrated with gas bubbles) in surface sediments of Cape Lookout Bight to the troposphere. Thus, the ebullitive mode of gas transport represents an effective mechanism for delivering reduced biogenic gases directly to the atmosphere.

  3. Noble gas as tracers for CO2 deep input in petroleum reservoirs

    NASA Astrophysics Data System (ADS)

    Pujol, Magali; Stuart, Finlay; Gilfillan, Stuart; Montel, François; Masini, Emmanuel

    2016-04-01

    The sub-salt hydrocarbon reservoirs in the deep offshore part of the Atlantic Ocean passive margins are a new key target for frontier oil and gas exploration. Type I source rocks locally rich in TOC (Total Organic Carbon) combined with an important secondary connected porosity of carbonate reservoirs overlain by an impermeable salt layer gives rise to reservoirs with high petroleum potential. However, some target structures have been found to be mainly filled with CO2 rich fluids. δ13C of the CO2 is generally between -9 and -4 permil, compatible with a deep source (metamorphic or mantle). Understanding the origin of the CO2 and the relative timing of its input into reservoir layers in regard to the geodynamic context appears to be a key issue for CO2 risk evaluation. The inertness and ubiquity of noble gases in crustal fluids make them powerful tools to trace the origin and migration of mixed fluids (Ballentine and Burnard 2002). The isotopic signature of He, Ne and Ar and the elemental pattern (He to Xe) of reservoir fluid from pressurized bottom hole samples provide an insight into fluid source influences at each reservoir depth. Three main end-members can be mixed into reservoir fluids (e.g. Gilfillan et al., 2008): atmospheric signature due to aquifer recharge, radiogenic component from organic fluid ± metamorphic influence, and mantle input. Their relative fractionation provides insights into the nature of fluid transport (Burnard et al., 2012)and its relative migration timing. In the studied offshore passive margin reservoirs, from both sides of South Atlantic margin, a strong MORB-like magmatic CO2 influence is clear. Hence, CO2 charge must have occurred during or after lithospheric break-up. CO2 charge(s) history appears to be complex, and in some cases requires several inputs to generate the observed noble gas pattern. Combining the knowledge obtained from noble gas (origin, relative timing, number of charges) with organic geochemical and thermodynamic

  4. Effects of submesoscale turbulence on ocean tracers

    NASA Astrophysics Data System (ADS)

    Smith, Katherine M.; Hamlington, Peter E.; Fox-Kemper, Baylor

    2016-01-01

    Ocean tracers such as carbon dioxide, nutrients, plankton, and oil advect, diffuse, and react primarily in the oceanic mixed layer where air-sea gas exchange occurs and light is plentiful for photosynthesis. There can be substantial heterogeneity in the spatial distributions of these tracers due to turbulent stirring, particularly in the submesoscale range where partly geostrophic fronts and eddies and small-scale three-dimensional turbulence are simultaneously active. In this study, a large eddy simulation spanning horizontal scales from 20 km down to 5 m is used to examine the effects of multiscale turbulent mixing on nonreactive passive ocean tracers from interior and sea-surface sources. The simulation includes the effects of both wave-driven Langmuir turbulence and submesoscale eddies, and tracers with different initial and boundary conditions are examined in order to understand the respective impacts of small-scale and submesoscale motions on tracer transport. Tracer properties are characterized using spatial fields and statistics, multiscale fluxes, and spectra, and the results detail how tracer mixing depends on air-sea tracer flux rate, tracer release depth, and flow regime. Although vertical fluxes of buoyancy by submesoscale eddies compete with mixing by Langmuir turbulence, vertical fluxes of tracers are often dominated by Langmuir turbulence, particularly for tracers that are released near the mixed-layer base or that dissolve rapidly through the surface, even in regions with pronounced submesoscale activity. Early in the evolution of some tracers, negative eddy diffusivities occur co-located with regions of negative potential vorticity, suggesting that symmetric instabilities or other submesoscale phenomenon may act to oppose turbulent mixing.

  5. Practical considerations in the use of stable isotope labelled compounds as tracers in clinical studies.

    PubMed

    Thompson, G N; Pacy, P J; Ford, G C; Halliday, D

    1989-05-01

    Increasingly widespread usage of stable isotope tracers to aid clinical diagnosis and support basic research has stemmed from both advances in mass spectrometry and the availability of competitively priced labelled compounds. Stable isotopes have been used generally to investigate normal and abnormal metabolic pathways, to estimate energy expenditure and body composition and to quantitate substrate flux and oxidation rates. Despite the fact that the underlying principles relating to the use of stable isotopes for in vivo studies are straightforward, careful consideration must be given to all aspects of human studies. This review highlights some of these, including choice of label and tracer molecule, mode of tracer administration and sampling site, analytical instrumentation, interpretation of data and ethical constraints.

  6. The use of Na-22 as a tracer for long-term bone mineral turnover studies.

    NASA Technical Reports Server (NTRS)

    Palmer, H. E.; Rieksts, G. A.; Palmer, R. F.; Gillis, M. F.

    1979-01-01

    Sodium-22 has been studied as a tracer for bone mineral metabolism in rats and dogs. When incorporated into bone during growth from birth to adulthood, the bone becomes uniformly tagged with Na-22, which is released through the metabolic turnover of the bone. The Na-22 not incorporated in the bone matrix is rapidly excreted within a few days when animals are fed high, but nontoxic levels of NaCl. The Na-22 tracer can be used to measure bone mineral loss in animals during space flight and in research on bone disease.

  7. Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain site characterization study. Progress report, October 1, 1994--December 31, 1994

    SciTech Connect

    Stetzenbach, K.; Farnham, I.

    1994-12-31

    The bromide anion has been used extensively as a tracer for mapping the flow of groundwater. It has proven to be both a safe and reliable groundwater tracer. The goal in this study is to find several tracing compounds with characteristics similar to the bromide anion to be used in multiple well tracing tests. Four groups of fluorinated organic acids were selected as candidates for groundwater tracers. These groups include fluorinated benzoic acids (FBA), fluorinated salicylic acids (FSA), fluorinated toluic acids (FTA), and fluorinated cinnamic acids (FCA). These compounds have been shown to move readily with the flow of water and do not adsorb to soil. They are also non-toxic. In this study, the retention of the fluorinated organic acids on to a soil column is compared to that of the bromide ion. The time required for the elution of each analyte from the soil column is measured using a UV-Vis detector. The soils consist of the light, medium, and dark tuffs used in the batch study. The work performed during this quarter consists of the continuation of the batch studies for the fluorinated benzoic acids and column studies for several potential tracer compounds.

  8. Evaluation of short-term tracer fluctuations in groundwater and soil air in a two year study

    NASA Astrophysics Data System (ADS)

    Jenner, Florian; Mayer, Simon; Aeschbach, Werner; Weissbach, Therese

    2016-04-01

    The application of gas tracers like noble gases (NGs), SF6 or CFCs in groundwater studies such as paleo temperature determination requires a detailed understanding of the dynamics of reactive and inert gases in the soil air with which the infiltrating water equilibrates. Due to microbial gas consumption and production, NG partial pressures in soil air can deviate from atmospheric air, an effect that could bias noble gas temperatures estimates if not taken into account. So far, such an impact on NG contents in groundwater has not been directly demonstrated. We provide the first long-term study of the above mentioned gas tracers and physical parameters in both the saturated and unsaturated soil zone, sampled continuously for more than two years near Mannheim (Germany). NG partial pressures in soil air correlate with soil moisture and the sum value of O2+CO2, with a maximal significant enhancement of 3-6% with respect to atmospheric air during summer time. Observed seasonal fluctuations result in a mass dependent fractionation of NGs in soil air. Concentrations of SF6 and CFCs in soil air are determined by corresponding fluctuations in local atmospheric air, caused by industrial emissions. Arising concentration peaks are damped with increasing soil depth. Shallow groundwater shows short-term NG fluctuations which are smoothed within a few meters below the water table. A correlation between NG contents of soil air and of groundwater is observable during strong recharge events. However, there is no evidence for a permanent influence of seasonal variations of soil air composition on shallow groundwater. Fluctuating NG contents in shallow groundwater are rather determined by variations of soil temperature and water table level. Our data gives evidence for a further temperature driven equilibration of groundwater with entrapped air bubbles within the topmost saturated zone, which permanently occurs even some years after recharge. Local subsurface temperature fluctuations

  9. Estimation of bias with the single-zone assumption in measurement of residential air exchange using the perfluorocarbon tracer gas method

    PubMed Central

    Van Ryswyk, K; Wallace, L; Fugler, D; MacNeill, M; Héroux, M È; Gibson, M D; Guernsey, J R; Kindzierski, W; Wheeler, A J

    2015-01-01

    Residential air exchange rates (AERs) are vital in understanding the temporal and spatial drivers of indoor air quality (IAQ). Several methods to quantify AERs have been used in IAQ research, often with the assumption that the home is a single, well-mixed air zone. Since 2005, Health Canada has conducted IAQ studies across Canada in which AERs were measured using the perfluorocarbon tracer (PFT) gas method. Emitters and detectors of a single PFT gas were placed on the main floor to estimate a single-zone AER (AER1z). In three of these studies, a second set of emitters and detectors were deployed in the basement or second floor in approximately 10% of homes for a two-zone AER estimate (AER2z). In total, 287 daily pairs of AER2z and AER1z estimates were made from 35 homes across three cities. In 87% of the cases, AER2z was higher than AER1z. Overall, the AER1z estimates underestimated AER2z by approximately 16% (IQR: 5–32%). This underestimate occurred in all cities and seasons and varied in magnitude seasonally, between homes, and daily, indicating that when measuring residential air exchange using a single PFT gas, the assumption of a single well-mixed air zone very likely results in an under prediction of the AER. PMID:25399878

  10. USING CONTINUOUS MONITORS FOR CONDUCTING TRACER STUDIES IN WATER DISTRIBUTION SYSTEMS

    EPA Science Inventory

    The use of online monitors for conducting a distribution system tracer study is proving to be an essential tool to accurately understand the flow dynamics in a distribution system. In a series of field testing sponsored by U. S. Environmental Protection Agency (EPA) and Greater ...

  11. [Studies on percutaneous absorption of ruyi jinhuang san patcher with radioisotope tracer].

    PubMed

    Zhao, H W; Shen, Z; Zhou, B; Lin, X; Ye, M

    1993-04-01

    Berberine is one of the active ingredients in Ruyi Jinhuang San Patcher. With 3H-berberine as the tracer, a radio-labelled method was used for determining percutaneous rate and drug concentration of berberine in plasma in vivo and in vitro. A study on the percutaneous rate of different technological plasters and various animal skins was also carried out.

  12. Comparison of two tracer gas dilution methods for the determination of clothing ventilation and of vapour resistance.

    PubMed

    Havenith, George; Zhang, Ping; Hatcher, Kent; Daanen, Hein

    2010-04-01

    Clothing microclimate ventilation is an important parameter in climatic stress and in contaminated environments. The two main methods for its determination (Crockford et al. (CR) 1972 and Lotens and Havenith (LH) 1988) were, after further development, compared in terms of reproducibility, validity and usability. Both methods were shown to have a good sensitivity and reproducibility (with average coefficients of variation 1.5-2.3% for the method alone and up to 7% for method and clothing/movement effects combined). They produced values very close to calibration values in forced ventilation tests (r = 0.988). Weak points for the CR method were the limits in the time constant of the measurement apparatus, causing an upper limit to the ventilation that can be reliably measured (around 800 l/min) and the method of measuring clothing microclimate volume. The original 'vacuum oversuit' (CR) method was cumbersome and prone to large errors. Alternative methods of measuring clothing microclimate volume (whole body scanner or manual circumference measurements) were shown to produce good results. For the LH method, the distribution of the tracer gas over the whole skin surface became a problem factor at very high ventilations (above 1000 l/min). As all methods use tracer gases (O(2), Ar, CO(2), SF(6)) with diffusivities smaller than that of water vapour, this potentially creates a problem in the calculation of vapour resistance from the ventilation values in the region where the emphasis of vapour transfer moves from diffusion to convection. In most real-life situations, where body and air movement are present, a correction is not however required because the error remains below 10%. STATEMENT OF RELEVANCE: Clothing ventilation indicates heat loss potential as well as risk of pollutants entering the clothing. Two main methods for its determination are compared and validated, identifying a number of issues. An in-depth analysis is given of the advantages and disadvantages of

  13. Numerical Simulations and Tracer Studies as a Tool to Support Water Circulation Modeling in Breeding Reservoirs

    NASA Astrophysics Data System (ADS)

    Zima, Piotr

    2014-12-01

    The article presents a proposal of a method for computer-aided design and analysis of breeding reservoirs in zoos and aquariums. The method applied involves the use of computer simulations of water circulation in breeding pools. A mathematical model of a pool was developed, and a tracer study was carried out. A simplified model of two-dimensional flow in the form of a biharmonic equation for the stream function (converted into components of the velocity vector) was adopted to describe the flow field. This equation, supplemented by appropriate boundary conditions, was solved numerically by the finite difference method. Next, a tracer migration equation was solved, which was a two-dimensional advection-dispersion equation describing the unsteady transport of a non-active, permanent solute. In order to obtain a proper solution, a tracer study (with rhodamine WT as a tracer) was conducted in situ. The results of these measurements were compared with numerical solutions obtained. The results of numerical simulations made it possible to reconstruct water circulation in the breading pool and to identify still water zones, where water circulation was impeded.

  14. Isotope pattern deconvolution as rising tool for isotope tracer studies in environmental research

    NASA Astrophysics Data System (ADS)

    Irrgeher, Johanna; Zitek, Andreas; Prohaska, Thomas

    2014-05-01

    During the last decade stable isotope tracers have emerged as versatile tool in ecological research. Besides 'intrinsic' isotope tracers caused by the natural variation of isotopes, the intentional introduction of 'extrinsic' enriched stable isotope tracers into biological systems has gained significant interest. Hereby the induced change in the natural isotopic composition of an element allows amongst others for studying the fate and fluxes of metals, trace elements and species in organisms or provides an intrinsic marker or tag of particular biological samples. Due to the shoreless potential of this methodology, the number of publications dealing with applications of isotope (double) spikes as tracers to address research questions in 'real world systems' is constantly increasing. However, some isotope systems like the natural Sr isotopic system, although potentially very powerful for this type of application, are still rarely used, mainly because their adequate measurement/determination poses major analytical challenges; as e.g. Sr is available in significant amounts in natural samples. In addition, biological systems underlie complex processes such as metabolism, adsorption/desorption or oxidation/reduction. As a consequence, classic evaluation approaches such as the isotope dilution mass spectrometry equation are often not applicable because of the unknown amount of tracer finally present in the sample. Isotope pattern deconvolution (IPD), based on multiple linear regression, serves as simplified alternative data processing strategy to double spike isotope dilution calculations. The outstanding advantage of this mathematical tool lies in the possibility of deconvolving the isotope pattern in a spiked sample without knowing the quantities of enriched isotope tracer being incorporated into the natural sample matrix as well as the degree of impurities and species-interconversion (e.g. from sample preparation). Here, the potential of IPD for environmental tracer

  15. Study of alternative tracer tests in characterizing transport in fractured rocks

    SciTech Connect

    Tsang, Y.W.

    1995-06-01

    Flow and transport calculations are carried out by numerical simulation for different tracer designs: single-well radially diverging/converging (huff-puff), single well radially converging, and two-well injection-withdrawal (doublet) in a 2D fracture zone. The fractured rocks are conceptualized as a dual-continuum: the well-connected fractures forming a heterogeneous continuum for advective transport, and the less permeable matrix forming a second continuum for tracer diffusion. Results show that the huff-puff design is a good diagnostic test for matrix diffusion. The two-well doublet design averages over a large volume and corrects for the extreme sensitivity to spatial heterogeneities of the single well converging test, but requires prior knowledge of presence or absence of matrix diffusion to give reliable estimate of transport parameters. Results of this study demonstrate that using a suite of different tracer designs is important to reduce the uncertainty in association with solving the inverse problem of tracer test interpretation to characterize transport in fracture rocks. 10 refs., 4 figs., 1 tab.

  16. Study of alternative tracer tests in characterizing transport in fractured rocks

    NASA Astrophysics Data System (ADS)

    Tsang, Y. W.

    Flow and transport calculations are carried out by numerical simulation for different tracer designs: single-well radially diverging /converging (huff-puff), single well radially converging, and two-well injection-withdrawal (doublet) in a 2D fracture zone. The fractured rocks are conceptualized as a dual-continuum: the well-connected fractures forming a heterogeneous continuum for advective transport, and the less permeable matrix forming a second continuum for tracer diffusion. Results show that the huff-puff design is a good diagnostic test for matrix diffusion. The two-well doublet design averages over a large volume and corrects for the extreme sensitivity to spatial heterogeneities of the single well converging test, but requires prior knowledge of presence or absence of matrix diffusion to give reliable estimate of transport parameters. Results of this study demonstrate that using a suite of different tracer designs is important to reduce the uncertainty in association with solving the inverse problem of tracer test interpretation to characterize transport in fracture rocks.

  17. Radio-tracer techniques for the study of flow in saturated porous materials

    USGS Publications Warehouse

    Skibitzke, H.E.; Chapman, H.T.; Robinson, G.M.; McCullough, Richard A.

    1961-01-01

    An experiment was conducted by the U.S. Geological Survey to determine the feasibility of using a radioactive substance as a tracer in the study of microscopic flow in a saturated porous solid. A radioactive tracer was chosen in preference to dye or other chemical in order to eliminate effects of the tracer itself on the flow system such as those relating to density, viscosity and surface tension. The porous solid was artificial "sandstone" composed of uniform fine grains of sand bonded together with an epoxy adhesive. The sides of the block thus made were sealed with an epoxy coating compound to insure water-tightness. Because of the chemical inertness of the block it was possible to use radioactive phosphorus (P32). Ion-exchange equilibrium was created between the block and nonradioactive phosphoric acid. Then a tracer tagged with P32 was injected into the block in the desired geometric configuration, in this case, a line source. After equilibrium in isotopic exchange was reached between the block and the line source, the block was rinsed, drained and sawn into slices. It was found that a quantitative analysis of the flow system may be made by assaying the dissected block. ?? 1961.

  18. New tracers identify hydraulic fracturing fluids and accidental releases from oil and gas operations.

    PubMed

    Warner, N R; Darrah, T H; Jackson, R B; Millot, R; Kloppmann, W; Vengosh, A

    2014-11-04

    Identifying the geochemical fingerprints of fluids that return to the surface after high volume hydraulic fracturing of unconventional oil and gas reservoirs has important applications for assessing hydrocarbon resource recovery, environmental impacts, and wastewater treatment and disposal. Here, we report for the first time, novel diagnostic elemental and isotopic signatures (B/Cl, Li/Cl, δ11B, and δ7Li) useful for characterizing hydraulic fracturing flowback fluids (HFFF) and distinguishing sources of HFFF in the environment. Data from 39 HFFFs and produced water samples show that B/Cl (>0.001), Li/Cl (>0.002), δ11B (25-31‰) and δ7Li (6-10‰) compositions of HFFF from the Marcellus and Fayetteville black shale formations were distinct in most cases from produced waters sampled from conventional oil and gas wells. We posit that boron isotope geochemistry can be used to quantify small fractions (∼0.1%) of HFFF in contaminated fresh water and likely be applied universally to trace HFFF in other basins. The novel environmental application of this diagnostic isotopic tool is validated by examining the composition of effluent discharge from an oil and gas brine treatment facility in Pennsylvania and an accidental spill site in West Virginia. We hypothesize that the boron and lithium are mobilized from exchangeable sites on clay minerals in the shale formations during the hydraulic fracturing process, resulting in the relative enrichment of boron and lithium in HFFF.

  19. Inductively coupled plasma mass spectrometry for stable isotope metabolic tracer studies of living systems

    SciTech Connect

    Luong, Elise

    1999-05-10

    This dissertation focuses on the development of methods for stable isotope metabolic tracer studies in living systems using inductively coupled plasma single and dual quadrupole mass spectrometers. Sub-nanogram per gram levels of molybdenum (Mo) from human blood plasma are isolated by the use of anion exchange alumina microcolumns. Million-fold more concentrated spectral and matrix interferences such as sodium, chloride, sulfate, phosphate, etc. in the blood constituents are removed from the analyte. The recovery of Mo from the alumina column is 82 ± 5% (n = 5). Isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) is utilized for the quantitative ultra-trace concentration determination of Mo in bovine and human blood samples. The average Mo concentration in reference bovine serum determined by this method is 10.2 ± 0.4 ng/g, while the certified value is 11.5 ± 1.1 ng/g (95% confidence interval). The Mo concentration of one pool of human blood plasma from two healthy male donors is 0.5 ± 0.1 ng/g. The inductively coupled plasma twin quadrupole mass spectrometer (ICP-TQMS) is used to measure the carbon isotope ratio from non-volatile organic compounds and bio-organic molecules to assess the ability as an alternative analytical method to gas chromatography combustion isotope ratio mass spectrometry (GC-combustion-IRMS). Trytophan, myoglobin, and β-cyclodextrin are chosen for the study, initial observation of spectral interference of 13C+ with 12C 1H+ comes from the incomplete dissociation of myoglobin and/or β-cyclodextrin.

  20. Sample site selection for tracer studies applying a unidirectional circulatory approach

    SciTech Connect

    Layman, D.K.; Wolfe, R.R.

    1987-08-01

    The optimal arterial or venous sites for infusion and sampling during isotopic tracer studies have not been established. This study determined the relationship of plasma and tissue enrichment (E) when isotopes were infused in an artery and sampled from a vein (av mode) or infused in a vein and sampled from an artery (va mode). Adult dogs were given primed constant infusions of (3-/sup 13/C)lactate, (1-/sup 13/C)leucine, and /sup 14/C-labeled bicarbonate. Simultaneous samples were drawn from the vena cava, aortic arch, and breath. Tissue samples were removed from skeletal muscle, liver, kidney, and gut. Breath samples were analyzed for /sup 14/CO/sub 2/ by liquid scintillation counting and plasma isotopic enrichments of (/sup 13/C)lactate, (/sup 13/C)leucine, and alpha-(/sup 13/C)ketoisocaproate (KIC) were determined by gas chromatography-mass spectrometry. By using the va mode, the plasma E for lactate and leucine were 30-40% above tissue E. The av mode provided an accurate reflection of tissue E for lactate, which equilibrates rapidly with tissues, and a reasonable estimate for leucine, which exchanges more slowly. The isotopic enrichment of plasma KIC more directly reflected tissue leucine E than did plasma leucine E, and KIC enrichment was insensitive to sampling site. We also evaluated theoretically a circulatory model that predicts venous isotopic enrichments when the va mode is used. We conclude that the av mode is optimal but that the problems arising from use of the va mode can be overcome by use of a metabolic product (i.e., KIC) or by calculation of venous specific activity with our circulatory mode.

  1. Experimental design for estimating parameters of rate-limited mass transfer: Analysis of stream tracer studies

    USGS Publications Warehouse

    Wagner, B.J.; Harvey, J.W.

    1997-01-01

    Tracer experiments are valuable tools for analyzing the transport characteristics of streams and their interactions with shallow groundwater. The focus of this work is the design of tracer studies in high-gradient stream systems subject to advection, dispersion, groundwater inflow, and exchange between the active channel and zones in surface or subsurface water where flow is stagnant or slow moving. We present a methodology for (1) evaluating and comparing alternative stream tracer experiment designs and (2) identifying those combinations of stream transport properties that pose limitations to parameter estimation and therefore a challenge to tracer test design. The methodology uses the concept of global parameter uncertainty analysis, which couples solute transport simulation with parameter uncertainty analysis in a Monte Carlo framework. Two general conclusions resulted from this work. First, the solute injection and sampling strategy has an important effect on the reliability of transport parameter estimates. We found that constant injection with sampling through concentration rise, plateau, and fall provided considerably more reliable parameter estimates than a pulse injection across the spectrum of transport scenarios likely encountered in high-gradient streams. Second, for a given tracer test design, the uncertainties in mass transfer and storage-zone parameter estimates are strongly dependent on the experimental Damkohler number, DaI, which is a dimensionless combination of the rates of exchange between the stream and storage zones, the stream-water velocity, and the stream reach length of the experiment. Parameter uncertainties are lowest at DaI values on the order of 1.0. When DaI values are much less than 1.0 (owing to high velocity, long exchange timescale, and/or short reach length), parameter uncertainties are high because only a small amount of tracer interacts with storage zones in the reach. For the opposite conditions (DaI >> 1.0), solute exchange

  2. Using Tracer Experiments To Study Phosphorus Transfer From Soil To Overland Flow

    NASA Astrophysics Data System (ADS)

    Vollmer, T.; Stamm, C.; Schaerer, M.; Sinaj, S.; Frossard, E.; Fluehler, H.

    Diffuse phosphorus (P) losses from agricultural land contribute to the eutrophication of surface water bodies in Switzerland. Grassland soils in areas of high animal stock densities are often prone to high P losses due to over-fertilization and a strong accumu- lation of P in the topsoil. In order to understand the effects of management practices and remediation measures on P transfer into runoff water at a small scale it is impor- tant to localize the sources of this phosphorus within the soil profile and to describe the water flows within the topsoil­overland flow system. We are studying the effects of remediation measures on P availability in the soil and on P concentrations in overland flow in a field experiment. We are using tracer exper- iments to examine the mixing behavior of water applied with a sprinkling device onto the soil surface with pre-event soil water and to trace the contribution of those two water sources to overland flow. Two plots were pre-irrigated with a solution of KBr in order to label the soil solu- tion. After a few days of equilibration, two fluorescent dyes were applied to different areas of the plots at a constant rate of 40 mm h-1. Surface runoff was analyzed for tracer concentrations. Small soil monoliths (0.35 * 0.25 *0.20 m3) were excavated and the tracer distribution within the blocks was mapped using a digital camera, optical filters, and tracer specific excitation light source. This tracing technique allowed for independent mapping of the distribution of two simultaneously applied tracers. The experiments demonstrated heterogenous infiltration of the dyes, negligible lat- eral translocation of the dyes within the soil, minimal transfer of the pre-applied Br- into overland flow, early breakthrough of the dye tracers in overland flow which was independent of the tracers sorption properties and a recovery of the dyes that corre- sponded to the runoff ratio. In all, the experiments indicate a very restricted interac- tion between

  3. A Study Plan for Determining Recharge Rates at the Hanford Site Using Environmental Tracers

    SciTech Connect

    Murphy, E. M.; Szecsody, J. E.; Phillips, S. J.

    1991-02-01

    This report presents a study plan tor estimating recharge at the Hanford Site using environmental tracers. Past operations at the Hanford Site have led to both soil and groundwater contamination, and recharge is one of the primary mechanisms for transporting contaminants through the vadose zone and into the groundwater. The prediction of contaminant movement or transport is one aspect of performance assessment and an important step in the remedial investigation/feasibility study (RI/FS) process. In the past, recharge has been characterized by collecting lysimeter data. Although lysimeters can generate important and reliable data, their limitations include 1) fixed location, 2) fixed sediment contents, 3) edge effects, 4) low rates, and 5) relatively short duration of measurement. These limitations impact the ability to characterize the spatial distribution of recharge at the Hanford Site, and thus the ability to predict contaminant movement in the vadose zone. An alternative to using fixed lysimeters for determining recharge rates in the vadose zone is to use environmental tracers. Tracers that have been used to study water movement in the vadose zone include total chloride, {sup 36}CI, {sup 3}H, and {sup 2}H/{sup 18}O. Atmospheric levels of {sup 36}CI and {sup 3}H increased during nuclear bomb testing in the Pacific, and the resulting "bomb pulse" or peak concentration can be measured in the soil profile. Locally, past operations at the Hanford Site have resu~ed in the atmospheric release of numerous chemical and isotopic tracers, including nitrate, {sup 129}I, and {sup 99}Tc. The radionuclides, in particular, reached a well-defined atmospheric peak in 1945. Atmospheric releases of {sup 129}I and {sup 99}Tc were greatly reduced by mid-1946, but nitrogen oxides continued to be released from the uranium separations facilities. As a result, the nitrate concentrations probably peaked in the mid-1950s, when the greatest number of separations facilities were operating

  4. Characterization of crushed tuff for the evaluation of the fate of tracers in transport studies in the unsaturated zone

    SciTech Connect

    Polzer, W.L.; Fuentes, H.R.; Raymond, R.; Bish, D.L.; Gladney, E.S.; Lopez, E.A.

    1987-03-01

    Results of field-scale (caisson) transport studies under unsaturated moisture and steady and nonsteady flow conditions indicate variability and a lack of conservation of mass in solute transport. The tuff materials used in that study were analyzed for the presence of tracers and of freshly precipitated material to help explain the variability and lack of conservation of mass. Selected tuff samples were characterized by neutron activation analysis for tracer identification, by x-ray diffraction for mineral identification, by petrographic analysis for identification of freshly precipitated material, and by x-ray fluorescence analysis for identification of major and trace elements. The results of these analyses indicate no obvious presence of freshly precipitated material that would retard tracer movement. The presence of the nonsorbing tracers (bromide and iodide) suggest the retention of these tracers in immobile water. The presence of the nonsorbing tracers (bromide and iodide) suggest the retention of these tracers in immobile water. The presence of sorbing and nonsorbing tracers on the tuff at some locations (even cesium at the 415-cm depth) and not at others suggests variability in transport. 15 refs., 14 figs., 9 tabs.

  5. Modeling of meteorology, tracer transport and chemistry for the Uintah Basin Winter Ozone Studies 2012 and 2013

    NASA Astrophysics Data System (ADS)

    Ahmadov, R.; McKeen, S. A.; Angevine, W. M.; Frost, G. J.; Roberts, J. M.; De Gouw, J. A.; Warneke, C.; Peischl, J.; Brown, S. S.; Edwards, P. M.; Wild, R. J.; Pichugina, Y. L.; Banta, R. M.; Brewer, A.; Senff, C. J.; Langford, A. O.; Petron, G.; Karion, A.; Sweeney, C.; Schnell, R. C.; Johnson, B.; Zamora, R. J.; Helmig, D.; Park, J.; Evans, J.; Stephens, C. R.; Olson, J. B.; Trainer, M.

    2013-12-01

    The Uintah Basin Winter Ozone Studies (UBWOS) field campaigns took place during winter of 2012 and 2013 in the Uintah Basin, Utah. The studies were aimed at characterizing meteorology, emissions of atmospheric constituents and air chemistry in a region abundant with oil and gas production, with associated emissions of various volatile organic compounds (VOCs) and NOx. High ozone pollution events were observed throughout the Uintah Basin during the winter of 2013, but not during the winter of 2012. A clear understanding of the processes leading to high ozone events is still lacking. We present here high spatiotemporal resolution simulations of meteorology, tracer transport and gas chemistry over the basin during January-February, 2012 and 2013 using the WRF/Chem regional photochemical model. Correctly characterizing the meteorology poses unique challenges due to complex terrain, cold-pool conditions, and shallow inversion layers observed during the winter of 2013. We discuss the approach taken to adequately simulate the meteorology over the basin and present evaluations of the modeled meteorology using surface, lidar and tethersonde measurements. Initial simulations use a passive tracer within the model as a surrogate for CH4 released from oil and gas wells. These tracer transport simulations show that concentrations of inert, emitted species near the surface in 2013 were 4-8 times higher than 2012 due to much shallower boundary layers and reduced winds in 2013. This is supported by in-situ measurements of CH4 made at the Horse Pool surface station during the field campaigns. Full photochemical simulations are forced by VOC and NOx emissions that are determined in a top-down approach, using observed emission ratios of VOC and NOx relative to CH4, along with available information of active wells, compressors, and processing plants. We focus on differences in meteorology, temperature, and radiation between the two winters in determining ozone concentrations in the

  6. Simultaneous imaging of fuel vapor mass fraction and gas-phase temperature inside gasoline sprays using two-line excitation tracer planar laser-induced fluorescence.

    PubMed

    Zigan, Lars; Trost, Johannes; Leipertz, Alfred

    2016-02-20

    This paper reports for the first time, to the best of our knowledge, on the simultaneous imaging of the gas-phase temperature and fuel vapor mass fraction distribution in a direct-injection spark-ignition (DISI) spray under engine-relevant conditions using tracer planar laser-induced fluorescence (TPLIF). For measurements in the spray, the fluorescence tracer 3-pentanone is added to the nonfluorescent surrogate fuel iso-octane, which is excited quasi-simultaneously by two different excimer lasers for two-line excitation LIF. The gas-phase temperature of the mixture of fuel vapor and surrounding gas and the fuel vapor mass fraction can be calculated from the two LIF signals. The measurements are conducted in a high-temperature, high-pressure injection chamber. The fluorescence calibration of the tracer was executed in a flow cell and extended significantly compared to the existing database. A detailed error analysis for both calibration and measurement is provided. Simultaneous single-shot gas-phase temperature and fuel vapor mass fraction fields are processed for the assessment of cyclic spray fluctuations.

  7. Impact of non-idealities in gas-tracer tests on the estimation of reaeration, respiration, and photosynthesis rates in streams.

    PubMed

    Knapp, Julia L A; Osenbrück, Karsten; Cirpka, Olaf A

    2015-10-15

    Estimating respiration and photosynthesis rates in streams usually requires good knowledge of reaeration at the given locations. For this purpose, gas-tracer tests can be conducted, and reaeration rate coefficients are determined from the decrease in gas concentration along the river stretch. The typical procedure for analysis of such tests is based on simplifying assumptions, as it neglects dispersion altogether and does not consider possible fluctuations and trends in the input signal. We mathematically derive the influence of these non-idealities on estimated reaeration rates and how they are propagated onto the evaluation of aerobic respiration and photosynthesis rates from oxygen monitoring. We apply the approach to field data obtained from a gas-tracer test using propane in a second-order stream in Southwest Germany. We calculate the reaeration rate coefficients accounting for dispersion as well as trends and uncertainty in the input signals and compare them to the standard approach. We show that neglecting dispersion significantly underestimates reaeration, and results between sections cannot be compared if trends in the input signal of the gas tracer are disregarded. Using time series of dissolved oxygen and the various estimates of reaeration, we infer respiration and photosynthesis rates for the same stream section, demonstrating that the bias and uncertainty of reaeration using the different approaches significantly affects the calculation of metabolic rates.

  8. A Mathematical Modeling Study of Tracer Mixing in a Continuous Casting Tundish

    NASA Astrophysics Data System (ADS)

    Chen, Chao; Jonsson, Lage Tord Ingemar; Tilliander, Anders; Cheng, Guoguang; Jönsson, Pär Göran

    2015-02-01

    A mathematical model based on a water model was developed to study the tracer mixing in a single strand tundish. The mixing behavior of black ink and KCl solution was simulated by a mixed composition fluid model, and the data were validated by water modeling results. In addition, a model that solves the scalar transport equation (STE) without any physical properties of the tracer was studied and the results were compared to predictions using the density-coupled model. Furthermore, the mixing behaviors of different amounts of KCl tracers were investigated. Before the model was established, KCl tracer properties such as the KCl molecule diffusion (KMD), the water molecule self-diffusion (WSD) in KCl solution, and the KCl solution viscosity (KV) were evaluated. The RTD curve of 250 mL KCl for the KMD case was closer to the water modeling results than that of the case implemented with only density. Moreover, the ensemble average deviation of the RTD curves of the cases implemented with KMD + WSD, KMD + KV, and KMD + WSD + KV to the KMD case is less than 0.7 pct. Thus, the water self-diffusion and KV were neglected, while the KCl density and KMD were implemented in the current study. The flow pattern of black ink was similar to the STE result i.e., the fluid flowed upwards toward the top surface and formed a large circulating flow at the outlet nozzle. The flow behavior of the 100, 150, and 250 mL KCl cases exhibited a strong tendency to sink to the tundish bottom, and subsequently flow through the holes in the dam. Thereafter, it propagated toward the outlet nozzle. Regarding the KCl tracer amount, the tracer concentration propagated to the outlet nozzle much faster for the larger amount case than for the smaller amount cases. However, the flow pattern for the 50 mL KCl case was somewhat different. The fluid propagated to the top surface which acted like black ink during the initial injection, and subsequently the fluid flowed throughout the holes at a much slower pace

  9. A Mathematical Modeling Study of Tracer Mixing in a Continuous Casting Tundish

    NASA Astrophysics Data System (ADS)

    Chen, Chao; Jonsson, Lage Tord Ingemar; Tilliander, Anders; Cheng, Guoguang; Jönsson, Pär Göran

    2014-09-01

    A mathematical model based on a water model was developed to study the tracer mixing in a single strand tundish. The mixing behavior of black ink and KCl solution was simulated by a mixed composition fluid model, and the data were validated by water modeling results. In addition, a model that solves the scalar transport equation (STE) without any physical properties of the tracer was studied and the results were compared to predictions using the density-coupled model. Furthermore, the mixing behaviors of different amounts of KCl tracers were investigated. Before the model was established, KCl tracer properties such as the KCl molecule diffusion (KMD), the water molecule self-diffusion (WSD) in KCl solution, and the KCl solution viscosity (KV) were evaluated. The RTD curve of 250 mL KCl for the KMD case was closer to the water modeling results than that of the case implemented with only density. Moreover, the ensemble average deviation of the RTD curves of the cases implemented with KMD + WSD, KMD + KV, and KMD + WSD + KV to the KMD case is less than 0.7 pct. Thus, the water self-diffusion and KV were neglected, while the KCl density and KMD were implemented in the current study. The flow pattern of black ink was similar to the STE result i.e., the fluid flowed upwards toward the top surface and formed a large circulating flow at the outlet nozzle. The flow behavior of the 100, 150, and 250 mL KCl cases exhibited a strong tendency to sink to the tundish bottom, and subsequently flow through the holes in the dam. Thereafter, it propagated toward the outlet nozzle. Regarding the KCl tracer amount, the tracer concentration propagated to the outlet nozzle much faster for the larger amount case than for the smaller amount cases. However, the flow pattern for the 50 mL KCl case was somewhat different. The fluid propagated to the top surface which acted like black ink during the initial injection, and subsequently the fluid flowed throughout the holes at a much slower pace

  10. A tracer study in an Alaskan gravel beach and its implications on the persistence of the Exxon Valdez oil.

    PubMed

    Li, Hailong; Boufadel, Michel C

    2011-06-01

    Despite great efforts including bioremediation, the 1989 Exxon Valdez oil spills persist in many gravel beaches in Prince William Sound, Alaska, USA. To explore this mystery, a lithium tracer study was conducted along two transects on one of these beaches. The tracer injections and transports were successfully simulated using the 2-dimensional numerical model MARUN. The tracer stayed much longer in the oil-persisting, right transect (facing landwand) than in the clean, left transect. If the tracer is approximately regarded as oils, oils in the upper layer would have more opportunities to enter the lower layer in the right transect than in the left one. This may qualitatively explain the oil persistence within the right transect. When the tracer is regarded as nutrients, the long stay of nutrients within the right transect implies that the oil persistence along the right transect was not due to the lack of nutrients during the bioremediation.

  11. Nitrate turnover in a peat soil under drained and rewetted conditions: results from a [(15)N]nitrate-bromide double-tracer study.

    PubMed

    Russow, Rolf; Tauchnitz, Nadine; Spott, Oliver; Mothes, Sibylle; Bernsdorf, Sabine; Meissner, Ralph

    2013-01-01

    Under natural conditions, peatlands are generally nitrate-limited. However, recent concerns about an additional N input into peatlands by atmospheric N deposition have highlighted the risk of an increased denitrification activity and hence the likelihood of a rise of emissions of the greenhouse gas nitrous oxide. Therefore, the aim of the present study was to investigate the turnover of added nitrate in a drained and a rewetted peatland using a [(15)N]nitrate-bromide double-tracer method. The double-tracer method allows a separation between physical effects (dilution, dispersion and dislocation) and microbial and chemical nitrate transformation by comparing with the conservative Br(-) tracer. In the drained peat site, low NO3(-) consumption rates have been observed. In contrast, NO3(-) consumption at the rewetted peat site rises rapidly to about 100% within 4 days after tracer application. Concomitantly, the (15)N abundances of nitrite and ammonium in soil water increased and lead to the conclusion that, besides commonly known NO3(-) reduction to nitrite (i.e. denitrification), a dissimilatory nitrate reduction to ammonium has simultaneously taken place. The present study reveals that increasing NO3(-) inputs into rewetted peatlands via atmospheric deposition results in a rapid NO3(-) consumption, which could lead to an increase in N2O emissions into the atmosphere.

  12. National Biomedical Tracer Facility (NBTF). Project definition study: Phase I

    SciTech Connect

    Lagunas-Solar, M.C.

    1995-02-15

    This report describes a five-year plan for the construction and commissioning of a reliable and versatile NBTF facility for the production of high-quality, high-yield radioisotopes for research, biomedical, and industrial applications. The report is organized in nine sections providing, in consecutive order, responses to the nine questions posed by the U.S. Department of Energy in its solicitation for the NBTF Project Definition Study. In order to preserve direct correspondence (e.g., Sec. 3 = 3rd item), this Introduction is numbered {open_quotes}0.{close_quotes} Accelerator and facility designs are covered in Section 1 (Accelerator Design) and Section 2 (Facility Design). Preliminary estimates of capital costs are detailed in Section 3 (Design and Construction Costs). Full licensing requirements, including federal, state, and local ordinances, are discussed in Section 4 (Permits). A plan for the management of hazardous materials to be generated by NBTF is presented in Section 5 (Waste Management). An evaluation of NBTF`s economic viability and its potential market impact is detailed in Section 6(Business Plan), and is complemented by the plans in Section 7 (Operating Plan) and Section 8 (Radioisotope Plan). Finally, a plan for NBTF`s research, education, and outreach programs is presented in Section 9 (Research and Education Programs).

  13. Solute movement in drained fen peat: a field tracer study in a Somerset (UK) wetland

    NASA Astrophysics Data System (ADS)

    Baird, Andrew J.; Gaffney, Simon W.

    2000-10-01

    Little is known about solute transport in peats, despite the obvious importance of solute transport on eco-hydrological processes in both managed and natural peatlands. To address this lack of knowledge, we investigated solute transport processes in an agricultural fen peat using a conservative KBr tracer. The main aim of the study was to elucidate solute transport behaviour in general in this peat, with a more specific aim of investigating whether preferential or bypassing flow occurred. The tracer moved through the peat more rapidly than expected, and the pattern of movement showed clear evidence of plot-scale bypassing flow. The data also provide evidence that bypassing flow occurs in pores at smaller scales. The implications of this study for management of wetland pastures in the Somerset Moors in south-west England are discussed.

  14. Alma observations of nearby luminous infrared galaxies with various agn energetic contributions using dense gas tracers

    SciTech Connect

    Imanishi, Masatoshi; Nakanishi, Kouichiro

    2014-07-01

    We present the results of our ALMA Cycle 0 observations, using HCN/HCO{sup +}/HNC J = 4-3 lines, of six nearby luminous infrared galaxies with various energetic contributions from active galactic nuclei (AGNs) estimated from previous infrared spectroscopy. These lines are very effective for probing the physical properties of high-density molecular gas around the hidden energy sources in the nuclear regions of these galaxies. We find that HCN to HCO{sup +} J = 4-3 flux ratios tend to be higher in AGN-important galaxies than in starburst-dominated regions, as was seen at the J = 1-0 transition, while there is no clear difference in the HCN-to-HNC J = 4-3 flux ratios among observed sources. A galaxy with a starburst-type infrared spectral shape and very large molecular line widths shows a high HCN-to-HCO{sup +} J = 4-3 flux ratio, which could be due to turbulence-induced heating. We propose that enhanced HCN J = 4-3 emission relative to HCO{sup +} J = 4-3 could be used to detect more energetic activity than normal starbursts, including deeply buried AGNs, in dusty galaxy populations.

  15. Field studies of streamflow generation using natural and injected tracers on Bickford and Walker Branch Watersheds

    SciTech Connect

    Genereux, D.; Hemond, H. . Dept. of Civil Engineering); Mulholland, P. )

    1992-05-01

    Field studies of streamflow generation were undertaken on two forested watersheds, the West Road subcatchment of Bickford Watershed in central Massachusetts and the West Fork of Walker Branch Watershed in eastern Tennessee. A major component of the research was development of a two-stage methodology for the use of naturally-occurring {sup 222}Rn as a tracer. The first of the two stages was solving a mass-balance equation for {sup 222}Rn around a stream reach of interest in order to calculate Rn{sub q}, the {sup 222}Rn content of the lateral inflow to the reach; a conservative tracer (chloride) and a volatile tracer (propane) were injected into the study stream to account for lateral inflow to, and volatilization from, the study reach. The second stage involved quantitative comparison of Rn{sub q} to the measured {sup 222}Rn concentrations of different subsurface waters in order to assess how important these waters were in contributing lateral inflow to the stream reach.

  16. Flow optimization study of a batch microfluidics PET tracer synthesizing device

    PubMed Central

    Elizarov, Arkadij M.; Meinhart, Carl; van Dam, R. Michael; Huang, Jiang; Daridon, Antoine; Heath, James R.; Kolb, Hartmuth C.

    2010-01-01

    We present numerical modeling and experimental studies of flow optimization inside a batch microfluidic micro-reactor used for synthesis of human-scale doses of Positron Emission Tomography (PET) tracers. Novel techniques are used for mixing within, and eluting liquid out of, the coin-shaped reaction chamber. Numerical solutions of the general incompressible Navier Stokes equations along with time-dependent elution scalar field equation for the three dimensional coin-shaped geometry were obtained and validated using fluorescence imaging analysis techniques. Utilizing the approach presented in this work, we were able to identify optimized geometrical and operational conditions for the micro-reactor in the absence of radioactive material commonly used in PET related tracer production platforms as well as evaluate the designed and fabricated micro-reactor using numerical and experimental validations. PMID:21072595

  17. STRATEGIES FOR QUANTIFYING PET IMAGING DATA FROM TRACER STUDIES OF BRAIN RECEPTORS AND ENZYMES.

    SciTech Connect

    Logan, J.

    2001-04-02

    A description of some of the methods used in neuroreceptor imaging to distinguish changes in receptor availability has been presented in this chapter. It is necessary to look beyond regional uptake of the tracer since uptake generally is affected by factors other than the number of receptors for which the tracer has affinity. An exception is the infusion method producing an equilibrium state. The techniques vary in complexity some requiring arterial blood measurements of unmetabolized tracer and multiple time uptake data. Others require only a few plasma and uptake measurements and those based on a reference region require no plasma measurements. We have outlined some of the limitations of the different methods. Laruelle (1999) has pointed out that test/retest studies to which various methods can be applied are crucial in determining the optimal method for a particular study. The choice of method will also depend upon the application. In a clinical setting, methods not involving arterial blood sampling are generally preferred. In the future techniques for externally measuring arterial plasma radioactivity with only a few blood samples for metabolite correction will extend the modeling options of clinical PET. Also since parametric images can provide information beyond that of ROI analysis, improved techniques for generating such images will be important, particularly for ligands requiring more than a one-compartment model. Techniques such as the wavelet transform proposed by Turkheimer et al. (2000) may prove to be important in reducing noise and improving quantitation.

  18. Measuring technique for thermal ionisation mass spectrometry of human tracer kinetic study with stable cerium isotopes.

    PubMed

    Keiser, Teresa; Höllriegl, Vera; Giussani, Augusto; Oeh, Uwe

    2011-06-01

    Thermal ionisation mass spectrometry (TIMS) method has been developed for the simultaneous detection of different cerium isotopes in biological samples (i.e., blood and urine) at very low concentrations. The work has been done in the frame of a biokinetic study, where different stable cerium isotopes have been administered orally and intravenously as tracers to the human body. In order to develop an appropriate detection method for the tracers in the biological samples, an optimum sample preparation technique has been set and adapted to the specific requirements of the analysis technique used, i.e., TIMS. For sample evaporation and ionisation, the double tantalum filament technique showed the best results. The ions produced were simultaneously collected on a secondary electron multiplier so that the isotopic ratios of the cerium isotopes in the biological samples could be measured. The technique has been optimised for the determination of cerium down to 1 ng loaded on the evaporation filament corresponding to cerium concentrations of down to 1 ng ml(-1) in the blood or urine samples. It has been shown that the technique is reliable in application and enables studies on cerium metabolism and biokinetics in humans without employing radioactive tracers.

  19. Gas-phase naphthalene concentration data recovery in ambient air and its relevance as a tracer of sources of volatile organic compounds

    NASA Astrophysics Data System (ADS)

    Uria-Tellaetxe, Iratxe; Navazo, Marino; de Blas, Maite; Durana, Nieves; Alonso, Lucio; Iza, Jon

    2016-04-01

    Despite the toxicity of naphthalene and the fact that it is a precursor of atmospheric photooxidants and secondary aerosol, studies on ambient gas-phase naphthalene are generally scarce. Moreover, as far as we are concerned, this is the first published one using long-term hourly ambient gas-phase naphthalene concentrations. In this work, it has been also demonstrated the usefulness of ambient gas-phase naphthalene to identify major sources of volatile organic compounds (VOC) in complex scenarios. Initially, in order to identify main benzene emission sources, hourly ambient measurements of 60 VOC were taken during a complete year together with meteorological data in an urban/industrial area. Later, due to the observed co-linearity of some of the emissions, a procedure was developed to recover naphthalene concentration data from recorded chromatograms to use it as a tracer of the combustion and distillation of petroleum products. The characteristic retention time of this compound was determined comparing previous GC-MS and GC-FID simultaneous analysis by means of relative retention times, and its concentration was calculated by using relative response factors. The obtained naphthalene concentrations correlated fairly well with ethene (r = 0.86) and benzene (r = 0.92). Besides, the analysis of daily time series showed that these compounds followed a similar pattern, very different from that of other VOC, with minimum concentrations at day-time. This, together with the results from the assessment of the meteorological dependence pointed out a coke oven as the major naphthalene and benzene emitting sources in the study area.

  20. Effect of Spatial Variations in Temperature, Permeability, and Water Saturation on Partitioning Gas Tracer Tests to Quantify Water in the Vadose Zone and in Landfills

    NASA Astrophysics Data System (ADS)

    Li, L.; Imhoff, P. T.

    2006-12-01

    The measurement of water saturation is important in the vadose zone and in the unsaturated porous media (refuse) in bioreactor landfills. The partitioning gas tracer test (PGTT) has been successfully used to measure water saturations in soils and landfills. However, the effectiveness of the this technique for obtaining average water saturations may depend on spatial variations in temperature (landfills), which result in spatially varying Henry's law constants, as well as spatial variability in water saturations and gas permeability. Investigations of the performance of PGTTs in heterogeneous porous media are needed to assess the utility of this measurement technique in such systems. A two dimensional modeling approach was used to investigate PGTT performance in soils and landfills with spatially varying properties. Temperature, permeability and water saturations were varied spatially to examine their effect on the accuracy of water saturation measurements. The influence of tracer diffusion on PGTT results was also examined. These simulations provide guidelines for applying PGTTs in soils and landfills where spatial variability of properties is significant. Keywords: water saturation, gas tracers, spatial heterogeneity, landfills

  1. Overview of SIMS-Based Experimental Studies of Tracer Diffusion in Solids and Application to Mg Self-Diffusion

    SciTech Connect

    Kulkarni, Nagraj S.; Bruce Warmack, Robert J.; Radhakrishnan, Bala; Hunter, Jerry L.; Sohn, Yongho; Coffey, Kevin R.; Murch, Graeme E.; Belova, Irina V.

    2014-09-23

    Tracer diffusivities provide the most fundamental information on diffusion in materials and are the foundation of robust diffusion databases. Compared to traditional radiotracer techniques that utilize radioactive isotopes, the secondary ion mass spectrometry (SIMS) based thin-film technique for tracer diffusion is based on the use of enriched stable isotopes that can be accurately profiled using SIMS. Experimental procedures & techniques that are utilized for the measurement of tracer diffusion coefficients are presented for pure magnesium, which presents some unique challenges due to the ease of oxidation. The development of a modified Shewmon-Rhines diffusion capsule for annealing Mg and an ultra-high vacuum (UHV) system for sputter deposition of Mg isotopes are discussed. Optimized conditions for accurate SIMS depth profiling in polycrystalline Mg are provided. An automated procedure for the correction of heat-up and cool-down times during tracer diffusion annealing is discussed. The non-linear fitting of a SIMS depth profile data using the thin film Gaussian solution to obtain the tracer diffusivity along with the background tracer concentration and tracer film thickness is discussed. An Arrhenius fit of the Mg self-diffusion data obtained using the low-temperature SIMS measurements from this study and the high-temperature radiotracer measurements of Shewmon and Rhines (1954) was found to be a good representation of both types of diffusion data that cover a broad range of temperatures between 250 - 627° C (523 900 K).

  2. Overview of SIMS-Based Experimental Studies of Tracer Diffusion in Solids and Application to Mg Self-Diffusion

    DOE PAGES

    Kulkarni, Nagraj S.; Bruce Warmack, Robert J.; Radhakrishnan, Bala; ...

    2014-09-23

    Tracer diffusivities provide the most fundamental information on diffusion in materials and are the foundation of robust diffusion databases. Compared to traditional radiotracer techniques that utilize radioactive isotopes, the secondary ion mass spectrometry (SIMS) based thin-film technique for tracer diffusion is based on the use of enriched stable isotopes that can be accurately profiled using SIMS. Experimental procedures & techniques that are utilized for the measurement of tracer diffusion coefficients are presented for pure magnesium, which presents some unique challenges due to the ease of oxidation. The development of a modified Shewmon-Rhines diffusion capsule for annealing Mg and an ultra-highmore » vacuum (UHV) system for sputter deposition of Mg isotopes are discussed. Optimized conditions for accurate SIMS depth profiling in polycrystalline Mg are provided. An automated procedure for the correction of heat-up and cool-down times during tracer diffusion annealing is discussed. The non-linear fitting of a SIMS depth profile data using the thin film Gaussian solution to obtain the tracer diffusivity along with the background tracer concentration and tracer film thickness is discussed. An Arrhenius fit of the Mg self-diffusion data obtained using the low-temperature SIMS measurements from this study and the high-temperature radiotracer measurements of Shewmon and Rhines (1954) was found to be a good representation of both types of diffusion data that cover a broad range of temperatures between 250 - 627° C (523 900 K).« less

  3. Salt marsh ecosystem biogeochemical responses to nutrient enrichment: a paired 15N tracer study.

    PubMed

    Drake, D C; Peterson, Bruce J; Galván, Kari A; Deegan, Linda A; Hopkinson, Charles; Johnson, J Michael; Koop-Jakobsen, K; Lemay, Lynsey E; Picard, Christian

    2009-09-01

    We compared processing and fate of dissolved NO3- in two New England salt marsh ecosystems, one receiving natural flood tide concentrations of approximately 1-4 micromol NO3-/ L and the other receiving experimentally fertilized flood tides containing approximately 70-100 micromol NO3-/ L. We conducted simultaneous 15NO3- (isotope) tracer additions from 23 to 28 July 2005 in the reference (8.4 ha) and fertilized (12.4 ha) systems to compare N dynamics and fate. Two full tidal cycles were intensively studied during the paired tracer additions. Resulting mass balances showed that essentially 100% (0.48-0.61 mol NO3-N.ha(-1).h(-1)) of incoming NO3- was assimilated, dissimilated, sorbed, or sedimented (processed) within a few hours in the reference system when NO3- concentrations were 1.3-1.8 micromol/L. In contrast, only 50-60% of incoming NO3- was processed in the fertilized system when NO3- concentrations were 84-96 micromol/L; the remainder was exported in ebb tidewater. Gross NO3- processing was approximately 40 times higher in the fertilized system at 19.34-24.67 mol NO3-N.ha(-1).h(-1). Dissimilatory nitrate reduction to ammonium was evident in both systems during the first 48 h of the tracer additions but <1% of incoming 15NO3- was exported as 15NH4+. Nitrification rates calculated by 15NO3- dilution were 6.05 and 4.46 mol.ha(-1).h(-1) in the fertilized system but could not be accurately calculated in the reference system due to rapid (<4 h) NO3- turnover. Over the five-day paired tracer addition, sediments sequestered a small fraction of incoming NO3-, although the efficiency of sequestration was 3.8% in the reference system and 0.7% in the fertilized system. Gross sediment N sequestration rates were similar at 13.5 and 12.6 mol.ha(-1).d(-1), respectively. Macrophyte NO3- uptake efficiency, based on tracer incorporation in aboveground tissues, was considerably higher in the reference system (16.8%) than the fertilized system (2.6%), although bulk uptake of NO3

  4. URCHIN: Reverse ray tracer

    NASA Astrophysics Data System (ADS)

    Altay, Gabriel; Theuns, Tom

    2014-12-01

    URCHIN is a Smoothed Particle Hydrodynamics (SPH) reverse ray tracer (i.e. from particles to sources). It calculates the amount of shielding from a uniform background that each particle experiences. Preservation of the adaptive density field resolution present in many gas dynamics codes and uniform sampling of gas resolution elements with rays are two of the benefits of URCHIN; it also offers preservation of Galilean invariance, high spectral resolution, and preservation of the standard uniform UV background in optically thin gas.

  5. A rapid method for the measurement of sulfur hexafluoride (SF6), trifluoromethyl sulfur pentafluoride (SF5CF3), and Halon 1211 (CF2ClBr) in hydrologic tracer studies

    USGS Publications Warehouse

    Busenberg, Eurybiades; Plummer, L. Niel

    2010-01-01

    A rapid headspace method for the simultaneous laboratory determination of intentionally introduced hydrologic tracers, sulfur hexafluoride (SF6), trifluoromethyl sulfur pentafluoride (SF5CF3), Halon 1211 (CF2ClBr), and other halocarbons in water and gases is described. The high sensitivity of the procedure allows for introduction of minimal tracer mass (a few grams) into hydrologic systems with a large dynamic range of analytical detection (dilutions to 1:108). Analysis times by gas chromatography with electron capture detector are less than 1 min for SF6; about 2 min for SF6 and SF5CF3; and 4 min for SF6, SF5CF3, and Halon 1211. Many samples can be rapidly collected, preserved in stoppered septum bottles, and analyzed at a later time in the laboratory. Examples are provided showing the effectiveness of the gas tracer test studies in varied hydrogeological settings.

  6. Neonatal Respiratory Diseases in the Newborn Infant: Novel Insights from Stable Isotope Tracer Studies.

    PubMed

    Carnielli, Virgilio P; Giorgetti, Chiara; Simonato, Manuela; Vedovelli, Luca; Cogo, Paola

    2016-01-01

    Respiratory distress syndrome is a common problem in preterm infants and the etiology is multifactorial. Lung underdevelopment, lung hypoplasia, abnormal lung water metabolism, inflammation, and pulmonary surfactant deficiency or disfunction play a variable role in the pathogenesis of respiratory distress syndrome. High-quality exogenous surfactant replacement studies and studies on surfactant metabolism are available; however, the contribution of surfactant deficiency, alteration or dysfunction in selected neonatal lung conditions is not fully understood. In this article, we describe a series of studies made by applying stable isotope tracers to the study of surfactant metabolism and lung water. In a first set of studies, which we call 'endogenous studies', using stable isotope-labelled intravenous surfactant precursors, we showed the feasibility of measuring surfactant synthesis and kinetics in infants using several metabolic precursors including plasma glucose, plasma fatty acids and body water. In a second set of studies, named 'exogenous studies', using stable isotope-labelled phosphatidylcholine tracer given endotracheally, we could estimate surfactant disaturated phosphatidylcholine pool size and half-life. Very recent studies are focusing on lung water and on the endogenous biosynthesis of the surfactant-specific proteins. Information obtained from these studies in infants will help to better tailor exogenous surfactant treatment in neonatal lung diseases.

  7. Accounting for Dispersion and time-dependent Input Signals during Gas Tracer Tests and their Effect on the Estimation of Reaeration, Respiration and Photosynthesis in Streams

    NASA Astrophysics Data System (ADS)

    Knapp, Julia; Osenbrück, Karsten; Olaf, Cirpka

    2015-04-01

    The variation of dissolved oxygen (DO) in streams, are caused by a number of processes, of which respiration and primary production are considered to be the most important ones (Odum, 1956; Staehr et al., 2012). Measuring respiration and photosynthesis rates in streams based on recorded time series of DO requires good knowledge on the reaeration fluxes at the given locations. For this, gas tracer tests can be conducted, and reaeration coefficients determined from the observed decrease in gas concentration along the stretch (Genereux and Hemond, 1990): ( ) --1- -cup- k2 = t2 - t1 ln Rcdown (1) with the gas concentrations measured at an upstream location, cup[ML-3], and a downstream location, cdown. t1[T] andt2 [T] denote the measurement times at the two locations and R [-] represents the recovery rate which can also be obtained from conservative tracer data. The typical procedure for analysis, however, contains a number of assumptions, as it neglects dispersion and does not take into account possible fluctuations of the input signal. We derive the influence of these aspects mathematically and illustrate them on the basis of field data obtained from a propane gas tracer test. For this, we compare the reaeration coefficients obtained from approaches with dispersion and/or a time-dependent input signals to the standard approach. Travel times and travel time distributions between the different measurement stations are obtained from a simultaneously performed conservative tracer test with fluorescein. In order to show the carry-over effect to metabolic rates, we furthermore estimate respiration and photosynthesis rates from the calculated reaeration coefficients and measured oxygen data. This way, we are able to show that neglecting dispersion significantly underestimates reaeration, and the impact of the time-dependent input concentration cannot be disregarded either. When estimated reaeration rates are used to calculate respiration and photosynthesis from measured

  8. 13C-Tracer and Gas Chromatography-Mass Spectrometry Analyses Reveal Metabolic Flux Distribution in the Oleaginous Microalga Chlorella protothecoides1[C][W][OA

    PubMed Central

    Xiong, Wei; Liu, Lixia; Wu, Chao; Yang, Chen; Wu, Qingyu

    2010-01-01

    The green alga Chlorella protothecoides has received considerable attention because it accumulates neutral triacylglycerols, commonly regarded as an ideal feedstock for biodiesel production. In order to gain a better understanding of its metabolism, tracer experiments with [U-13C]/[1-13C]glucose were performed with heterotrophic growth of C. protothecoides for identifying the metabolic network topology and estimating intracellular fluxes. Gas chromatography-mass spectrometry analysis tracked the labeling patterns of protein-bound amino acids, revealing a metabolic network consisting of the glycolysis, the pentose phosphate pathway, and the tricarboxylic acid cycle with inactive glyoxylate shunt. Evidence of phosphoenolpyruvate carboxylase, phosphoenolpyruvate carboxykinase, and malic enzyme activity was also obtained. It was demonstrated that the relative activity of the pentose phosphate pathway to glycolysis under nitrogen-limited environment increased, reflecting excess NADPH requirements for lipid biosynthesis. Although the growth rate and cellular oil content were significantly altered in response to nitrogen limitation, global flux distribution of C. protothecoides remained stable, exhibiting the rigidity of central carbon metabolism. In conclusion, quantitative knowledge on the metabolic flux distribution of oleaginous alga obtained in this study may be of value in designing strategies for metabolic engineering of desirable bioproducts. PMID:20720172

  9. Tracer study of oxygen and hydrogen uptake by Mg alloys in air with water vapor

    DOE PAGES

    Brady, M. P.; Fayek, M.; Meyer, H. M.; ...

    2015-05-15

    We studied the pure oxidation of Mg, Mg–3Al–1Zn (AZ31B), and Mg–1Zn–0.25Zr–<0.5Nd (ZE10A) at 85 °C in humid air using sequential exposures with H218O and D216O for water vapor. Incorporation of 18O in the hydroxide/oxide films indicated that oxygen from water vapor participated in the reaction. Moreover, penetration of hydrogen into the underlying metal was observed, particularly for the Zr- and Nd-containing ZE10A. Isotopic tracer profiles suggested a complex mixed inward/outward film growth mechanism.

  10. Using trees to remediate tritium contaminated groundwater: a modeling and tracer study.

    SciTech Connect

    Rebel, Karin, Theodora

    2004-01-01

    Rebel, Karin, T. 2004. Using trees to remediate tritium contaminated groundwater: a modeling and tracer study. Ph.D Dissertation. Cotnell University. Ithaca, New York. 174 pp. Abstract: We have developed a spatially explicit model of water and tritium fluxes in the vadose zone in order to simulate water uptake and subsurface lateral movement in coniferous and mixed hardwood - coniferous forests on Coastal Plain soils of the southern United States. These Coastal Plain soils are characteristically sand overlying slowly permeable clays found at depths of 30 to 200 cm, and can form temporarily saturated, unconfined aquifers. Ten hectares of the modeled watershed was periodically irrigated with tritium enriched water. We used the tritium enriched water as a tracer to validate the model. The model was used to optimize irrigation, to evaluate the amount of tritium entering the atmosphere due to evapotranspiration and to quantify water and tritium fluxes in texture contrast soils. Using tritium as a tracer, we have studied how tree species and canopy position effect water and solutes uptake from different parts of the soil profile. We clipped branches to obtain leaf water from over-and understory laurel oak (Quercus Laurifolia) and over- and understory pine (Pinus elliottii and Pinus taeda), which was then analyzed for tritium. We found that for early successional trees (Pinus spp.) and trees in the overstory proportionally more water was taken up from deeper in the soil compared to the hardwoods or trees in the understory, which took up proportionally more water from the soil surface. These differences are important for understanding competition for resources within a forest and in predicting the hydrologic response to forest management practices such as thinning.

  11. Field Studies of Streamflow Generation Using Natural and Injected Tracers on Bickford and Walker Branch Watersheds

    SciTech Connect

    Genereux, D.

    1992-01-01

    Field studies of streamflow generation were undertaken on two forested watersheds, the West Road subcatchment of Bickford Watershed in central Massachusetts and the West Fork of Walker Branch Watershed in eastern Tennessee. A major component of the research was development of a two-stage methodology for the use of naturally-occurring {sup 222}Rn as a tracer. The first of the two stages was solving a mass-balance equation for {sup 222}Rn around a stream reach of interest in order to calculate [Rn]{sub q}, the {sup 222}Rn content of the lateral inflow to the reach; a conservative tracer (chloride) and a volatile tracer (propane) were injected into the study stream to account for lateral inflow to, and {sup 222}Rn volatilization from, the study reach. The second stage involved quantitative comparison of [Rn]{sub q} to the measured {sup 222}Rn concentrations of different subsurface waters in order to assess how important these waters were in contributing lateral inflow to the stream reach. The method was first applied to a 34 m stream reach at Bickford during baseflow; results suggested that {ge} 70% of the lateral inflow could be considered vadose zone water (water which had been in a saturated zone for less than a few days), and the remainder ''soil groundwater'' or ''saturated zone water'' (which had a longer residence time in a soil saturated zone). The method was then applied to two stream reaches on the West Fork of Walker Branch over a wide range of flow conditions; four springs were also investigated. It was found that springwater and inflow to the stream could be viewed as a mixture of water from three end members: the two defined at Bickford (vadose zone water and soil groundwater) and a third (bedrock groundwater) to account for the movement of water through fractured dolomite bedrock. Calcium was used as a second naturally-occurring tracer to distinguish bedrock groundwater from the other two end members. The behavior indicated by the three

  12. ALMA OBSERVATIONS OF THE SUBMILLIMETER DENSE MOLECULAR GAS TRACERS IN THE LUMINOUS TYPE-1 ACTIVE NUCLEUS OF NGC 7469

    SciTech Connect

    Izumi, Takuma; Kohno, Kotaro; Ikarashi, Soh; Aalto, Susanne; Doi, Akihiro; Espada, Daniel; Fathi, Kambiz; Harada, Nanase; Hsieh, Pei-Ying; Matsushita, Satoki; Hatsukade, Bunyo; Hattori, Takashi; Imanishi, Masatoshi; Iono, Daisuke; Ishizuki, Sumio; Nagai, Hiroshi; Krips, Melanie; Martín, Sergio; Meier, David S.; Nakai, Naomasa; and others

    2015-09-20

    We present Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 1 observations of the central kiloparsec region of the luminous type 1 Seyfert galaxy NGC 7469 with unprecedented high resolution (0.″5 ×0.″4 = 165 × 132 pc) at submillimeter wavelengths. Utilizing the wide bandwidth of ALMA, we simultaneously obtained HCN(4–3), HCO{sup +}(4–3), CS(7–6), and partially CO(3–2) line maps, as well as the 860 μm continuum. The region consists of the central ∼1″ component and the surrounding starburst ring with a radius of ∼1.″5–2.″5. Several structures connect these components. Except for CO(3–2), these dense gas tracers are significantly concentrated toward the central ∼1″, suggesting their suitability to probe the nuclear regions of galaxies. Their spatial distribution resembles well those of centimeter and mid-infrared continuum emissions, but it is anticorrelated with the optical one, indicating the existence of dust-obscured star formation. The integrated intensity ratios of HCN(4–3)/HCO{sup +}(4–3) and HCN(4–3)/CS(7–6) are higher at the active galactic nucleus (AGN) position than at the starburst ring, which is consistent with our previous findings (submillimeter-HCN enhancement). However, the HCN(4–3)/HCO{sup +}(4–3) ratio at the AGN position of NGC 7469 (1.11 ± 0.06) is almost half of the corresponding value of the low-luminosity type 1 Seyfert galaxy NGC 1097 (2.0 ± 0.2), despite the more than two orders of magnitude higher X-ray luminosity of NGC 7469. But the ratio is comparable to that of the close vicinity of the AGN of NGC 1068 (∼1.5). Based on these results, we speculate that some heating mechanisms other than X-ray (e.g., mechanical heating due to an AGN jet) can contribute significantly for shaping the chemical composition in NGC 1097.

  13. Using rare earth element tracers and neutron activation analysis to study rill erosion process.

    PubMed

    Li, Mian; Li, Zhan-bin; Ding, Weng-feng; Liu, Pu-ling; Yao, Wen-yi

    2006-03-01

    Spatially averaged soil erosion data provide little information on the process of rill erosion. The dynamically varied data on the temporal and spatial distributions in the rill erosion process are needed to better understand the erosion process and reveal its innate characteristics. The objectives of this study were to examine the feasibility and effectiveness of rare earth element (REE) tracers and the neutron activation analysis (NAA) method on the study of the rill erosion process and to reveal quantitatively the relationships and characteristics of temporal and spatial distributions of sediment yield in rill erosion. Four REEs were used to study the changeable process of rill erosion at 4 slope positions. Four water inflow rates were applied to a 0.3 x 5 m soil bed at 3 slopes of 10.5%, 15.8% and 21.2% in scouring experiments. All of the runoff was collected in the experiment. Each sample was air-dried and well mixed. Then 20 g of each sample was sieved through 100-mesh and about a 50 mg sample was weighed for analysis of the four elemental compositions by NAA. Results indicate that the REE tracers and NAA method can be used to not only quantitatively determine soil erosion amounts on different slope segments, but also to reveal the changeable process of rill erosion amount. All of the relative errors of the experimental results were less than 25%, which is considered satisfactory on the study of rill erosion process.

  14. Contributions to the Study of Blood Brain Flux Using Radioactive Tracers

    PubMed Central

    Mureşan, Ioan; Cosma, Ioan

    2017-01-01

    In this paper, we present an original radiocirculographic method for investigates of cerebral blood flow, which has proven to be very useful, simple, and efficient for studies of brain hemodynamics. Physical considerations on injected radioactive tracer in cardiovascular system, allowed us to state a relationship for the blood flux, F, valued as the amount of fluid-blood that traverses a vascular segment in unit time. All these theoretical facts, along with a host of remarkable clinical results, are presented in a doctoral thesis entitled “The cerebral Hemodynamics in Essential Hypertension and Arteriosclerosis” of the eminent doctor Ioan Mures,an, who died in 1984, at only 50 years old. Using tracers marked with radioactive chrome 51Cr and iodine 131I, it was studied, for patients with various vascular diseases the blood circulation in other territories as an echo of cerebral blood flow. Outstanding results, relating to physiology, diagnosis, and therapy of some diseases, have been obtained. Through intensive collaborations, this method has been operationalized at the University Clinics of Cluj. Here, thousands of patients have been investigated, obtaining quantifiable information which highlighted the patient's condition by emergent and incident blood flows in the global circulatory process and related to other vascular segments. PMID:28217013

  15. Gas chromatography coupled to mass spectrometry for analyses of organic compounds and biomarkers as tracers for geological, environmental, and forensic research.

    PubMed

    Medeiros, Patricia M; Simoneit, Bernd R T

    2007-07-01

    Gas chromatography, especially when coupled with mass spectrometry, is the analytical method of choice for elucidation of biomarker compounds present in organic mixtures extracted from geological, environmental, and biological samples. This review describes the biomarker concept, i. e., the precursor natural products to the geological/environmental derivatives, and their application as multi-tracers in the geosphere and ambient environment. The mass spectrometric methods currently utilized for such analyses are reviewed with a general key to the literature, and typical examples of applications using GC-MS are also described.

  16. Geophysical Methods, Tracer Leakage, and Flow Modeling Studies at the West Pearl Queen Carbon Sequestration/EOR Pilot Site

    NASA Astrophysics Data System (ADS)

    Bromhal, G. S.; Wilson, T. H.; Wells, A.; Diehl, R.; Smith, D. H.

    2003-12-01

    Recently, a few thousand tons of CO2 were injected into the West Pearl Queen field, a depleted oil reservoir in southeastern New Mexico, for a pilot carbon sequestration project. Small amounts of 3 different perfluorocarbon tracers were injected with the CO2. Approximately 50 capillary absorption tube samplers (CATS) were located across the field within 2m of the grounds surface to detect the tracers in extremely small (~10-13L) quantities. After only several days, the CATS detected quantities of tracers at distances of up to 350m from the injection well. Greater amounts of tracers were detected in the different directions. The underground transport mechanism(s) are uncertain; however, appearance of tracer in the CATS after only a 6 day period suggests that CO2 movement may have occurred through near-surface processes. Subsequent tracer measurements made over 10 and 54 day time periods revealed continued tracer leakage. To try to understand the tracer information, we conducted lineament interpretations of the area using a black and white aerial photo taken in 1949, digital orthophotos, and Landsat TM imagery. Lineament interpretations revealed distinct northeast and northwest trending lineament sets. These directions coincided roughly with the direction of tracer-leakage into areas northwest and southwest of the injection well. The near-surface geology consists of a few-feet thick veneer of late Pleistocene and Holocene sand dunes covering the middle Pleistocene Mescalero caliche. A survey of the caliche was made using ground penetrating radar (GPR) to attempt to identify any preferential migration pathways. Modeling studies also were performed to identify the potential leakage pathways at the site. Because of the relatively fast appearance of tracers at large distances from the injection well, simple diffusion through the surface layers was ruled out. Wind patterns in the area have also made transport through the atmosphere and back into the ground highly unlikely

  17. SF6 Tracer Release Study: A Contaminant Fate Study in Newtown Creek

    NASA Astrophysics Data System (ADS)

    Schmieder, P. J.; Ho, D. T.; Peter, S.; Simpson, H. J.; Flores, S.; Dugan, W. A.

    2004-12-01

    Newtown Creek is a 5.5km creek that discharges into the East River, a 25km strait connecting Long Island Sound to the north and the New York Harbor to the south. Surface runoff dominates the freshwater input into the creek, for natural tributaries no longer exist. The areas directly adjacent to the creek are highly industrialized, and New York City's largest Water Pollution Control Plant (WPCP) discharges directly into creek. In August 2004, we injected sulfur hexafluoride (SF6) into Newtown creek to study the fate of oil seeping into the creek from an underground oil spill and the fate of nutrient rich effluent from the WPCP. We monitored SF6 in Newtown Creek, the East River, and the Upper Bay of New York Harbor for 7 consecutive days following the injection in order to investigate the spreading patterns and transport mechanics of waters exiting the creek, and to determine the ultimate fate of the contaminants/solutes originating in Newtown Creek. Dissolved oxygen (DO) measurements were collected simultaneously with SF6 measurements. A strong DO gradient exists in the creek, where waters in the upper reaches are anoxic. We use SF6 data to calculate mean residence times for Newtown Creek waters. SF6 was detected above background concentrations approximately 15km to the south of the creek at the Verrazano Bridge only 1 day after the tracer injection. By combining the movements of the SF6 distribution, the position of the oxygen gradient, and the residence time of Newtown Creek water, we can determine a lower boundary for oxygen consumption rates.

  18. Dual tracer autoradiographic study with thallium-201 and radioiodinated fatty acid in cardiomyopathic hamsters

    SciTech Connect

    Kurata, C.; Kobayashi, A.; Yamazaki, N.

    1989-01-01

    To investigate the usefulness of myocardial scintigraphy with radioiodinated 15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid (BMIPP) in cardiomyopathy, quantitative dual tracer autoradiographic study with /sup 201/Tl and (/sup 125/I)BMIPP was performed in 27 cardiomyopathic Bio 14.6 Syrian hamsters and eight normal hamsters. Furthermore, 16 Bio 14.6 Syrian hamsters aged 21 days were divided into verapamil-treated (during 70 days) and control groups (respectively, n = 8), and autoradiography with /sup 201/Tl and (/sup 125/I)BMIPP was performed. Quantitative autoradiography demonstrated an uncoupling of /sup 201/Tl and (/sup 125/I)BMIPP distributions and a regional heterogeneity of (/sup 125/I)BMIPP distribution in cardiomyopathic hamsters aged more than 2 mo, while normal hamsters showed only mild heterogeneity of (/sup 125/I)BMIPP distribution without an uncoupling of tracers. Age-matched comparison between normal and cardiomyopathic hamsters (5-8 mo old) demonstrated that a difference between their (/sup 125/I)BMIPP distributions are more marked than that between their /sup 201/Tl distributions. Furthermore, (/sup 125/I)BMIPP visualized effects of verapamil on cardiomyopathy more distinctly than did /sup 201/Tl. In conclusion, myocardial imaging with (/sup 123/I)BMIPP could be useful for investigating cardiomyopathy and evaluating the efficacy of therapeutic intervention in patients with cardiomyopathy.

  19. Investigation of Contaminant Transport and Dispersion in New York Harbor by a High Resolution SF6 Tracer Study

    NASA Astrophysics Data System (ADS)

    Caplow, T.; Schlosser, P.; Ho, D. T.

    2002-12-01

    Sulfur hexafluoride (SF6) has been used successfully as a deliberate tracer for rivers, estuaries, and coastal areas, due to its inert nature, non-toxicity, and extremely low detection limit. An automated, high-resolution SF6 measurement system mounted on a boat was recently developed for several projects on the Hudson River. The system has a sampling interval of two minutes and a detection limit of 1 x 10-14 mol L-1. Real-time data visualization enables revisions of sampling strategy during the experiment. A single injection has allowed observation of advection rates, dispersion processes, and air-water gas exchange for up to two weeks, and longer experiments are possible. This equipment, with minor modifications, was applied to New York Harbor in July 2002. New York Harbor is one of the busiest seaports in the United States, processing nearly \\100 billion in cargo each year. Most of the shipping facilities are located in Newark Bay (approximately 15 km^{2}) or in two adjacent channels: the Kill van Kull (6 km long) and the Arthur Kill (20 km long). Newark Bay, which is mostly saline, is fed by the Hackensack and Passaic Rivers, both of which flow through heavily industrialized areas. Ultimately, these waters drain through the Kills to Raritan Bay and the Atlantic Ocean. Due to a combination of point sources, runoff, wastewater treatment plants, and emissions from the shipping industry, Newark Bay and the Kills receive a large volume and variety of contaminants, including petroleum, heavy metals, PCBs, and dioxins. In addition, much of the area is subject to ongoing and extensive navigational dredging, causing widespread re-suspension of previously deposited contaminants. A small quantity (ca. 2 mols) of SF_{6}$ was injected into northern Newark Bay to investigate the spreading of water throughout the Bay, the Kills, and the tidal portions of the Passaic and Hackensack Rivers. The tracer was successfully monitored across most of this area for 12 consecutive days

  20. Testing cosmic ray acceleration with radio relics: a high-resolution study using MHD and tracers

    NASA Astrophysics Data System (ADS)

    Wittor, D.; Vazza, F.; Brüggen, M.

    2017-02-01

    Weak shocks in the intracluster medium may accelerate cosmic-ray protons and cosmic-ray electrons differently depending on the angle between the upstream magnetic field and the shock normal. In this work, we investigate how shock obliquity affects the production of cosmic rays in high-resolution simulations of galaxy clusters. For this purpose, we performed a magnetohydrodynamical simulation of a galaxy cluster using the mesh refinement code ENZO. We use Lagrangian tracers to follow the properties of the thermal gas, the cosmic rays and the magnetic fields over time. We tested a number of different acceleration scenarios by varying the obliquity-dependent acceleration efficiencies of protons and electrons, and by examining the resulting hadronic γ-ray and radio emission. We find that the radio emission does not change significantly if only quasi-perpendicular shocks are able to accelerate cosmic-ray electrons. Our analysis suggests that radio-emitting electrons found in relics have been typically shocked many times before z = 0. On the other hand, the hadronic γ-ray emission from clusters is found to decrease significantly if only quasi-parallel shocks are allowed to accelerate cosmic ray protons. This might reduce the tension with the low upper limits on γ-ray emission from clusters set by the Fermi satellite.

  1. A tracer study of ventilation in the Japan/East Sea

    NASA Astrophysics Data System (ADS)

    Postlethwaite, C. F.; Rohling, E. J.; Jenkins, W. J.; Walker, C. F.

    2005-06-01

    During the Circulation Research in East Asian Marginal Seas (CREAMS) summer cruises in 1999, a suite of samples was collected for tracer analysis. Oxygen isotopes combined with tritium-helium ventilation timescales and noble gas measurements give unique insights into the ventilation of water masses in the Japan/East Sea (JES). In particular, noble gases and oxygen isotopes are indicators of brine rejection, which may assist in explaining the recent changes observed in the ventilation of the JES. Oxygen isotope data presented here indicate that both thermally driven convection and brine rejection have played significant roles in deep-water formation but that brine rejection is unlikely to be a significant contributor at the moment. A 6-box ventilation model of the JES, calibrated with tritium and helium-3 measurements, performed better when a significant decrease of dense-water formation rates in the mid-1960s was incorporated. However, the model calculations suggest that Japan Sea Intermediate Water formation is still occurring. Subduction of sea-ice melt water may be a significant ventilation mechanism for this water mass, based on an argon saturation minimum at the recently ventilated salinity minimum in the northwestern sector of the JES. The salinity and oxygen isotope budgets imply a potential bottom-water formation rate of 3.97±0.89×10 12 m 3 yr -1 due to brine rejection, which could account for a time averaged fraction of between 25% and 35% of the ventilation of subsurface water formation in the JES.

  2. Evaluation of the ERP dispersion model using Darlington tracer-study data. Report No. 90-200-K

    SciTech Connect

    Wright, S.C.

    1990-01-01

    In this study, site-boundary atmospheric dilution factors calculated by the atmospheric dispersion model used in the ERP (Emergency Response Planning) computer code were compared to data collected during the Darlington tracer study. The purpose of this comparison was to obtain estimates of model uncertainty under a variety of conditions. This report provides background on ERP, the ERP dispersion model and the Darlington tracer study. Model evaluation techniques are discussed briefly, and the results of the comparison of model calculations with the field data are presented and reviewed.

  3. Rocky Flats 1990--91 winter validation tracer study: Volume 1

    SciTech Connect

    Brown, K.J.

    1991-10-01

    During the winter of 1990--91, North American Weather Consultants (NAWC) and its subcontractor, ABB Environmental Services (ABBES), conducted a Winter Validation Study (WVS) for EG&G Rocky Flats involving 12 separate tracer experiments conducted between February 3 and February 19, 1991. Six experiments were conducted during nighttime hours and four experiments were conducted during daytime hours. In addition, there was one day/night and one night/day transitional experiment conducted. The primary purpose of the WVS was to gather data to further the approval process for the Terrain Responsive Atmospheric Code (TRAC). TRAC is an atmospheric dispersion model developed and operated at the Department of Energy`s (DOE`s) Rocky Flats Plant (RFP) north of Denver, Colorado. A secondary objective was to gather data that will serve to validate the TRAC model physics.

  4. Tracer study of oxygen and hydrogen uptake by Mg alloys in air with water vapor

    SciTech Connect

    Brady, M. P.; Fayek, M.; Meyer, H. M.; Leonard, D. N.; Elsentriecy, H. H.; Unocic, K. A.; Anovitz, L. M.; Cakmak, E.; Keiser, J. R.; Song, G. L.; Davis, B.

    2015-05-15

    We studied the pure oxidation of Mg, Mg–3Al–1Zn (AZ31B), and Mg–1Zn–0.25Zr–<0.5Nd (ZE10A) at 85 °C in humid air using sequential exposures with H218O and D216O for water vapor. Incorporation of 18O in the hydroxide/oxide films indicated that oxygen from water vapor participated in the reaction. Moreover, penetration of hydrogen into the underlying metal was observed, particularly for the Zr- and Nd-containing ZE10A. Isotopic tracer profiles suggested a complex mixed inward/outward film growth mechanism.

  5. Isotope tracer study of hydrogen spillover on carbon-based adsorbents for hydrogen storage.

    PubMed

    Lachawiec, Anthony J; Yang, Ralph T

    2008-06-17

    A composite material comprising platinum nanoparticles supported on molecular sieve templated carbon was synthesized and found to adsorb 1.35 wt % hydrogen at 298 K and 100 atm. The isosteric heat of adsorption for the material at low coverage was approximately 14 kJ/mol, and it approached a value of 10.6 kJ/mol as coverage increased for pressures at and above 1 atm. The increase in capacity is attributed to spillover, which is observed with the use of isotopic tracer TPD. IRMOF-8 bridged to Pt/C, a material known to exhibit hydrogen spillover at room temperature, was also studied with the hydrogen-deuterium scrambling reaction for comparison. The isotherms were reversible. For desorption, sequential doses of H2 and D2 at room temperature and subsequent TPD yield product distributions that are strong indicators of the surface diffusion controlled reverse spillover process.

  6. Hydrological Tracer Studies at a DOE IFRC Site in Rifle, Colorado

    NASA Astrophysics Data System (ADS)

    Gupta, M.; Williams, K. H.; Berman, E. S.; Conrad, M. E.

    2010-12-01

    Research activities at the Department of Energy Integrated Field Research Challenge (IFRC) site in Rifle, Colorado, have demonstrated that uranium can successfully be removed from groundwater through stimulation of indigenous metal-reducing bacteria, such as members of the Geobacteraceae. While such removal strategies may be effective over short timescales, the large inventory of uranium sorbed to aquifer sediments contributes to a diffuse and widespread contaminant plume at the Rifle site, leading to persistent uranium contamination of groundwater. Complicating the long-term plume behavior are seasonal changes in aquifer properties (e.g. fluctuating water levels, variations in dissolved oxygen and organic carbon, etc.) that accompany snowmelt and elevated river stage in the Colorado River. As the impact of such changes on contaminant behavior at Rifle is poorly understood, development of novel methods, such as isotopic techniques, is warranted to better constrain aquifer flow properties and resolve surface water-groundwater interactions that may influence long-term uranium mobility. In addition to floodplain scale (ca. 10 hectare) studies of uranium mobility, ongoing research at Rifle is investigating coupled approaches to desorb and reductively immobilize pools of sorbed and aqueous uranium. Performed as part of the “Super 8” field experiment (2010), a variety of conservative and non-conservative chemical compounds were injected into the Rifle aquifer to assess transport properties and quantify rates of reductive immobilization of uranium under different alkalinity conditions. Conservative tracers included sodium bromide (20mM), deuterium (500‰), and O-18 (25‰), whereas reactive amendments included sodium bicarbonate (50mM) and sodium acetate (6mM); the latter two were designed to enhance desorption of uranium from sediments and stimulate the activity of uranium-reducing microorganisms, respectively. The need to introduce the reactive amendments at

  7. Quantifying the Contribution of Grape Hexoses to Wine Volatiles by High-Precision [U13C]-Glucose Tracer Studies

    PubMed Central

    Nisbet, Mark A.; Tobias, Herbert J.; Brenna, J. Thomas; Sacks, Gavin L.; Mansfield, Anna Katharine

    2016-01-01

    Many fermentation volatiles important to wine aroma potentially arise from yeast metabolism of hexose sugars, but assessing the relative importance of these pathways is challenging due to high endogenous hexose substrate concentrations. To overcome this problem, gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS) was used to measure high-precision 13C/12C isotope ratios of volatiles in wines produced from juices spiked with tracer levels (0.01–1 APE) of uniformly labeled [U-13C]-glucose. The contribution of hexose to individual volatiles was determined from the degree of 13C enrichment. As expected, straight-chain fatty acids and their corresponding ethyl esters were derived almost exclusively from hexoses. Most fusel alcohols and their acetate esters were also majority hexose-derived, indicating the importance of anabolic pathways for their formation. Only two compounds were not derived primarily from hexoses (hexanol and isobutyric acid). This approach can be extended to other food systems or substrates for studying precursor–product relationships. PMID:24960193

  8. The relationship between inert gas wash-out and radioactive tracer microspheres in measurement of bone blood flow: effect of decreased arterial supply and venous congestion on bone blood flow in an animal model.

    PubMed

    Kiaer, T; Dahl, B; Lausten, G S

    1993-01-01

    Several methods have been employed in the study of bone perfusion. We used a method of determining inert gas wash-out by mass spectrometry in the study of blood flow rates in pigs. The method was validated by comparison of the result obtained with inert gas wash-out to that with measurement by microspheres. Furthermore, the effect of decreased inlet flow and venous congestion on the bone perfusion data was tested. The undisturbed bone blood flow was not significantly different when measured with wash-out of inert gas (7 +/- 0.7 ml/min/100 g) or with microspheres (9 +/- 2.9 ml/min/100 g), and the methods were correlated. Perfusion was reduced significantly, to 20% of the original value, after arterial occlusion. The changes in wash-out curves and accumulation of radioactive tracer provided substantial evidence for impaired intraosseous circulation following venous obstruction also. In conclusion, the study showed that this method of determining inert gas wash-out is feasible for studies of local perfusion rates in bone. The flow rates obtained by wash-out correlated well with the results of microsphere studies. In this animal model, both methods detected a fivefold reduction in flow rate after clamping of the arterial inflow. Obstruction of the venous outflow also impaired blood flow and lowered the cellular supply.

  9. Studying coupled hydrological and micro-biological processes by means of tracer injections and mathematical models

    NASA Astrophysics Data System (ADS)

    Worman, A.; Kjellin, J. P.; Lindahl, A.; Johansson, H.

    2005-05-01

    To throw light on coupled hydrological, chemical and microbiological processes in treatment wetlands, this study uses both radioactive water and reactive tracers. A tracer mixture consisting of tritiated water, P-32 in the form of PO4- and N-15 in the form of N2O was injected to the 2.6 hectare large Ekeby wetland, Sweden. From the breakthrough curves of tritium, the mean residence time of water in pond 1 can be estimated to be about 3 to 3.5 days. The total injected activity of phosphorus was 17.98 GBq and about 13.73 GBq was recovered at the outlet during the investigation period ending 10 days and 16 hours after the start of the injection. This implies that 24% of the phosphate solution was removed in the November - December period in which the experiment was performed. The total injected amount of N-15 was 42.1 grams and 29.6 grams was retained at the effluent. This means that 30% of the nitrogen was either retained in the wetland or removed due to denitrification. An analysis of regular monitoring data shows that the annual removal rate in the entire wetland (each flow line passes two ponds in series) is about 50% for total phosphorus and 25% for total nitrogen. Probably, the most important mechanism for this removal is adsorption onto particulate matter and deposition. Analyses of vegetation material indicate that a certain (minor) fraction was adsorbed to submersed and emerging macrophytes, like Elodera Canadensis, Thypa sp. (Cattail) and Glyceria sp. (Manna grass). A 2D mathematical model for both water flow and solute transport could explain the N-transport through the wetland. The model accounts for the rate-limited exchange with bed sediments and denitrification in the water and bed sediment. Independent batch tests indicate a particularly high microbiological activity in the bed sediments. The rate-limited exchange with the bed limits also the denitrification capacity of the wetland.

  10. Conducting Graduate Tracer Studies for Quality Assurance in East African Universities: A Focus on Graduate Students Voices on Quality Culture

    ERIC Educational Resources Information Center

    Badiru, Egesah Omar; Wahome, Mary

    2016-01-01

    The purpose of this paper is to propose a guide for graduate trace studies (GTS) to be adopted by universities and other higher education institutions (HEIs) in East Africa. Their essential role notwithstanding, graduate tracer studies present viable opportunities through which quality assurance (QA) can be institutionalized and mainstreamed in…

  11. The properties of 235Np as a tracer and yield monitor in studies of the environmental behaviour of neptunium

    NASA Astrophysics Data System (ADS)

    Harvey, B. R.; Sutton, G. A.

    1987-02-01

    The production, detection and decay scheme of 235Np are discussed with reference to the potential application of this nuclide as a tracer and alternative yield monitor for the analysis of 237Np in environmental materials. Improved detection efficiency, which results from assay by counting the L X-ray emissions on an Si(Li) detector, is shown to reduce substantially the problem caused by contamination of the tracer by 237Np. A most important use for 235Np is seen to be in the study of the oxidation states of neptunium in the environment.

  12. The Fischa-Dagnitz spring, Southern Vienna Basin: a multi tracer time series study re-assessing earlier conceptual assumptions.

    NASA Astrophysics Data System (ADS)

    Suckow, Axel; Gerber, Christoph; Kralik, Martin; Sültenfuss, Jürgen; Purtschert, Roland

    2013-04-01

    The gravel aquifer of the Southern Vienna Basin is a very important backup drinking water resource for the city of Vienna. A discharge location, the Fischa-Dagnitz spring in the Southern Vienna Basin, Austria, was re-investigated in 2011, five years after the gas exchange tracer test published in (Stolp et al., 2010), and sampled for stable isotopes 18O/2H, tritium, 3He, SF6 and 85Kr (Gerber et al., 2012). Additionally, new tritium time series data (Davis et al., 1967), previously not considered in Stolp et al. (2010), were included. These show a higher and earlier tritium peak of >300 TU in 1965 in the discharge of the Fischa-Dagnitz spring as compared to 221 TU in 1972 considered in Stolp et al. (2010). The new 3He, SF6 and 85Kr gas tracer data from 2011 confirm the earlier finding for 3He of Stolp et al. (2010) and indicate a more recent equilibration with the atmosphere than the water bound tracers 18O, 2H and tritium. A new modelling attempt using the Lumpy code (Suckow, 2012) confirmed the discrepancy between the tritium data and the gaseous tracers 3He, SF6 and 85Kr. No steady-state combination of local recharge (represented by an exponential model) and Schwarza river infiltration flowing through the gravel aquifer (represented by a parallel dispersion model) can equally well explain both the tritium time series and the gas tracer results. A revised conceptual model proposes that a pinching of the aquifer at unconformities in the gravel body or a fault zone known in the gravel body forces groundwater along the flow path closer to the surface and exposes it to the atmosphere. This would tend to reset the "dating" clock for the gaseous tracers 3He, SF6 and 85Kr, which can equilibrate quickly with the atmosphere, but not for tritium, which marks the transport behaviour of the water itself. These findings are of importance also for other multi-tracer assessments of groundwater movement in phreatic aquifer systems. References: Davis, G.H., Payne, B.R., Dincer, T

  13. Textural characterization of media composed of compacted pieces of cardboard and polyethylene using a gas tracer method.

    PubMed

    Kacem, M; Salvador, S; Quintard, M

    2009-02-01

    The aim of this work is the experimental determination of effective transport properties of porous media consisting of compacted pieces of cardboard and polyethylene (PE). The proposed method itself is more general and can be applied to many different materials and contexts. Three major transport properties were determined: porosity, tortuosity factor and permeability. Three parameters characterizing the media were varied over a wide range: the bulk density, the size of the elements entering the mix, and the proportion of cardboard and PE in the mix. The properties were measured by means of a specially designed experimental device based on miscible gas tracing. The porosity and tortuosity factor were simultaneously determined by parametric identification, based on the experimental sample output response to an inlet gas concentration step change compared to the results of a direct numerical model. Permeability was calculated in the standard way from the measurement of the pressure drop across the sample. The reproducibility of the measurements was very good. It was found that changing the material density of the medium significantly affects all three structural properties. When the bulk density is varied between 300 and 900 kg m(-3), the tortuosity factor varies in a range as large as 18-8 and the permeability decreases by a ratio of 2-3. The tortuosity factor shows unusual variation, characterized by a decrease when density is increased above 500 kg m(-3). The size of the elements does not significantly affect the structural properties of the medium in the range of parameters studied.

  14. The Voices of Their Childhood: Families and Early Years' Practitioners Developing Emancipatory Methodologies through a Tracer Study

    ERIC Educational Resources Information Center

    Whalley, Margy; Arnold, Cath; Lawrence, Penny; Peerless, Sally

    2012-01-01

    The Pen Green Tracer Study questions the difference we may or may not have made to children's lives. An initial cohort of young people, now aged between 11-20, revisited their nursery in 2010. Their stories prompted discussion on parental involvement and advocacy within the education system, key worker attachment, and children's sense of self. Our…

  15. The Experience of Receiving and Then Losing a Scholarship: A Tracer Study of Secondary School Scholarship Recipients in Uganda

    ERIC Educational Resources Information Center

    Watson, Cathy; Chapman, David W.; Okurut, Charles Opolot

    2014-01-01

    This study reports findings of a tracer that investigated differences in the profile and subsequent experiences of scholarship recipients in Uganda who were able to complete the lower secondary school cycle (O level) without interruption (N = 174) and those that dropped out before completing their O-level cycle (N = 51), thereby losing their…

  16. Performance of Higher National Diploma of Building Technology Graduates in the Construction Industry: A Tracer Study in Kumasi Metropolis, Ghana

    ERIC Educational Resources Information Center

    Awere, E.; Edu-Buandoh, K. B. M.; Dadzie, D. K.; Aboagye, J. A.

    2016-01-01

    Building Technology graduates from Ghanaian Polytechnics seek employment in the construction industry, yet little information is known as to whether their tertiary education is really related to and meeting the actual needs of their prospective employers in the construction industry. The tracer study was conducted to ascertain the performance of…

  17. Innovative techniques for the description of reservoir heterogeneity using tracers. Second technical annual progress report, October 1991--September 1992

    SciTech Connect

    Pope, G.A.; Sepehrnoori, K.

    1992-12-31

    This second annual report on innovative uses of tracers for reservoir characterization contains four sections each describing a novel use of oilfield tracers. The first section describes and illustrates the use of a new single-well tracer test to estimate wettability. This test consists of the injection of brine containing tracers followed by oil containing tracers, a shut-in period to allow some of the tracers to react, and then production of the tracers. The inclusion of the oil injection slug with tracers is unique to this test, and this is what makes the test work. We adapted our chemical simulator, UTCHEM, to enable us to study this tracer method and made an extensive simulation study to evaluate the effects of wettability based upon characteristic curves for relative permeability and capillary pressure for differing wetting states typical of oil reservoirs. The second section of this report describes a new method for analyzing interwell tracer data based upon a type-curve approach. Theoretical frequency response functions were used to build type curves of ``transfer function`` and ``phase spectrum`` that have dimensionless heterogeneity index as a parameter to characterize a stochastic permeability field. We illustrate this method by analyzing field tracer data. The third section of this report describes a new theory for interpreting interwell tracer data in terms of channeling and dispersive behavior for reservoirs. Once again, a stochastic approach to reservoir description is taken. The fourth section of this report describes our simulation of perfluorocarbon gas tracers. This new tracer technology developed at Brookhaven National Laboratory is being tested at the Elk Hills Naval Petroleum Reserve No. 1 in California. We report preliminary simulations made of these tracers in one of the oil reservoirs under evaluation with these tracers in this field. Our compostional simulator (UTCOMP) was used for this simulation study.

  18. Subsurface barrier integrity verification using perfluorocarbon tracers

    SciTech Connect

    Sullivan, T.M.; Heiser, J.; Milian, L.; Senum, G.

    1996-12-01

    Subsurface barriers are an extremely promising remediation option to many waste management problems. Gas phase tracers include perfluorocarbon tracers (PFT`s) and chlorofluorocarbon tracers (CFC`s). Both have been applied for leak detection in subsurface systems. The focus of this report is to describe the barrier verification tests conducted using PFT`s and analysis of the data from the tests. PFT verification tests have been performed on a simulated waste pit at the Hanford Geotechnical facility and on an actual waste pit at Brookhaven National Laboratory (BNL). The objective of these tests were to demonstrate the proof-of-concept that PFT technology can be used to determine if small breaches form in the barrier and for estimating the effectiveness of the barrier in preventing migration of the gas tracer to the monitoring wells. The subsurface barrier systems created at Hanford and BNL are described. The experimental results and the analysis of the data follow. Based on the findings of this study, conclusions are offered and suggestions for future work are presented.

  19. Integration of stable carbon isotope, microbial community, dissolved hydrogen gas, and 2HH2O tracer data to assess bioaugmentation for chlorinated ethene degradation in fractured rocks

    USGS Publications Warehouse

    Révész, Kinga M.; Lollar, Barbara Sherwood; Kirshtein, Julie D.; Tiedeman, Claire R.; Imbrigiotta, Thomas E.; Goode, Daniel J.; Shapiro, Allen M.; Voytek, Mary A.; Lancombe, Pierre J.; Busenberg, Eurybiades

    2014-01-01

    An in situ bioaugmentation (BA) experiment was conducted to understand processes controlling microbial dechlorination of trichloroethene (TCE) in groundwater at the Naval Air Warfare Center (NAWC), West Trenton, NJ. In the BA experiment, an electron donor (emulsified vegetable oil and sodium lactate) and a chloro-respiring microbial consortium were injected into a well in fractured mudstone of Triassic age. Water enriched in 2H was also injected as a tracer of the BA solution, to monitor advective transport processes. The changes in concentration and the δ13C of TCE, cis-dichloroethene (cis-DCE), and vinyl chloride (VC); the δ2H of water; changes in the abundance of the microbial communities; and the concentration of dissolved H2 gas compared to pre- test conditions, provided multiple lines of evidence that enhanced biodegradation occurred in the injection well and in two downgradient wells. For those wells where the biodegradation was stimulated intensively, the sum of the molar chlorinated ethene (CE) concentrations in post-BA water was higher than that of the sum of the pre-BA background molar CE concentrations. The concentration ratios of TCE/(cis-DCE + VC) indicated that the increase in molar CE concentration may result from additional TCE mobilized from the rock matrix in response to the oil injection or due to desorption/diffusion. The stable carbon isotope mass-balance calculations show that the weighted average 13C isotope of the CEs was enriched for around a year compared to the background value in a two year monitoring period, an effective indication that dechlorination of VC was occurring. Insights gained from this study can be applied to efforts to use BA in other fractured rock systems. The study demonstrates that a BA approach can substantially enhance in situ bioremediation not only in fractures connected to the injection well, but also in the rock matrix around the well due to processes such as diffusion and desorption. Because the effect of the

  20. Integration of stable carbon isotope, microbial community, dissolved hydrogen gas, and ²HH₂O tracer data to assess bioaugmentation for chlorinated ethene degradation in fractured rocks.

    PubMed

    Révész, Kinga M; Lollar, Barbara Sherwood; Kirshtein, Julie D; Tiedeman, Claire R; Imbrigiotta, Thomas E; Goode, Daniel J; Shapiro, Allen M; Voytek, Mary A; Lacombe, Pierre J; Busenberg, Eurybiades

    2014-01-01

    An in situ bioaugmentation (BA) experiment was conducted to understand processes controlling microbial dechlorination of trichloroethene (TCE) in groundwater at the Naval Air Warfare Center (NAWC), West Trenton, NJ. In the BA experiment, an electron donor (emulsified vegetable oil and sodium lactate) and a chloro-respiring microbial consortium were injected into a well in fractured mudstone of Triassic age. Water enriched in ²H was also injected as a tracer of the BA solution, to monitor advective transport processes. The changes in concentration and the δ¹³C of TCE, cis-dichloroethene (cis-DCE), and vinyl chloride (VC); the δ²H of water; changes in the abundance of the microbial communities; and the concentration of dissolved H₂ gas compared to pre- test conditions, provided multiple lines of evidence that enhanced biodegradation occurred in the injection well and in two downgradient wells. For those wells where the biodegradation was stimulated intensively, the sum of the molar chlorinated ethene (CE) concentrations in post-BA water was higher than that of the sum of the pre-BA background molar CE concentrations. The concentration ratios of TCE/(cis-DCE+VC) indicated that the increase in molar CE concentration may result from additional TCE mobilized from the rock matrix in response to the oil injection or due to desorption/diffusion. The stable carbon isotope mass-balance calculations show that the weighted average ¹³C isotope of the CEs was enriched for around a year compared to the background value in a two year monitoring period, an effective indication that dechlorination of VC was occurring. Insights gained from this study can be applied to efforts to use BA in other fractured rock systems. The study demonstrates that a BA approach can substantially enhance in situ bioremediation not only in fractures connected to the injection well, but also in the rock matrix around the well due to processes such as diffusion and desorption. Because the effect

  1. Tracer airflow measurement system (TRAMS)

    DOEpatents

    Wang, Duo

    2007-04-24

    A method and apparatus for measuring fluid flow in a duct is disclosed. The invention uses a novel high velocity tracer injector system, an optional insertable folding mixing fan for homogenizing the tracer within the duct bulk fluid flow, and a perforated hose sampling system. A preferred embodiment uses CO.sub.2 as a tracer gas for measuring air flow in commercial and/or residential ducts. In extant commercial buildings, ducts not readily accessible by hanging ceilings may be drilled with readily plugged small diameter holes to allow for injection, optional mixing where desired using a novel insertable foldable mixing fan, and sampling hose.

  2. Diatoms as a tracer of hydrological connectivity: the Oak Creek case study (Oregon, USA)

    NASA Astrophysics Data System (ADS)

    Antonelli, Marta; Martínez-Carreras, Nuria; Frentress, Jay; Pfister, Laurent

    2015-04-01

    The vast heterogeneity and complexity of rainfall-runoff transformation processes expresses itself in a multitude of water sources and flowpaths - ultimately resulting in the well-known intricacy of hydrological connectivity. Pioneering work of Pfister et al. (2009) conducted in the Weierbach catchment (0.45 km2, NW Luxembourg, semi-oceanic climate) demonstrated the potential for diatoms (unicellular, eukaryotic algae) to be used as a tracer of hydrological connectivity. Diatoms originating from terrestrial habitats had been shown to be systematically flushed from the riparian areas into the stream during storm events. Here, we present a study conducted in the Oak Creek(0.17 km2, Oregon, Mediterranean climate), characterised by a large riparian area. Our first working hypothesis (H1) stipulates that diatoms are an ubiquitous tracer of fast hydrological flowpaths. The second hypothesis (H2) states that the riparian area is the major reservoir of terrestrial diatoms that contributes to the flushing process during rainfall events. A winter rainfall-runoff event was monitored in March 2012. Diatom samples were collected from soil, moss, epipelon and streamwater in order to characterise the communities along the hillslope-riparian-stream (HRS) continuum. Diatoms in each sample were also assigned to different wetness categories (according to Van Dam et al., 1994). The catchment was instrumented with an ISCO automatic streamwater sampler and the samples were analysed for conductivity, 18O, 2H, chemical elements and presence/abundance of diatoms belonging to different wetness categories. Our results show that the percentage of diatom species originating from habitats located outside of the stream evolves along the rising and falling limbs of the hydrograph. This observation confirms the event-related flushing of diatoms from terrestrial habitats to the stream and, consequently, the potential for diatoms to be used for the detection of hydrological connectivity in the

  3. Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain site characterization study. Final report

    SciTech Connect

    Stetzenbach, K.; Farnham, I.

    1996-06-01

    Extensive tracer testing is expected to take place at the C-well complex in the Nevada Test Site as part of the Yucca Mountain Site Characterization Project. The C-well complex consists of one pumping well, C3, and two injection wells, C1 and C2 into which tracer will be introduced. The goal of this research was to provide USGS with numerous tracers to completed these tests. Several classes of fluorinated organic acids have been evaluated. These include numerous isomers of fluorinated benzoic acids, cinnamic acids, and salicylic acids. Also several derivatives of 2-hydroxy nicotinic acid (pyridone) have been tested. The stability of these compounds was determined using batch and column tests. Ames testing (mutagenicity/carcinogenicity) was conducted on the fluorinated benzoic acids and a literature review of toxicity of the fluorobenzoates and three perfluoro aliphatic acids was prepared. Solubilities were measured and method development work was performed to optimize the detection of these compounds. A Quality Assurance (QA) Program was developed under existing DOE and USGS guidelines. The program includes QA procedures and technical standard operating procedures. A tracer test, using sodium iodide, was performed at the C-well complex. HRC chemists performed analyses on site, to provide real time data for the USGS hydrologists and in the laboratories at UNLV. Over 2,500 analyses were performed. This report provides the results of the laboratory experiments and literature reviews used to evaluate the potential tracers and reports on the results of the iodide C-well tracer test.

  4. Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain Site characterization study; Progress report, April 1, 1993--June 30, 1993

    SciTech Connect

    Dombrowski, T.; Stetzenbach, K.

    1993-08-01

    This report is in two parts one for the fluorinated benzoic acids and one for the fluorinated aliphatic acids. The assumptions made in the report regarding the amount of tracer that will be used, dilution of the tracer during the test and the length of exposure (if any) to individuals drinking the water were made by the authors. These assumptions must really come from the USGS hydrologists in charge of the c-well tracer testing program. Accurate estimates of dilution of the tracer during the test are also important because of solubility limitations of some of the tracers. Three of the difluorobenzoic acids have relatively low solubilities and may not be usable if the dilution estimates are large. The toxicologist that reviewed the document agreed with our conclusion that the fluorinated benzoic and toluic acids do not represent a health hazard if used under the conditions as outlined in the report. We are currently testing 15 of these compounds, and if even if three difluorobenzoic acids cannot be used because of solubility limitations we will still have 12 tracers. The toxicologist felt that the aliphatic fluorinated acids potentially present more of a health risk than the aromatic. This assessment was based on the fact of a known allergic response to halothane anesthetic. This risk, although minimal, is known and he felt that was enough reason to recommend against their use. The authors feel that the toxicologists interpretation of this risk was overly conservative, however, we will not go against his recommendation at this time for the following reasons. First, without the aliphatic compounds we still have 12 to 15 fluorinated aromatic acids which, should be enough for the c-well tests. Second, to get a permit to use aliphatic compounds would undoubtedly require a hearing which could be quite lengthy.

  5. Collisional decoherence of a tracer particle moving in one dimension

    SciTech Connect

    Kamleitner, Ingo

    2010-11-15

    We study decoherence of the external degree of freedom of a tracer particle moving in a one-dimensional dilute Boltzmann gas. We find that phase averaging is the dominant decoherence effect, rather than information exchange between tracer and gas particles. While a coherent superposition of two wave packets with different mean positions quickly turns into a mixed state, it is demonstrated that such superpositions of different momenta are robust to phase averaging, until the two wave packets acquire a different position due to the different velocity of each wave packet.

  6. Sinks for nitrogen inputs in terrestrial ecosystems: a meta-analysis of 15N tracer field studies

    USGS Publications Warehouse

    Templer, P.H.; Mack, M.C.; Chapin, F. S.; Christenson, L.M.; Compton, J.E.; Crook, H.D.; Currie, W.S.; Curtis, C.J.; Dail, D.B.; D'Antonio, C. M.; Emmett, B.A.; Epstein, H.E.; Goodale, C.L.; Gundersen, P.; Hobbie, S.E.; Holland, K.; Hooper, D.U.; Hungate, B.A.; Lamontagne, S.; Nadelhoffer, K.J.; Osenberg, C.W.; Perakis, S.S.; Schleppi, P.; Schimel, J.; Schmidt, I.K.; Sommerkorn, M.; Spoelstra, J.; Tietema, A.; Wessel, W.W.; Zak, D.R.

    2012-01-01

    Effects of anthropogenic nitrogen (N) deposition and the ability of terrestrial ecosystems to store carbon (C) depend in part on the amount of N retained in the system and its partitioning among plant and soil pools. We conducted a meta-analysis of studies at 48 sites across four continents that used enriched 15N isotope tracers in order to synthesize information about total ecosystem N retention (i.e., total ecosystem 15N recovery in plant and soil pools) across natural systems and N partitioning among ecosystem pools. The greatest recoveries of ecosystem 15N tracer occurred in shrublands (mean, 89.5%) and wetlands (84.8%) followed by forests (74.9%) and grasslands (51.8%). In the short term (15N tracer application), total ecosystem 15N recovery was negatively correlated with fine-root and soil 15N natural abundance, and organic soil C and N concentration but was positively correlated with mean annual temperature and mineral soil C:N. In the longer term (3–18 months after 15N tracer application), total ecosystem 15N retention was negatively correlated with foliar natural-abundance 15N but was positively correlated with mineral soil C and N concentration and C: N, showing that plant and soil natural-abundance 15N and soil C:N are good indicators of total ecosystem N retention. Foliar N concentration was not significantly related to ecosystem 15N tracer recovery, suggesting that plant N status is not a good predictor of total ecosystem N retention. Because the largest ecosystem sinks for 15N tracer were below ground in forests, shrublands, and grasslands, we conclude that growth enhancement and potential for increased C storage in aboveground biomass from atmospheric N deposition is likely to be modest in these ecosystems. Total ecosystem 15N recovery decreased with N fertilization, with an apparent threshold fertilization rate of 46 kg N·ha-1·yr-1 above which most ecosystems showed net losses of applied 15N tracer in response to N fertilizer addition.

  7. Sinks for nitrogen inputs in terrestrial ecosystems: a meta-analysis of 15N tracer field studies.

    PubMed

    Templer, P H; Mack, M C; Chapin, F S; Christenson, L M; Compton, J E; Crook, H D; Currie, W S; Curtis, C J; Dail, D B; D'Antonio, C M; Emmett, B A; Epstein, H E; Goodale, C L; Gundersen, P; Hobbie, S E; Holland, K; Hooper, D U; Hungate, B A; Lamontagne, S; Nadelhoffer, K J; Osenberg, C W; Perakis, S S; Schleppi, P; Schimel, J; Schmidt, I K; Sommerkorn, M; Spoelstra, J; Tietema, A; Wessel, W W; Zak, D R

    2012-08-01

    Effects of anthropogenic nitrogen (N) deposition and the ability of terrestrial ecosystems to store carbon (C) depend in part on the amount of N retained in the system and its partitioning among plant and soil pools. We conducted a meta-analysis of studies at 48 sites across four continents that used enriched 15N isotope tracers in order to synthesize information about total ecosystem N retention (i.e., total ecosystem 15N recovery in plant and soil pools) across natural systems and N partitioning among ecosystem pools. The greatest recoveries of ecosystem 15N tracer occurred in shrublands (mean, 89.5%) and wetlands (84.8%) followed by forests (74.9%) and grasslands (51.8%). In the short term (< 1 week after 15N tracer application), total ecosystem 15N recovery was negatively correlated with fine-root and soil 15N natural abundance, and organic soil C and N concentration but was positively correlated with mean annual temperature and mineral soil C:N. In the longer term (3-18 months after 15N tracer application), total ecosystem 15N retention was negatively correlated with foliar natural-abundance 15N but was positively correlated with mineral soil C and N concentration and C:N, showing that plant and soil natural-abundance 15N and soil C:N are good indicators of total ecosystem N retention. Foliar N concentration was not significantly related to ecosystem 15N tracer recovery, suggesting that plant N status is not a good predictor of total ecosystem N retention. Because the largest ecosystem sinks for 15N tracer were below ground in forests, shrublands, and grasslands, we conclude that growth enhancement and potential for increased C storage in aboveground biomass from atmospheric N deposition is likely to be modest in these ecosystems. Total ecosystem 15N recovery decreased with N fertilization, with an apparent threshold fertilization rate of 46 kg N x ha(-1) x yr(-1) above which most ecosystems showed net losses of applied 15N tracer in response to N fertilizer

  8. A study of positrons from Soviet nuclear powered satellites as tracers for magnetospheric research

    SciTech Connect

    Hones, E.W. Jr. )

    1990-01-01

    Two Soviet satellites carrying nuclear reactors operated in circular 790 km orbits (65{degree} inclination) in 1987 and 1988. Positrons generated in the satellites' surfaces by the intense reactor gamma radiation escaped and were trapped for periods of minutes to hours in the geomagnetic field. These positrons have been observed on many occasions by gamma ray sensors on the SMM satellite (in 500 km orbit) which identify the positrons by the 511 keV gamma rays created when they annihilate in the satellite surface. The SMM detector provides a time resolution of 64 milliseconds. It has recorded positron rise-times of less than 0.5 second (corresponding to about 1 positron gyroradius) on many occasions as it encounters the low-L edge of positrons injected by the Soviet satellites as far as half-way around the earth. We are studying the potential of these sharply defined positron shells as magnetospheric tracers and as a means for examining particle diffusion and loss processes. 3 refs., 5 figs.

  9. Sediments as tracers for transport and deposition processes in peri-alpine lakes: A case study

    NASA Astrophysics Data System (ADS)

    Righetti, Maurizio; Toffolon, Marco; Lucarelli, Corrado; Serafini, Michele

    2011-12-01

    SummaryThe benthic sediment fingerprint is analysed in the small peri-alpine lake Levico (Trentino, Italy) to identify the causes of recurrent phenomena of turbidity peaks, particularly evident in a littoral region of the water body. In order to study the sediment transport processes, we exploit the fact that the sediment supply from the major tributary has a specific chemical composition, which differs from that of the nearby lake basin. Three elements (Fe, Al, K) have been used as tracers to identify the source and the deposition patterns of tributary sediments, and another typical element, Si, has been critically analysed because of its dual (allochthonous and autochthonous) origin. Several samples of the benthic material have been analysed using SEM-EDS, and the results of the sedimentological characterisation have been compared with the patterns of sediment accumulation at the bed of the lake obtained using a three-dimensional numerical model, in response to the tributary supply under different external forcing and stratification conditions. The coupled use of field measurements and numerical results suggests that the turbidity phenomena are strongly related to the deposition of the sediments supplied by the tributary stream, and shows that it is possible to reconstruct the process of local transport when the tributary inflow is chemically specific.

  10. The use of air as a natural tracer infractured hydrothermal systems, Los Azufres, Mexico, case study

    SciTech Connect

    Mario Cesar Sudrez Arriaga; Hector Gutierrez Puente, Josefina Moreno Ochoa

    1991-01-01

    Injection of atmospheric air mixed with cold water has been occurring since 1982 at the Los Azufres geothermal field. Several chemical and thermodynamical evidences show that air injection into this fractured hydrothermal system could be considered as a long term natural tracer test. Nitrogen and Argon separated from the air mixture migrate, under the action of the induced injection-extraction gradient, from reinjection sectors to production zones following preferential paths closely related to high permeability conduits. A coarse numerical estimation of the average permeability tensor existing at Tejamaniles, the southern sector, explains the unsuccessful recovery of the artificial tracer tests performed in past years: the anisotropic nature of the fractured volcanic rock would demand considerably quantities of tracer in order to be detected at the producing wells, especially when fluid extraction was low. At the same time concentrations of calcium, cesium, chloride, potassium, rubidium and sodium, are increasing in the liquid produced by the oldest wells of this field's sector.

  11. Feasibility Study of Non-Radioactive Tracers for Monitoring Injected Water in Oil Reservoirs

    NASA Astrophysics Data System (ADS)

    Sawamura, H.; Nishimura, K.; Mituishi, H.; Muta, T.; Schweitzer, J. S.

    This paper discusses the results of analyses conducted on non-radioactive tracers that can be used in combination with the sea water injected into a well for monitoring the water permeating through the oil reservoir by a nuclear logging tool utilizing a pulsed neutron generator. The model of the pulsed neutron tool is constructed to permit Monte Carlo Simulations to be performed of the tool response to the presence of non-radioactive tracers to achieve a desirable level of the neutron absorbing cross sections in the sea water injected into and permeating through the oil reservoirs. Sensitivity analyses of the tool response of the nuclear logging tool were performed for two types of non-radioactive tracers, ammonium tetraborate and gadolinium chloride.

  12. An Analytical Solution for Slug-Tracer Tests in FracturedReservoirs

    SciTech Connect

    Shan, Chao; Pruess, Karsten

    2005-03-02

    The transport of chemicals or heat in fractured reservoirs is strongly affected by the fracture-matrix interfacial area. In a vapor-dominated geothermal reservoir, this area can be estimated by inert gas tracer tests, where gas diffusion between the fracture and matrix causes the tracer breakthrough curve (BTC) to have a long tail determined by the interfacial area. For water-saturated conditions, recent studies suggest that sorbing solute tracers can also generate strong tails in BTCs that may allow a determination of the fracture-matrix interfacial area. To theoretically explore such a useful phenomenon, this paper develops an analytical solution for BTCs in slug-tracer tests in a water-saturated fractured reservoir. The solution shows that increased sorption should have the same effect on BTCs as an increase of the diffusion coefficient. The solution is useful for understanding transport mechanisms, verifying numerical codes, and for identifying appropriate chemicals as tracers for the characterization of fractured reservoirs.

  13. Laboratory characterization of non-aqueous phase liquid/tracer interaction in support of a vadose zone partitioning interwell tracer test

    NASA Astrophysics Data System (ADS)

    Deeds, Neil E.; McKinney, Daene C.; Pope, Gary A.

    2000-01-01

    Contaminant characterization is important for successful remediation of non-aqueous phase liquids (NAPLs) in the unsaturated zone. A partitioning interwell tracer test (PITT) can provide a good estimate of average subsurface NAPL saturations. Screening experiments were completed in the laboratory to evaluate several gas tracers for a PITT study to be completed in the vadose zone at Kirtland Air Force Base in Albuquerque, NM. Four perfluorocarbon tracers were found to be suitable for this PITT. Further laboratory column studies were completed using contaminated field soil to measure the partition coefficients between the tracers and the NAPL. The results from the column studies showed that the air/NAPL tracer partition coefficients ranged from 8.8±0.6 to 71±3. This range of partition coefficients is suitable for detection of NAPL saturations in the field of 0.002 to 0.14.

  14. Exploring Hydrofluorocarbons as Groundwater Age Tracers (Invited)

    NASA Astrophysics Data System (ADS)

    Haase, K. B.; Busenberg, E.; Plummer, L. N.; Casile, G.; Sanford, W. E.

    2013-12-01

    Groundwater dating tracers are an essential tool for analyzing hydrologic conditions in groundwater systems. Commonly used tracers for dating post-1940's groundwater include sulfur hexafluoride (SF6), chlorofluorocarbons (CFCs), 3H-3He, and other isotopic tracers (85Kr, δ2H and δ18O isotopes, etc.). Each tracer carries a corresponding set of advantages and limitations imposed by field, analytical, and interpretive methods. Increasing the number available tracers is appealing, particularly if they possess inert chemical properties and unique temporal emission histories from other tracers. Atmospherically derived halogenated trace gases continue to hold untapped potential for new tracers, as they are generally inert and their emission histories are well documented. SF5CF3, and CFC-13 were previously shown to have application as dating tracers, though their low mixing ratios and low solubility require large amounts of water to be degassed for their quantification. Two related groups of compounds, hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) are hypothesized to be potential age tracers, having similar mixing ratios to the CFCs and relatively high solubility. However, these compounds yield gas chromatography electron capture detector (GC-ECD) responses that are 10-2 -10-5 less than CFC-12, making purge and trap or field stripping GC-ECD approaches impractical. Therefore, in order to use dissolved HCFCs and HFCs as age tracers, different approaches are needed. To solve this problem, we developed an analytical method that uses an atomic emission detector (GC-AED) in place of an ECD to detect fluorinated compounds. In contrast to the ECD, the AED is a universally sensitive, highly linear, elementally specific detector. The new GC-AED system is being used to measure chlorodifluoromethane (HCFC-22), 1,1,1,2-tetrafluoroethane (HFC-134a), and other fluorinated compounds in one liter water samples to study their potential as age dating tracers. HCFC-22 is a

  15. A numerical study of gas transport in human lung models

    NASA Astrophysics Data System (ADS)

    Lin, Ching-Long; Hoffman, Eric A.

    2005-04-01

    Stable Xenon (Xe) gas has been used as an imaging agent for decades in its radioactive form, is chemically inert, and has been used as a ventilation tracer in its non radioactive form during computerized tomography (CT) imaging. Magnetic resonance imaging (MRI) using hyperpolarized Helium (He) gas and Xe has also emerged as a powerful tool to study regional lung structure and function. However, the present state of knowledge regarding intra-bronchial Xe and He transport properties is incomplete. As the use of these gases rapidly advances, it has become critically important to understand the nature of their transport properties and to, in the process, better understand the role of gas density in general in determining regional distribution of respiratory gases. In this paper, we applied the custom developed characteristic-Galerkin finite element method, which solves the three-dimensional (3D) incompressible variable-density Navier-Stokes equations, to study the transport of Xe and He in the CT-based human lung geometries, especially emulating the washin and washout processes. The realistic lung geometries are segmented and reconstructed from CT images as part of an effort to build a normative atlas (NIH HL-064368) documenting airway geometry over 4 decades of age in healthy and disease-state adult humans. The simulation results show that the gas transport process depends on the gas density and the body posture. The implications of these results on the difference between washin and washout time constants are discussed.

  16. Using dissolved noble gas and isotopic tracers to evaluate the vulnerability of groundwater resources in a small, high elevation catchment to predicted climate changes

    SciTech Connect

    Singleton, M J; Moran, J E

    2009-10-02

    We use noble gas concentrations and multiple isotopic tracers in groundwater and stream water in a small high elevation catchment to provide a snapshot of temperature, altitude, and physical processes at the time of recharge; and to determine subsurface residence times of different groundwater components. They identify three sources that contribute to groundwater flow: (1) seasonal groundwater recharge with short travel times, (2) water from bedrock aquifers that have elevated radiogenic {sup 4}He, and (3) upwelling of deep fluids that have 'mantle' helium and hydrothermal carbon isotope signatures. Although a bimodal distribution in apparent groundwater age indicates that groundwater storage times range from less than a year to several decades, water that recharges seasonally is the largest likely contributor to stream baseflow. Under climate change scnearios with earlier snowmelt, the groundwater that moves through the alluvial aquifer seasonally will be depleted earlier, providing less baseflow and possible extreme low flows in the creek during summer and fall. Dissolved noble gas measurements indciate recharge temperatures are 5 to 11 degrees higher than would be expected for direct influx of snowmelt, and that excess air concentrations are lower than would be expected for recharge through bedrock fractures. Instead, recharge likely occurs over diffuse vegetated areas, as indicated by {delta}{sup 13}C-DIC values that are consistent with incorporation of CO{sub 2} from soil respiration. Recharge temperatures are close to or slightly higher than mean annual air temperature, and are consistent with recharge during May and June, when snowpack melting occurs.

  17. Transport study in unsaturated porous media by tracer experiment in a dichromatic X-ray experimental device

    NASA Astrophysics Data System (ADS)

    Latrille, C.; Néel, M. C.

    2013-05-01

    Estimating contaminant migration in the context of waste disposal and/or environmental remediation of polluted soils requires a complete understanding of the underlying transport processes. In unsaturated porous media, water content is one of the most determining parameters to describe solute migration because it impacts directly on solute pore velocity. However, numerous studies are satisfied with only a global or a partial spatial distribution of water content within the studied porous media. Therefore, distribution of water content in porous media must be precisely achieved to optimize transport processes modeling. Tracer experiments with downward flow were performed on the BEETI experimental device equipped with a sand column. Water content and concentration profiles of tracer (KI) were measured along the column during experiment. The relative dispersion of water content, calculated along the column, gives an idea of influence of this parameter on transport properties. A relationship between pore velocity, Darcy flow velocity and water content is proposed.

  18. Comparison of [11C]cocaine binding at tracer and pharmacological doses of baboon brain: A PET study

    SciTech Connect

    Volkow, N.D.; Fowler, J.S.; Logan, J.

    1994-05-01

    In vitro studies have shown that cocaine (C) binds to both high and low affinity sites on the dopamine transporter (DAT). We have previously characterized the binding of tracer doses of [{sup 11}C]cocaine (C*)to a high affinity site on the DAT. To assess if in vivo C also binds to low affinity sites we used PET to compare binding of tracer doses (17.8{plus_minus}12.2 {mu}g C) of C* to pharmacological doses (8 mg of C coadministered with C*). Sixteen paired studies were done to assess test/retest variability, specific versus non specific binding and to characterize binding profile. Dynamic scans were started immediately after injection of C* (5-8 mCi) for 50 min on the CTI-931 (6 x 6 x 6.5 mm FWHM). Time activity curves for tissue concentration and for unchanged tracer in plasma were used to calculate the transport constant between plasma and tissue (K1) and to obtain the distribution volume (DV). The ratio of the DV in striatum (ST) to that in cerebellum (CB) (which corresponds to Bmax/Kd-1) was used as model parameter. Peak brain uptake of C* was significantly higher for tracer than for pharmacological doses (0.041 versus 0.033 % dose/cc), as were the values for K1 (1.07{plus_minus}0.21 versus 0.68{plus_minus}0.26 (t=3.0 p<0.01)). Repeated measures were reproducible for tracer ({plus_minus}2%) and pharmacological doses of C* ({plus_minus}4%). Tracer dose C* showed highest binding and slowest clearance in ST which was reduced by C (0.5-2.0 mg/kg iv, -25 to -30%) and by drugs that inhibit DAT (2mg/kg nomifensine - 21%, 0.5 mg/kg methylphenidate -12%) and was increased by serotonin transporter inhibitors (5HT-Ti) (2 mg/kg citalopram +11%, 0.5 mg/kg fluoxetine +6%) and not changed by NE transporter inhibitors (0.5 mg/kg desipramine or 2 mg/kg tomoxetine). The increase with (5HT-Ti) may reflect neurotransmitter interactions or changes in bioavailability. At pharmacological doses C* showed homogeneous distribution and was not changed by C nor by any of the above drugs.

  19. OTEC gas-desorption studies

    SciTech Connect

    Chen, F.C.; Golshani, A.

    1981-01-01

    OTEC gas desorption studies were initiated with the goal of mitigating these effects and were carried out in four areas: (1) vacuum deaeration in a packed column, (2) deaeration in a barometric water intake system, (3) noncondensibles disposal through hydraulic air compression, and (4) OTEC deaeration subsystems' analysis. Laboratory experiments to date have completed the vacuum deaeration test of three different kinds of packings, barometric intake deaeration experiments, and a series of hydraulic air compression tests. Preliminary analyses based on the experimental data have shown that, as compared to the previous baseline study, reduction both in deaerator cost and pumping power can be realized with a combination of barometric intake and packed column deaeration. The design and operation of the gas desorption test loop, experimental and computer simulation results obtained, and an analysis of OTEC deaeration subsystem design based on the test results and their implication on OTEC open-cycle power systems are presented.

  20. 40K-40Ca systematics as a Tracer of Silicate Weathering: A Himalayan case study

    NASA Astrophysics Data System (ADS)

    Davenport, Jesse; Caro, Guillaume; France-Lanord, Christian

    2015-04-01

    This study investigates the use of the 40K-40Ca system as a tracer to better quantify the contributions of silicate and carbonate lithologies in the dissolved load of major Himalayan rivers. Previous work using Sr isotopes as a proxy for silicate weathering has been complicated by the redistribution of radiogenic 87Sr between silicate and carbonate lithologies, particularly in the Lesser Himalaya, where dolomites exhibit 87Sr/86Sr ratios as high as 0.85. The 40Ca signature of carbonates, on the other hand, appears to be remarkably resistant to metamorphism and dolomitization [1]. It was therefore anticipated that the 40K-40Ca system could circumvent issues associated with such secondary events, and yield more robust constraints on the relative contribution of silicate vs. carbonate lithologies in dissolved river loads. The main difficulty in applying the 40K-40Ca decay scheme as a tracer lies in the analytical precision required to measure small variations (~1 ɛ-unit) on the large 40Ca isotope (96.9%). This difficulty can now be overcome using the Finnigan Triton TIMS, which allows measurements of the 40Ca/44Ca ratio with external precision of 0.35 ɛ-unit in multidynamic mode. Using this method, we generated high-precision 40Ca data on carbonates/dolomites, bedload sediments, dissolved load, and clay samples originating from and representing the main litho-tectonic units of the Himalaya. Our results show that metamorphosed dolomites from the Lesser Himalaya (LH) exhibit no radiogenic 40Ca excess despite highly variable 87Sr/86Sr signatures (0.73-0.85). Thus, all Himalayan carbonates appear to be characterized by a homogeneous ɛ40Ca=0. In contrast, silicate material is radiogenic, with ɛ40Ca averaging +1 in the Tethyan Sedimentary Series (TSS), +1.6 in the High Himalaya crystalline (HHC) and +4 ɛ-units in the LH. Results obtained from a series of 35 Himalayan rivers (including the Brahmaputra, Ganga and its main tributaries) show that ɛ40Ca in the

  1. Determining CO2 storage potential during miscible CO2 enhanced oil recovery: Noble gas and stable isotope tracers

    USGS Publications Warehouse

    Shelton, Jenna L.; McIntosh, Jennifer C.; Hunt, Andrew; Beebe, Thomas L; Parker, Andrew D; Warwick, Peter; Drake, Ronald; McCray, John E.

    2016-01-01

    Rising atmospheric carbon dioxide (CO2) concentrations are fueling anthropogenic climate change. Geologic sequestration of anthropogenic CO2 in depleted oil reservoirs is one option for reducing CO2 emissions to the atmosphere while enhancing oil recovery. In order to evaluate the feasibility of using enhanced oil recovery (EOR) sites in the United States for permanent CO2 storage, an active multi-stage miscible CO2flooding project in the Permian Basin (North Ward Estes Field, near Wickett, Texas) was investigated. In addition, two major natural CO2 reservoirs in the southeastern Paradox Basin (McElmo Dome and Doe Canyon) were also investigated as they provide CO2 for EOR operations in the Permian Basin. Produced gas and water were collected from three different CO2 flooding phases (with different start dates) within the North Ward Estes Field to evaluate possible CO2 storage mechanisms and amounts of total CO2retention. McElmo Dome and Doe Canyon were sampled for produced gas to determine the noble gas and stable isotope signature of the original injected EOR gas and to confirm the source of this naturally-occurring CO2. As expected, the natural CO2produced from McElmo Dome and Doe Canyon is a mix of mantle and crustal sources. When comparing CO2 injection and production rates for the CO2 floods in the North Ward Estes Field, it appears that CO2 retention in the reservoir decreased over the course of the three injections, retaining 39%, 49% and 61% of the injected CO2 for the 2008, 2010, and 2013 projects, respectively, characteristic of maturing CO2 miscible flood projects. Noble gas isotopic composition of the injected and produced gas for the flood projects suggest no active fractionation, while δ13CCO2 values suggest no active CO2dissolution into formation water, or mineralization. CO2 volumes capable of dissolving in residual formation fluids were also estimated along with the potential to store pure-phase supercritical CO2. Using a combination

  2. AIR INFILTRATION MEASUREMENTS USING TRACER GASES: A LITERATURE REVIEW

    EPA Science Inventory

    The report gives results of a literature review of air filtration measurements using tracer gases, including sulfur hexafluoride, hydrogen, carbon monoxide, carbon dioxide, nitrous oxide, and radioactive argon and krypton. Sulfur hexafluoride is the commonest tracer gas of choice...

  3. You are not always what we think you eat. Selective assimilation across multiple whole-stream isotopic tracer studies

    SciTech Connect

    Dodds, W. K.; Collins, S. M.; Hamilton, S. K.; Tank, J. L.; Johnson, S.; Webster, J. R.; Simon, K. S.; Whiles, M. R.; Rantala, H. M.; McDowell, W. H.; Peterson, S. D.; Riis, T.; Crenshaw, C. L.; Thomas, S. A.; Kristensen, P. B.; Cheever, B. M.; Flecker, A. S.; Griffiths, N. A.; Crowl, T.; Rosi-Marshall, E. J.; El-Sabaawi, R.; Martí, E.

    2014-10-01

    Analyses of 21 15N stable isotope tracer experiments, designed to examine food web dynamics in streams around the world, indicated that the isotopic composition of food resources assimilated by primary consumers (mostly invertebrates) poorly reflected the presumed food sources. Modeling indicated that consumers assimilated only 33–50% of the N available in sampled food sources such as decomposing leaves, epilithon, and fine particulate detritus over feeding periods of weeks or more. Thus, common methods of sampling food sources consumed by animals in streams do not sufficiently reflect the pool of N they assimilate. Lastly, Isotope tracer studies, combined with modeling and food separation techniques, can improve estimation of N pools in food sources that are assimilated by consumers.

  4. You are not always what we think you eat. Selective assimilation across multiple whole-stream isotopic tracer studies

    DOE PAGES

    Dodds, W. K.; Collins, S. M.; Hamilton, S. K.; ...

    2014-10-01

    Analyses of 21 15N stable isotope tracer experiments, designed to examine food web dynamics in streams around the world, indicated that the isotopic composition of food resources assimilated by primary consumers (mostly invertebrates) poorly reflected the presumed food sources. Modeling indicated that consumers assimilated only 33–50% of the N available in sampled food sources such as decomposing leaves, epilithon, and fine particulate detritus over feeding periods of weeks or more. Thus, common methods of sampling food sources consumed by animals in streams do not sufficiently reflect the pool of N they assimilate. Lastly, Isotope tracer studies, combined with modeling andmore » food separation techniques, can improve estimation of N pools in food sources that are assimilated by consumers.« less

  5. Isotope Tracers To Study the Environmental Fate and Bioaccumulation of Metal-Containing Engineered Nanoparticles: Techniques and Applications.

    PubMed

    Yin, Yongguang; Tan, Zhiqiang; Hu, Ligang; Yu, Sujuan; Liu, Jingfu; Jiang, Guibin

    2017-03-08

    The rapidly growing applicability of metal-containing engineered nanoparticles (MENPs) has made their environmental fate, biouptake, and transformation important research topics. However, considering the relatively low concentration of MENPs and the high concentration of background metals in the environment and in organisms, tracking the fate of MENPs in environment-related scenarios remains a challenge. Intrinsic labeling of MENPs with radioactive or stable isotopes is a useful tool for the highly sensitive and selective detection of MENPs in the environment and organisms, thus enabling tracing of their transformation, uptake, distribution, and clearance. In this review, we focus on radioactive/stable isotope labeling of MENPs for their environmental and biological tracing. We summarize the advantages of intrinsic radioactive/stable isotopes for MENP labeling and discuss the considerations in labeling isotope selection and preparation of labeled MENPs, as well as exposure routes and detection of labeled MENPs. In addition, current practice in the use of radioactive/stable isotope labeling of MENPs to study their environmental fate and bioaccumulation is reviewed. Future perspectives and potential applications are also discussed, including imaging techniques for radioactive- and stable-isotope-labeled MENPs, hyphenated multistable isotope tracers with speciation analysis, and isotope fractionation as a MENP tracer. It is expected that this critical review could provide the necessary background information to further advance the applications of isotope tracers to study the environmental fate and bioaccumulation of MENPs.

  6. Warm gas TVC design study

    NASA Technical Reports Server (NTRS)

    Moorhead, S. B., Jr.

    1973-01-01

    A warm gas thrust vector control system was studied to optimize the injection geometry for a specific engine configuration, and an injection valve was designed capable of meeting the base line requirements. To optimize injection geometry, studies were made to determine the performance effects of varying injection location, angle, port size, and port configuration. Having minimized the injection flow rate required, a warm gas valve was designed to handle the required flow. A direct drive hydraulic servovalve capable of operating with highly contaminated hydraulic fluid was designed. The valve is sized to flow 15 gpm at 3000 psia and the direct drive feature is capable of applying a spool force of 200 pounds. The baseline requirements are the development of 6 deg of thrust vector control utilizing 2000 F (total temperature) gas for 180 seconds on a 1.37 million pound thrust engine burning LOX and RP-1 at a chamber pressure of 250 psia with a 155 inch long conical nozzle having a 68 inch diameter throat and a 153 inch diameter exit.

  7. Uptake of HNO3 to deliquescent sea-salt particles: a study using the short-lived radioactive isotope tracer 13N

    NASA Astrophysics Data System (ADS)

    Guimbaud, C.; Arens, F.; Gutzwiller, L.; Gäggeler, H. W.; Ammann, M.

    2002-10-01

    The uptake of HNO3 to deliquescent airborne sea-salt particles (RH = 55%, P = 760 torr, T = 300 K) at concentrations from 2 to 575 ppbv is measured in an aerosol flow tube using 13N as a tracer. Small particles ( 70 nm diameter) are used in order to minimize the effect of diffusion in the gas phase on the mass transfer. Below 100 ppbv, an uptake coefficient (gupt) of 0.50 ± 0.20 is derived. At higher concentrations, the uptake coefficient decreases along with the consumption of aerosol chloride. Data interpretation is further supported by using the North American Aerosol Inorganics Model (AIM), which predicts the aqueous phase activities of ions and the gas-phase partial pressures of H2O, HNO3, and HCl at equilibrium for the NaCl/HNO3/H2O system. These simulations show that the low concentration data are obtained far from equilibrium, which implies that the uptake coefficient derived is equal to the mass accommodation coefficient under these conditions. The observed uptake coefficient can serve as input to modeling studies of atmospheric sea-salt aerosol chemistry. The main sea-salt aerosol burden in the marine atmosphere is represented by coarse mode particles (> 1 µm diameter). This implies that diffusion in the gas-phase is the limiting step to HNO3 uptake until the sea-salt has been completely processed.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  9. Arctic ocean ventilation studied with a suite of anthropogenic halocarbon tracers.

    PubMed

    Krysell, M; Wallace, D W

    1988-11-04

    The chlorofluoromethanes (CFMs: CCl(2)F(2) and CCl(3)F), methyl chloroform (CH(3)CCl(3)), and carbon tetrachloride (CCl(4)) have been measured in deep waters of the Arctic Ocean. Oceanic and atmospheric inventories of these compounds result from known anthropogenic releases; because the CFMs and CCl(4) are also chemically nonreactive, they can be used as transient tracers of ocean circulation. The input history of CCl(4) is longer than that of any other transient tracer identified to date( approximately 70 years). This long input history, together with an e-folding time scale of increase(tau) of approximately 28 years, makes CCl(4) potentially the most useful tracer for calibrating models of the oceanic uptake of the fossil-fuel CO(2) transient(tau approximately 25 years). The bottom water of the Nansen Basin, Arctic Ocean, has detectable CCl(4) but undetectable CFM(s) and CH(3)CCl(3), which suggests either that the bottom water is approximately 50 years old, or that there is a small, nonanthropogenic component of atmospheric CCl(4)(<6 parts per trillion by volume).

  10. Petroleum characterization by perfluorocarbon tracers

    SciTech Connect

    Senum, G.I.; Fajer, R.W. ); Harris, B.R. Jr. ); DeRose, W.E. ); Ottaviani, W.L. )

    1992-02-01

    Perfluorocarbon tracers (PFTs), a class of six compounds, were used to help characterize the Shallow Oil Zone (SOZ) reservoir at the Naval Petroleum Reserve in California (NPRC) at Elk Hills. The SOZ reservoir is undergoing a pilot gas injection program to assess the technical feasibility and economic viability of injecting gas into the SOZ for improved oil recovery. PFTs were utilized in the pilot gas injection to qualitatively assess the extent of the pilot gas injection so as to determine the degree of gas containment within the SOZ reservoir.

  11. Multiple tracer study in Horonobe, northern Hokkaido, Japan: 2. Depletion of chlorofluorocarbons (CFCs) estimated using 3H/3He index and lumped parameter models

    NASA Astrophysics Data System (ADS)

    Kashiwaya, Koki; Hasegawa, Takuma; Nakata, Kotaro; Tomioka, Yuichi; Mizuno, Takashi

    2015-05-01

    The conservativeness of chlorofluorocarbons (CFC-12, CFC-11, and CFC-113) in an environment rich in organic carbon was evaluated using multiple tracer analyses and lumped parameter models (LPMs). Wells on a coastal plain in Horonobe, northern Hokkaido, Japan, were studied. The CFC concentrations in groundwater from 22 wells were measured, converted into atmospheric mixing ratios (CARs), and compared with estimated ratios (EARs) obtained from 3H/3He values and LPMs. The degree of CFC depletion was expressed as the percentage of the CAR relative to the EAR, and was less than 43% for CFC-12 and 28% for CFC-11 (but one well had unusual values). CFC-113 was depleted more than the other CFCs, and could not be detected in most wells. The CFC depletion mechanisms were different in each of the three well groups. Groundwater of northern Shimonuma wells (NSW) was oxic and oxidative, so CFC depletion in the NSW could be attributed to sorption by organic carbon in the lignite and peat in the aquifers. Groundwater of southern Shimonuma wells (SSW) was anoxic and reductive. The northerly SSW are supplied from the aquifer that supplies the most of the NSW, so CFC depletion in the SSW was caused by degradation under sulfate-reducing and methanogenic conditions, in addition to sorption by lignite in the northerly SSW. Gas stripping, contamination from a local source, and methane interfering with the CFC analysis were found in groundwater of Hamasato wells (HW). One well of HW was not affected by these problems, but the CFCs were depleted by microbial degradation. Assuming that the CFC depletion mechanisms follow first-order reaction kinetics, reaction rate constants of 2.7 y-1 for CFC-12 and 2.8 y-1 for CFC-11 were estimated. Microbial degradation, sorption, gas stripping of CFCs, and methane formation processes are enhanced in environments rich in organic carbon. Special attention is required when CFCs are used as transient tracers in such environments. The combination of multiple

  12. A radiogenic isotope tracer study of transatlantic dust transport from Africa to the Caribbean

    USGS Publications Warehouse

    Kumar, A.; Abouchami, W.; Galer, S.J.G.; Garrison, V.H.; Williams, E.; Andreae, M.O.

    2014-01-01

    Many studies have suggested that long-range transport of African desert dusts across the Atlantic Ocean occurs, delivering key nutrients and contributing to fertilization of the Amazon rainforest. Here we utilize radiogenic isotope tracers – Sr, Nd and Pb – to derive the provenance, local or remote, and pathways of dust transport from Africa to the Caribbean. Atmospheric total suspended particulate (TSP) matter was collected in 2008 on quartz fibre filters, from both sides of the Atlantic Ocean at three different locations: in Mali (12.6°N, 8.0°W; 555 m a.s.l.), Tobago (11.3°N, 60.5°W; 329 m a.s.l.) and the U.S. Virgin Islands (17.7°N, 64.6°W; 27 m a.s.l.). Both the labile phase, representative of the anthropogenic signal, and the refractory detrital silicate fraction were analysed. Dust deposits and soils from around the sampling sites were measured as well to assess the potential contribution from local sources to the mineral dust collected. The contribution from anthropogenic sources of Pb was predominant in the labile, leachate phase. The overall similarity in Pb isotope signatures found in the leachates is attributed to a common African source of anthropogenic Pb, with minor inputs from other sources, such as from Central and South America. The Pb, Sr and Nd isotopic compositions in the silicate fraction were found to be systematically more radiogenic than those in the corresponding labile phases. In contrast, Nd and Sr isotopic compositions from Mali, Tobago, and the Virgin Islands are virtually identical in both leachates and residues. Comparison with existing literature data on Saharan and Sahelian sources constrains the origin of summer dust transported to the Caribbean to mainly originate from the Sahel region, with some contribution from northern Saharan sources. The source regions derived from the isotope data are consistent with 7-day back-trajectory analyses, demonstrating the usefulness of radiogenic isotopes in tracing dust provenance and

  13. Water, methanol and dense gas tracers in the local ULIRG Arp 220: results from the new SEPIA Band 5 Science Verification campaign

    NASA Astrophysics Data System (ADS)

    Galametz, M.; Zhang, Z.-Y.; Immer, K.; Humphreys, E.; Aladro, R.; De Breuck, C.; Ginsburg, A.; Madden, S. C.; Møller, P.; Arumugam, V.

    2016-10-01

    We present a line survey of the ultraluminous infrared galaxy Arp 220, taken with the newly installed SEPIA (Swedish-European Southern Observatory PI receiver for APEX) Band 5 instrument on APEX (Atacama Pathfinder Experiment). We illustrate the capacity of SEPIA to detect the 183.3 GHz H2O 31,3-22,0 line against the atmospheric H2O absorption feature. We confirm the previous detection of the HCN(2-1) line, and detect new transitions of standard dense gas tracers such as HNC(2-1), HCO+(2-1), CS(4-3), C34S(4-3) and HC3N(20-19). We also detect HCN(2-1) v2 = 1 and the 193.5 GHz methanol (4-3) group for the first time. The absence of time variations in the megamaser water line compared to previous observations seems to rule out an AGN nuclear origin for the line. It could, on the contrary, favour a thermal origin instead, but also possibly be a sign that the megamaser emission is associated with star-forming cores washed out in the beam. We finally discuss how the new transitions of HCN, HNC and HCO+ refine our knowledge of the interstellar medium physical conditions in Arp 220.

  14. The Numerical Simulation of a Tracer-Release Field Project to Study Motion within the Nocturnal Boundary Layer

    NASA Astrophysics Data System (ADS)

    Werth, D. W.; Leclerc, M. Y.; Buckley, R.; Parker, M.; Kurzeja, R.; Duarte, H. F.; Zhang, G.; Durden, D.

    2009-12-01

    The Savannah River National Laboratory (SRNL), Brookhaven National Laboratory (BNL), the University of Georgia (UGA), and the National Oceanic and Atmospheric Administration (NOAA) conducted a regional tracer experiment to study the nocturnal behavior of CO2 in the vicinity of an instrumented tall tower during two nights on May 11th and 12th, 2009. The experiment consisted of a release of five perfluorocarbon tracer (PFTs) compounds in twelve unique locations in Aiken County, South Carolina. Intensive meteorological measurements including in-situ turbulence were made in conjunction with the release and sampling of the PFTs. A 300m tower was also used to collect data from higher levels, allowing us to determine the extent to which the tracer was mixed vertically. Lagrangian plume simulations performed during the experiment demonstrated transport over distances of >8 km, and correlated well with in situ sampling. The area was characterized by heavy vegetation cover, and carbon dioxide concentrations were also monitored in an effort to determine how respiration and advection affect CO2 levels in the stable layer. Tracer release locations were carefully selected via a fine-scale mesoscale modeling study of similar nights. The purpose of these experiments was to provide data that will be used to increase the understanding of the terrestrial carbon budget, especially with respect to nocturnal boundary layer (NBL) phenomena such as low level jets and breaking gravity waves. Using these data, a simulation of the motion of the tracer within the boundary layer was developed using the Regional Atmospheric Modeling System (RAMS) mesoscale model coupled to a tracer model. The RAMS model was also coupled to the Simple Biosphere (SiB) vegetation model, which allowed for the simulation of the release of carbon dioxide into the NBL. The simulation results are used to validate the NBL hypothesis of CO2 monitoring, by which the release of CO2 can be correlated with the accumulation

  15. Radioisotope tracer studies in the NASA Skylab ethothermic brazing experiment M-552

    NASA Technical Reports Server (NTRS)

    Braski, D. N.; Adair, H. L.; Kobisk, E. H.

    1974-01-01

    The first use of radioisotope tracer for mapping flow patterns during brazing of metal components in a space environment (near-zero gravity) proved successful. A nickel ferrule was brazed to a nickel tube with Lithobraze BT (71.8% Ag, 28% Cu, 0.2% Li) which contained a trace amount of radioactive Ag-110. Mapping of the flow of the braze alloy in the annulus formed between the tube and the concentric ferrule was determined by counting the radiation intensity as a function of position in the braze joint. Significant information concerning the thermal history of the braze was determined.

  16. Historical and contemporary stable isotope tracer approaches to studying mammalian protein metabolism.

    PubMed

    Wilkinson, Daniel James

    2016-05-16

    Over a century ago, Frederick Soddy provided the first evidence for the existence of isotopes; elements that occupy the same position in the periodic table are essentially chemically identical but differ in mass due to a different number of neutrons within the atomic nucleus. Allied to the discovery of isotopes was the development of some of the first forms of mass spectrometers, driven forward by the Nobel laureates JJ Thomson and FW Aston, enabling the accurate separation, identification, and quantification of the relative abundance of these isotopes. As a result, within a few years, the number of known isotopes both stable and radioactive had greatly increased and there are now over 300 stable or radioisotopes presently known. Unknown at the time, however, was the potential utility of these isotopes within biological disciplines, it was soon discovered that these stable isotopes, particularly those of carbon ((13) C), nitrogen ((15) N), oxygen ((18) O), and hydrogen ((2) H) could be chemically introduced into organic compounds, such as fatty acids, amino acids, and sugars, and used to "trace" the metabolic fate of these compounds within biological systems. From this important breakthrough, the age of the isotope tracer was born. Over the following 80 yrs, stable isotopes would become a vital tool in not only the biological sciences, but also areas as diverse as forensics, geology, and art. This progress has been almost exclusively driven through the development of new and innovative mass spectrometry equipment from IRMS to GC-MS to LC-MS, which has allowed for the accurate quantitation of isotopic abundance within samples of complex matrices. This historical review details the development of stable isotope tracers as metabolic tools, with particular reference to their use in monitoring protein metabolism, highlighting the unique array of tools that are now available for the investigation of protein metabolism in vivo at a whole body down to a single protein

  17. Groundwater age structure and palaeo hydrogeology over a 500 kyr time scale revealed from Krypton 81and a multiple tracer study: Great Artesian Basin

    NASA Astrophysics Data System (ADS)

    Love, A. J.; Purtschert, R.; Jiang, W.; Lu, Z.; Tosaki, Y.; Fulton, S.; Wohling, D.; Shand, P.; Broder, L.; Aeschbach, W.; Rousseau=Gueutin, P.

    2013-12-01

    We report on the most comprehensive set of krypton -81 data to be analysed so far. Our study site is on the western margin of the Great Artesian Basin (GAB). The study area is focused on the western margin of the GAB between the Finke River system in the Northern Territory and the iconic Dalhousie springs in South Australia. This represents the direction of groundwater flow from recharge to discharge through the Dalhousie spring complex. Because of its vast size and the potential for large regional flow systems to occur, the GAB has been considered an ideal basin to test emerging groundwater dating techniques such as Cl-36 and He-4. However both of these techniques are subjected to large degrees of uncertainty, as they require a detailed understanding of different sources and sinks of these two isotopes. Contrasting this Kr-81 is considered to be an ideal tracer as it contains only one source, the atmosphere with no or at most minimal sub surface production. For the first time we have provided a comprehensive suite of analyse not only of Cl-36, He-4, C-14, Ar-39, stable isotopes of the water molecule and noble gases but also, Kr-85 and Kr-81. Our results indicate a spectrum of 'groundwater ages' ranging from modern as indicated by thermonuclear C-14 and Ar-39 up to hundreds of thousands of years as indicated by Kr-81, Cl-36 and He-4. The data set indicates a wide range of stable isotopes of the water molecule as well as variability in noble gas recharge temperatures that suggest that not only has this region been subjected to changes in climate in the recharge zone but also testaments to a changes in the dominate direction of rainfall indicated by a change in recharge mechanism at the beginning of the Holocene. As suggested previously this groundwater flow transect may represent an ideal 'type section' for testing new and emerging environmental tracers in hydrogeology.

  18. Performance evaluation of AERMOD, CALPUFF, and legacy air dispersion models using the Winter Validation Tracer Study dataset

    NASA Astrophysics Data System (ADS)

    Rood, Arthur S.

    2014-06-01

    The performance of the steady-state air dispersion models AERMOD and Industrial Source Complex 2 (ISC2), and Lagrangian puff models CALPUFF and RATCHET were evaluated using the Winter Validation Tracer Study dataset. The Winter Validation Tracer Study was performed in February 1991 at the former Rocky Flats Environmental Technology Site near Denver, Colorado. Twelve, 11-h tests were conducted where a conservative tracer was released and measured hourly at 140 samplers in concentric rings 8 km and 16 km from the release point. Performance objectives were unpaired maximum one- and nine-hour average concentration, location of plume maximum, plume impact area, arc-integrated concentration, unpaired nine-hour average concentration, and paired ensemble means. Performance objectives were aimed at addressing regulatory compliance, and dose reconstruction assessment questions. The objective of regulatory compliance is not to underestimate maximum concentrations whereas for dose reconstruction, the objective is an unbiased estimate of concentration in space and time. Performance measures included the fractional bias, normalized mean square error, geometric mean, geometric mean variance, correlation coefficient, and fraction of observations within a factor of two. The Lagrangian puff models tended to exhibit the smallest variance, highest correlation, and highest number of predictions within a factor of two compared to the steady-state models at both the 8-km and 16-km distance. Maximum one- and nine-hour average concentrations were less likely to be under-predicted by the steady-state models compared to the Lagrangian puff models. The characteristic of the steady-state models not to under-predict maximum concentrations make them well suited for regulatory compliance demonstration, whereas the Lagrangian puff models are better suited for dose reconstruction and long range transport.

  19. Study of sediment movement in an irrigated maize-cotton system combining rainfall simulations, sediment tracers and soil erosion models

    NASA Astrophysics Data System (ADS)

    Guzmán, Gema; Laguna, Ana; Cañasveras, Juan Carlos; Boulal, Hakim; Barrón, Vidal; Gómez-Macpherson, Helena; Giráldez, Juan Vicente; Gómez, José Alfonso

    2015-05-01

    Although soil erosion is one of the main threats to agriculture sustainability in many areas of the world, its processes are difficult to measure and still need a better characterization. The use of iron oxides as sediment tracers, combined with erosion and mixing models opens up a pathway for improving the knowledge of the erosion and redistribution of soil, determining sediment sources and sinks. In this study, magnetite and a multivariate mixing model were used in rainfall simulations at the micro-plot scale to determine the source of the sediment at different stages of a furrow-ridge system both with (+T) and without (-T) wheel tracks. At a plot scale, magnetite, hematite and goethite combined with two soil erosion models based on the kinematic wave approach were used in a sprinkler irrigation test to study trends in sediment transport and tracer dynamics along furrow lengths under a wide range of scenarios. In the absence of any stubble cover, sediment contribution from the ridges was larger than the furrow bed one, almost 90%, while an opposite trend was observed with stubble, with a smaller contribution from the ridge (32%) than that of the bed, at the micro-plot trials. Furthermore, at a plot scale, the tracer concentration analysis showed an exponentially decreasing trend with the downstream distance both for sediment detachment along furrows and soil source contribution from tagged segments. The parameters of the distributed model KINEROS2 have been estimated using the PEST Model to obtain a more accurate evaluation. Afterwards, this model was used to simulate a broad range of common scenarios of topography and rainfall from commercial farms in southern Spain. Higher slopes had a significant influence on sediment yields while long furrow distances allowed a more efficient water use. For the control of runoff, and therefore soil loss, an equilibrium between irrigation design (intensity, duration, water pattern) and hydric needs of the crops should be

  20. Numerical simulation of a natural gradient tracer experiment for the natural attenuation study: flow and physical transport.

    PubMed

    Julian, H E; Boggs, J M; Zheng, C; Feehley, C E

    2001-01-01

    Results are presented for numerical simulations of ground water flow and physical transport associated with a natural gradient tracer experiment conducted within a heterogeneous alluvial aquifer of the Natural Attenuation Study (NATS) site near Columbus, Mississippi. A principal goal of NATS is to evaluate biogeochemical models that predict the rate and extent of natural biodegradation under field conditions. This paper describes the initial phase in the model evaluation process, i.e., calibration of flow and physical transport models that simulate conservative bromide tracer plume evolution during NATS. An initial large-scale flow model (LSM) is developed encompassing the experimental site and surrounding region. This model is subsequently scaled down in telescopic fashion to an intermediate-scale ground water flow model (ISM) covering the tracer-monitoring network, followed by a small-scale transport model (SSM) focused on the small region of hydrocarbon plume migration observed during NATS. The LSM uses inferred depositional features of the site in conjunction with hydraulic conductivity (K) data from aquifer tests and borehole flowmeter tests to establish large-scale K and flow field trends in and around the experimental site. The subsequent ISM incorporates specified flux boundary conditions and large-scale K trends obtained from the calibrated LSM, while preserving small-scale K structure based on some 4000 flowmeter data for solute transport modeling. The configuration of the ISM-predicted potentiometric surface approximates that of the observed surface within a root mean squared error of 0.15 m. The SSM is based on the dual-domain mass-transfer approach. Despite the well-recognized difficulties in modeling solute transport in extremely heterogeneous media as found at the NATS site, the dual-domain model adequately reproduced the observed bromide concentration distributions. Differences in observed and predicted bromide concentration distributions are

  1. Natural Attenuation Of Creosote Contamination In A Tidally Forced Anaerobic Aquifer: A Tracer Study Using C14-naphthalene

    NASA Astrophysics Data System (ADS)

    Bianchin, M.; Lesser, L.; Smith, L.; Barker, J. F.; Butler, B.; Aravena, R.; Beckie, R.

    Historic practices at a wood-preserving facility along a major river in the lower main- land of British Columbia have contaminated the underlying tidally forced anaerobic aquifer. Creosote from the source zone, found mostly as an immobile separate phase, is dissolving and forming an aqueous-phase plume, which is discharging from the aquifer at the river bottom. Previous studies could only explain the plume shape by invoking an attenuation process such as degradation or sorption. A careful study of the on-shore portion of the aquifer using in-situ and laboratory microcosms could not detect any measurable degradation. Similarly, sorption could not explain the plume shape. Here we present the results of a tracer study conducted in the off-shore portion of the aquifer. C14-labeled naphthalene, bromide and deuterated water were intro- duced into the portion of the aquifer beneath the river. Water samples were collected and analyzed for bromide, C-14 naphthalene and C14-labeled CO2, a likely degra- dation product. While C-14 CO2 has been detected, the levels are low, suggesting a very slow degradation process. The study is unique in several respects, including the methodologies used to sample the aquifer beneath the river and the use of a radio- labeled tracer in the field.

  2. Halon-1301, a new Groundwater Age Tracer

    NASA Astrophysics Data System (ADS)

    Beyer, Monique; van der Raaij, Rob; Morgenstern, Uwe; Jackson, Bethanna

    2015-04-01

    Groundwater dating is an important tool to assess groundwater resources in regards to direction and time scale of groundwater flow and recharge and to assess contamination risks and manage remediation. To infer groundwater age information, a combination of different environmental tracers, such as tritium and SF6, are commonly used. However ambiguous age interpretations are often faced, due to a limited set of available tracers and limitations of each tracer method when applied alone. There is a need for additional, complementary groundwater age tracers. We recently discovered that Halon-1301, a water soluble and entirely anthropogenic gaseous substance, may be a promising candidate [Beyer et al, 2014]. Halon-1301 can be determined along with SF6, SF5CF3 and CFC-12 in groundwater using a gas chromatography setup with attached electron capture detector developed by Busenberg and Plummer [2008]. Halon-1301 has not been assessed in groundwater. This study assesses the behaviour of Halon-1301 in water and its suitability as a groundwater age tracer. We determined Halon-1301 in 17 groundwater and various modern (river) waters sites located in 3 different groundwater systems in the Wellington Region, New Zealand. These waters have been previously dated with tritium, CFC-12, CFC-11 and SF6 with mean residence times ranging from 0.5 to over 100 years. The waters range from oxic to anoxic and some show evidence of CFC contamination or degradation. This allows us to assess the different properties affecting the suitability of Halon-1301 as groundwater age tracer, such as its conservativeness in water and local contamination potential. The samples are analysed for Halon-1301 and SF6simultaneously, which allows identification of issues commonly faced when using gaseous tracers such as contamination with modern air during sampling. Overall we found in the assessed groundwater samples Halon-1301 is a feasible new groundwater tracer. No sample indicated significantly elevated

  3. The potential of silica encapsulated DNA magnetite microparticles (SiDNAMag) for multi-tracer studies in subsurface hydrology

    NASA Astrophysics Data System (ADS)

    Willem Foppen, Jan; Bogaard, Thom; van Osnabrugge, Bart; Puddu, Michela; Grass, Robert

    2015-04-01

    With tracer experiments, knowledge on solute transport, travel times, flow pathways, source areas, and linkages between infiltration and exfiltration zones in subsurface hydrological studies can be obtained. To overcome the well-known limitations of artificial tracers, we report here the development and application of an inexpensive method to produce large quantities of environmentally friendly 150-200 nm microparticles composed of a magnetite core to which small fragments of synthetic 80 nt ssDNA were adsorbed, which were then covered by a layer of inert silica (acronym: SiDNAMag). The main advantages of using DNA are the theoretically unlimited amount of different DNA tracers and the low DNA detection limit using the quantitative polymerase chain reaction (qPCR); the main advantage of the silica layer is to prevent DNA decay, while the magnetite core facilitates magnetic separation, recovery and up-concentration. In 10 cm columns of saturated quartz sand, we first injected NaCl, a conservative salt tracer, and measured the breakthrough. Then, we injected SiDNAMag suspended in water of known composition, harvested the SiDNAMag in column effluent samples, and measured the DNA concentration via qPCR after dissolving the SiDNAMag. The results indicated that the timing of the rising limb of the DNA breakthrough curve, the plateau phase and the falling limb were identical to the NaCl breakthrough curve. However, the relative maximum DNA concentration reached during the plateau phase was around 0.3, indicating that around 70% of the SiDNAMag mass was retained in the column. From these results we inferred that SiDNAMag was not retarded and therefore not subject to equilibrium sorption. Instead, first order irreversible kinetic attachment appeared to be the dominant retention mechanism. Based on our results, we speculate that, despite significant retention, due to the low DNA detection limit and the possibility of magnetic up-concentration, the use of SiDNAMag is a very

  4. Determination of stream reaeration coefficients by use of tracers

    USGS Publications Warehouse

    Kilpatrick, F.A.; Rathbun, R.E.; Yotsukura, Nobuhiro; Parker, G.W.; DeLong, L.L.

    1987-01-01

    Stream reaeration is the physical absorption of oxygen from the atmosphere by a flowing stream. This is the primary process by which a stream replenishes the oxygen consumed in the biodegradation of organic wastes. Prior to 1965, reaeration rate coefficients could be estimated only by indirect methods. In 1965, a direct method of measuring stream reaeration coefficients was developed in which a radioactive tracer gas was injected into a stream--the tracer gas being desorbed from the stream inversely to how oxygen would be absorbed. The technique has since been modified by substituting hydrocarbon gases for the radioactive tracer gas. The slug-injection and constant-rate injection methods of performing gas tracer desorption measurements are described. Emphasis is on the use of rhodamine WT dye as a relatively conservative tracer and propane as the nonconservative gas tracer, on planning field tests, methods of injection, sampling and analysis, and computational techniques to compute desorption and reaeration coefficients. (Author 's abstract)

  5. Diffusive partitioning tracer test for the quantification of nonaqueous phase liquid (NAPL) in the vadose zone: Performance evaluation for heterogeneous NAPL distribution

    NASA Astrophysics Data System (ADS)

    Werner, David; Karapanagioti, Hrissi K.; Höhener, Patrick

    2009-08-01

    A partitioning tracer test based on gas-phase diffusion in the vadose zone yields estimates of the residual nonaqueous phase liquid (NAPL) saturation. The present paper investigates this technique further by studying diffusive tracer breakthrough curves in the vadose zone for a heterogeneous NAPL distribution. Tracer experiments were performed in a lysimeter with a horizontal layer of artificial kerosene embedded in unsaturated sand. Tracer disappearance curves at the injection point and tracer breakthrough curves at some distance from the injection point were measured inside and outside of the NAPL layer. A numerical code was used to generate independent model predictions based on the physicochemical sand, NAPL, and tracer properties. The measured and modeled tracer breakthrough curves were in good agreement confirming the validity of important modeling assumptions such as negligible sorption of chlorofluorocarbon (CFC) tracers to the uncontaminated sand and their fast reversible partitioning between the soil air and the NAPL phase. Subsequently, the model was used to investigate different configurations of NAPL contamination. The experimental and model results show that the tracer disappearance curves of a single-well diffusive partitioning tracer test (DPTT) are dominated by the near-field presence of NAPL around the tip of the soil gas probe. In contrast, breakthrough curves of inter-well tracer tests reflect the NAPL saturation in between the probes, although there is no unique interpretation of the tracer signals if the NAPL distribution is heterogeneous. Numerical modeling is useful for the planning of a DPTT application. Simulations suggest that several cubic meters of soil can be investigated with a single inter-well partitioning tracer test of 24-hour duration by placing the injection point in the center of the investigated soil volume and probes at up to 1 m distance for the monitoring of gaseous tracers.

  6. Diffusive partitioning tracer test for the quantification of nonaqueous phase liquid (NAPL) in the vadose zone: performance evaluation for heterogeneous NAPL distribution.

    PubMed

    Werner, David; Karapanagioti, Hrissi K; Höhener, Patrick

    2009-08-11

    A partitioning tracer test based on gas-phase diffusion in the vadose zone yields estimates of the residual nonaqueous phase liquid (NAPL) saturation. The present paper investigates this technique further by studying diffusive tracer breakthrough curves in the vadose zone for a heterogeneous NAPL distribution. Tracer experiments were performed in a lysimeter with a horizontal layer of artificial kerosene embedded in unsaturated sand. Tracer disappearance curves at the injection point and tracer breakthrough curves at some distance from the injection point were measured inside and outside of the NAPL layer. A numerical code was used to generate independent model predictions based on the physicochemical sand, NAPL, and tracer properties. The measured and modeled tracer breakthrough curves were in good agreement confirming the validity of important modeling assumptions such as negligible sorption of chlorofluorocarbon (CFC) tracers to the uncontaminated sand and their fast reversible partitioning between the soil air and the NAPL phase. Subsequently, the model was used to investigate different configurations of NAPL contamination. The experimental and model results show that the tracer disappearance curves of a single-well diffusive partitioning tracer test (DPTT) are dominated by the near-field presence of NAPL around the tip of the soil gas probe. In contrast, breakthrough curves of inter-well tracer tests reflect the NAPL saturation in between the probes, although there is no unique interpretation of the tracer signals if the NAPL distribution is heterogeneous. Numerical modeling is useful for the planning of a DPTT application. Simulations suggest that several cubic meters of soil can be investigated with a single inter-well partitioning tracer test of 24-hour duration by placing the injection point in the center of the investigated soil volume and probes at up to 1 m distance for the monitoring of gaseous tracers.

  7. Report on 10-ton retort tracer testing: tests S76 through S79

    SciTech Connect

    Turner, T.F.

    1985-07-01

    An oil shale retort with contrasting permeability regions has been studied using gas tracer techniques. The Western Research Institute's 10-ton retort was loaded with oil shale of various size ranges resulting in different void fractions. Four retorting and tracer runs were performed on the retort. For each run, tracer injections were made into the main air flow inlet and into taps near the top of the retort. Detection taps were located at four levels in the retort with five taps on each level in tests S76 through S78. There were six taps on each level in run S79. The oil shale rubble bed was configured with a cylindrical nonuniform region on the center line of the retort in tests S76 through S78. In run S79 two side-by-side regions with differing bed properties were tracer tested and retorted. Response times were calculated from the tracer response curves. The tracer response times from in-bed tracer tests correlate with oil yield and with bed properties. Response times from the inlet-to-outlet tracer tests correlate with total oil yield through a first-order relationship with sweep efficiencies. 8 refs., 6 figs., 1 tab.

  8. Birth Outcomes in a Prospective Pregnancy–Birth Cohort Study of Environmental Risk Factors in Kuwait: The TRACER Study

    PubMed Central

    AlSeaidan, Mohammad; Al Wotayan, Rihab; Christophi, Costas A.; Al-Makhseed, Massouma; Awad, Yara Abu; Nassan, Feiby; Ahmed, Ayah; Abraham, Smitha; Boley, Robert Bruce; James-Todd, Tamarra; Wright, Rosalind J.; Dockery, Douglas W.; Behbehani, Kazem

    2016-01-01

    Background Rapid development and westernisation in Kuwait and other Gulf states have been accompanied by rising rates of obesity, diabetes, asthma, and other chronic conditions. Prenatal experiences and exposures may be important targets for intervention. We undertook a prospective pregnancy–birth cohort study in Kuwait, the TRansgenerational Assessment of Children’s Environmental Risk (TRACER) Study, to examine prenatal risk factors for early childhood obesity. This article describes the methodology and results of follow-up through birth. Methods Women were recruited at antenatal clinical visits. Interviewers administered questionnaires during the pregnancy and collected and banked biological samples. Children are being followed up with quarterly maternal interviews, annual anthropometric measurements, and periodic collection of biosamples. Frequencies of birth outcomes (i.e. stillbirth, preterm birth, small and large for gestational age, and macrosomia) were calculated as a function of maternal characteristics and behaviours. Results Two thousand four hundred seventy-eight women were enrolled, and 2254 women were followed to delivery. Overall, frequencies of stillbirth (0.6%), preterm birth (9.3%), and small for gestational age (7.4%) were comparable to other developed countries, but not strongly associated with maternal characteristics or behaviours. Macrosomia (6.1%) and large for gestational age (23.0%) were higher than expected and positively associated with pre-pregnancy maternal overweight/obesity. Conclusions A large birth cohort has been established in Kuwait. The collected risk factors and banked biosamples will allow examination of the effects of prenatal exposures on the development of chronic disease in children. Initial results suggest that maternal overweight/obesity before pregnancy should be targeted to prevent macrosomia and its associated sequelae of childhood overweight/obesity. PMID:27193754

  9. SEAPORT LIQUID NATURAL GAS STUDY

    SciTech Connect

    COOK,Z.

    1999-02-01

    The Seaport Liquid Natural Gas Study has attempted to evaluate the potential for using LNG in a variety of heavy-duty vehicle and equipment applications at the Ports of Los Angeles and Oakland. Specifically, this analysis has focused on the handling and transport of containerized cargo to, from and within these two facilities. In terms of containerized cargo throughput, Los Angeles and Oakland are the second and sixth busiest ports in the US, respectively, and together handle nearly 4.5 million TEUs per year. At present, the landside handling and transportation of containerized cargo is heavily dependent on diesel-powered, heavy-duty vehicles and equipment, the utilization of which contributes significantly to the overall emissions impact of port-related activities. Emissions from diesel units have been the subject of increasing scrutiny and regulatory action, particularly in California. In the past two years alone, particulate matter from diesel exhaust has been listed as a toxic air contaminant by CAM, and major lawsuits have been filed against several of California's largest supermarket chains, alleging violation of Proposition 65 statutes in connection with diesel emissions from their distribution facilities. CARE3 has also indicated that it may take further regulatory action relating to the TAC listing. In spite of these developments and the very large diesel emissions associated with port operations, there has been little AFV penetration in these applications. Nearly all port operators interviewed by CALSTART expressed an awareness of the issues surrounding diesel use; however, none appeared to be taking proactive steps to address them. Furthermore, while a less controversial issue than emissions, the dominance of diesel fuel use in heavy-duty vehicles contributes to a continued reliance on imported fuels. The increasing concern regarding diesel use, and the concurrent lack of alternative fuel use and vigorous emissions reduction activity at the Ports provide

  10. Linking trace gas measurements and molecular tracers of organic matter in aerosols for identification of ecosystem sources and types of wildfires in Central Siberia

    NASA Astrophysics Data System (ADS)

    Panov, A. V.; Prokushkin, A. S.; Korets, M. A.; Bryukhanov, A. V.; Myers-Pigg, A. N.; Louchouarn, P.; Sidenko, N. V.; Amon, R.; Andreae, M. O.; Heimann, M.

    2016-11-01

    Summer 2012 was one of the extreme wildfire years in Siberia. At the surface air monitoring station “ZOTTO” (60°48'N, 89°21'E, 114 m a.s.l.) in Central Siberia we observed biomass burning (BB) influence on the ongoing atmospheric measurements within more than 50 % of the time in June-July 2012 that indicates a 30 times greater wildfire signal compared to previously reported ordinary biomass burning signature for the study area. While previous studies thoroughly estimated a relative input of BB into aerosol composition (i.e. size distribution, physical and optical parameters etc.) at ZOTTO, in this paper we characterize the source apportionment of the smoke aerosols with molecular tracer techniques from large-scale wildfires occurred in 2012 in the two prevailing types of Central Siberian ecosystems: complexes of pine forests and bogs and dark coniferous forests. Wildfires in the selected ecosystems are highly differed by their combustion phase (flaming/smoldering), the type of fire (crown/ground), biomass fuel, and nature of soil that greatly determines the smoke particle composition. Anhydrosugars (levoglucosan and its isomers) and lignin phenols taken as indicators of the sources and the state of particulate matter (PM) inputs in the specific fire plumes were used as powerful tools to compare wildfires in different environmental conditions and follow the role and contribution of different sources of terrestrial organic matter in the transport of BB pollutants into the pristine atmosphere of boreal zone in Central Siberia.

  11. Chemical parameters as natural tracers in hydrogeology: a case study of Louros karst system, Greece

    NASA Astrophysics Data System (ADS)

    Katsanou, K.; Lambrakis, N.; D'Alessandro, W.; Siavalas, G.

    2016-11-01

    The Louros Basin hosts one of the most important karst systems of Epirus Prefecture (Greece) and plays a key role in supplying three counties with drinking water. Aiming to investigate the origin of groundwater and its flow patterns, a multi-tracer approach was used to describe and evaluate the hydrogeology of the system. Therefore, 271 surface water and groundwater samples were collected and analyzed for physicochemical parameters, major ions, and trace and rare earth elements, as well as stable isotopes (δ18O and δ2H). These data provided meaningful tracing of the water origin, water-rock interaction processes, and relationships among the aquifers. In particular, the elaboration of the major ions supported by the distribution of rare earth elements indicated that there are three aquifers located at different levels hosted in the Senonian and Pantokrator limestone formations. These aquifers are hydraulically interconnected by a cascade and constitute the Louros karst system which is drained by the homonymous river. Hydrochemical and isotopic data revealed that the Louros karst system is isolated from the adjacent northern Ioannina Basin and it is being recharged by precipitation. Higher groundwater salinity, where present, is mainly associated with increased water-rock interaction due to longer and deeper hydrologic flow, favoring the dissolution of evaporitic, carbonate and phosphate minerals.

  12. Chemical parameters as natural tracers in hydrogeology: a case study of Louros karst system, Greece

    NASA Astrophysics Data System (ADS)

    Katsanou, K.; Lambrakis, N.; D'Alessandro, W.; Siavalas, G.

    2017-03-01

    The Louros Basin hosts one of the most important karst systems of Epirus Prefecture (Greece) and plays a key role in supplying three counties with drinking water. Aiming to investigate the origin of groundwater and its flow patterns, a multi-tracer approach was used to describe and evaluate the hydrogeology of the system. Therefore, 271 surface water and groundwater samples were collected and analyzed for physicochemical parameters, major ions, and trace and rare earth elements, as well as stable isotopes (δ18O and δ2H). These data provided meaningful tracing of the water origin, water-rock interaction processes, and relationships among the aquifers. In particular, the elaboration of the major ions supported by the distribution of rare earth elements indicated that there are three aquifers located at different levels hosted in the Senonian and Pantokrator limestone formations. These aquifers are hydraulically interconnected by a cascade and constitute the Louros karst system which is drained by the homonymous river. Hydrochemical and isotopic data revealed that the Louros karst system is isolated from the adjacent northern Ioannina Basin and it is being recharged by precipitation. Higher groundwater salinity, where present, is mainly associated with increased water-rock interaction due to longer and deeper hydrologic flow, favoring the dissolution of evaporitic, carbonate and phosphate minerals.

  13. A study of the accuracy of neutrally buoyant bubbles used as flow tracers in air

    NASA Technical Reports Server (NTRS)

    Kerho, Michael F.

    1993-01-01

    Research has been performed to determine the accuracy of neutrally buoyant and near neutrally buoyant bubbles used as flow tracers in air. Theoretical, computational, and experimental results are presented to evaluate the dynamics of bubble trajectories and factors affecting their ability to trace flow-field streamlines. The equation of motion for a single bubble was obtained and evaluated using a computational scheme to determine the factors which affect a bubble's trajectory. A two-dimensional experiment was also conducted to experimentally determine bubble trajectories in the stagnation region of NACA 0012 airfoil at 0 deg angle of attack using a commercially available helium bubble generation system. Physical properties of the experimental bubble trajectories were estimated using the computational scheme. These properties included the density ratio and diameter of the individual bubbles. the helium bubble system was then used to visualize and document the flow field about a 30 deg swept semispan wing with simulated glaze ice. Results were compared to Navier-Stokes calculations and surface oil flow visualization. The theoretical and computational analysis have shown that neutrally buoyant bubbles will trace even the most complex flow patterns. Experimental analysis revealed that the use of bubbles to trace flow patterns should be limited to qualitative measurements unless care is taken to ensure neutral buoyancy. This is due to the difficulty in the production of neutrally buoyant bubbles.

  14. Radioisotope tracer studies of inorganic carbon and Ca in microbially derived CaCO3

    USGS Publications Warehouse

    Yates, Kimberly K.; Robbins, Lisa L.

    1999-01-01

    Microbial calcification significantly impacts the cycling and deposition of inorganic carbon. This research employs 45Ca and 14C techniques as radioisotopic tracers to examine the role of cellular cycling of Ca2+ and inorganic carbon in CaCO3 precipitation by the unicellular green alga Nannochloris atomus. Implications of the effects of these physiological aspects on CaCO3 precipitation and the effects of microbial calcification on CaCO3 δ13C ratios are discussed. Results from pulse/chase experiments indicate that intracellular Ca2+ is incorporated into extracellular CaCO3. Intracellular inorganic carbon leaks from cells within 10 to 12 s after injection of unlabelled NaHCO3, providing a source of inorganic carbon for extracellular CaCO3. Cellular expulsion of calcium plays a key role in increasing the CaCO3 saturation state at the site of calcification. The δ13C ratios of microbial carbonates may vary depending on the amount of photorespiratory CO2 incorporated.

  15. Use of a portable, automated, open-circuit gas quantification system and the sulfur hexafluoride tracer technique for measuring enteric methane emissions in Holstein cows fed ad libitum or restricted

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The sulfur hexafluoride tracer technique (SF**6) is a commonly used method for measuring CH**4 enteric emissions in ruminants. Studies using SF**6 have shown large variation in CH**4 emissions data, inconsistencies in CH**4 emissions across studies, and potential methodological errors. Therefore, th...

  16. Study of Formation Mechanisms of Gas Hydrate

    NASA Astrophysics Data System (ADS)

    Yang, Jia-Sheng; Wu, Cheng-Yueh; Hsieh, Bieng-Zih

    2015-04-01

    Gas hydrates, which had been found in subsurface geological environments of deep-sea sediments and permafrost regions, are solid crystalline compounds of gas molecules and water. The estimated energy resources of hydrates are at least twice of that of the conventional fossil fuel in the world. Gas hydrates have a great opportunity to become a dominating future energy. In the past years, many laboratory experiments had been conducted to study chemical and thermodynamic characteristics of gas hydrates in order to investigate the formation and dissociation mechanisms of hydrates. However, it is difficult to observe the formation and dissociation of hydrates in a porous media from a physical experiment directly. The purpose of this study was to model the dynamic formation mechanisms of gas hydrate in porous media by reservoir simulation. Two models were designed for this study: 1) a closed-system static model with separated gas and water zones; this model was a hydrate equilibrium model to investigate the behavior of the formation of hydrates near the initial gas-water contact; and 2) an open-system dynamic model with a continuous bottom-up gas flow; this model simulated the behavior of gas migration and studied the formation of hydrates from flowed gas and static formation water in porous media. A phase behavior module was developed in this study for reservoir simulator to model the pressure-volume-temperature (PVT) behavior of hydrates. The thermodynamic equilibriums and chemical reactions were coupled with the phase behavior module to have functions modelling the formation and dissociation of hydrates from/to water and gas. The simulation models used in this study were validated from the code-comparison project proposed by the NETL. According to the modelling results of the closed-system static model, we found that predominated location for the formation of hydrates was below the gas-water contact (or at the top of water zone). The maximum hydrate saturation

  17. A Simulation Study on Translation-Rotation Decoupling and its Dependence on Tracer Shape in Two Dimensional Colloids

    NASA Astrophysics Data System (ADS)

    Kim, Jeongmin; Sung, Bong June

    2015-03-01

    Near the glass transition, translation is often faster than expected from the viscosity of liquids unlike rotation. It is the well-known translation-rotation decoupling phenomenon. In this poster, we present the dependence of the decoupling on tracer shape in two-dimensional (2D) colloids using three representative tracer shapes (diamond, distorted diamond and square). We find that near the freezing (liquid-hexatic) transition, the translation-rotation decoupling occurs for all tracers regardless of shapes, but trends are different for different shape. In 2D, there exists an orientationally ordered liquid phase called a hexatic phase between isotropic liquid and solid phases. Entering the hexatic phase, 2D colloids exhibit the heterogeneous dynamics with several dynamic regions of different mobility like glass-forming liquids. We find that the observed decoupling of tracer diffusion is attributed to the dynamic heterogeneity of 2D colloids. To our surprise, the shape-dependence of decoupling trend relate closely to the rotational diffusion of tracers. Square shape tracer disturbs the hexagonal ordering of 2D colloids, thus resulting in faster rotation of square tracers, which is not observed for diamond shape tracers.

  18. Technical note: Can the sulfur hexafluoride tracer gas technique be used to accurately measure enteric methane production from ruminally cannulated cattle?

    PubMed

    Beauchemin, K A; Coates, T; Farr, B; McGinn, S M

    2012-08-01

    An experiment was conducted to determine whether using ruminally cannulated cattle affects the estimate of enteric methane (CH(4)) emissions when using the sulfur hexafluoride (SF(6)) tracer technique with samples taken from a head canister. Eleven beef cattle were surgically fitted with several types of ruminal cannula (2C, 3C, 3C+washer, 9C; Bar Diamond, Parma, ID). The 2C and 3C models (outer and inner flanges with opposite curvature) had medium to high leakage, whereas the 9C models (outer and inner flanges with the same curvature) provided minimum to moderate leakage of gas. A total of 48 cow-day measurements were conducted. For each animal, a permeation tube containing sulfur hexafluoride (SF(6)) was placed in the rumen, and a sample of air from around the nose and mouth was drawn through tubing into an evacuated canister (head canister). A second sample of air was collected from outside the rumen near the cannula into another canister (cannula canister). Background concentrations were also monitored. The methane (CH(4)) emission was estimated from the daily CH(4) and SF(6) concentrations in the head canister (uncorrected). The permeation SF(6) release rate was then partitioned based on the proportion of the SF(6) concentration measured in the head vs. the cannula canister. The CH(4) emissions at each site were calculated using the two release rates and the two CH(4):SF(6) concentration ratios. The head and cannula emissions were summed to obtain the total emission (corrected). The difference (corrected - uncorrected) in CH4 emission was attributed to the differences in CH(4):SF(6) ratio at the 2 exit locations. The proportions of CH(4) and SF(6) recovered at the head were greater (P < 0.001) for the 9C cannulas (64% and 66%) compared with the other cannulas, which were similar (P > 0.05; 2C, 6% and 4%; 3C, 17% and 15%; 3C+washer, 19% and 14%). Uncorrected CH(4) emissions were ± 10% of corrected emissions for 53% of the cow-day measurements. Only when more

  19. Olfacto-retinalis pathway in Austrolebias charrua fishes: a neuronal tracer study.

    PubMed

    Rosillo, J C; Olivera-Bravo, S; Casanova, G; García-Verdugo, J M; Fernández, A S

    2013-12-03

    The olfacto-retinal centrifugal system, a constant component of the central nervous system that appears to exist in all vertebrate groups, is part of the terminal nerve (TN) complex. TN allows the integration of different sensory modalities, and its anatomic variability may have functional and evolutionary significance. We propose that the olfacto-retinal branch of TN is an important anatomical link that allows the functional interaction between olfactory and visual systems in Austrolebias. By injecting three different neuronal tracers (biocytin, horseradish peroxidase, and 1,1'-dioctadecyl-3,3,3',3'tetramethyl-indocarbocyanine perchlorate (DiI)) in the left eye of Austrolebias charrua fishes, we identified the olfacto-retinal branch of TN and related neuronal somas that were differentiable by location, shape, and size. The olfacto-retinal TN branch is composed of numerous thin axons that run ventrally along the olfactory bulb (OB) and telencephalic lobes, and appears to originate from a group of many small monopolar neurons located in the rostral portion of both the ipsi- and contralateral OB (referred to as region 1). Labeled cells were found in two other regions: bipolar and multipolar neurons in the transition between the OB and telencephalic lobes (region 2) and two other groups in the preoptic/pretectal area (region 3). In this last region, the most rostral group is constituted by monopolar pear-shaped neurons and may belong to the septo-preoptic TN complex. The second group, putatively located in the pretectal region, is formed by pseudounipolar neurons and coincides with a conserved vertebrate nucleus of the centrifugal retinal system not involved in the TN complex. The found that connections between the olfactory and visual systems via the olfacto-retinal TN branch suggest an early interaction between these sensory modalities, and contribute to the identification of their currently unknown circuital organization.

  20. VOXEL-LEVEL MAPPING OF TRACER KINETICS IN PET STUDIES: A STATISTICAL APPROACH EMPHASIZING TISSUE LIFE TABLES1

    PubMed Central

    O’Sullivan, Finbarr; Muzi, Mark; Mankoff, David A.; Eary, Janet F.; Spence, Alexander M.; Krohn, Kenneth A.

    2014-01-01

    Most radiotracers used in dynamic positron emission tomography (PET) scanning act in a linear time-invariant fashion so that the measured time-course data are a convolution between the time course of the tracer in the arterial supply and the local tissue impulse response, known as the tissue residue function. In statistical terms the residue is a life table for the transit time of injected radiotracer atoms. The residue provides a description of the tracer kinetic information measurable by a dynamic PET scan. Decomposition of the residue function allows separation of rapid vascular kinetics from slower blood-tissue exchanges and tissue retention. For voxel-level analysis, we propose that residues be modeled by mixtures of nonparametrically derived basis residues obtained by segmentation of the full data volume. Spatial and temporal aspects of diagnostics associated with voxel-level model fitting are emphasized. Illustrative examples, some involving cancer imaging studies, are presented. Data from cerebral PET scanning with 18F fluoro-deoxyglucose (FDG) and 15O water (H2O) in normal subjects is used to evaluate the approach. Cross-validation is used to make regional comparisons between residues estimated using adaptive mixture models with more conventional compartmental modeling techniques. Simulations studies are used to theoretically examine mean square error performance and to explore the benefit of voxel-level analysis when the primary interest is a statistical summary of regional kinetics. The work highlights the contribution that multivariate analysis tools and life-table concepts can make in the recovery of local metabolic information from dynamic PET studies, particularly ones in which the assumptions of compartmental-like models, with residues that are sums of exponentials, might not be certain. PMID:25392718

  1. Stable Isotope Composition of Molecular Oxygen in Soil Gas and Groundwater: A Potentially Robust Tracer for Diffusion and Oxygen Consumption Processes

    NASA Astrophysics Data System (ADS)

    Aggarwal, Pradeep K.; Dillon, M. A.

    1998-02-01

    We have measured the concentration and isotopic composition of molecular oxygen in soil gas and groundwater. At a site near Lincoln, Nebraska, USA, soil gas oxygen concentrations ranged from 13.8 to 17.6% at depths of 3-4 m and the δ 18O values ranged mostly from 24.0 to 27.2‰ (SMOW). The concentration of dissolved oxygen in a perched aquifer in the Texas Panhandle (depth to water ˜76 m) was about 5 mg/L and the δ 18O values were 21.2-22.9‰. The δ 18O of soil gas oxygen in our study are higher and those of dissolved oxygen are lower than the δ 18O of atmospheric oxygen (23.5‰). A model for the oxygen concentration and isotopic composition in soil gas was developed using the molecular diffusion theory. The higher δ 18O values in soil gas at the Nebraska site can be explained by the effects of diffusion and soil respiration (plant root and bacterial) on the isotopic composition of molecular oxygen. The lower δ 18O of dissolved oxygen at the Texas site indicates that oxygen consumption below the root zone in the relatively thick unsaturated zone here may have occurred with a different fractionation factor (either due to inorganic consumption or due to low respiration rates) than that observed for the dominant pathways of plant root and bacterial respiration. It is concluded that the use of the concentration and isotopic composition of soil gas and dissolved oxygen should provide a robust tool for studying the subsurface gaseous diffusion and oxygen consumption processes.

  2. Modeling and interpretation of two-phase flow and tracer studies from a subbituminous coal seam in the San Juan basin of New Mexico

    SciTech Connect

    Nuttall, H.E.; Travis, B.J.

    1980-01-01

    Field and modeling studies were performed to characterize two-phase flow within the natural cleat structure of an upper Cretaceous subbituminous coal seam. A two borehole pattern with open completion was used in a study of dewatering and tracer residence time distribution. Air was pumped into a five meter thick seam located about 170 meters below the surface. Krypton 85 was used as the airborne tracer. Air inflow and air and water production rates and tracer arrival times were monitored. The field tests were simulated with a two-phase, three component, porous flow code. Results showed that the air inflow and air and water outflow rates and breakthrough times could not be modeled assuming a uniform darcy-type permeability. The use of a pressure dependent permeability did provide, however, a much better match with the field data.

  3. Analysis of tracer and thermal transients during reinjection

    SciTech Connect

    Kocabas, I.

    1989-10-01

    This work studied tracer and thermal transients during reinjection in geothermal reserviors and developed a new technique which combines the results from interwell tracer tests and thermal injection-backflow tests to estimate the thermal breakthrough times. Tracer tests are essential to determine the degree of connectivity between the injection wells and the producing wells. To analyze the tracer return profiles quantitatively, we employed three mathematical models namely, the convection-dispersion (CD) model, matrix diffusion (MD) model, and the Avodnin (AD) model, which were developed to study tracer and heat transport in a single vertical fracture. We considered three types of tracer tests namely, interwell tracer tests without recirculation, interwell tracer tests with recirculation, and injection-backflow tracer tests. To estimate the model parameters, we used a nonlinear regression program to match tracer return profiles to the solutions.

  4. Short communication: Use of a portable, automated, open-circuit gas quantification system and the sulfur hexafluoride tracer technique for measuring enteric methane emissions in Holstein cows fed ad libitum or restricted.

    PubMed

    Dorich, C D; Varner, R K; Pereira, A B D; Martineau, R; Soder, K J; Brito, A F

    2015-04-01

    The objective of this study was to measure enteric CH4 emissions using a new portable automated open-circuit gas quantification system (GQS) and the sulfur hexafluoride tracer technique (SF6) in midlactation Holstein cows housed in a tiestall barn. Sixteen cows averaging 176 ± 34 d in milk, 40.7 ± 6.1 kg of milk yield, and 685 ± 49 kg of body weight were randomly assigned to 1 out of 2 treatments according to a crossover design. Treatments were (1) ad libitum (adjusted daily to yield 10% orts) and (2) restricted feed intake [set to restrict feed by 10% of baseline dry matter intake (DMI)]. Each experimental period lasted 22d, with 14 d for treatment adaptation and 8d for data and sample collection. A common diet was fed to the cows as a total mixed ration and contained 40.4% corn silage, 11.2% grass-legume haylage, and 48.4% concentrate on a dry matter basis. Spot 5-min measurements using the GQS were taken twice daily with a 12-h interval between sampling and sampling times advanced 2h daily to account for diurnal variation in CH4 emissions. Canisters for the SF6 method were sampled twice daily before milking with 4 local background gas canisters inside the barn analyzed for background gas concentrations. Enteric CH4 emissions were not affected by treatments and averaged 472 and 458 g/d (standard error of the mean = 18 g/d) for ad libitum and restricted intake treatments, respectively (data not shown). The GQS appears to be a reliable method because of the relatively low coefficients of variation (ranging from 14.1 to 22.4%) for CH4 emissions and a moderate relationship (coefficient of determination = 0.42) between CH4 emissions and DMI. The SF6 resulted in large coefficients of variation (ranging from 16.0 to 111%) for CH4 emissions and a poor relationship (coefficient of determination = 0.17) between CH4 emissions and DMI, likely because of limited barn ventilation and high background gas concentration. Research with improved barn ventilation systems or

  5. O-18 tracer studies of Al2O3 scale formation on NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Reddy, K. P. R.; Cooper, A. R.; Smialek, J. L.

    1982-01-01

    Diffusion processes in Al2O3 scales formed on NiCrAl + Zr alloys were studied by the proton activation technique employing the O-18 isotope as a tracer. The O-18 profiles identified a zone of oxide penetration beneath the external scale. Both this subscale formation and the outer Al2O3 scale thickness were shown by this technique to increase with Zr content in the alloy. Estimated kp's from scale thicknesses were in agreement with gravimetric measurements for various Zr levels. Alternate exposures in O-16 and O-18 revealed that oxygen inward transport was the primary growth mechanism. A qualitative analysis of these O-18 profiles indicated that the oxygen transport was primarily via short-circuit paths, such as grain boundaries.

  6. Tracer tomography (in) rocks!

    NASA Astrophysics Data System (ADS)

    Somogyvári, Márk; Jalali, Mohammadreza; Jimenez Parras, Santos; Bayer, Peter

    2016-04-01

    Physical behavior of fractured aquifers is rigorously controlled by the presence of interconnected conductive fractures, as they represent the main pathways for flow and transport. Ideally, they are simulated as a discrete fracture network (DFN) in a model to capture the role of fracture system geometry, i.e. fracture length, height, and width (aperture/transmissivity). Such network may be constrained by prior geological information or direct data resources such as field mapping, borehole logging and geophysics. With the many geometric features, however, calibration of a DFN to measured data is challenging. This is especially the case when spatial properties of a fracture network need to be calibrated to flow and transport data. One way to increase the insight in a fractured rock is by combining the information from multiple field tests. In this study, a tomographic configuration that combines multiple tracer tests is suggested. These tests are conducted from a borehole with different injection levels that act as sources. In a downgradient borehole, the tracer is recorded at different levels or receivers, in order to maximize insight in the spatial heterogeneity of the rock. As tracer here we chose heat, and temperature breakthrough curves are recorded. The recorded tracer data is inverted using a novel stochastic trans-dimensional Markov Chain Monte Carlo procedure. An initial DFN solution is generated and sequentially modified given available geological information, such as expected fracture density, orientation, length distribution, spacing and persistency. During this sequential modification, the DFN evolves in a trans-dimensional inversion space through adding and/or deleting fracture segments. This stochastic inversion algorithm requires a large number of thousands of model runs to converge, and thus using a fast and robust forward model is essential to keep the calculation efficient. To reach this goal, an upwind coupled finite difference method is employed

  7. The Transient Tracers in the Ocean (TTO) program: The North Atlantic Study, 1981; The Tropical Atlantic Study, 1983

    NASA Astrophysics Data System (ADS)

    Brewer, Peter G.; Sarmiento, Jorge L.; Smethie, William M.

    1985-01-01

    The scientific papers here collected result from the Transient Tracers in the Ocean (TTO) program. The two parts of this major geochemical and physical oceanographie expedition took place in the North Atlantic Ocean in 1981 and in the Tropical Atlantic in 1983 on the research vessel Knorr of the Woods Hole Oceanographie Institution. The expeditions, sponsored by the National Science Foundation and the U.S. Department of Energy (North Atlantic only), were designed to observe the passage of man-made geochemical tracers into the interior of the ocean. The foundations for such an experiment were laid in the 1972-1978 GEOSECS program. Here, for the first time, a systematic survey revealed the penetration into the thermocline and deep ocean of the products of man's military/industrial activities, principally tritium and carbon-14 resulting from atmospheric testing of nuclear weapons, which terminated with the nuclear test ban treaty in 1962.

  8. On the use of flow-storage repartitions derived from artificial tracer tests for geothermal reservoir characterization in the Malm-Molasse basin: a theoretical study

    NASA Astrophysics Data System (ADS)

    Dewi, Dina Silvia; Osaigbovo Enomayo, Augustine; Mohsin, Rizwan; Karmakar, Shyamal; Ghergut, Julia; Sauter, Martin

    2016-04-01

    needed to calculate FSR. Looking at the Sauerlach example, we find that premature interruption of tracer sampling systematically leads to overestimating the reservoir's storage capacity and underestimating its flow capacity, with misestimation generally increasing as the bedded/reef interfacial area per volume is increased. It is interesting to correlate these findings with the tracer-based approach to facies identification for the shallower Malm aquifers of the Southern Franconian Alb, proposed by Seiler et al. (1989, 1995) and with expectations from the direct (i. e., distributed-parameter) modeling of matrix-diffusive effects (Maloszewski and Zuber 1985) on measured tracer signals. References: Maloszewski P, Zuber A (1985) On the theory of tracer experiments in fissured rocks with a porous matrix, Journal of Hydrology, 79, 333-358 Seiler K-P, Behrens H, Wolf M (1995) Use of artificial and environmental tracers to study storage and drainage of groundwater in the Franconian Alb, Germany, and the consequences for groundwater protection, Proc Isotopes in Water Resources Management, 2, 135-146 (IAEA, Vienna) Seiler K-P, Maloszewski P, Behrens H (1989) Hydrodynamic dispersion in karstified limestones and dolomites in the Upper Jurassic of the Franconian Alb, FRG, Journal of Hydrology, 108, 235-247 Shook G M (2003) A Simple, Fast Method of Estimating Fractured Reservoir Geometry from Tracer Tests, Geothermal Resources Council Transactions, 27, 407-411 Financial support from the German Federal Ministry for Economic Affairs and Energy is gratefully acknowledged. - Gefördert durch BMWi aufgrund eines Beschlusses des Deutschen Bundestages (FKZ 0325515 "TRENDS").

  9. INL Tracer Interpretation

    SciTech Connect

    2007-03-27

    This spreadsheet application is for tracer test analysis. The analyses are based on the first temporal moment of a tracer. The governing equations are briefly discussed, and the individual steps required of the user are outlined. A series of Excel macros written in Visual Basic calculate mean residence time, swept pore volume, and flow-storage geometry from a tracer history.

  10. Study of Gas Solid Flow Characteristics in Cyclone Inlet Ducts of A300Mwe CFB Boiler

    NASA Astrophysics Data System (ADS)

    Tang, J. Y.; Lu, X. F.; Lai, J.; Liu, H. Z.

    Gas solid flow characteristics in cyclone's inlet duct of a 300MW CFB boiler were studied in a cold circulating fluidized bed (CFB) experimental setup according to a 410t/h CFB boiler with a scale of 10∶1. Tracer particles were adopted in the experiment and their motion trajectories in the two kinds of cyclone's inlet ducts were photographed by a high-speed camera. By analyzing the motion trajectories of tracer particles, acceleration performance of particle phases in the two inlet ducts was obtained. Results indicate that the acceleration performance of particles in the long inlet duct is better than that in the short inlet duct, but the pressure drop of the long inlet duct is higher. Meanwhile, under the same operating conditions, both the separation efficiency and the pressure drop of the cyclone are higher when the cyclone is connected with the long inlet duct. Figs 11, Tabs 4 and refs 10.

  11. Tracer tests in geothermal resource management

    NASA Astrophysics Data System (ADS)

    Axelsson, G.

    2013-05-01

    Geothermal reinjection involves injecting energy-depleted fluid back into geothermal systems, providing an effective mode of waste-water disposal as well as supplementary fluid recharge. Cooling of production boreholes is one of the main disadvantages associated with reinjection, however. Tracer testing is an important tool for reinjection studies because tracer tests actually have a predictive power since tracer transport is orders of magnitude faster than cold-front advancement around reinjection boreholes. A simple and efficient method of tracer test interpretation, assuming specific flow channels connecting reinjection and production boreholes, is available. It simulates tracer return profiles and estimates properties of the flow channels, which are consequently used for predicting the production borehole cooling. Numerous examples are available worldwide on the successful application of tracer tests in geothermal management, many involving the application of this interpretation technique. Tracer tests are also used for general subsurface hydrological studies in geothermal systems and for flow rate measurements in two-phase geothermal pipelines. The tracers most commonly used in geothermal applications are fluorescent dyes, chemical substances and radioactive isotopes. New temperature-resistant tracers have also been introduced and high-tech tracers are being considered.

  12. The effect of wind and currents on gas exchange in an estuarine system

    NASA Technical Reports Server (NTRS)

    Broecker, W. S.; Ledwell, J. R.; Bopp, R.

    1987-01-01

    The objectives were to develop a non-volatile tracer to use in gas exchange experiments in laterally unconfined systems and to study applications of deliberate tracers in limnology and oceanography. Progress was made on both fronts but work on the development of the non-volatile tracer proved to be more difficult and labor intensive that anticipated so no field experiments using non-volatile tracers was performed as yet. In the search for a suitable non-volatile tracer for an ocean scale gas exchange experiment a tracer was discovered which does not have the required sensitivity for a large scale experiment, but is very easy to analyze and will be well suited for smaller experiments such as gas exchange determinations on rivers and streams. Sulfur hexafluoride, SF6, was used successfully as a volatile tracer along with tritium as a non-volatile tracer to study gas exchange rates from a primary stream. This is the first gas exchange experiment in which gas exchange rates were determined on a head water stream where significant groundwater input occurs along the reach. In conjunction with SF6, Radon-222 measurements were performed on the groundwater and in the stream. The feasibility of using a combination of SF6 and radon is being studied to determine groundwater inputs and gas exchange of rates in streams with significant groundwater input without using a non-volatile tracer.

  13. A field tracer study of attenuation of atrazine, hexazinone and procymidone in a pumice sand aquifer.

    PubMed

    Pang, L; Close, M E

    2001-12-01

    A field tracer experiment, simulating point source contamination, was conducted to investigate attenuation and transport of atrazine, hexazinone and procymidone in a volcanic pumice sand aquifer. Preliminary laboratory incubation tests were also carried out to determine degradation rates. Field transport of the pesticides was observed to the significant under non-equilibrium conditions. Therefore, a two-region/two-site non-equilibrium transport model, N3DADE, was used for analysis of the field data. A lump reduction rate constant was used in this paper to encompass all the irreversible reduction processes (e.g. degradation, irreversible adsorption, complexation and filtration for the pesticides adsorbed into particles and colloids) which are assumed to follow a first-order rate law. Results from the field experiment suggest that (a) hexazinone was the most mobile (retardation factor R = 1.4) and underwent least mass reduction; (b) procymidone was the least mobile (R = 9.26) and underwent the greatest mass reduction; (c) the mobility of atrazine (R = 4.45) was similar to that of rhodamine WT (R = 4.10). Hence, rhodamine WT can be used to delimit the appearance of atrazine in pumice sand groundwater. Results from the incubation tests suggest that (a) hexazinone was degraded only in the mixture of groundwater and aquifer material (degradation rate constant = 4.36 x 10(-3) day-1); (b) procymidone was degraded not only in the mixture of groundwater and aquifer material (rate constant = 1.12 x 10(-2) day-1) but also in the groundwater alone (rate constant = 2.79 x 10(-2) and-1); (c) atrazine was not degraded over 57 days incubation in either the mixture of aquifer material and groundwater or the groundwater alone. Degradation rates measured in the batch tests were much lower than the total reduction rates. This suggests that not only degradation but also other irreversible processes are important in attenuating pesticides under field conditions. Hence, the use of

  14. The Reanalysis for Stratospheric Trace-gas Studies

    NASA Technical Reports Server (NTRS)

    Pawson, Steven; Li, Shuhua

    2002-01-01

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

  15. Kinetic measurements of bone mineral metabolism: The use of Na-22 as a tracer for long-term bone mineral turnover studies

    NASA Technical Reports Server (NTRS)

    Palmer, H. E.

    1978-01-01

    Sodium-22 was studied as a tracer for bone mineral metabolism in rats and dogs. When incorporated into bone during growth from birth to adulthood, the bone becomes uniformly tagged with (22)Na which is released through the metabolic turnover of the bone. The (22)Na which is not incorporated in the bone matrix is rapidly excreted within a few days when animals are fed high but nontoxic levels of NaCl. The (22)Na tracer can be used to measure bone mineral loss in animals during space flight and in research on bone disease.

  16. Using Tracer Technology to Characterize Contaminated Pipelines

    SciTech Connect

    Maresca, Joseph, W., Jr., Ph.D.; Bratton, Wesley, L., Ph.D., P.E.; Dickerson, Wilhelmina; Hales, Rochelle

    2005-12-30

    The Pipeline Characterization Using Tracers (PCUT) technique uses conservative and partitioning, reactive or other interactive tracers to remotely determine the amount of contaminant within a run of piping or ductwork. The PCUT system was motivated by a method that has been successfully used to characterize subsurface soil contaminants and is similar in operation to that of a gas chromatography column. By injecting a ?slug? of both conservative and partitioning tracers at one end (or section) of the piping and measuring the time history of the concentration of the tracers at the other end (or another section) of the pipe, the presence, location, and amount of contaminant within the pipe or duct can be determined. The tracers are transported along the pipe or duct by a gas flow field, typically air or nitrogen, which has a velocity that is slow enough so that the partitioning tracer has time to interact with the contaminant before the tracer slug completely passes over the contaminate region. PCUT not only identifies the presence of contamination, it also can locate the contamination along the pipeline and quantify the amount of residual. PCUT can be used in support of deactivation and decommissioning (D&D) of piping and ducts that may have been contaminated with hazardous chemicals such as chlorinated solvents, petroleum products, radioactive materials, or heavy metals, such as mercury.

  17. Microanalytical isotope ratio measurements and elemental mapping using laser ablation ICP-MS for tissue thin sections: zinc tracer studies in rats.

    PubMed

    Urgast, Dagmar S; Ou, Ou; Gordon, Margaret-Jane; Raab, Andrea; Nixon, Graeme F; Kwun, In-Sook; Beattie, John H; Feldmann, Jörg

    2012-01-01

    The kinetics of zinc absorption, metabolism and excretion is extensively studied by nutritionists. Stable isotopes of zinc can be used to identify body zinc compartments that have different turnover kinetics. Since the compartments might belong to physiological subsections of different organs, there is a need for microsampling analysis to determine isotope ratios of the trace element zinc in tissue samples. Here, we study the feasibility to use laser ablation coupled to quadrupole ICP-MS for the determination of zinc tracers given to rats at different time points with the aim to generate isotope ratio bioimages of heart tissue. A double tracer ((70)Zn and (67)Zn) experiment with rats was designed to label the exchangeable zinc pool as well as the stable zinc pool. The isotope ratios determined by laser ablation ICP-MS were evaluated by additional measurements of tissue digests. Accumulated tracers which made up more than 0.1% of total zinc could be identified in the tissues of the treated rats. It was established that at least 50 measurements from the microsampling were necessary to distinguish between controls and a tracer treated rat resulting in reduced resolution of the bioimage. With the parameters used, features in the tissue thin sections of at least 250 μm(2) in size are necessary to detect the incorporation of a tracer. When different time points have to be measured, higher precisions are required and therefore a larger area needs to be ablated (1 mm(2)). Using the bioimages and pool measurements from one physiological feature, it was possible to show that the aorta cell walls incorporate the zinc tracer at the different time points.

  18. NPS Gas Gun for Planar Impact Studies

    NASA Astrophysics Data System (ADS)

    Cheong Ho, Chien; Hixson, Robert

    2009-11-01

    The Naval Postgraduate School (NPS) commissioned a Gas Gun for shock wave studies on 9^th October 2009, by performing the first experiment. The Gas Gun is the key element of NPS Shock Wave Research Program within the Physics Department, where well-characterized planar impacts are essential for obtaining high quality data, to characterize a solid material. This first experiment was very successful, and returned key data on the quality of the impact conditions created. The Gas Gun is designed by SANDIA NATIONAL LABORATORIES, and the NPS spent twelve months fabricating the components of the Gas Gun and six months assembling the Gas Gun. Three inch projectile are launched at velocities up to 0.5 km/s, creating high pressure and temperature states that can be used to characterize the fundamental response of relevant materials to dynamic loading. The projectile is launched from a `wrap around' gas breech where helium gas is pressurized to relatively low pressure. This gas is used to accelerate the projectile down a 3m barrel. Upon impact, the speed of the projectile and the flatness of the impact is measured, via a stepped circular pin array circuit. The next stage of development for the Gas Gun is to integrate a Velocity Interferometer System for Any Reflector (VISAR). The VISAR sees all the waves that flow through the target plate as a result of the impact. This is a key diagnostic for determining material properties under dynamic loading conditions.

  19. Fluorescence characteristics of the fuel tracers triethylamine and trimethylamine for the investigation of fuel distribution in internal combustion engines.

    PubMed

    Lind, Susanne; Aßmann, Simon; Zigan, Lars; Will, Stefan

    2016-03-01

    Laser-induced fluorescence based on fuel tracers like amines is a suitable measurement technique for mixing studies in internal combustion (IC) engines. Triethylamine has often been used in gasoline IC engines; however, no detailed fluorescence characterization for excitation at 263 or 266 nm is available. Trimethylamine (TMA) exhibits high potential as a gaseous fuel tracer but little information about TMA fluorescence is currently available. A picosecond laser source combined with a streak camera equipped with a spectrograph was used to determine the spectral fluorescence emission and fluorescence decay time of both tracers. The tracers were investigated at various temperatures and pressures in a calibration cell with nitrogen as bath gas. The results provide an in-depth understanding of the fluorescence characteristics of both tracers and allow assessment of their application to the investigation of fuel distribution in IC engines.

  20. A CFD study of gas-solid jet in a CFB riser flow

    SciTech Connect

    Li, Tingwen; Guenther, Chris

    2012-03-01

    Three-dimensional high-resolution numerical simulations of a gas–solid jet in a high-density riser flow were conducted. The impact of gas–solid injection on the riser flow hydrodynamics was investigated with respect to voidage, tracer mass fractions, and solids velocity distribution. The behaviors of a gas–solid jet in the riser crossflow were studied through the unsteady numerical simulations. Substantial separation of the jetting gas and solids in the riser crossflow was observed. Mixing of the injected gas and solids with the riser flow was investigated and backmixing of gas and solids was evaluated. In the current numerical study, both the overall hydrodynamics of riser flow and the characteristics of gas–solid jet were reasonably predicted compared with the experimental measurements made at NETL.

  1. Flammable Gas Safety Self-Study 52827

    SciTech Connect

    Glass, George

    2016-03-17

    This course, Flammable Gas Safety Self-Study (COURSE 52827), presents an overview of the hazards and controls associated with commonly used, compressed flammable gases at Los Alamos National Laboratory (LANL).

  2. Evaluating the accretion of meteoritic debris and interplanetary dust particles in the GPC-3 sediment core using noble gas and mineralogical tracers

    NASA Astrophysics Data System (ADS)

    Darrah, Thomas H.; Poreda, Robert J.

    2012-05-01

    Extraterrestrial (ET) noble gases (helium and neon) in 35 sediment samples from Central Pacific core LL-44 GPC-3 demonstrate the variable flux of interplanetary dust particles (IDPs) and major meteorite impacts over the past 70 Ma (21-72 Ma). Spinel mineralogical and chemical compositions clearly distinguish major impact events from the continuous flux of IDPs, including the well-established Cretaceous/Tertiary (K/T) and late Eocene (E/O) impact boundaries. No spinel grains with chemical or mineralogical evidence of a distinctly ET origin were found in an extensive survey of 'background' samples (i.e. non E/O or K/T boundary) suggesting that either the carrier grains for ET noble gas occur within the Fe-Ti oxide mineral fraction observed in this study (found to include ilmenite and ulvospinel) or are too small for identification by SEM. The presence of ilmenite and ulvospinel suggest lunar regolith is a potential source for ET noble gas-rich particles. Noble gas analysis on both the EMF (extractable magnetic fraction) and the Bulk minus EMF (Bulk - EMF) show that the He and Ne compositions are consistent with partially degassed noble gas signatures of zero-age magnetic grains (Z-MAG) and stratospheric interplanetary dust particles (IDPs). Conclusive evidence for a 'planetary' (Ne-A) noble gas signature is found only in the bulk sediments at the K/T boundary, although all GPC-3 K/T fractions (Bulk, EMF, and HF Digestion) plot along a mixing line between planetary (Ne-A) and solar wind (SW). Spinels from major impact boundaries (K/T; E/O) exhibit dendritic texture and elevated [Ni], consistent with previous reports. In contrast to the otherwise consistent [3He] signal from IDPs, the [3He] at the known impact boundaries (K/T and E/O) actually decreases. These anomalously low [3He] are accompanied by significantly elevated [Ne] and significantly lower (3He/20Ne)solar ratios (˜10× lower) produced by both preferentially degassing of He relative to Ne at times of

  3. Results from air-injection and tracer testing in the Upper Tiva Canyon, Bow Ridge Fault, and upper Paintbrush contact alcoves of the Exploratory Studies Facility, August 1994 through July 1996, Yucca Mountain, Nevada

    SciTech Connect

    LeCain, G.D.

    1998-09-01

    The Yucca Mountain Project is a US Department of Energy (DOE) scientific study to evaluate the potential for geologic disposal of high-level radioactive waste in an unsaturated-zone desert environment. The US Geological Survey (USGS) has been conducting geologic and hydrologic studies of the potential repository site for the DOE. These studies are to quantify the geologic and hydrologic characteristics of Yucca Mountain and to conceptualize and model gas and liquid flow at the potential repository site. Single-hole and cross-hole air-injection and tracer testing was conducted in alcoves located in the underground Exploratory Studies Facility (ESF) to quantify the permeability and porosity values of the fractured and unfractured volcanic rocks (tuff). The permeability and porosity of these tuffs control the movement of fluids in Yucca Mountain. Study of these parameters provides an understanding of fluid flow in the unsaturated zone, and the parameters can be used in unsaturated-zone numerical modeling to estimate fluid flux through the mountain. This report presents the results from air-injection and tracer testing conducted in the upper Tiva Canyon alcove (UTCA), the Bow Ridge Fault alcove (BRFA), and the upper Paintbrush contact alcove (UPCA) by the USGS from August 1994 through July 1996. The locations of the alcoves and their relations to the potential repository are shown in a figure.

  4. An Analysis of Whole Body Tracer Kinetics in Dynamic PET Studies With Application to Image-Based Blood Input Function Extraction

    PubMed Central

    Huang, Jian; O’Sullivan, Finbarr

    2014-01-01

    In a positron emission tomography (PET) study, the local uptake of the tracer is dependent on vascular delivery and retention. For dynamic studies the measured uptake time-course information can be best interpreted when knowledge of the time-course of tracer in the blood is available. This is certainly true for the most established tracers such as 18F-Fluorodeoxyglucose (FDG) and 15O-Water (H2O). Since direct sampling of blood as part of PET studies is increasingly impractical, there is ongoing interest in image-extraction of blood time-course information. But analysis of PET-measured blood pool signals is complicated because they will typically involve a combination of arterial, venous and tissue information. Thus, a careful appreciation of these components is needed to interpret the available data. To facilitate this process, we propose a novel Markov chain model for representation of the circulation of a tracer atom in the body. The model represents both arterial and venous time-course patterns. Under reasonable conditions equilibration of tracer activity in arterial and venous blood is achieved by the end of the PET study—consistent with empirical measurement. Statistical inference for Markov model parameters is a challenge. A penalized nonlinear least squares process, incorporating a generalized cross-validation score, is proposed. Random effects analysis is used to adaptively specify the structure of the penalty function based on historical samples of directly measured blood data. A collection of arterially sampled data from PET studies with FDG and H2O is used to illustrate the methodology. These data analyses are highly supportive of the overall modeling approach. An adaptation of the model to the problem of extraction of arterial blood signals from imaging data is also developed and promising preliminary results for cerebral and thoracic imaging studies with FDG and H2O are obtained. PMID:24770914

  5. Doublet Tracer Testing in Klamath Falls, Oregon

    SciTech Connect

    Gudmundsson, J.S.; Johnson, S.E.; Horne, R.N.; Jackson, P.B.; Culver, G.G.

    1983-12-15

    A tracer test was carried out in a geothermal doublet system to study the injection behavior of a developed reservoir known to be fractured. The doublet produces about 320 gpm of 160 F water that is used for space heating and then injected; the wells are spaced 250 ft apart. Tracer breakthrough was observed in 2 hours and 45 minutes in the production well, indicating fracture flow. However, the tracer concentrations were low and indicated porous media flow; the tracers mixed with a reservoir volume much larger than a fracture.

  6. Plant uptake of cations under nutrient limitation: An environmental tracer study using Ca/Sr and K/Rb ratios

    NASA Astrophysics Data System (ADS)

    Shi, Z.; Keller, C. K.; Stacks, D.; Grant, M.; Harsh, J. B.; Letourneau, M.; Gill, R. A.; Balogh-Brunstad, Z.; Thomashow, L.; Dohnalkova, A.

    2012-12-01

    Vascular plant growth builds soils and ecosystem nutrient capital by sequestering and partitioning atmospheric CO2 into organic matter and continental runoff and driving terrestrial water and energy balances. Plant root-system functions, e.g. nutrient mobilization and uptake, are altered by environmental stress. However, the stress-response relationships are poorly understood. Chemical tracers have potential for assessing contributions of nutrients from various nutrient pools. Our objective is to quantitatively study how varying degrees of nutrient limitation (and corresponding needs to extract base cations from mineral sources) influence Ca and K uptake functions in a plant-root-mineral system. We are studying plant-driven mineral weathering in column experiments with red pine (Pinus resinosa) seedlings. The columns contain quartz sand amended with anorthite and biotite that constitute the sole mineral sources of Ca and K. These minerals also contain known amounts of Sr and Rb, which exhibit chemical behavior similar to Ca and K, respectively. The solution source of Ca and K was varied by adding 0% (no dissolved Ca and K), 10%, 30%, or 100% of a full strength Ca and K nutrient solution through irrigation water in which both Sr and Rb concentrations were negligible. Selected columns were destructively sampled at 3, 6 and 9 months to harvest biomass and measure plant uptake of cations. We used Ca/Sr and K/Rb ratio results to estimate the contributions of Ca and K from mineral and solution sources. For the 0% nutrient treatment, the Ca/Sr and K/Rb ratios in total biomass at 3 months, compared with those in the mineral phases, suggested preferential uptake of Ca and K over Sr and Rb, respectively, and allowed us to determine uptake discrimination factors for both cations. The K/Rb ratios in total biomass increased with greater K availability in the solution source, as expected, but Ca/Sr ratios did not show any dependence on Ca availability in the solution source

  7. Biological tracer method

    DOEpatents

    Strong-Gunderson, Janet M.; Palumbo, Anthony V.

    1998-01-01

    The present invention is a biological tracer method for characterizing the movement of a material through a medium, comprising the steps of: introducing a biological tracer comprising a microorganism having ice nucleating activity into a medium; collecting at least one sample of the medium from a point removed from the introduction point; and analyzing the sample for the presence of the biological tracer. The present invention is also a method for using a biological tracer as a label for material identification by introducing a biological tracer having ice nucleating activity into a material, collecting a sample of a portion of the labelled material and analyzing the sample for the presence of the biological tracer.

  8. Biological tracer method

    DOEpatents

    Strong-Gunderson, J.M.; Palumbo, A.V.

    1998-09-15

    The present invention is a biological tracer method for characterizing the movement of a material through a medium, comprising the steps of: introducing a biological tracer comprising a microorganism having ice nucleating activity into a medium; collecting at least one sample of the medium from a point removed from the introduction point; and analyzing the sample for the presence of the biological tracer. The present invention is also a method for using a biological tracer as a label for material identification by introducing a biological tracer having ice nucleating activity into a material, collecting a sample of a portion of the labelled material and analyzing the sample for the presence of the biological tracer. 2 figs.

  9. NEXT GENERATION GAS TURBINE SYSTEMS STUDY

    SciTech Connect

    Benjamin C. Wiant; Ihor S. Diakunchak; Dennis A. Horazak; Harry T. Morehead

    2003-03-01

    Under sponsorship of the U.S. Department of Energy's National Energy Technology Laboratory, Siemens Westinghouse Power Corporation has conducted a study of Next Generation Gas Turbine Systems that embraces the goals of the DOE's High Efficiency Engines and Turbines and Vision 21 programs. The Siemens Westinghouse Next Generation Gas Turbine (NGGT) Systems program was a 24-month study looking at the feasibility of a NGGT for the emerging deregulated distributed generation market. Initial efforts focused on a modular gas turbine using an innovative blend of proven technologies from the Siemens Westinghouse W501 series of gas turbines and new enabling technologies to serve a wide variety of applications. The flexibility to serve both 50-Hz and 60-Hz applications, use a wide range of fuels and be configured for peaking, intermediate and base load duty cycles was the ultimate goal. As the study progressed the emphasis shifted from a flexible gas turbine system of a specific size to a broader gas turbine technology focus. This shift in direction allowed for greater placement of technology among both the existing fleet and new engine designs, regardless of size, and will ultimately provide for greater public benefit. This report describes the study efforts and provides the resultant conclusions and recommendations for future technology development in collaboration with the DOE.

  10. Effect of different transport observations on inverse modeling results: case study of a long-term groundwater tracer test monitored at high resolution

    PubMed Central

    Rasa, Ehsan; Foglia, Laura; Mackay, Douglas M.; Scow, Kate M.

    2014-01-01

    Conservative tracer experiments can provide information useful for characterizing various subsurface transport properties. This study examines the effectiveness of three different types of transport observations for sensitivity analysis and parameter estimation of a three-dimensional site-specific groundwater flow and transport model: conservative tracer breakthrough curves (BTCs), first temporal moments of BTCs (m1), and tracer cumulative mass discharge (Md) through control planes combined with hydraulic head observations (h). High-resolution data obtained from a 410-day controlled field experiment at Vandenberg Air Force Base, California (USA), have been used. In this experiment, bromide was injected to create two adjacent plumes monitored at six different transects (perpendicular to groundwater flow) with a total of 162 monitoring wells. A total of 133 different observations of transient hydraulic head, 1,158 of BTC concentration, 23 of first moment, and 36 of mass discharge were used for sensitivity analysis and parameter estimation of nine flow and transport parameters. The importance of each group of transport observations in estimating these parameters was evaluated using sensitivity analysis, and five out of nine parameters were calibrated against these data. Results showed the advantages of using temporal moment of conservative tracer BTCs and mass discharge as observations for inverse modeling. PMID:24672283

  11. Effect of different transport observations on inverse modeling results: case study of a long-term groundwater tracer test monitored at high resolution.

    PubMed

    Rasa, Ehsan; Foglia, Laura; Mackay, Douglas M; Scow, Kate M

    2013-11-01

    Conservative tracer experiments can provide information useful for characterizing various subsurface transport properties. This study examines the effectiveness of three different types of transport observations for sensitivity analysis and parameter estimation of a three-dimensional site-specific groundwater flow and transport model: conservative tracer breakthrough curves (BTCs), first temporal moments of BTCs (m1), and tracer cumulative mass discharge (Md) through control planes combined with hydraulic head observations (h). High-resolution data obtained from a 410-day controlled field experiment at Vandenberg Air Force Base, California (USA), have been used. In this experiment, bromide was injected to create two adjacent plumes monitored at six different transects (perpendicular to groundwater flow) with a total of 162 monitoring wells. A total of 133 different observations of transient hydraulic head, 1,158 of BTC concentration, 23 of first moment, and 36 of mass discharge were used for sensitivity analysis and parameter estimation of nine flow and transport parameters. The importance of each group of transport observations in estimating these parameters was evaluated using sensitivity analysis, and five out of nine parameters were calibrated against these data. Results showed the advantages of using temporal moment of conservative tracer BTCs and mass discharge as observations for inverse modeling.

  12. Determinants of the use of different types of health care provider in urban China: a tracer illness study of URTI.

    PubMed

    Qian, Dongfu; Lucas, Henry; Chen, Jiaying; Xu, Ling; Zhang, Yaoguang

    2010-12-01

    With the reform of urban health delivery systems in China, concern has been growing about the effect of these changes on health care demand and utilization at basic-level health institutions, especially Community Health Services Centers (CHC). Using data from the fourth China National Health Services Survey (NHSS) that was conducted in 2008, the authors conducted a tracer illness study of urban people with acute upper respiratory tract infections (URTI) to examine the factors that affect their use of different outpatient health care providers. The study addresses the observed demand for both public and private providers and is believed to be the first to attempt this for urban China. The findings indicate that overall private clinics are important sources of medical care for low consumption households, that insured patients are less likely to use private clinics and more likely to use CHC and that children are more likely to see a high-level provider. A number of other factors, including city size and severity of illness were found to play a role in determining provider utilization. We discuss the policy implications of the results in terms of meeting the health care needs of the urban population in China.

  13. Achievements and opportunities from ESF Research Networking Programme: Natural molecular structures as drivers and tracers of terrestrial C fluxes, and COST Action 639: Greenhouse gas budget of soils under changing climate and land use

    NASA Astrophysics Data System (ADS)

    Boeckx, P.; Rasse, D.; Jandl, R.

    2009-04-01

    One of the activities of the European Science Foundation (ESF, www.esf.org) is developing European scale Research Networking Programmes (RNPs). RNPs lay the foundation for nationally funded research groups to address major scientific and research infrastructure issues, in order to advance the frontiers of existing science. MOLTER (www.esf.org/molter or www.molter.no) is such an RNP. MOLTER stands for "Natural molecular structures as drivers and tracers of terrestrial C fluxes" aims at stimulating the use of isotopic and organic chemistry to study carbon stabilization and biogeochemistry in terrestrial ecosystems and soils in particular. The understanding of the formation, stabilization and decomposition of complex organic compounds in the environment is currently being revolutionized by advanced techniques in identification, quantification, and origin tracing of functional groups and individual molecules. MOLTER focuses on five major research themes: - Molecular composition and turnover time of soil organic matter; - Plant molecular structures as drivers of C stabilisation in soils; - Fire transformations of plant and soil molecular structures - Molecular markers in soils; - Dissolved organic molecules in soils: origin, functionality and transport. These research themes are covered via the following activities: - Organisation of international conferences; - Organisation of specific topical workshops; - Organisation of summer schools for PhD students; - Short- and long-term exchange grants for scientists. MOLTER is supported by research funding or performing agencies from Austria, Belgium, France, Germany, the Netherlands, Norway, Romania, Spain, Sweden, Switzerland and the United Kingdom. The ESF is also the implementing agency of COST (European Cooperation in Science and Technology, www.cost.esf.org), one of the longest-running European instruments supporting cooperation among scientists and researchers across Europe. COST Action 639 "Greenhouse gas budget of

  14. Source apportionment of atmospheric water over East Asia - a source tracer study in CAM5.1

    NASA Astrophysics Data System (ADS)

    Pan, Chen; Zhu, Bin; Gao, Jinhui; Kang, Hanqing

    2017-02-01

    The atmospheric water tracer (AWT) method is implemented in the Community Atmosphere Model version 5.1 (CAM5.1) to quantitatively identify the contributions of various source regions to precipitation and water vapour over East Asia. Compared to other source apportionment methods, the AWT method was developed based on detailed physical parameterisations, and can therefore trace the behaviour of atmospheric water substances directly and exactly. According to the simulation, the northern Indian Ocean (NIO) is the dominant oceanic moisture source region for precipitation over the Yangtze River valley (YRV) and southern China (SCN) in summer, while the north-western Pacific (NWP) dominates during other seasons. Evaporation over the South China Sea (SCS) is responsible for only 2.7-3.7 % of summer precipitation over the YRV and SCN. In addition, the Indo-China Peninsula is an important terrestrial moisture source region (annual contribution of ˜ 10 %). The overall relative contribution of each source region to the water vapour amount is similar to the corresponding contribution to precipitation over the YRV and SCN. A case study for the SCS shows that only a small part ( ≤ 5.5 %) of water vapour originates from local evaporation, whereas much more water vapour is supplied by the NWP and NIO. In addition, because evaporation from the SCS represents only a small contribution to the water vapour over the YRV and SCN in summer, the SCS mainly acts as a water vapour transport pathway where moisture from the NIO and NWP meet.

  15. Fundamental study on gas monitoring in celss

    NASA Astrophysics Data System (ADS)

    Nishi, I.; Tateishi, T.; Tomizawa, G.; Nitta, K.; Oguchi, M.

    A mass spectrometer and computer system was developed for conducting a fundamental study on gas monitoring in CELSS. Respiration and metabolism of the hamster and photosynthesis of the Spirulina were measured in a combination system consisting of a hamster chamber and a Spirulina cultivator. They are connected through a membrane gas exchanger. Some technical problems were examined. In the mass spectrometric gas monitoring, a simultaneous multi-sample measurement was developed by employing a rotating exchange valve. Long term precise measurement was obtained by employing an automatic calibration system. The membrane gas sampling probe proved to be useful for long term measurement. The cultivation rate of the Spirulina was effectively changed by controlling CO2 and light supply. The experimental results are helpful for improving the hamster-spirulina system.

  16. Fundamental study on gas monitoring in CELSS

    NASA Technical Reports Server (NTRS)

    Nishi, I.; Tateishi, T.; Tomizawa, G.; Nitta, K.; Oguchi, M.

    1987-01-01

    A mass spectrometer and computer system was developed for conducting a fundamental study on gas monitoring in a Controlled Ecological Life Support System. Respiration and metabolism of the hamster and photosynthesis of the Spirulina were measured in a combination system consisting of a hamster chamber and a Spirulina cultivator. They are connected through a membrane gas exchanger. Some technical problems were examined. In the mass spectrometric gas monitoring, a simultaneous multisample measurement was developed by employing a rotating exchange valve. Long term precise measurement was obtained by employing an automatic calibration system. The membrane gas sampling probe proved to be useful for long term measurement. The cultivation rate of the Spirulina was effectively changed by controlling CO2 and light supply. The experimental results are helpful for improving the hamster-spirulina system.

  17. Isotope tracer studies of diffusion in silicates and of geological transport processes using actinide elements

    SciTech Connect

    Wasserburg, G.J.

    1992-01-01

    The following are reported: high abundance sensitivity mass spectrometer for U-Th studies; [sup 238]U-[sup 230]Th disequilibrium in recent lavas from Iceland; water-rock interaction from U-Th studies; resonance ionization mass spectrometry of Os and Ti isotopes; and self-diffusion of Mg.

  18. High temperature gas-cooled reactor: gas turbine application study

    SciTech Connect

    Not Available

    1980-12-01

    The high-temperature capability of the High-Temperature Gas-Cooled Reactor (HTGR) is a distinguishing characteristic which has long been recognized as significant both within the US and within foreign nuclear energy programs. This high-temperature capability of the HTGR concept leads to increased efficiency in conventional applications and, in addition, makes possible a number of unique applications in both electrical generation and industrial process heat. In particular, coupling the HTGR nuclear heat source to the Brayton (gas turbine) Cycle offers significant potential benefits to operating utilities. This HTGR-GT Application Study documents the effort to evaluate the appropriateness of the HTGR-GT as an HTGR Lead Project. The scope of this effort included evaluation of the HTGR-GT technology, evaluation of potential HTGR-GT markets, assessment of the economics of commercial HTGR-GT plants, and evaluation of the program and expenditures necessary to establish HTGR-GT technology through the completion of the Lead Project.

  19. Aerosol transport and wet scavenging in deep convective clouds: A case study and model evaluation using a multiple passive tracer analysis approach

    NASA Astrophysics Data System (ADS)

    Yang, Qing; Easter, Richard C.; Campuzano-Jost, Pedro; Jimenez, Jose L.; Fast, Jerome D.; Ghan, Steven J.; Wang, Hailong; Berg, Larry K.; Barth, Mary C.; Liu, Ying; Shrivastava, Manishkumar B.; Singh, Balwinder; Morrison, Hugh; Fan, Jiwen; Ziegler, Conrad L.; Bela, Megan; Apel, Eric; Diskin, Glenn S.; Mikoviny, Tomas; Wisthaler, Armin

    2015-08-01

    Wet scavenging of aerosols by continental deep convective clouds is studied for a supercell storm complex observed over Oklahoma during the Deep Convective Clouds and Chemistry campaign. A new passive-tracer-based transport analysis framework is developed to characterize convective transport using vertical profiles of several passive trace gases. For this case, the analysis estimates that observed passive gas mixing ratios in the upper troposphere convective outflow consist of 47% low level (<3 km) inflow air, 32% entrained midtroposphere air, and 21% upper troposphere air. The new analysis framework is used to estimate aerosol wet scavenging efficiencies. Observations yield high overall scavenging efficiencies of 81% for submicron aerosol mass. Organic, sulfate, and ammonium aerosols have similar wet scavenging efficiencies (80%-84%). The apparent scavenging efficiency for nitrate aerosol is much lower (57%), but the scavenging efficiency for nitrate aerosol plus nitric acid combined (84%) is close to the other species. Scavenging efficiencies for aerosol number are high for larger particles (84% for 0.15-2.5 µm diameter) but are lower for smaller particles (64% for 0.03-0.15 µm). The storm is simulated using the chemistry version of the Weather Research and Forecasting model. Compared to the observation-based analysis, the standard model strongly underestimates aerosol scavenging efficiencies by 32% and 41% in absolute differences for submicron mass and number. Adding a new treatment of secondary activation significantly improves simulated aerosol scavenging, producing wet scavenging efficiencies that are only 7% and 8% lower than observed efficiencies. This finding emphasizes the importance of secondary activation for aerosol wet removal in deep convective storms.

  20. Aerosol transport and wet scavenging in deep convective clouds: a case study and model evaluation using a multiple passive tracer analysis approach

    SciTech Connect

    Yang, Qing; Easter, Richard C.; Campuzano-Jost, Pedro; Jimenez, Jose L.; Fast, Jerome D.; Ghan, Steven J.; Wang, Hailong; Berg, Larry K.; Barth, Mary; Liu, Ying; Shrivastava, ManishKumar B.; Singh, Balwinder; Morrison, H.; Fan, Jiwen; Ziegler, Conrad L.; Bela, Megan; Apel, Eric; Diskin, G. S.; Mikoviny, Tomas; Wisthaler, Armin

    2015-08-20

    The effect of wet scavenging on ambient aerosols in deep, continental convective clouds in the mid-latitudes is studied for a severe storm case in Oklahoma during the Deep Convective Clouds and Chemistry (DC3) field campaign. A new passive-tracer based transport analysis framework is developed to characterize the convective transport based on the vertical distribution of several slowly reacting and nearly insoluble trace gases. The passive gas concentration in the upper troposphere convective outflow results from a mixture of 47% from the lower level (0-3 km), 21% entrained from the upper troposphere, and 32% from mid-atmosphere based on observations. The transport analysis framework is applied to aerosols to estimate aerosol transport and wet-scavenging efficiency. Observations yield high overall scavenging efficiencies of 81% and 68% for aerosol mass (Dp < 1μm) and aerosol number (0.03< Dp < 2.5μm), respectively. Little chemical selectivity to wet scavenging is seen among observed submicron sulfate (84%), organic (82%), and ammonium (80%) aerosols, while nitrate has a much lower scavenging efficiency of 57% likely due to the uptake of nitric acid. Observed larger size particles (0.15 - 2.5μm) are scavenged more efficiently (84%) than smaller particles (64%; 0.03 - 0.15μm). The storm is simulated using the chemistry version of the WRF model. Compared to the observation based analysis, the standard model underestimates the wet scavenging efficiency for both mass and number concentrations with low biases of 31% and 40%, respectively. Adding a new treatment of secondary activation significantly improves simulation results, so that the bias in scavenging efficiency in mass and number concentrations is reduced to <10%. This supports the hypothesis that secondary activation is an important process for wet removal of aerosols in deep convective storms.

  1. NOAA EPA Near-Roadway Sound Barrier Atmospheric Tracer Study 2008

    EPA Science Inventory

    A roadway toxics dispersion study was conducted at the Idaho National Laboratory to document the effects on concentrations of roadway emissions behind a roadside sound barrier in various conditions of atmospheric stability. The key finding was that reduced concentrations were me...

  2. Coupling Cover Crops with Alternative Swine Manure Application Strategies: Manure-15N Tracer Studies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Integration of rye cover crops with alternative liquid swine (Sus scrofa L.) manure application strategies may enhance retention of manure N in corn (Zea mays L.) - soybean [Glycine max (L.) Merr] cropping systems. The objective of this study was to quantify uptake of manure derived-N by a rye (Seca...

  3. Interpreting Multiple Environmental Tracer Data in a Perialpine Catchment

    NASA Astrophysics Data System (ADS)

    Onnis, G. A.; Althaus, R.; Klump, S.; Purtschert, R.; Kipfer, R.; Hendricks-Franssen, H.; Stauffer, F.; Kinzelbach, W.

    2008-12-01

    A case study for the environmental tracers Tritium, Helium-3 and Krypton-85 in a small sand-gravel aquifer catchment in Northern Switzerland is presented. The groundwater flow is determined by means of Stochastic Inverse Modelling, using available transient hydraulic head and transmissivity (T) data to calibrate the transmissivity field with the Sequential Self-Calibration Technique as implemented in the code INVERTO. The evaluation of the aquifer recharge and its discharge via natural springs is independently performed and confirmed through comparison of simulated and observed head after the inversion procedure. A number of equally-likely transmissivity field realizations honoring both transmissivity and transient head measurements is generated, establishing the basis for environmental tracer transport modeling. The impact of the spatially-variable, thick unsaturated zone (>10 m) on tracer transport is accounted for by means of a numerical solution to the vertical advection-dispersion equation. Starting from the measured tracer concentrations in the atmosphere, the input history to the saturated zone is reconstructed for different groundwater table depths. Environmental tracer transport in the saturated zone is investigated for each calibrated T -realization. The transport simulation results are in general fair for all tracers and can well reproduce the tracer data at most observation locations, with a small uncertainty bandwidth related to the T -parameter. Ad-hoc zonation of transport parameters (vadose zone gas-phase tortuosity and saturated porosity) can help in achieving a simultaneous match of the tracer data at all locations. However, the model can account for only 20% of the amplitude of the high-frequency oscillations in Krypton-85 concentrations observed at one pumping station. Short term variations of the recharge rate and of the actual pumping rate can account for a further 10% each to the Krypton-85 concentration fluctuations amplitudes. The origin of

  4. Isotope Tracer Studies of Diffusion in Sillicates and of Geological Transport Processes Using Actinide Elements

    SciTech Connect

    Wasserburg, Gerald J

    2008-07-31

    The objectives were directed toward understanding the transport of chemical species in nature, with particular emphasis on aqueous transport in solution, in colloids, and on particles. Major improvements in measuring ultra-low concentrations of rare elements were achieved. We focused on two areas of studies: (1) Field, laboratory, and theoretical studies of the transport and deposition of U, Th isotopes and their daughter products in natural systems; and (2) Study of calcium isotope fractionation effects in marine carbonates and in carbonates precipitated in the laboratory, under controlled temperature, pH, and rates of precipitation. A major study of isotopic fractionation of Ca during calcite growth from solution has been completed and published. It was found that the isotopic shifts widely reported in the literature and attributed to biological processes are in fact due to a small equilibrium fractionation factor that is suppressed by supersaturation of the solution. These effects were demonstrated in the laboratory and with consideration of the solution conditions in natural systems, where [Ca{sup 2+}] >> [CO{sub 3}{sup 2-}] + [HCO{sub 3}{sup -}]. The controlling rate is not the diffusion of Ca, as was earlier proposed, but rather the rate of supply of [CO{sub 3}{sup 2-}] ions to the interface. This now opens the issues of isotopic fractionation of many elements to a more physical-chemical approach. The isotopic composition of Ca {Delta}({sup 44}Ca/{sup 40}Ca) in calcite crystals has been determined relative to that in the parent solutions by TIMS using a double spike. Solutions were exposed to an atmosphere of NH{sub 3} and CO{sub 2}, provided by the decomposition of (NH4)2CO3. Alkalinity, pH, and concentrations of CO{sub 3}{sup 2-}, HCO{sub 3}{sup -}, and CO{sub 2} in solution were determined. The procedures permitted us to determine {Delta}({sup 44}Ca/{sup 40}Ca) over a range of pH conditions, with the associated ranges of alkalinity. Two solutions with

  5. Magnetofossils as tracers of oxygenation change: a case study from the stratified Pettaquamscutt River Estuary

    NASA Astrophysics Data System (ADS)

    Chen, A. P.; Berounsky, V. M.; Chan, M. K.; Moskowitz, B. M.; Andrade Lima, E.; Kopp, R. E.; Cady, C.; Weiss, B. P.; Hesse, P. P.

    2013-12-01

    Magnetotactic bacteria (MB) are motile organisms commonly found around the oxic-anoxic-interface (OAI) in sediments and stratified water columns. Magnetite and greigite crystals synthesized by MB intracellularly, termed magnetosomes, can be preserved in sediments as magnetofossils. Changes in OAI thickness (due to changes in temperature, clathrate dissociation & methane oxidation, organic carbon supply/oxidation, or sedimentation rate) would produce proportional changes in MB population and sedimentary magnetofossil concentration. While potentially useful as an oxygenation proxy, magnetofossil quantification techniques and variables controlling their preservation in sediments need to be better understood. Most prior work focused on cultured magnetite-MB and sediment mixtures while studies of greigite-MB (found just below the OAI in the sulfidic hypolimnion) is lacking because axenic cultures do not exist. To address these issues, we study wild magnetite- and greigite-MB from the seasonally stratified Pettaquamscutt River Estuary Upper Basin (RI, USA) as a function of water depth, d. Transmission electron microscope imaging of 21 MB (377 magnetosomes) revealed a complexity in wild MB not found in cultures. From d=3.9 m-7.0 m, live-cell assays confirmed the presence of multiple MB morphotypes, both north- (majority) and south-seeking (minority), and a few magnetic protists. Based on a previous microscopy study just 1.4 km south of Upper Basin (Bazylinski et al., 1995), magnetite-MB are expected for d<5.0 m, mix magnetite- and greigite-MB for 5.0 m6.0 m. Coercivity distributions for all depths are characterized by a small variance, reflecting uniformity in magnetosome size. Interestingly, despite changing from dominant magnetite to greigite-MB with increasing depth, the median coercivity remained largely unchanged. Median coercivity is therefore not diagnostic of magnetosome mineralogy. We also report ferromagnetic resonance

  6. Tracer study of batch sedimentation. [Resin beads - 45 and 62. mu. m in diameter

    SciTech Connect

    Bigot, P.C.; Lee, A.H.

    1982-04-01

    The initial particle-concentration profile in batch settling tests was assessed and determined to be uniform. Two sets of data for batch-settling tests using cobalt-57-traced ion-exchange resin beads (45 and 62 ..mu..m in diameter) were compared with existing theories and models. A single suspended-solids zone was observed in agreement with the predictions of Dixon; the Richardson-Zaki correlation predicted the settling velocity as a function of void fraction to within 5%. Studies with a bimodal particle-size distribution of equal fraction of 45- and 62-..mu..m particles showed that the larger particles settled at the same velocity as in a single-particle-size distribution but that the smaller ones settled slower than for a single-particle-size distribution at a given void fraction. The ratio of the settling velocity of the smaller particles in a bimodal-particle-size distribution u/sub b/ to the settling velocity of these particles in a single particle-size distribution u/sub s/ was correlated by raising to the (3.78 +- 0.47) power the effective void fraction of the resulting upper settling zone containing only the smaller particles.

  7. A hydrological tracer study of water uptake depth in a Scots pine forest under two different water regimes.

    PubMed

    Plamboeck, A H; Grip, H; Nygren, U

    1999-05-01

    Little is known about the vertical distribution of water uptake by trees under different water supply regimes, the subject of this study, conducted in a Scots pine stand on sandy loam in northern Sweden. The objective was to determine the water uptake distribution in pines under two different water regimes, desiccation (no precipitation) and irrigation (2 mm day(-1) in July and 1 mm day(-1) in August), and to relate the uptake to water content, root and soil texture distributions. The natural (18)O gradient in soil water was exploited, in combination with two added tracers, (2)H at 10 cm and (3)H at 20 cm depth. Extraction of xylem sap and water from the soil profile then enabled evaluation of relative water uptake from four different soil depths (humus layer, 0-10, 10-25 and 25-55 cm) in each of two 50-m(2) plots per treatment. In addition, water content, root biomass and soil texture were determined. There were differences in vertical water uptake distribution between treatments. In July, the pines at the irrigated and desiccated plots took up 50% and 30%, respectively, of their water from the upper layers, down to 25 cm depth. In August, the pines on the irrigated plots took up a greater proportion of their water from layers below 25 cm deep than they did in July. In a linear regression, the mean hydraulic conductivity for each mineral soil horizon explained a large part of the variation in relative water uptake. No systematic variation in the residual water uptake correlated to the root distribution. It was therefore concluded that the distribution of water uptake by the pines at Åheden was not a function of root density in the mineral soil, but was largely determined by the unsaturated hydraulic conductivity.

  8. Monitoring High Velocity Salt Tracer via 4D Electrical Resistivity Tomography - Possibility for Salt Tracer Tomography

    NASA Astrophysics Data System (ADS)

    Doro, K. O.; Cirpka, O. A.; Patzelt, A.; Leven, C.

    2014-12-01

    Hydrogeological testing in a tomographic sequence as shown by the use of hydraulic tomography, allows an improvement of the spatial resolution of subsurface parameters. In this regard, recent studies show increasing interest in tracer tomography which involves sequential and spatially separated tracer injections and the measurement of their corresponding tracer breakthrough at different locations and depths. Such concentration measurements however require large experimental efforts and can be simplified by geophysical tracer monitoring techniques such as electrical resistivity. In this study, we present the use of 4-D, cross-hole electrical resistivity tomography (ERT) for monitoring salt tracer experiments in high velocity flow fields. For our study, we utilized a set up that enables the conduction of salt tracer experiments with complete recovery within 84 hours over a transport distance of 16 m. This allows the repetition of the experiments with different injection depths for a tomographic salt tracer testing. For ERT monitoring, we designed modular borehole electrodes for repeated usage in a flexible manner. We also assess the use of a high speed resistivity data acquisition mode for field scale tracer monitoring ensuring high spatial and temporal resolution without sacrificing data accuracy. We applied our approach at the Lauswiesen test site, Tübingen, Germany. In our 10 m × 10 m tracer monitoring domain with 16 borehole electrodes, we acquired 4650 data points in less than 18 minutes for each monitoring cycle. Inversion results show that the tracer could be successfully imaged using this approach. The results show that repeated salt tracer tests can be efficiently monitored at a high resolution with ERT which gives the possibility for salt tracer tomography at field scale. Our results also provide a data base for extending current hydrogeophysical inversion approaches to field scale data.

  9. Tracers in rainfall simulation experiments to study the onset of the wet season in Eastern Mediterranean limestone environments

    NASA Astrophysics Data System (ADS)

    Lange, Jens

    2010-05-01

    from adjacent rocky areas. Once the plot was saturated, 80-90% of the applied rainfall became surface runoff. About 14% of the flow collected during the second day originated from water applied during the first day. Both water sources obviously mixed in saturated soil reservoirs and contributed in variable percentages to surface flow. The second plot was located above a karstic cave. Additionally to soil moisture and surface runoff, the drip response of cave stalactites was measured. This time electrical conductivity and bromide were used to study recharge processes, water origin and mixing inside a 28 m vadose zone. Bromide tracing allowed identification of quick direct flow paths. Under dry preconditions, 80 mm of artificial rainfall applied in less than seven hours was not enough to initiate significant downward water percolation. Most water was required to fill uppermost soil and rock storages. During the second day of sprinkling, higher water contents in soils and karst cavities facilitated piston flow effects and a more intense response of the cave drips. Both experiments yielded point estimates for seasonal thresholds of runoff generation and groundwater recharge. The filling of the unsaturated zone, including soil and rock storages, was found to be an important precondition for the onset of surface runoff and groundwater recharge. By mixing analysis, continuously applied tracers identified the dominating processes: saturation excess overland flow for runoff generation and piston flow for water percolation. Overall, a higher seasonal threshold for water percolation than for the generation of surface runoff was found.

  10. Surface studies of gas sensing metal oxides.

    PubMed

    Batzill, Matthias; Diebold, Ulrike

    2007-05-21

    The relation of surface science studies of single crystal metal oxides to gas sensing applications is reviewed. Most metal oxide gas sensors are used to detect oxidizing or reducing gases and therefore this article focuses on surface reduction processes and the interaction of oxygen with these surfaces. The systems that are discussed are: (i) the oxygen vacancy formation on the surface of the ion conductor CeO(2)(111); (ii) interaction of oxygen with TiO(2) (both adsorption processes and the incorporation of oxygen into the TiO(2)(110) lattice are discussed); (iii) the varying surface composition of SnO(2)(101) and its consequence for the adsorption of water; and (iv) Cu modified ZnO(0001)-Zn surfaces and its interaction with oxygen. These examples are chosen to give a comprehensive overview of surface science studies of different kinds of gas sensing materials and to illustrate the potential that surface science studies have to give fundamental insight into gas sensing phenomena.

  11. Tracer attenuation in groundwater

    NASA Astrophysics Data System (ADS)

    Cvetkovic, Vladimir

    2011-12-01

    The self-purifying capacity of aquifers strongly depends on the attenuation of waterborne contaminants, i.e., irreversible loss of contaminant mass on a given scale as a result of coupled transport and transformation processes. A general formulation of tracer attenuation in groundwater is presented. Basic sensitivities of attenuation to macrodispersion and retention are illustrated for a few typical retention mechanisms. Tracer recovery is suggested as an experimental proxy for attenuation. Unique experimental data of tracer recovery in crystalline rock compare favorably with the theoretical model that is based on diffusion-controlled retention. Non-Fickian hydrodynamic transport has potentially a large impact on field-scale attenuation of dissolved contaminants.

  12. Synthesis, characterization, and monkey positron emission tomography (PET) studies of [18F]Y1-973, a PET tracer for the neuropeptide Y Y1 receptor.

    PubMed

    Hostetler, Eric D; Sanabria-Bohórquez, Sandra; Fan, Hong; Zeng, Zhizhen; Gantert, Liza; Williams, Mangay; Miller, Patricia; O'Malley, Stacey; Kameda, Minoru; Ando, Makoto; Sato, Nagaaki; Ozaki, Satoshi; Tokita, Shigeru; Ohta, Hisashi; Williams, David; Sur, Cyrille; Cook, Jacquelynn J; Burns, H Donald; Hargreaves, Richard

    2011-02-14

    Neuropeptide Y receptor subtype 1 (NPY Y1) has been implicated in appetite regulation, and antagonists of NPY Y1 are being explored as potential therapeutics for obesity. An NPY Y1 PET tracer is useful for determining the level of target engagement by NPY Y1 antagonists in preclinical and clinical studies. Here we report the synthesis and evaluation of [(18)F]Y1-973, a novel PET tracer for NPY Y1. [(18)F]Y1-973 was radiolabeled by reaction of a primary chloride with [(18)F]KF/K2.2.2 followed by deprotection with HCl. [(18)F]Y1-973 was produced with high radiochemical purity (>98%) and high specific activity (>1000 Ci/mmol). PET studies in rhesus monkey brain showed that the distribution of [(18)F]Y1-973 was consistent with the known NPY Y1 distribution; uptake was highest in the striatum and cortical regions and lowest in the pons, cerebellum nuclei, and brain stem. Blockade of [(18)F]Y1-973 uptake with NPY Y1 antagonist Y1-718 revealed a specific signal that was dose-dependently reduced in all regions of grey matter to a similarly low level of tracer uptake, indicative of an NPY Y1 specific signal. In vitro autoradiographic studies with [(18)F]Y1-973 in rhesus monkey and human brain tissue slices revealed an uptake distribution consistent with the in vivo PET studies. Highest binding density was observed in the dentate gyrus, caudate-putamen, and cortical regions; moderate binding density in the hypothalamus and thalamus; and lowest binding density in the globus pallidus and cerebellum. In vitro saturation binding studies in rhesus monkey and human caudate-putamen homogenates confirmed a similarly high B(max)/K(d) ratio for [(18)F]Y1-973, suggesting the tracer may provide a specific signal in human brain of similar magnitude to that observed in rhesus monkey. [(18)F]Y1-973 is a suitable PET tracer for imaging NPY Y1 in rhesus monkey with potential for translation to human PET studies.

  13. Laser Studies of Gas Phase Radical Reactions.

    DTIC Science & Technology

    1989-01-01

    Acremonium chrysogenum , was prepared according to the published procedure [6]. This fungal enzyme had a specific activity of 0.023 IUmg1, and was estimated to...Dist-lbitionj Avdielbiity Codes jAvail atidjor Dist 6a A-I . p -1- Laser Studies of Gas Phase Radical Reactions G. Hancock Physical Chemistry...some additional experiments concerning the formation of carbene radicals in liquid phase enzyme cleavage studies are described. Keywords Laser

  14. Development of Kinetic Interface Sensitive Tracers (KIS-Tracer) for Supercritical Carbon Dioxide Injections into Deep Saline Aquifers

    NASA Astrophysics Data System (ADS)

    Schaffer, M.; Maier, F.; Licha, T.; Sauter, M.

    2012-04-01

    The storage of captured CO2 into geological formations is recently one of the most promising technologies to mitigate anthropogenic greenhouse gas emissions into the earth's atmosphere. Deep saline aquifers are considered as the most potential sequestration sites of CO2 due to their huge storage capacities of several thousand Gt. Ongoing research deals mainly with the investigation of relevant physico-chemical processes, the fate of CO2 and the risk assessment during and after supercritical CO2 (scCO2) injections. The occurring processes at the interface between injected scCO2 and formation brine play a major role to evaluate the fate and behavior of scCO2 in the reservoir. This is because the interface represents a reactive zone where numerous physico-chemical processes like dissolution of scCO2 in water as well as dissolution and precipitation of minerals take place. In most cases it is desired to maximize the interface size to increase the storage efficiency. Therefore, knowledge on interface size and dynamics would allow the observation of plume spreading and the detection of mixing or fingering effects. In order to gain this information innovative tracers are necessary which are able to quantify the temporal and spatial development of scCO2/water interfaces. As a result, it may be possible to assess the storage efficiency and to optimize subsequent injections. Up to now, such time-dependent tracers for reservoir studies are not available and limited to equilibrium tracers (known as partitioning and interfacial tracers, respectively). Therefore, novel reactive tracers (KIS-Tracers) are developed to overcome this gap. The idea is to find suitable molecules which allow the implementation of a defined chemical reaction at the interface. Due to the known kinetic constants the change of interface size can be characterized over time. The new tracer is injected together with the supercritical CO2 (scCO2) into a deep saline aquifer. Afterwards, the tracer adsorbs at

  15. New physical Lagrangian tracer

    SciTech Connect

    Zak, B.D.

    1984-01-01

    A physical Lagrangian tracer will be operational and available for use within the near future. The tracer is an adjustable buoyancy constant volume balloon with an onboard microprocessor to serve an appropriate array of sensors, and to control buoyancy. Tracking and data reporting is to be accomplished via the ARGOS satellite-borne data system, yielding both a local and a world-wide capability. 5 references, 1 figure.

  16. Effect of motion on tracer activity determination in CT attenuation corrected PET images: A lung phantom study

    SciTech Connect

    Pevsner, Alex; Nehmeh, Sadek A.; Humm, John L.; Mageras, Gig S.; Erdi, Yusuf E.

    2005-07-15

    Respiratory motion is known to affect the quantitation of {sup 18}FDG uptake in lung lesions. The aim of the study was to investigate the magnitude of errors in tracer activity determination due to motion, and its dependence upon CT attenuation at different phases of the motion cycle. To estimate these errors we have compared maximum activity concentrations determined from PET/CT images of a lung phantom at rest and under simulated respiratory motion. The NEMA 2001 IEC body phantom, containing six hollow spheres with diameters 37, 28, 22, 17, 13, and 10 mm, was used in this study. To mimic lung tissue density, the phantom (excluding spheres) was filled with low density polystyrene beads and water. The phantom spheres were filled with {sup 18}FDG solution setting the target-to-background activity concentration ratio at 8:1. PET/CT data were acquired with the phantom at rest, and while it was undergoing periodic motion along the longitudinal axis of the scanner with a range of displacement being 2 cm, and a period of 5 s. The phantom at rest and in motion was scanned using manufacturer provided standard helical/clinical protocol, a helical CT scan followed by a PET emission scan. The moving phantom was also scanned using a 4D-CT protocol that provides volume image sets at different phases of the motion cycle. To estimate the effect of motion on quantitation of activities in six spheres, we have examined the activity concentration data for (a) the stationary phantom, (b) the phantom undergoing simulated respiratory motion, and (c) a moving phantom acquired with PET/4D-CT protocol in which attenuation correction was performed with CT images acquired at different phases of motion cycle. The data for the phantom at rest and in motion acquired with the standard helical/clinical protocol showed that the activity concentration in the spheres can be underestimated by as much as 75%, depending on the sphere diameter. We have also demonstrated that fluctuations in sphere

  17. The Reanalysis for Stratospheric Trace Gas Studies

    NASA Technical Reports Server (NTRS)

    Pawson, Steven

    2003-01-01

    The "Reanalysis for Stratospheric Trace Gas Studies" (ReSTS) project intends to provide a state-of-the-art meteorological dataset for use in chemistry-transport models (CTMs). The initial focus is on the period from May 1991 until April 1995, which encompasses the initial few years of observations from NASA's Upper Atmosphere Research Satellite (UARS) as well as the abrupt increase and slow decay of volcanic aerosol loading from Mount Pinatubo. The reanalysis is being performed using NASA's operational "GEOS-4" data assimilation system. The results presented in this paper will begin with an overview of the meteorology of the ReSTS period, validating the ReSTS data against independent analyses, followed by an evaluation of the system statistics (the "Observation minus Forecast" for different input data types). Some sensitivities to the assumptions made in the assimilation process will be presented, including aspects of the forecast model and the statistical model used in the observation-forecast merging. Aspects of trace-gas transport will be discussed, focussing on the on-line water vapor distribution (which is a quasi-inert trace gas in the stratosphere), off-line transport studies of ozone and selected long-lived species, as well as assimilated ozone. The results will be discussed in the context of transport studies and our ability to use reanalyzed datasets to examine long-term variations in the meteorology and composition of the middle atmosphere.

  18. Asian Tracer Experiment and Atmospheric Modeling (TEAM) Project: Draft Field Work Plan for the Asian Long-Range Tracer Experiment

    SciTech Connect

    Allwine, K Jerry; Flaherty, Julia E.

    2007-08-01

    This report provides an experimental plan for a proposed Asian long-range tracer study as part of the international Tracer Experiment and Atmospheric Modeling (TEAM) Project. The TEAM partners are China, Japan, South Korea and the United States. Optimal times of year to conduct the study, meteorological measurements needed, proposed tracer release locations, proposed tracer sampling locations and the proposed durations of tracer releases and subsequent sampling are given. Also given are the activities necessary to prepare for the study and the schedule for completing the preparation activities leading to conducting the actual field operations. This report is intended to provide the TEAM members with the information necessary for planning and conducting the Asian long-range tracer study. The experimental plan is proposed, at this time, to describe the efforts necessary to conduct the Asian long-range tracer study, and the plan will undoubtedly be revised and refined as the planning goes forward over the next year.

  19. A tracer analysis study on the redistribution and oxidization of endogenous carbon monoxide in the human body.

    PubMed

    Sawano, Makoto; Shimouchi, Akito

    2010-09-01

    Past studies have suggested that some carbon monoxide (CO) moves from blood haemoglobin to tissue cells and that mitochondrial cytochrome c oxidase oxidizes CO to carbon dioxide (CO(2)). However, no study has demonstrated this redistribution and oxidization of CO under physiological conditions. The objective of this study was to trace the redistribution and oxidization of CO in the human body by detecting (13)CO(2) production after the inhalation of (13)CO. In Experiment 1, we asked a healthy subject to inhale 50 ppm (13)CO gas. In Experiment 2, we circulated heparinized human blood in a cardio-pulmonary bypass circuit and supplied 50 ppm (13)CO gas to the oxygenator. We sequentially sampled exhaled and output gases and measured the (13)CO(2)/(12)CO(2) ratios. In Experiment 1, the exhaled (13)CO(2)/(12)CO(2) ratio increased significantly between 4 to 31 h of (13)CO inhalation. In Experiment 2, the output (13)CO(2)/(12)CO(2) ratio showed no significant increase within 36 h of (13)CO input. Experiment 1 demonstrated the oxidization of CO in the human body under physiological conditions. Experiment 2 confirmed that oxidization does not occur in the circulating blood and indicated the redistribution of CO from blood carboxyhaemoglobin to tissue cells.

  20. Use of geochemical and isotope tracers to assess groundwater dependency of a terrestrial ecosystem: case study from southern Poland

    NASA Astrophysics Data System (ADS)

    Zurek, Anna J.; Witczak, Stanislaw; Kania, Jaroslaw; Rozanski, Kazimierz; Dulinski, Marek; Wachniew, Przemyslaw

    2015-04-01

    The presented study was aimed at better understanding of the functioning of groundwater dependent terrestrial ecosystem (GDTE) located in the south of Poland. The studied GDTE consists of a valuable forest stand (Niepolomice Forest) and associated wetland (Wielkie Bloto fen). It relies not only on shallow, unconfined aquifer but indirectly also on groundwater originating from the deeper confined aquifer, underlying the Quaternary cover and separated from it by an aquitard of variable thickness. The main objective of the study was to evaluate the contribution of groundwater to the water balance of the studied GDTE and thereby assess the potential risk to this system associated with intense exploitation of the deeper aquifer. The Wielkie Błoto fen area and the adjacent parts of Niepolomice Forest are drained by the Dluga Woda stream with 8.2 km2 of gauged catchment area. Hydrometric measurements, carried out on the Dluga Woda stream over two-year period (August 2011 - August 2013) were supplemented by chemical and isotope analyses of stream water, monitored on monthly basis. Physico-chemical parameters of the stream water (SEC, pH, Na content, Na/Cl molar ratio) and isotope tracers (deuterium, oxygen-18 and tritium) were used to quantify the expected contribution of groundwater seepage from the deeper aquifer to the water balance of the Dluga Woda catchment. The mean transit time of water through the catchment, derived from temporal variations of δ18O and tritium content in the Dluga Woda stream, was in the order of three months. This fast component of the total discharge of Dluga Woda stream is associated surface runoff and groundwater flow paths through the Quaternary cover. The slow component devoid of tritium and probably originated from the deeper Neogene aquifer is equal to approximately 30% of the total discharge. The relationships between the physico-chemical parameters of the stream water and the flow rate of Dluga Woda clearly indicate that the monitored

  1. Studies on sensitive Raman gas detectors

    NASA Astrophysics Data System (ADS)

    Zuo, Duluo; Xu, Yongyue; Wang, Xinbing; Xiong, Youhui

    2013-05-01

    Recent studies on signal enhancement of spontaneous Raman scattering for developing of sensitive Raman gas detectors are reported. Raman scattering is a gas detecting method with high feasibility, but usually its signal is very low. To improve the level and the quality of the Raman signal, the effects of pumping laser source, sample cell, and optical arrangement are studied in detail. It is found that not only the wall of sample cell will give a wide Raman or fluorescence background which will decrease the sensitivity, but the dichroic beam splitter will also contribute considerable background if it is not aligned properly. The sample cell of hollow fiber is characterized by its high responsibility as well as its high background and low signal contrast. When the hollow fiber is replaced by a free-space sample cell consisted of metal-coated parabolic reflector, the wide background is largely suppressed. If there is no common optical elements between the pumping and collecting optical systems, the wide background will be cut down obviously, which is proved by the intracavity-enhanced Raman scattering in a He-Ne laser. These experimental results will be helpful for the research and developing of highly sensitive Raman gas detectors.

  2. DETECTION OF HIGH MOLECULAR WEIGHT ORGANIC TRACERS IN VEGETATION SMOKE SAMPLES BY HIGH-TEMPERATURE GAS CHROMATOGRAPHY-MASS SPECTROMETRY. (R823990)

    EPA Science Inventory

    High-temperature high-resolution gas chromatography
    (HTGC) is an established technique for the separation of
    complex mixtures of high molecular weight (HMW) compounds
    which do not elute when analyzed on conventional GC
    columns. The combination of this technique wit...

  3. Experimental study of the effect of test-well arrangement for partitioning interwell tracer test on the estimation of NAPL saturation

    NASA Astrophysics Data System (ADS)

    Kim, B.; Kim, Y.; Yeo, I.; Yongcheol Kim, In Wook Yeo

    2011-12-01

    Partitioning interwell tracer test (PITT) is a method to quantify and qualify a contaminated site with NAPLs through a degree of retardation of partitioning tracers compared to a conservative one. Although PITT is known to be a more effective method to measure the saturation of spatially-distributed NAPL contaminant than the point investigation method, the saturation estimation from PITT is reported to be underestimated due to various factors including heterogeneity of the media, adsorption, source zone NAPL architecture, and long tailing in breakthrough curves of partitioning tracers. Analytical description of PITT assumes that the injection-pumping well pair is on the line of ambient groundwater flow direction, but the test-well pair could easily be off the line in the field site, which could be another erroneous factor in analyzing PITT data. The purpose of this work is to study the influence of the angle of the test-well pair to ambient groundwater flow direction based on the result from PITT. The experiments were conducted in a small-scale 3D sandbox with dimensions of 0.5 m × 0.4 m × 0.15 m (LWH) of stainless steel. The surface is covered and sealed with a plexiglass plate to make the physical model a confined aquifer. Eight full-screened wells of Teflon material were installed along the perimeter of a 50 mm circle with 45 degree intervals in the middle of the physical model. Both ends of the sand box are connected to constant head reservoirs. The physical model was wet-packed with sieved and washed sand. Trichloroethylene (TCE) and bromide were used as the contaminant and the conservative tracer, respectively. Hexanol, 2,4-dimethyl-3-pentanol and 6-methyl-2-heptanol were used as partitioning tracers. Before the injection of TCE, a PITT was conducted to measure adsorption coefficient of partitioning tracers to the sand material. TCE of 4.5 mL, dyed with Sudan IV, was injected into the inner part of the circle of the wells. PITTs using the test-well pair

  4. Single-well tracer test sensitivity w. r. to hydrofrac and matrix parameters (case study for the Horstberg site in the N-German Sedimentary Basin)

    NASA Astrophysics Data System (ADS)

    Ghergut, I.; Behrens, H.; Holzbecher, E.; Jung, R.; Sauter, M.; Tischner, T.

    2012-04-01

    are, as well, sensitive w. r. to X, but the effects of increasing X, upon tracer signals, are largely indistinguishable from those of increasing Solling porosity. Further numerical simulations of heat and solute tracer transport in above-named test settings reveal significant disparities between parameter sensitivities attainable in the same kind of test (A, B) conducted at different layers, as well as between solute concentration and temperature signal sensitivities w. r. to transport parameters in one and the same test (C). Why? - Test A features fracture flow, and dual-continuum transport, whereas test B features single-continuum flow and transport (within the host rock, with negligible losses to the hydrofrac). Flow is rapid in test A (being fracture-dominated), but slow in test B (being confined to the host rock). In test C, fluid first flows through the hydrofrac mainly, next it 'must' flow through the upper sandstone; heat transport is dominated by matrix diffusion across the hydrofrac (along which it thus experiences strong retardation), whereas solute transport is dominated by matrix micro-fissure and intra-particle diffusion within the upper sandstone (where it experiences strong retardation). We examine the implications of these findings upon the inversion of transport-effective hydrofrac parameters from measured tracer signals, and upon the tracer-based predictability of the system's thermal lifetime under different operation schemes. [1]http://www.geothermal-energy.org/pdf/IGAstandard/SGW/2005/jung.pdf [2]http://www.geothermal-energy.org/pdf/IGAstandard/WGC/2010/2272.pdf Acknowledgement: This study is funded by MWK Niedersachsen (Lower-Saxony's Science and Culture Ministry) and by Baker Hughes (Celle) within task units 'G6' and 'G7' of the Collaborative Research Project 'gebo' (Geothermal Energy and High-Performance Drilling).

  5. Numerical Simulations of Airflows and Tracer Transport in the Southwestern United States.

    NASA Astrophysics Data System (ADS)

    Yamada, Tetsuji

    2000-03-01

    Project MOHAVE (Measurement of Haze and Visual Effects) produced a unique set of tracer data over the southwestern United States. During the summer of 1992, a perfluorocarbon tracer gas was released from the Mohave Power Project (MPP), a large coal-fired facility in southern Nevada. Three-dimensional atmospheric models, the Higher-Order Turbulence Model for Atmospheric Circulation-Random Puff Transport and Diffusion (HOTMAC-RAPTAD), were used to simulate the concentrations of tracer gas that were observed during a portion of the summer intensive period of Project MOHAVE. The study area extended from northwestern Arizona to southern Nevada and included Lake Mead, the Colorado River Valley, the Grand Canyon National Park, and MPP. The computational domain was 368 km in the east-west direction by 252 km in the north-south direction. Rawinsonde and radar wind profiler data were used to provide initial and boundary conditions to HOTMAC simulations. HOTMAC with a horizontal grid spacing of 4 km was able to simulate the diurnal variations of drainage and upslope flows along the Grand Canyon and Colorado River Valley. HOTMAC also captured the diurnal variations of turbulence, which played important roles for the transport and diffusion simulations by RAPTAD. The modeled tracer gas concentrations were compared with observations. The model's performance was evaluated statistically.

  6. Selection of Actinide Chemical Analogues for WIPP Tests: Potential Nonradioactive Sorbing and Nonsorbing Tracers for Study of Ion Transport in the Environment

    SciTech Connect

    Dale Spall; Robert Villarreal

    1998-08-01

    Chemical characteristics of the actinides (Th, U, Np, Pu, Am) have been studied relative to nonradioactive chemical elements that have similar characteristics in an attempt to identify a group of actinide chemical analogues that are nonradioactive. In general, the chemistries of the actinides, especially U, Np, Pu, and Am, are very complex and attempts to identify a single chemical analogue for each oxidation state were not successful. However, the rationale for selecting a group of chemical analogues that would mimic the actinides as a group is provided. The categorization of possible chemical analogues (tracers) with similar chemical properties was based on the following criteria. Categorization was studied according.

  7. Testing and comparison of four ionic tracers to measure stream flow loss by multiple tracer injection

    USGS Publications Warehouse

    Zellweger, G.W.

    1994-01-01

    An injectate containing lithium, sodium, chloride and bromide was added continuously at five sites along a 507 m study reach of St Kevin Gulch, Lake County, Colorado to determine which sections of the stream were losing water to the stream bed and to ascertain how well the four tracers performed. The acidity of the stream (pH 3.6) made it possible for lithium and sodium, which are normally absorbed by ion exchange with stream bed sediment, to be used as conservative tracers. Net flow losses as low as 0.81 s-1, or 8% of flow, were calculated between measuring sites. By comparing the results of simultaneous injection it was determined whether subsections of the study reach were influent or effluent. Evaluation of tracer concentrations along 116 m of stream indicated that all four tracers behaved conservatively. Discharges measured by Parshall flumes were 4-18% greater than discharges measured by tracer dilution. -from Author

  8. Solar-gas systems impact analysis study

    NASA Astrophysics Data System (ADS)

    Neill, C. P.; Hahn, E. F.; Loose, J. C.; Poe, T. E.; Hirshberg, A. S.; Haas, S.; Preble, B.; Halpin, J.

    1984-07-01

    The impacts of solar/gas technologies on gas consumers and on gas utilities were measured separately and compared against the impacts of competing gas and electric systems in four climatic regions of the U.S. A methodology was developed for measuring the benefits or penalties of solar/gas systems on a combined basis for consumers sand distribution companies. It is shown that the combined benefits associated with solar/gas systems are generally greatest when the systems are purchased by customers who would have otherwise chosen high-efficiency electric systems (were solar/gas systems not available in the market place). The role of gas utilities in encouraging consumer acceptance of solar/gas systems was also examined ion a qualitative fashion. A decision framework for analyzing the type and level of utility involvement in solar/gas technologies was developed.

  9. Tracer mixing at fracture intersections

    SciTech Connect

    Li, Guomin

    2001-02-10

    Discrete network models are one of the approaches used to simulate a dissolved contaminant, which is usually represented as a tracer in modeling studies, in fractured rocks. The discrete models include large numbers of individual fractures within the network structure, with flow and transport described on the scale of an individual fracture. Numerical simulations for the mixing characteristics and transfer probabilities of a tracer through a fracture intersection are performed for this study. A random-walk, particle-tracking model is applied to simulate tracer transport in fracture intersections by moving particles through space using individual advective and diffusive steps. The simulation results are compared with existing numerical and analytical solutions for a continuous intersection over a wide range of Peclet numbers. This study attempts to characterize the relative concentration at the outflow branches for a continuous intersection with different flow fields. The simulation results demonstrate that the mixing characteristics at the fracture intersections are a function not only of the Peclet number but also of the flow field pattern.

  10. Gas Gun Studies of Interface Wear Effects

    NASA Astrophysics Data System (ADS)

    Jackson, Tyler; Kennedy, Greg; Thadhani, Naresh

    2011-06-01

    The characteristics of interface wear were studied by performing gas gun experiments at velocities up to 1 km/s. The approach involved developing coefficients of constitutive strength models for Al 6061 and OFHC-Cu, then using those to design die geometry for interface wear gas gun experiments. Taylor rod-on-anvil impact experiments were performed to obtain coefficients of the Johnson-Cook constitutive strength model by correlating experimentally obtained deformed states of impacted samples with those predicted using ANSYS AUTODYN hydrocode. Simulations were used with validated strength models to design geometry involving acceleration of Al rods through a copper concentric cylindrical angular extrusion die. Experiments were conducted using 7.62 mm and 80 mm diameter gas guns. Differences in the microstructure of the interface layer and microhardness values illustrate that stress-strain conditions produced during acceleration of Al through the hollow concentric copper die, at velocities less than 800 m/s, result in formation of a layer via solid state alloying due to severe plastic deformation, while higher velocities produce an interface layer consisting of melted and re-solidified aluminum.

  11. Experimental Study of Coal and Gas Outbursts Related to Gas-Enriched Areas

    NASA Astrophysics Data System (ADS)

    Tu, Qingyi; Cheng, Yuanping; Guo, Pinkun; Jiang, Jingyu; Wang, Liang; Zhang, Rong

    2016-09-01

    A coal and gas outburst can lead to a catastrophic failure in a coal mine. These outbursts usually occur where the distribution of coal seam gas is abnormal, commonly in tectonic belts. To study the effects of the abnormal distribution of this gas on outbursts, an experimental apparatus to collect data on simulated coal seam outbursts was constructed. Experiments on specimens containing discrete gas-enriched areas were run to induce artificial gas outbursts and further study of these outbursts using data from the experiment was conducted. The results suggest that more gas and outburst energy are contained in gas-enriched areas and this permits these areas to cause an outburst easily, even though the gas pressure in them is lower. During mining, the disappearance of the sealing effect of a coal pillar establishes the occurrence conditions for an outburst. When the enriched gas and outburst energy in the gas-enriched area is released suddenly, a reverse unloading wave and a high gas pressure gradient are formed, which have tension effects on the coal. Under these effects, the fragmentation degree of the coal intensifies and the intensity of the outburst increases. Because a high gas pressure gradient is maintained near the exposed surface and the enriched energy release reduces the coal strength, the existence of a gas-enriched area in coal leads to a faster outburst and the average thickness of the spall is smaller than where is no gas-enriched area.

  12. Tracer-based prediction of thermal reservoir lifetime: scope, limitations, and the role of thermosensitive tracers

    NASA Astrophysics Data System (ADS)

    Ghergut, I.; Behrens, H.; Karmakar, S.; Licha, T.; Nottebohm, M.; Sauter, M.

    2012-04-01

    correlation between (early) tracer signals and (later) thermal breakthrough can be re-established. Thus, thermosensitive tracers are indispensable for predicting thermal breakthrough, in such geothermal reservoirs whose 'hydrogeological personality' is given by a finite set of fractures, with flow occurring both across and along the fractures. In terms of the 'gebo benchmark-model' typology investigated by Hördt et al. (2011) [http://eposters.agu.org/abstracts/models-of-geothermal-reservoirs-as-a-basis-for-interdisciplinary-cooperation/] , such systems combine flow and transport patterns of the 'petrothermal' type and of the so-called 'deep-aquifer' type: across the fractures, heat is travelling faster than conservative-solute tracers; along the fractures, conservative-solute tracers experience much less retardation by transversal exchange (matrix diffusion), than heat; fluid (and tracer) flow is not limited to the fractures; matrix flow yields essential contribution to prolonging the fluid (and tracer) residence time. Thermal lifetime results from the opposite effects of fracture aperture as an: advection-related parameter: fluid travel time increases with increasing fracture aperture advection-unrelated parameter: fracture - matrix exchange rate increases with decreasing fracture aperture, which accelerates transport across the fracture, but retards transport along the fracture. In conservative-solute tracer signals, all these fracture aperture effects on tracer transport are masked by the very long residence time associated with the matrix flow component. Thermosensitive tracers are able to 'magnify' the visibility of fracture aperture effects against matrix flow effects. Acknowledgment: This study benefits from thermosensitive-tracer research conducted within the projects Smart Tracers and LOGRO, funded by the German Ministry for Environment, Nature Conservation and Nuclear Safety (BMU, 0327579 and 0325111B) and by Energie Baden-Württemberg (EnBW).

  13. Development of a novel two color tracer perfusion technique for the hydrodynamic study of aqueous outflow in bovine eyes

    PubMed Central

    Jing-yin, ZHU; Wen, YE; Hai-yan, GONG

    2010-01-01

    Background Elevation of intraocular pressure is usually associated with primary open angle glaucoma and caused by increased outflow resistance. A two-color fluorescent tracer technique was developed to investigate the hydrodynamics of aqueous humor outflow with changing intraocular pressure within the same eye, to better understand the relationship between outflow facility and effective filtration area. Methods Eighteen enucleated bovine eyes were first perfused at 30 mmHg with Dulbecco’s phosphate-buffered saline containing 5.5 mmol/L D-glucose. After a stable baseline facility, red fluorescent microspheres (0.5 μm, 0.002% v/v) were exchanged and perfused. Eyes in the one-color control group (n=6) were immediately perfused with fixative. In the experimental group (n=6), eyes were perfused with green tracer after intraocular pressure reduced to 7 mmHg, while in the two-color control group (n=6), eyes were perfused with green tracer with intraocular pressure remaining at 30 mmHg. All 12 eyes were then perfusion-fixed. Outflow facility was continuously recorded in all eyes. Confocal images were taken along the inner wall of the aqueous plexus and the percent of the effective filtration length (PEFL; length of inner wall exhibiting tracer labeling/total length of inner wall) was measured. The relationships between outflow facility and PEFL were analyzed statistically. Results No significant differences were found in baseline facilities (μl·min−1·mmHg−1) among the three groups (the experimental group: 0.93±0.12; the two-color control group: 0.90±0.19; the one-color control group: 0.98±0.13). In the experimental group, the outflow facility was significantly higher at 7 mmHg (4.29±1.01) than that at 30 mmHg (1.90±0.67, P <0.001), which corresponded to a significant increase in the PEFL at 7 mmHg (54.70±8.42) from that at 30 mmHg ((11.76±4.56)%, P <0.001). The PEFL labeled by red fluorescent microspheres in the experimental group ((11.76±4.56)%) showed

  14. Determination of stream reaeration coefficients by use of tracers

    USGS Publications Warehouse

    Kilpatrick, F.A.; Rathbun, R.E.; Yotsukura, Nobuhiro; Parker, G.W.; DeLong, L.L.

    1989-01-01

    Stream reaeration is the physical absorption of oxygen from the atmosphere by a flowing stream. This is the primary process by which a stream replenishes the oxygen consumed in the biodegradation of organic wastes. Prior to 1965, reaeration rate coefficients could be estimated only by indirect methods. In 1965, a direct method of measuring stream reaeration coefficients was developed whereby a radioactive tracer gas was injected into a stream-the principle being that the tracer gas would be desorbed from the stream inversely to how oxygen would be absorbed. The technique has since been modified by substituting hydrocarbon gases for the radioactive tracer gas. This manual describes the slug-injection and constant-rate-injection methods of measuring gas-tracer desorption. Emphasis is on the use of rhodamine WT dye as a relatively conservative tracer and propane as the nonconservative gas tracer, on planning field tests, on methods of injection, sampling, and analysis, and on techniques for computing desorption and reaeration coefficients.

  15. Dating of young groundwater using tritium and gaseous tracers (SF6, SF5CF3, CFC-12, H-1301): case study from southern Poland

    NASA Astrophysics Data System (ADS)

    Rozanski, Kazimierz; Bartyzel, Jakub; Dulinski, Marek; Kuc, Tadeusz; Sliwka, Ireneusz; Mochalski, Pawel; Kania, Jaroslaw; Witczak, Stanislaw

    2013-04-01

    Groundwater is an important source of potable water in many countries. While it covers ca. 50% of the global drinking water needs, in Europe this share is even higher, reaching approximately 70%. Nowadays, this strategic resource is at risk due to anthropogenic pollutants of various nature entering shallow aquifers. Proper management of groundwater resources requires thorough understanding of groundwater dynamics on time scales characteristic for the history of pollutant input to groundwater. The bomb-tritium has been used for several decades now as a tracer of choice to detect recent recharge and to quantify groundwater residence times on time scales extending from several years to several decades. The lumped-parameter modeling was the most often employed approach in this context. Since nowadays atmospheric concentrations of tritium are approaching natural levels in most parts of the world, the usage of this tracer has become more problematic. Therefore, there is a growing interest in alternative indicators of groundwater age in shallow aquifers. Anthropogenic trace gases present in the atmosphere, such as freons (CFC-11, CFC-12, CFC-113) and sulfur hexafluoride (SF6), have been applied in numerous case studies as substitutes of tritium. Here we present the results of a comprehensive study aimed at quantifying mean residence time of groundwater in the recharge area of porous sandy aquifer system located in the southern Poland. The principal economic role of the aquifer, consisting of two water-bearing strata, is to provide potable water for public and private users. The yield of the aquifer is insufficient to meet all the needs and, as a consequence, licensing conflicts arise between water supply companies and industry on the amount of water available for safe exploitation. To quantify residence time distribution (RTD) functions of water parcels arriving at the production wells located in the recharge area of the aquifer, tritium along with several gaseous tracers

  16. CO, NOx and 13CO2 as tracers for fossil fuel CO2: results from a pilot study in Paris during winter 2010

    NASA Astrophysics Data System (ADS)

    Lopez, M.; Schmidt, M.; Delmotte, M.; Colomb, A.; Gros, V.; Janssen, C.; Lehman, S. J.; Mondelain, D.; Perrussel, O.; Ramonet, M.; Xueref-Remy, I.; Bousquet, P.

    2013-08-01

    Measurements of the mole fraction of the CO2 and its isotopes were performed in Paris during the MEGAPOLI winter campaign (January-February 2010). Radiocarbon (14CO2) measurements were used to identify the relative contributions of 77% CO2 from fossil fuel consumption (CO2ff from liquid and gas combustion) and 23% from biospheric CO2 (CO2 from the use of biofuels and from human and plant respiration: CO2bio). These percentages correspond to average mole fractions of 26.4 ppm and 8.2 ppm for CO2ff and CO2bio, respectively. The 13CO2 analysis indicated that gas and liquid fuel contributed 70% and 30%, respectively, of the CO2 emission from fossil fuel use. Continuous measurements of CO and NOx and the ratios CO/CO2ff and NOx/CO2ff derived from radiocarbon measurements during four days make it possible to estimate the fossil fuel CO2 contribution over the entire campaign. The ratios CO/CO2ff and NOx/CO2ff are functions of air mass origin and exhibited daily ranges of 7.9 to 14.5 ppb ppm-1 and 1.1 to 4.3 ppb ppm-1, respectively. These ratios are consistent with different emission inventories given the uncertainties of the different approaches. By using both tracers to derive the fossil fuel CO2, we observed similar diurnal cycles with two maxima during rush hour traffic.

  17. Evaluation of C-14 as a natural tracer for injected fluids at theAidlin sector of The Geysers geothermal system through modeling ofmineral-water-gas Reactions

    SciTech Connect

    Dobson, Patrick; Sonnenthal, Eric; Lewicki, Jennifer; Kennedy, Mack

    2006-06-01

    A reactive-transport model for 14C was developed to test its applicability to the Aidlin geothermal system. Using TOUGHREACT, we developed a 1-D grid to evaluate the effects of water injection and subsequent water-rock-gas interaction on the compositions of the produced fluids. A dual-permeability model of the fracture-matrix system was used to describe reaction-transport processes in which the permeability of the fractures is many orders of magnitude higher than that of the rock matrix. The geochemical system included the principal minerals (K-feldspar, plagioclase, calcite, silica polymorphs) of the metagraywackes that comprise the geothermal reservoir rocks. Initial simulation results predict that the gas-phase CO2 in the reservoir will become more enriched in 14C as air-equilibrated injectate water (with a modern carbon signature) is incorporated into the system, and that these changes will precede accompanying decreases in reservoir temperature. The effects of injection on 14C in the rock matrix will be lessened somewhat because of the dissolution of matrix calcite with ''dead'' carbon.

  18. Hydrochemistry and boron isotopes as natural tracers in the study of groundwaters from North Chianan Plain, Taiwan.

    PubMed

    Lu, Hsueh-Yu

    2014-01-01

    In this paper, hydrochemistry and boron isotopes are successfully applied to elucidate hydrogeological processes by the use of natural tracers. The hydrochemical analysis identifies four end-members in the hydrochemical evolution of groundwater from the North Chianan plain groundwater district. A few groundwater contain extraordinary chlorine concentrations of up to 48,000 mg l(-1). However, the hydrochemistry of groundwater only reveals that high saline water is a dominant factor in groundwater hydrochemistry. It is thought that these groundwater experienced precipitation of carbonates during seawater evaporation that did not involve the precipitation of gypsum. Boron isotopes are very efficient tracers in determining the source of salinisation. The boron isotopes reveal the results of mixing of evaporated seawater and water-sediment interaction. In general, the boron isotope ratio of the groundwater is controlled by a two-end-member mixing system, which is composed of evaporated seawater (isotopically heavy) and fresh surface water (isotopically light). Due to a long lagoonal period in the coastal plain, the groundwaters in the downstream area generally have high Cl/B ratios and relatively heavy boron isotope ratios while those in the upstream area are composed of low Cl/B and light boron isotopes. However, there is not a resolvable mixing trend between the Cl/B ratio and the isotopic composition of boron. It is probably obscured by a highly variable boron isotope ratio in fresh surface water and through fractionation associated with water-rock interaction. Both factors would decrease the boron isotope ratio but one effect cannot be distinguished from the other.

  19. Synthesis of a novel polyamidoamine dendrimer conjugating with alkali blue as a lymphatic tracer and study on the lymphatic targeting in vivo.

    PubMed

    Yang, Rui; Xia, Suxia; Ye, Tiantian; Yao, Jianhua; Zhang, Ruizhi; Wang, Shujun; Wang, Siling

    2016-09-01

    In this study, a novel lymphatic tracer polyamidoamin-alkali blue (PAMAM-AB) was synthesized in order to evaluate the intra-lymphatic targeting ability and lymphatic tropism of PAMAM-AB after subcutaneous administration. UV-Vis, FT-IR, NMR and HPLC characterization were performed to prove the successful synthesis of PAMAM-AB. The calculated AB payload of PAMAM-AB conjugate was seven per dendrimer molecule (27.16% by weight). Hydrolysis stability of PAMAM-AB in vitro was evaluated, which was stable in PBS and human plasma. Lymphatic tracing were studied to determine the blue-stained intensity of PAMAM-AB in right popliteral lymph nodes (PLNs), iliac lymph nodes (ILNs) and para-aortic lymph nodes (PALNs) after subcutaneous administration. The pharmacokinetics and biodistribution of PAMAM-AB in mice were investigated. PLNs, ILNs and PALNs could be obviously blue-stained within 10 min after PAMAM-AB administration, and displayed a more rapid lymphatic absorption, a higher AUC value in lymph nodes and a longer lymph nodes residence time compared with methylene blue solution (MB-S), MB water-in-oil microemulsion (MB-ME), MB multiple microemulsion (MB-MME). Enhanced lymphatic drainage from the injection site and uptake into lymph of PAMAM-AB indicated that PAMAM-AB possesses the double function of lymphatic tracing and lymphatic targeting, and suggested the potential for the development of lymphatic targeting vectors or as a lymphatic tracer in its own right.

  20. Tracer studies to characterize the effects of roadside noise barriers on near-road pollutant dispersion under varying atmospheric stability conditions

    NASA Astrophysics Data System (ADS)

    Finn, Dennis; Clawson, Kirk L.; Carter, Roger G.; Rich, Jason D.; Eckman, Richard M.; Perry, Steven G.; Isakov, Vlad; Heist, David K.

    2010-01-01

    A roadway toxics dispersion study was conducted at the Idaho National Laboratory (INL) to document the effects on concentrations of roadway emissions behind a roadside sound barrier in various conditions of atmospheric stability. The homogeneous fetch of the INL, controlled emission source, lack of other manmade or natural flow obstructions, and absence of vehicle-generated turbulence reduced the ambiguities in interpretation of the data. Roadway emissions were simulated by the release of an atmospheric tracer (SF 6) from two 54 m long line sources, one for an experiment with a 90 m long noise barrier and one for a control experiment without a barrier. Simultaneous near-surface tracer concentration measurements were made with bag samplers on identical sampling grids downwind from the line sources. An array of six 3-d sonic anemometers was employed to measure the barrier-induced turbulence. Key findings of the study are: (1) the areal extent of higher concentrations and the absolute magnitudes of the concentrations both increased as atmospheric stability increased; (2) a concentration deficit developed in the wake zone of the barrier with respect to concentrations at the same relative locations on the control experiment at all atmospheric stabilities; (3) lateral dispersion was significantly greater on the barrier grid than the non-barrier grid; and (4) the barrier tended to trap high concentrations near the "roadway" (i.e. upwind of the barrier) in low wind speed conditions, especially in stable conditions.

  1. Estimates of tracer-based piston-flow ages of groundwater from selected sites: National Water-Quality Assessment Program, 2006-2010

    USGS Publications Warehouse

    Shapiro, Stephanie D.; Plummer, L. Niel; Busenberg, Eurybiades; Widman, Peggy K.; Casile, Gerolamo C.; Wayland, Julian E.; Runkle, Donna L.

    2012-01-01

    Piston-flow age dates were interpreted from measured concentrations of environmental tracers from 812 National Water-Quality Assessment (NAWQA) Program groundwater sites from 27 Study Units across the United States. The tracers of interest include chlorofluorocarbons (CFCs), sulfur hexafluoride (SF6), and tritium/helium-3 (3H/3He). Tracer data compiled for this analysis were collected from 2006 to 2010 from groundwater wells in NAWQA studies, including: * Land-Use Studies (LUS, shallow wells, usually monitoring wells, located in recharge areas under dominant land-use settings), * Major-Aquifer Studies (MAS, wells, usually domestic supply wells, located in principal aquifers and representing the shallow drinking water supply), * Flow System Studies (FSS, networks of clustered wells located along a flowpath extending from a recharge zone to a discharge zone, preferably a shallow stream) associated with Land-Use Studies, and * Reference wells (wells representing groundwater minimally impacted by anthropogenic activities) also associated with Land-Use Studies. Tracer data were evaluated using documented methods and are presented as aqueous concentrations, equivalent atmospheric concentrations (for CFCs and SF6), and tracer-based piston-flow ages. Selected ancillary data, such as redox data, well-construction data, and major dissolved-gas (N2, O2, Ar, CH4, and CO2) data, also are presented. Recharge temperature was inferred using climate data (approximated by mean annual air temperature plus 1°C [MAAT +1°C]) as well as major dissolved-gas data (N2-Ar-based) where available. The N2-Ar-based temperatures showed significantly more variation than the climate-based data, as well as the effects of denitrification and degassing resulting from reducing conditions. The N2-Ar-based temperatures were colder than the climate-based temperatures in networks where recharge was limited to the winter months when evapotranspiration was reduced. The tracer-based piston-flow ages

  2. [NEURONS IN VISUAL THALAMIC CENTERS OF TURTLES, PROJECTING UPON THE TELENCEPHALON, EXPRESS DIFFERENT TYPES OF CALCIUM-BINDING PROTEINS: COMBINED IMMUNOHISTOCHEMICAL AND TRACER STUDY].

    PubMed

    Kenigfest, N B; Belekhova, M G

    2015-01-01

    In turtles (Testudo horsfieldi, Emys orbicularis) the immunoreactivity for calbindin (CB), parvalbumin (PV), calretinin (CR), and colocalization of PV and CB in neurons of visual thalamic nuclei (Rot, GLD) projecting to the telencephalon were studied using combined immunohistochemical and tracer method. The predominance of CB-ir neurons in Rot, CB-ir and CR-ir neurons in GLD and a lower amount of PV-ir neurons in both nuclei were shown. With double labeling fluoroimmunohistochemistry technique the colocalization of PV with CB was revealed in the majority of PV-ir neurons and in a fewer number of CB-ir neurons within both nuclei. After delivery of horseradish peroxidase into the telencephalic projection fields of Rot and GLD, retrograde labeling was found in the corresponding thalamic projection neurons immunoreactive for every protein investigated. After fluorescent tracer (Fluoro Gold) injection into the same telencephalic regions retrograde labeling was observed in Rot and GLD neurons, immunoreactive only for PV or CB, as well in neurons with colocalization of the both proteins. These data support predominance of CB-ir component in the rotundo-telencephalic pathway and CB/CR components in the geniculo-telencephalic pathway in turtles. The role of functional specialization in segregation of neurons expressing different types of calcium-binding proteins is postulated.

  3. Geologic studies of deep natural gas resources

    USGS Publications Warehouse

    Dyman, T. S.; Kuuskraa, V.A.

    2001-01-01

    In 1995, the USGS estimated a mean resource of 114 trillion cubic feet of undiscovered technically recoverable natural gas in plays deeper than 15,000 feet/4,572 meters in onshore regions of the United States. This volume summarizes major conclusions of ongoing work. Chapters A and B address the areal extent of drilling and distribution of deep basins in the U.S. Chapter C summarizes distribution of deep sedimentary basins and potential for deep gas in the former Soviet Union. Chapters D and E are geochemical papers addressing source-rock issues and deep gas generation. Chapter F develops a probabilistic method for subdividing gas resources into depth slices, and chapter G analyzes the relative uncertainty of estimates of deep gas in plays in the Gulf Coast Region. Chapter H evaluates the mechanism of hydrogenation of deep, high-rank spent kerogen by water, with subsequent generation of methane-rich HC gas.

  4. Metabolic flux analysis of Arthrobacter sp. CGMCC 3584 for cAMP production based on 13C tracer experiments and gas chromatography-mass spectrometry.

    PubMed

    Niu, Huanqing; Chen, Yong; Yao, Shiwei; Liu, Lixia; Yang, Chen; Li, Bingbing; Liu, Dong; Xie, Jingjing; Chen, Xiaochun; Wu, Jinglan; Ying, Hanjie

    2013-12-01

    Arthrobacter sp. CGMCC 3584 are able to produce cAMP from glucose by the purine synthesis pathway via de novo or salvage biosynthesis. In order to gain an improved understanding of its metabolism, (13)C-labeling experiment and gas chromatography-mass spectrometry (GC-MS) analysis were employed to determine the metabolic network structure and estimate the intracellular fluxes. GC-MS analysis helps to reflect the activity of the intracellular pathways and reactions. The metabolic network mainly contains glycolytic and pentose phosphate pathways, the tricarboxylic acid cycle, and the inactive glyoxylate shunt. Hypoxanthine as a precursor of cAMP and sodium fluoride as an inhibitor of glycolysis were found to increase the cAMP production, as well as the flux through the PP pathway. The effects of adding hypoxanthine and sodium fluoride are discussed based on the enzyme assays and metabolic flux analysis. In conclusion, our results provide quantitative insights into how cells manipulate the metabolic network under different culture conditions and this may be of value in metabolic regulation for desirable production.

  5. Isotopic Tracer Study of Hydraulic Transfer Between Native Woody Shrubs and Associated Annual Crops Under Dry Conditions in the Sahel

    NASA Astrophysics Data System (ADS)

    Bogie, Nathaniel; Bayala, Roger; Diedhiou, Ibrahima; Fogel, Marilyn; Dick, Richard; Ghezzehei, Teamrat A.

    2015-04-01

    Erratic precipitation at the beginning and end of the rainy season combined with short drought periods during the cropping season pose a major challenge for rain-fed agriculture and food security in the Sahel. Research has shown that intercropping annual crops with native evergreen woody shrubs in Senegal can greatly increase crop productivity. Hydraulic redistribution (HR), or the diurnal rewetting of dry soil by the pathway of the root system that extends into wetter soil has been found in many plants and climates worldwide. The HR pathway could be a factor in Senegal where water provided by shrubs aids crop growth during dry periods but this has not been confirmed. Therefore, the objective was to determine the ability of shrubs to provide water to millet plants using the deuterium tracer. Penisetum glaucum (Pearl Millet) was grown in association with the native woody shrub Guiera senegalensis under drip irrigation until 68 days after sowing, followed by a with holding of water during late flowering and early grain-filling stage. Within 10 days the soils in the stressed plots became extremely dry with water potentials ranging from -0.5 Mpa to -3.0 Mpa at 20cm depth. Twenty days after the initiation of water stress, vials of isotopically enriched deuterium tracer was sealed around cut roots of three separate shrubs at a depth of 1.0 m followed by sampling of aboveground tissue from injection shrubs and closely growing crop plants over a period of five days. Using cryogenic vacuum distillation, plant water samples were extracted from plant tissue. With lab work completed on two replications, a highly enriched deuterium signal was observed in the tissue water of the shrub beginning twelve hours after the injection. In the same replication thirty-six hours after the beginning of injection, a highly enriched pulse of deuterium in the crop growing directly adjacent to the injection shrub was observed. In a concurrent injection to a nearby shrub under much drier

  6. Seasonal variation of secondary organic aerosol tracers in Central Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Shen, R.-Q.; Ding, X.; He, Q.-F.; Cong, Z.-Y.; Yu, Q.-Q.; Wang, X.-M.

    2015-08-01

    Secondary organic aerosol (SOA) affects the earth's radiation balance and global climate. High-elevation areas are sensitive to global climate change. However, at present, SOA origins and seasonal variations are understudied in remote high-elevation areas. In this study, particulate samples were collected from July 2012 to July 2013 at the remote Nam Co (NC) site, Central Tibetan Plateau and analyzed for SOA tracers from biogenic (isoprene, monoterpenes and β-caryophyllene) and anthropogenic (aromatics) precursors. Among these compounds, isoprene SOA (SOAI) tracers represented the majority (26.6 ± 44.2 ng m-3), followed by monoterpene SOA (SOAM) tracers (0.97 ± 0.57 ng m-3), aromatic SOA (SOAA) tracer (2,3-dihydroxy-4-oxopentanoic acid, DHOPA, 0.25 ± 0.18 ng m-3) and β-caryophyllene SOA tracer (β-caryophyllenic acid, 0.09 ± 0.10 ng m-3). SOAI tracers exhibited high concentrations in the summer and low levels in the winter. The similar temperature dependence of SOAI tracers and isoprene emission suggested that the seasonal variation of SOAI tracers at the NC site was mainly influenced by the isoprene emission. The ratio of high-NOx to low-NOx products of SOAI (2-methylglyceric acid to 2-methyltetrols) was highest in the winter and lowest in the summer, due to the influence of temperature and relative humidity. The seasonal variation of SOAM tracers was impacted by monoterpenes emission and gas-particle partitioning. During the summer to the fall, temperature effect on partitioning was the dominant process influencing SOAM tracers' variation; while the temperature effect on emission was the dominant process influencing SOAM tracers' variation during the winter to the spring. SOAM tracer levels did not elevate with increased temperature in the summer, probably resulting from the counteraction of temperature effects on emission and partitioning. The concentrations of DHOPA were 1-2 orders of magnitude lower than those reported in the urban regions of the world

  7. A review of methods for modelling environmental tracers in groundwater: Advantages of tracer concentration simulation

    NASA Astrophysics Data System (ADS)

    Turnadge, Chris; Smerdon, Brian D.

    2014-11-01

    Mathematical models of varying complexity have been developed since the 1960s to interpret environmental tracer concentrations in groundwater flow systems. This review examines published studies of model-based environmental tracer interpretation, the progress of different modelling approaches, and also considers the value of modelling tracer concentrations directly rather than estimations of groundwater age. Based on citation metrics generated using the Web of Science and Google Scholar reference databases, the most highly utilised interpretation approaches are lumped parameter models (421 citations), followed closely by direct age models (220 citations). A third approach is the use of mixing cell models (99 citations). Although lumped parameter models are conceptually simple and require limited data, they are unsuitable for characterising the internal dynamics of a hydrogeological system and/or under conditions where large scale anthropogenic stresses occur within a groundwater basin. Groundwater age modelling, and in particular, the simulation of environmental tracer transport that explicitly accounts for the accumulation and decay of tracer mass, has proven to be highly beneficial in constraining numerical models. Recent improvements in computing power have made numerical simulation of tracer transport feasible. We argue that, unlike directly simulated ages, the results of tracer mass transport simulation can be compared directly to observations, without needing to correct for apparent age bias or other confounding factors.

  8. Tracer for circulation determinations

    SciTech Connect

    Moore, H.; Santos, S.; Wysong, R. D.

    1985-03-19

    An improved tracer particle is described comprising an ion exchange core having a polymer coating thereon, the coated ion exchange core having a reaction site capable of reacting with a compound containing an oxirane group, said coated ion exchange core having been treated with a compound containing an oxirane group to react with said coated ion exchange core causing an increase in mass of the tracer particle. Preferably, the ion exchange core is labelled with a radionuclide. These particles have improved characteristics including improved stability against leaching and improved handling properties. Such particles are useful in circulatory determinations involving the injection of the particles as a suspension in a physiologically acceptable carrier or medium into the circulatory system of animals.

  9. Communication: Ab initio study of O{sub 4}H{sup +}: A tracer molecule in the interstellar medium?

    SciTech Connect

    Xavier, George D.; Bernal-Uruchurtu, Margarita I.; Hernández-Lamoneda, Ramón

    2014-08-28

    The structure and energetics of the protonated molecular oxygen dimer calculated via ab initio methods is reported. We find structures that share analogies with the eigen and zundel forms for the protonated water dimer although the symmetrical sharing of the proton is more prevalent. Analysis of different fragmentation channels show charge transfer processes which indicate the presence of conical intersections for various states including the ground state. An accurate estimate for the proton affinity of O{sub 4} leads to a significantly larger value (5.6 eV) than for O{sub 2} (4.4 eV), implying that the reaction H{sub 3}{sup +} + O{sub 4} → O{sub 4}H{sup +} + H{sub 2} is exothermic by 28 Kcal/mol as opposed to the case of O{sub 2} which is nearly thermoneutral. This opens up the possibility of using O{sub 4}H{sup +} as a tracer molecule for oxygen in the interstellar medium.

  10. Overlapping and nonoverlapping cortical projections to cortex of the superior temporal sulcus in the rhesus monkey: double anterograde tracer studies.

    PubMed

    Seltzer, B; Cola, M G; Gutierrez, C; Massee, M; Weldon, C; Cusick, C G

    1996-06-24

    To examine how fibers from functionally distinct cortical zones interrelate within their target areas of the superior temporal sulcus (STS) in the rhesus monkey, separate anterograde tracers were injected in two different regions of the same hemisphere known to project to the STS. Paired injections were placed in dorsal prearcuate cortex and the caudal inferior parietal lobule (IPL), interconnected regions that are part of a hypothesized distributed network concerned with visuospatial analysis or directed attention; in a presumed auditory region of the superior temporal gyrus (STG) and in extrastriate visual cortex, the caudal IPL and lower rim of the intraparietal sulcus; and in dorsal prearcuate cortex and the STG. Overlapping and nonoverlapping projections were then examined in STS visual and polysensory areas. Prefrontal and parietal fibers directly overlapped extensively in area MST and all subdivisions of presumed polysensory cortex (areas TPOc, TPOi, and TPOr), although nonoverlapping connections were also found. Although STG and IPL fibers targeted all TPO subdivisions, connections were to nonoverlapping, but often adjacent, columns. Paired prefrontal and STG injections revealed largely nonoverlapping vertical columns of connections but substantial overlap within layers VI and I or areas TPOc and TPOi. The findings suggest that area TPO contains differently connected modules that may maintain at least initial segregation of visual versus auditory inputs. Other modules within area TPO receive directly converging input from the posterior parietal and the prefrontal cortices and may participate in a distributed cortical network concerned with visuospatial functions.

  11. Novel and non-traditional use of stable isotope tracers to study metal bioavailability from natural particles

    USGS Publications Warehouse

    Croteau, Marie-Noële; Cain, Daniel J.; Fuller, Christopher C.

    2013-01-01

    We devised a novel tracing approach that involves enriching test organisms with a stable metal isotope of low natural abundance prior to characterizing metal bioavailability from natural inorganic particles. In addition to circumventing uncertainties associated with labeling natural particles and distinguishing background metals, the proposed "reverse labeling" technique overcomes many drawbacks inherent to using radioisotope tracers. Specifically, we chronically exposed freshwater snails (Lymnaea stagnalis) to synthetic water spiked with Cu that was 99.4% 65Cu to increase the relative abundance of 65Cu in the snail’s tissues from 32% to >80%. The isotopically enriched snails were then exposed to benthic algae mixed with Cu-bearing Fe–Al particles collected from the Animas River (Colorado), an acid mine drainage impacted river. We used 63Cu to trace Cu uptake from the natural particles and inferred their bioavailability from calculation of Cu assimilation into tissues. Cu assimilation from these particles was 44%, indicating that 44% of the particulate Cu was absorbed by the invertebrate. This demonstrates that inorganic particulate Cu can be bioavailable. The reverse labeling approach shows great potential in various scientific areas such as environmental contamination and nutrition for addressing questions involving uptake of an element that naturally has multiple isotopes.

  12. Past leaded gasoline emissions as a nonpoint source tracer in riparian systems: A study of river inputs to San Francisco Bay

    USGS Publications Warehouse

    Dunlap, C.E.; Bouse, R.; Flegal, A.R.

    2000-01-01

    Variations in the isotopic composition of lead in 1995-1998 river waters flowing into San Francisco Bay trace the washout of lead deposited in the drainage basin from leaded gasoline combustion. At the confluence of the Sacramento and San Joaquin rivers where they enter the Bay, the isotopic compositions of lead in the waters define a linear trend away from the measured historical compositions of leaded gas in California. The river waters are shifted away from leaded gasoline values and toward an isotopic composition similar to Sierra Nevadan inputs which became the predominant source of sedimentation in San Francisco Bay following the onset of hydraulic gold mining in 1853. Using lead isotopic compositions of hydraulic mine sediments and average leaded gasoline as mixing end members, we calculate that more than 50% of the lead in the present river water originated from leaded gasoline combustion. The strong adsorption of lead (log K(d) > 7.4) to particulates appears to limit the flushing of gasoline lead from the drainage basin, and the removal of that lead from the system may have reached an asymptotic limit. Consequently, gasoline lead isotopes should prove to be a useful nonpoint source tracer of the environmental distribution of particle- reactive anthropogenic metals in freshwater systems.

  13. Nanoparticle tracers in calcium carbonate porous media

    NASA Astrophysics Data System (ADS)

    Li, Yan Vivian; Cathles, Lawrence M.; Archer, Lynden A.

    2014-08-01

    Tracers are perhaps the most direct way of diagnosing subsurface fluid flow pathways for ground water decontamination and for natural gas and oil production. Nanoparticle tracers could be particularly effective because they do not diffuse away from the fractures or channels where flow occurs and thus take much less time to travel between two points. In combination with a chemical tracer they can measure the degree of flow concentration. A prerequisite for tracer applications is that the particles are not retained in the porous media as the result of aggregation or sticking to mineral surfaces. By screening eight nanoparticles (3-100 nm in diameter) for retention when passed through calcium carbonate packed laboratory columns in artificial oil field brine solutions of variable ionic strength we show that the nanoparticles with the least retention are 3 nm in diameter, nearly uncharged, and decorated with highly hydrophilic polymeric ligands. The details of these column experiments and the tri-modal distribution of zeta potential of the calcite sand particles in the brine used in our tests suggests that parts of the calcite surface have positive zeta potential and the retention of negatively charged nanoparticles occurs at these sites. Only neutral nanoparticles are immune to at least some retention.

  14. Journal: Efficient Hydrologic Tracer-Test Design for Tracer ...

    EPA Pesticide Factsheets

    Hydrological tracer testing is the most reliable diagnostic technique available for the determination of basic hydraulic and geometric parameters necessary for establishing operative solute-transport processes. Tracer-test design can be difficult because of a lack of prior knowledge of the basic hydraulic and geometric parameters desired and the appropriate tracer mass to release. A new efficient hydrologic tracer-test design (EHTD) methodology has been developed to facilitate the design of tracer tests by root determination of the one-dimensional advection-dispersion equation (ADE) using a preset average tracer concentration which provides a theoretical basis for an estimate of necessary tracer mass. The method uses basic measured field parameters (e.g., discharge, distance, cross-sectional area) that are combined in functional relatipnships that descrive solute-transport processes related to flow velocity and time of travel. These initial estimates for time of travel and velocity are then applied to a hypothetical continuous stirred tank reactor (CSTR) as an analog for the hydrological-flow system to develop initial estimates for tracer concentration, tracer mass, and axial dispersion. Application of the predicted tracer mass with the hydraulic and geometric parameters in the ADE allows for an approximation of initial sample-collection time and subsequent sample-collection frequency where a maximum of 65 samples were determined to be necessary for descri

  15. A tracer study for assessing the interactions between hydraulic retention time and transport processes in a wetland system for nutrient removal.

    PubMed

    Chang, Ni-Bin; Xuan, Zhemin; Wanielista, Martin P

    2012-03-01

    In this study, a new-generation subsurface upflow wetland (SUW) system packed with the unique sorption media was introduced for nutrient removal. To explore the interface between hydraulic and environmental performance, a tracer study was carried out in concert with a transport model to collectively provide hydraulic retention time (7.1 days) and compelling evidence of pollutant fate and transport processes. Research findings indicate that our pollution-control media demonstrate smooth nutrient removal efficiencies across different sampling port locations given the appropriate size distribution conversant with the anticipated hydraulic patterns and layered structure among the sorption media components. The sizable capacity for nutrient removal in this bioprocess confirms that SUW is a promising substitute for an extension of traditional on-site wastewater treatment systems.

  16. Lidar Tracking of Multiple Fluorescent Tracers: Method and Field Test

    NASA Technical Reports Server (NTRS)

    Eberhard, Wynn L.; Willis, Ron J.

    1992-01-01

    Past research and applications have demonstrated the advantages and usefulness of lidar detection of a single fluorescent tracer to track air motions. Earlier researchers performed an analytical study that showed good potential for lidar discrimination and tracking of two or three different fluorescent tracers at the same time. The present paper summarizes the multiple fluorescent tracer method, discusses its expected advantages and problems, and describes our field test of this new technique.

  17. Tracers and Tracer Testing: Design, Implementation, Tracer Selection, and Interpretation Methods

    SciTech Connect

    G. Michael Shook; Shannon L.; Allan Wylie

    2004-01-01

    Conducting a successful tracer test requires adhering to a set of steps. The steps include identifying appropriate and achievable test goals, identifying tracers with the appropriate properties, and implementing the test as designed. When these steps are taken correctly, a host of tracer test analysis methods are available to the practitioner. This report discusses the individual steps required for a successful tracer test and presents methods for analysis. The report is an overview of tracer technology; the Suggested Reading section offers references to the specifics of test design and interpretation.

  18. Experimental Study of Gas Hydrate Dynamics

    NASA Astrophysics Data System (ADS)

    Fandino, O.; Ruffine, L.

    2011-12-01

    Important quantities of methane and other gases are trapped below the seafloor and in the permafrost by an ice-like solid, called gas hydrates or clathrate hydrates. The latter is formed when water is mixing with different gases at high pressures and low temperatures. Due to a their possible use as a source of energy [1] or the problematic related to flow assurance failure in pipelines [2] the understanding of their processes of formation/destabilisation of these structures becomes a goal for many laboratories research as well as industries. In this work we present an experimental study on the stochastic behaviour of hydrate formation from a bulk phase. The method used here for the experiments was to repeat several time the same hydrate formation procedure and to notice the different from one experiment to another. A variable-volume type high-pressure apparatus with two sapphire windows was used. This device, already presented by Ruffine et al.[3], allows us to perform both kinetics and phase equilibrium measurements. Three initial pressure conditions were considered here, 5.0 MPa, 7.5 MPa and 10.0 MPa. Hydrates have been formed, then allowed to dissociate by stepwise heating. The memory effect has also been investigated after complete dissociation. It turned out that, although the thermodynamics conditions of formation and/or destabilization were reproducible. An attempt to determine the influence of pressure on the nucleation induction time will be discussed. References 1. Sum, A. K.; Koh, C. A.; Sloan, E. D., Clathrate Hydrates: From Laboratory Science to Engineering Practice. Industrial & Engineering Chemistry Research 2009, 48, 7457-7465. 2. Sloan, E. D., A changing hydrate paradigm-from apprehension to avoidance to risk management. Fluid Phase Equilibria 2005, 228, 67-74. 3. Ruffine, L.; Donval, J. P.; Charlou, J. L.; Cremière, A.; Zehnder, B. H., Experimental study of gas hydrate formation and destabilisation using a novel high-pressure apparatus. Marine

  19. A study of interstellar aldehydes and enols as tracers of a cosmic ray-driven nonequilibrium synthesis of complex organic molecules

    PubMed Central

    Abplanalp, Matthew J.; Gozem, Samer; Krylov, Anna I.; Shingledecker, Christopher N.; Herbst, Eric; Kaiser, Ralf I.

    2016-01-01

    Complex organic molecules such as sugars and amides are ubiquitous in star- and planet-forming regions, but their formation mechanisms have remained largely elusive until now. Here we show in a combined experimental, computational, and astrochemical modeling study that interstellar aldehydes and enols like acetaldehyde (CH3CHO) and vinyl alcohol (C2H3OH) act as key tracers of a cosmic-ray-driven nonequilibrium chemistry leading to complex organics even deep within low-temperature interstellar ices at 10 K. Our findings challenge conventional wisdom and define a hitherto poorly characterized reaction class forming complex organic molecules inside interstellar ices before their sublimation in star-forming regions such as SgrB2(N). These processes are of vital importance in initiating a chain of chemical reactions leading eventually to the molecular precursors of biorelevant molecules as planets form in their interstellar nurseries. PMID:27382172

  20. Radioactive tracer study of Cs{sup +}, Co{sup 2+}, and Eu{sup 3+} sorption on shungite III of the Zazhogino Site

    SciTech Connect

    Kuznetsov, R.A.; Kalinin, A.I.; Bondarenko, V.V.

    1995-03-01

    Sorption characteristics of shungite III of the Zazhogino site with respect to Cs{sup +}, Co{sup 2+}, and Eu{sup 3+} cations have been studied by the radioactive tracer method. It was found that the kinetics of the sorption is slow and the equilibrium is attained in about 7 days. At pH 5, the distribution coefficients of Cs{sup +}, Co{sup 2+}, and Eu{sup 3+} are 35, 47, and 660, respectively. The dependence of the distribution coefficients on the pH of aqueous solution was determined. The exchange capacity for Eu{sup 3+} at pH 6 is 36 {mu}eq g{sup -1}. The modification of shungite by treating with toluene or hydrofluoric acid significantly improves its sorption properties.

  1. Positional Enrichment by Proton Analysis (PEPA): A One-Dimensional (1) H-NMR Approach for (13) C Stable Isotope Tracer Studies in Metabolomics.

    PubMed

    Vinaixa, Maria; Rodríguez, Miguel A; Aivio, Suvi; Capellades, Jordi; Gómez, Josep; Canyellas, Nicolau; Stracker, Travis H; Yanes, Oscar

    2017-03-20

    A novel metabolomics approach for NMR-based stable isotope tracer studies called PEPA is presented, and its performance validated using human cancer cells. PEPA detects the position of carbon label in isotopically enriched metabolites and quantifies fractional enrichment by indirect determination of (13) C-satellite peaks using 1D-(1) H-NMR spectra. In comparison with (13) C-NMR, TOCSY and HSQC, PEPA improves sensitivity, accelerates the elucidation of (13) C positions in labeled metabolites and the quantification of the percentage of stable isotope enrichment. Altogether, PEPA provides a novel framework for extending the high-throughput of (1) H-NMR metabolic profiling to stable isotope tracing in metabolomics, facilitating and complementing the information derived from 2D-NMR experiments and expanding the range of isotopically enriched metabolites detected in cellular extracts.

  2. Positional Enrichment by Proton Analysis (PEPA): A One‐Dimensional 1H‐NMR Approach for 13C Stable Isotope Tracer Studies in Metabolomics

    PubMed Central

    Rodríguez, Miguel A.; Aivio, Suvi; Capellades, Jordi; Gómez, Josep; Canyellas, Nicolau; Stracker, Travis H.

    2017-01-01

    Abstract A novel metabolomics approach for NMR‐based stable isotope tracer studies called PEPA is presented, and its performance validated using human cancer cells. PEPA detects the position of carbon label in isotopically enriched metabolites and quantifies fractional enrichment by indirect determination of 13C‐satellite peaks using 1D‐1H‐NMR spectra. In comparison with 13C‐NMR, TOCSY and HSQC, PEPA improves sensitivity, accelerates the elucidation of 13C positions in labeled metabolites and the quantification of the percentage of stable isotope enrichment. Altogether, PEPA provides a novel framework for extending the high‐throughput of 1H‐NMR metabolic profiling to stable isotope tracing in metabolomics, facilitating and complementing the information derived from 2D‐NMR experiments and expanding the range of isotopically enriched metabolites detected in cellular extracts. PMID:28220994

  3. NEXT GENERATION GAS TURBINE (NGGT) SYSTEMS STUDY

    SciTech Connect

    Unknown

    2001-12-05

    Building upon the 1999 AD Little Study, an expanded market analysis was performed by GE Power Systems in 2001 to quantify the potential demand for an NGGT product. This analysis concluded that improvements to the US energy situation might be best served in the near/mid term (2002-2009) by a ''Technology-Focused'' program rather than a specific ''Product-Focused'' program. Within this new program focus, GEPS performed a parametric screening study of options in the three broad candidate categories of gas turbines: aero-derivative, heavy duty, and a potential hybrid combining components of the other two categories. GEPS's goal was to determine the best candidate systems that could achieve the DOE PRDA expectations and GEPS's internal design criteria in the period specified for initial product introduction, circa 2005. Performance feasibility studies were conducted on candidate systems selected in the screening task, and critical technology areas were identified where further development would be required to meet the program goals. DOE PRDA operating parameters were found to be achievable by 2005 through evolutionary technology. As a result, the study was re-directed toward technology enhancements for interim product introductions and advanced/revolutionary technology for potential NGGT product configurations. Candidate technologies were identified, both evolutionary and revolutionary, with a potential for possible development products via growth step improvements. Benefits were analyzed from two perspectives: (1) What would be the attributes of the top candidate system assuming the relevant technologies were developed and available for an NGGT market opportunity in 2009/2010; and (2) What would be the expected level of public benefit, assuming relevant technologies were incorporated into existing new and current field products as they became available. Candidate systems incorporating these technologies were assessed as to how they could serve multiple applications

  4. Can Positron Emission Tomography/Computed Tomography with the Dual Tracers Fluorine-18 Fluoroestradiol and Fluorodeoxyglucose Predict Neoadjuvant Chemotherapy Response of Breast Cancer? ----A Pilot Study

    PubMed Central

    Yang, Zhongyi; Sun, Yifei; Xue, Jing; Yao, Zhifeng; Xu, Junyan; Cheng, Jingyi; Shi, Wei; Zhu, Beiling; Zhang, Yongping; Zhang, Yingjian

    2013-01-01

    Objective To assess the clinical value of dual tracers Positron emission tomography/computed tomography (PET/CT) 18F-fluoroestradiol (18F-FES) and 18F-fluorodeoxyglucose (18F-FDG) in predicting neoadjuvant chemotherapy response (NAC) of breast cancer. Methods Eighteen consecutive patients with newly diagnosed, non-inflammatory, stage II and III breast cancer undergoing NAC were included. Before chemotherapy, they underwent both 18F-FES and 18F-FDG PET/CT scans. Surgery was performed after three to six cycles of chemotherapy. Tumor response was graded and divided into two groups: the responders and non-responders. We used the maximum standardized uptake value (SUVmax) to qualify each primary lesion. Results Pathologic analysis revealed 10 patients were responders while the other 8 patients were non-responders. There was no statistical difference of SUVmax-FDG and tumor size between these two groups (P>0.05). On the contrary, SUVmax-FES was lower in responders (1.75±0.66 versus 4.42±1.14; U=5, P=0.002); and SUVmax-FES/FDG also showed great value in predicting outcome (0.16±0.06 versus 0.54±0.22; U=5, P=0.002). Conclusions Our study showed 18F-FES PET/CT might be feasible to predict response of NAC. However, whether the use of dual tracers 18F-FES and 18F-FDG has complementary value should be further studied. PMID:24205151

  5. How to chase a tracer - combining conventional salt tracer testing and direct push electrical conductivity profiling for enhanced aquifer characterization

    NASA Astrophysics Data System (ADS)

    Vienken, Thomas; Huber, Emanuel; Kreck, Manuel; Huggenberger, Peter; Dietrich, Peter

    2017-01-01

    Tracer testing is a well-established technique in hydrogeological site characterization. However, certain a priori knowledge of the hydraulic regime is required beforehand to avoid test failure, e.g. miss of tracer. In this study, we propose a novel tracer test concept for the hydraulic characterization of shallow unconsolidated sedimentary deposits when only scarce a priori information on the hydraulic regime is available. Therefore, we combine conventional salt tracer testing with direct push vertical high resolution electrical conductivity logging. The proposed tracer test concept was successfully tested on coarse, braided river deposits of the Tagliamento River, Italy. With limited a priori information available two tracer tests were performed in three days to reliably determine ground water flow direction and velocity allowing on-site decision-making to adaptively install observation wells for reliable breakthrough curve measurements. Furthermore, direct push vertical electrical profiling provided essential information about the plume characteristics with outstanding measurement resolution and efficiency.

  6. Tracer-Test Planning Using the Efficient Hydrologic Tracer ...

    EPA Pesticide Factsheets

    Hydrological tracer testing is the most reliable diagnostic technique available for establishing flow trajectories and hydrologic connections and for determining basic hydraulic and geometric parameters necessary for establishing operative solute-transport processes. Tracer-test design can be difficult because of a lack of prior knowledge of the basic hydraulic and geometric parameters desired and the appropriate tracer mass to release. A new efficient hydrologic tracer-test design (EHTD) methodology has been developed that combines basic measured field parameters (e.g., discharge, distance, cross-sectional area) in functional relationships that describe solute-transport processes related to flow velocity and time of travel. The new method applies these initial estimates for time of travel and velocity to a hypothetical continuously stirred tank reactor as an analog for the hydrologic flow system to develop initial estimates for tracer concentration and axial dispersion, based on a preset average tracer concentration. Root determination of the one-dimensional advection-dispersion equation (ADE) using the preset average tracer concentration then provides a theoretical basis for an estimate of necessary tracer mass.Application of the predicted tracer mass with the hydraulic and geometric parameters in the ADE allows for an approximation of initial sample-collection time and subsequent sample-collection frequency where a maximum of 65 samples were determined to be

  7. Use of environmental tracers to study the chemical evolution of shallow ground water in a karst area of northern Florida

    SciTech Connect

    Katz, B.G. ); Plummer, L.N.; Busenberg, E. )

    1993-03-01

    The pathways of shallow ground-water flow in poorly confined aquifer systems of northern FL are influenced by inflow to and outflow from numerous sinkhole lakes that are characteristic of the Sand Hills karst region. Ground-water samples were collected immediately upgradient and downgradient from Lake Barco at depths of 1.6--29 m below the water table from observation wells completed in the surficial aquifer system, the intermediate confining unit (icu), and the Upper Floridan aquifer. Samples were also collected of rainfall, lake water, and ground water at a depth of 4.1 m beneath the lake bottom. The environmental tracers tritium and chlorofluorocarbons were used to estimate mean residence times of water and rates of chemical mass transfer along flow paths. Water samples collected from wells upgradient of the lake were oxic and had CFC-model recharge dates between 1971 and 1986. The content of delta H-2 and delta O-18 of water from the two aquifer systems and the icu was nearly identical to the isotopic composition of rainfall. Changes in the chemical composition of the ground water with depth were simulated by reacting rainfall with minerals and dissolved gases that exist in the hydrogeologic units. Ground-water samples collected from sites beneath and downgradient of the lake were anoxic, with measured concentrations of hydrogen sulfide and methane ranging from 0.02--0.58 mg/l and 0.30--6.1 mg/l, respectively. CFC-model recharge dates ranged from 1956 to 1983. The data indicated that ground water downgradient of the lake is being recharged by leakage of lake water. The chemical composition of ground water is influenced by the movement of lake water through reducing, organic-rich sediments accumulated at the bottom. Along the downgradient flow paths, the water chemistry evolves from the composition of lake water and is modified by subsequent reactions including reduction of sulfate and ferric iron, methanogenesis, and dissolution and precipitation of minerals.

  8. Natural gas consumption prediction in Slovenian industry - a case study

    NASA Astrophysics Data System (ADS)

    Kovačič, Miha; Šarler, Božidar; Župerl, Uroš

    2016-09-01

    In accordance with the regulations of the Energy Agency of the Republic of Slovenia, each natural gas supplier regulates and determines the charges for the differences between the ordered (predicted) and the actually supplied quantities of natural gas. Yearly charges for these differences represent up to 2% of supplied natural gas costs. All the natural gas users, especially industry, have huge problems finding the proper method for efficient natural gas consumption prediction and, consequently, the decreasing of mentioned costs. In this study, prediction of the natural gas consumption in Štore Steel Ltd. (steel plant) is presented. On the basis of production data, several models for natural gas consumption have been developed using linear regression, genetic programming and artificial neural network methods. The genetic programming approach outperformed linear regression and artificial neural networks.

  9. Time Dependent Studies of Reactive Shocks in the Gas Phase

    DTIC Science & Technology

    1978-11-16

    1 LEVEL NRL Memorandum Report 3W tO Time Dependent Studies of Reactive Shocks in the Gas Phase E.S. ORAN, ’T.R. YOUNG and J.P. BORIS Laboratory for...34-• TIME DEPENDENT STUDIES OF REACTIVE SHOCKS IN THE GAS PHASE I. Introduction This paper presents results obtained from a detailed numerical...chemical kinetics, reaction products, and intermediates produced in reactive gas mixtures ignited by the propagation of a shock front. The model is based

  10. Cumulus cloud transport of transient tracers

    NASA Technical Reports Server (NTRS)

    Gidel, L. T.

    1983-01-01

    A theoretical framework is developed for including cumulus cloud transport, rainout of water soluble gases, and aqueous phase chemistry into gas phase photochemical models. Cloud populations are represented as ensemble distributions of individual clouds of various heights. An individual cloud is represented as a one-dimensional, steady state plume with height-independent radius entraining air from the boundary of the cloud. The model is applied to several hypothetical atmospheric tracers to show how clouds may affect the tropospheric distributions of ozone, NO(y), SO2, peroxyacetylnitrate, hydrocarbons, and other gases. Although the numerical experiments were based on cloud mass fluxes from diagnostic studies in the tropics and thus are not representative of the entire globe, it was found that an increasing mixing ratio with height in the free troposphere can be produced for some gases with only a surface source when clouds are present. This suggests that some reactive tropospheric species with primarily surface sources may play a somewhat more important role in tropospheric chemistry than is presently believed depending on the global distribution of cloud mass fluxes. Deficiencies in existing photochemical models due to the way clouds are typically treated are discussed.

  11. Gas release and conductivity modification studies

    NASA Technical Reports Server (NTRS)

    Linson, L. M.; Baxter, D. C.

    1979-01-01

    The behavior of gas clouds produced by releases from orbital velocity in either a point release or venting mode is described by the modification of snowplow equations valid in an intermediate altitude regime. Quantitative estimates are produced for the time dependence of the radius of the cloud, the average internal energy, the translational velocity, and the distance traveled. The dependence of these quantities on the assumed density profile, the internal energy of the gas, and the ratio of specific heats is examined. The new feature is the inclusion of the effect of the large orbital velocity. The resulting gas cloud models are used to calculate the characteristics of the field line integrated Pedersen conductivity enhancements that would be produced by the release of barium thermite at orbital velocity in either the point release or venting modes as a function of release altitude and chemical payload weight.

  12. Final report on the use of gaseous tracers in WRI's 10-ton nonuniform oil shale retorting tests

    SciTech Connect

    Turner, T.F.; Moore, D.F.

    1985-12-01

    For tests on nonuniform oil shale retorting, Western Research Institute's 10-ton retort was loaded with shale rubble in zones of different permeability. The permeability of any given zone was determined by the particle size range loaded into that zone. The retort was studied using gas tracer techniques and flow model simulations. Results of these tracer studies are discussed in this report. Nine retorting and tracer runs were made on the retort. For each run, tracer injections were made into the main air flow inlet and into taps near the top of the retort. Detection taps were located at four levels in the retort with five taps on each level in tests S71 through S78 and six taps on each level in run S79. The oil shale rubble bed was configured with a cylindrical core in tests S71 through S78 and with two side-by-side regions with differing bed properties in test S79. Relationships are shown between the tracer response and sweep efficiency, oil yield, and local yield. Model simulations are compared with tracer responses and indicate fair agreement between model-estimated and measured response times but poor agreement on the shapes of the response curves. Although the data are scattered, there is suggestive evidence that the sweep efficiency of a retort can be determined using simple inlet-to-outlet tracer tests. Oil yield can also be predicted for the operating conditions used for the nonuniform retorting tests. More tests on retorts with intermediate degrees of nonuniformity must be made to confirm the correlations developed in this study. 15 refs., 9 figs.

  13. [Laser Raman Spectroscopy and Its Application in Gas Hydrate Studies].

    PubMed

    Fu, Juan; Wu, Neng-you; Lu, Hai-long; Wu, Dai-dai; Su, Qiu-cheng

    2015-11-01

    Gas hydrates are important potential energy resources. Microstructural characterization of gas hydrate can provide information to study the mechanism of gas hydrate formation and to support the exploitation and application of gas hydrate technology. This article systemly introduces the basic principle of laser Raman spectroscopy and summarizes its application in gas hydrate studies. Based on Raman results, not only can the information about gas composition and structural type be deduced, but also the occupancies of large and small cages and even hydration number can be calculated from the relative intensities of Raman peaks. By using the in-situ analytical technology, laser Raman specstropy can be applied to characterize the formation and decomposition processes of gas hydrate at microscale, for example the enclathration and leaving of gas molecules into/from its cages, to monitor the changes in gas concentration and gas solubility during hydrate formation and decomposition, and to identify phase changes in the study system. Laser Raman in-situ analytical technology has also been used in determination of hydrate structure and understanding its changing process under the conditions of ultra high pressure. Deep-sea in-situ Raman spectrometer can be employed for the in-situ analysis of the structures of natural gas hydrate and their formation environment. Raman imaging technology can be applied to specify the characteristics of crystallization and gas distribution over hydrate surface. With the development of laser Raman technology and its combination with other instruments, it will become more powerful and play a more significant role in the microscopic study of gas hydrate.

  14. Study the gas sensing properties of boron nitride nanosheets

    SciTech Connect

    Sajjad, Muhammad; Feng, Peter

    2014-01-01

    Graphical abstract: - Highlights: • We synthesized boron nitride nanosheets (BNNSs) on silicon substrate. • We analyzed gas sensing properties of BNNSs-based gas-sensor device. • CH{sub 4} gas is used to measure gas-sensing properties of the device. • Quick response and recovery time of the device is recorded. • BNNSs showed excellent sensitivity to the working gas. - Abstract: In the present communication, we report on the synthesis of boron nitride nanosheets (BNNSs) and study of their gas sensing properties. BNNSs are synthesized by irradiating pyrolytic hexagonal boron nitride (h-BN) target using CO{sub 2} laser pulses. High resolution transmission electron microscopic measurements (HRTEM) revealed 2-dientional honeycomb crystal lattice structure of BNNSs. HRTEM, electron diffraction, XRD and Raman scattering measurements clearly identified h-BN. Gas sensing properties of synthesized BNNSs were analyzed with prototype gas sensor using methane as working gas. A systematic response curve of the sensor is recorded in each cycle of gas “in” and “out”; suggesting excellent sensitivity and high performance of BNNSs-based gas-sensor.

  15. Evaluation of anthropogenic secondary organic aerosol tracers from aromatic hydrocarbons

    NASA Astrophysics Data System (ADS)

    Al-Naiema, Ibrahim M.; Stone, Elizabeth A.

    2017-02-01

    Products of secondary organic aerosol (SOA) from aromatic volatile organic compounds (VOCs) - 2,3-dihydroxy-4-oxopentanoic acid, dicarboxylic acids, nitromonoaromatics, and furandiones - were evaluated for their potential to serve as anthropogenic SOA tracers with respect to their (1) ambient concentrations and detectability in PM2.5 in Iowa City, IA, USA; (2) gas-particle partitioning behaviour; and (3) source specificity by way of correlations with primary and secondary source tracers and literature review. A widely used tracer for toluene-derived SOA, 2,3-dihydroxy-4-oxopentanoic acid was only detected in the particle phase (Fp = 1) at low but consistently measurable ambient concentrations (averaging 0.3 ng m-3). Four aromatic dicarboxylic acids were detected at relatively higher concentrations (9.1-34.5 ng m-3), of which phthalic acid was the most abundant. Phthalic acid had a low particle-phase fraction (Fp = 0.26) likely due to quantitation interferences from phthalic anhydride, while 4-methylphthalic acid was predominantly in the particle phase (Fp = 0.82). Phthalic acid and 4-methylphthalic acid were both highly correlated with 2,3-dihydroxy-4-oxopentanoic acid (rs = 0.73, p = 0.003; rs = 0.80, p < 0.001, respectively), suggesting that they were derived from aromatic VOCs. Isophthalic and terephthalic acids, however, were detected only in the particle phase (Fp = 1), and correlations suggested association with primary emission sources. Nitromonoaromatics were dominated by particle-phase concentrations of 4-nitrocatechol (1.6 ng m-3) and 4-methyl-5-nitrocatechol (1.6 ng m-3) that were associated with biomass burning. Meanwhile, 4-hydroxy-3-nitrobenzyl alcohol was detected in a lower concentration (0.06 ng m-3) in the particle phase only (Fp = 1) and is known as a product of toluene photooxidation. Furandiones in the atmosphere have only been attributed to the photooxidation of aromatic hydrocarbons; however the substantial partitioning toward the gas phase

  16. Metal hydrides studied in gas discharge tube

    NASA Astrophysics Data System (ADS)

    Bozhinova, I.; Kolev, S.; Popov, Tsv.; Pashov, A.; Dimitrova, M.

    2016-05-01

    A novel construction of gas discharge tube has been tested for production of high densities of metal hydrydes. Its performance turned out to be comparable with the existing sources of the same type and even better. First results of the tests on NiH are reported and critically analysed. Plans for future modifiaction of the construction and application of the tube are discussed.

  17. EPA GAS PHASE CHEMISTRY CHAMBER STUDIES

    EPA Science Inventory

    Gas-phase smog chamber experiments are being performed at EPA in order to evaluate a number of current chemical mechanisms for inclusion in EPA regulatory and research models. The smog chambers are 9000 L in volume and constructed of 2-mil teflon film. One of the chambers is co...

  18. Case Study: Natural Gas Regional Transport Trucks

    SciTech Connect

    Laughlin, M.; Burnham, A.

    2016-08-01

    Learn about Ryder System, Inc.'s experience in deploying nearly 200 CNG and LNG heavy-duty trucks and construction and operation of L/CNG stations using ARRA funds. Using natural gas in its fleet, Ryder mitigated the effects of volatile fuel pricing and reduced lifecycle GHGs by 20% and petroleum by 99%.

  19. Study of gas purifiers for the CMS RPC detector

    NASA Astrophysics Data System (ADS)

    Benussi, L.; Bianco, S.; Colafranceschi, S.; Fabbri, F. L.; Felli, F.; Ferrini, M.; Giardoni, M.; Greci, T.; Paolozzi, A.; Passamonti, L.; Piccolo, D.; Pierluigi, D.; Russo, A.; Saviano, G.; Buontempo, S.; Cimmino, A.; de Gruttola, M.; Fabozzi, F.; Iorio, A. O. M.; Lista, L.; Paolucci, P.; Baesso, P.; Belli, G.; Pagano, D.; Ratti, S. P.; Vicini, A.; Vitulo, P.; Viviani, C.; Guida, R.; Sharma, A.

    2012-01-01

    The CMS RPC muon detector utilizes a gas recirculation system called closed loop (CL) to cope with large gas mixture volumes and costs. A systematic study of CL gas purifiers has been carried out over 400 days between July 2008 and August 2009 at CERN in a low-radiation test area, with the use of RPC chambers with currents monitoring, and gas analysis sampling points. The study aimed to fully clarify the presence of pollutants, the chemistry of purifiers used in the CL, and the regeneration procedure. Preliminary results on contaminants release and purifier characterization are reported.

  20. An integrated study of nutrient leaching and greenhouse gas emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nutrient leaching and greenhouse gas emission are two of the primary environmental impacts of crop production. These processes have been studied at great length separately, but few integrated studies of leaching and greenhouse gas emission have been conducted. We measured nutrient leaching and green...

  1. 20 CFR 718.105 - Arterial blood-gas studies.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 20 Employees' Benefits 3 2010-04-01 2010-04-01 false Arterial blood-gas studies. 718.105 Section 718.105 Employees' Benefits EMPLOYMENT STANDARDS ADMINISTRATION, DEPARTMENT OF LABOR FEDERAL COAL MINE... at rest or during exercise. No blood-gas study shall be performed if medically contraindicated. (b)...

  2. Dilution and stoichiometry effects on gas reburning: An experimental study

    SciTech Connect

    Bilbao, R.; Alzueta, M.U.; Millera, A.; Prada, L.

    1997-06-01

    Gas reburning is a NO{sub x} reduction technique that can be applied to different combustion systems. The influence of stoichiometry and dilution effects on the efficiency of the gas reburning process has been studied from an experimental point of view at a temperature of 1,100 C. Methane, ethane, and natural gas have been used as reburning fuels. The results obtained show that both stoichiometry and dilution level are very important parameters for the performance of the process.

  3. Experimental studies of gas-aerosol reactions

    NASA Astrophysics Data System (ADS)

    Gupta, Anand

    1991-05-01

    The aqueous phase oxidation of SO2 by H2O2 is believed to the principle mechanism for atmospheric sulfate formation in cloud droplets. However, no studies in noncloud aerosol systems have been reported. The objective is to quantify the importance of the noncloud liquid phase reactions of SO2 by H2O2 in the atmosphere. Growth rates of submicron droplets exposed to SO2 and H2O2 were measured using the tandem differential mobility analyzer (TDMA) technique (Rader and McMurry, 1986). The technique uses differential mobility analyzers (DMA's) to generate monodisperse particles and to measure particle size after the reaction. To facilitate submicron monodisperse droplet production with the DMA, a low-ion-concentration charter capable of generating singly charged particles up to 1.0 microns was developed and experimentally evaluated. The experiments were performed using dry and deliquesced (NH4)2SO4 particles with SO2 and H2O2 concentrations from 0-860 ppb and 0-150 ppb, respectively. No growth was observed for dry particles. For droplets greater than or equal to 0.3 microns, the fractional diameter growth was independent of particle size and for droplets less than or equal to 0.2 microns, it decreased as particle size decreased. The observed decrease is due to NH3 evaporation. As ammonia evaporates, droplet pH decreases causing the oxidation rate to decrease, leading to a lower growth rate. To predict the size-dependent growth rates, a theoretical model was developed using solution thermodynamics, gas/particle equilibrium, and chemical kinetics. The experimental and theoretical results are in reasonable agreement. For dry (NH4)2SO4 particles exposed to SO2, H2O2, NH3, and H2O vapor, surface reaction-controlled growth was observed. Particle growth was very sensitive to particle composition. No growth was observed for Polystyrene latex particles, whereas (NH4)2SO4 particles doped with catalysts (Fe(2+), Fe(3+), Mn(2+) and Cu(2+)) in a molar ratio of 1:500 grew slower than

  4. Experimental Studies of Gas-Aerosol Reactions

    NASA Astrophysics Data System (ADS)

    Gupta, Anand

    1991-02-01

    The aqueous phase oxidation of SO_2 by H_2O_2 is believed to be the principle mechanism for atmospheric sulfate formation in cloud droplets. However, no studies in noncloud aerosol systems have been reported. The objective of this thesis is to quantify the importance of the noncloud liquid phase reactions of SO_2 by H_2O_2 in the atmosphere. In this thesis growth rates of submicron droplets exposed to SO_2 and H_2 O_2 were measured using the tandem differential mobility analyzer (TDMA) technique (Rader and McMurry, 1986). The technique uses differential mobility analyzers (DMAs) to generate monodisperse particles and to measure particle size after the reaction. To facilitate submicron monodisperse droplet production with the DMA, a low-ion-concentration charger capable of generating singly charged particles up to 1.0 μm was developed and experimentally evaluated. The experiments were performed using dry and deliquesced (NH_4)_2SO _4 particles with SO_2 and H_2O_2 concentrations from 0-860 ppb and 0-150 ppb, respectively. No growth was observed for dry particles. For droplets >=0.3 mum, the fractional diameter growth was independent of particle size and for droplets <=0.2 mum, it decreased as particle size decreased. The observed decrease is due to NH_3 evaporation. As ammonia evaporates, droplet pH decreases causing the oxidation rate to decrease, leading to a lower growth rate. To predict the size-dependent growth rates, a theoretical model was developed using solution thermodynamics, gas/particle equilibrium and chemical kinetics. The experimental and theoretical results are in reasonable agreement. For dry (NH_4) _2SO_4 particles exposed to SO_2, H_2O _2, NH_3 and H_2O vapor, surface reaction-controlled growth was observed. Particle growth was very sensitive to particle composition. No growth was observed for Polystyrene latex particles, whereas (NH_4) _2SO_4 particles doped with catalysts (Fe^{2+} , Fe^{3+}, Mn ^{2+}, Cu^{2+ }) in a molar ratio of 1:500 grew

  5. Little study sees large growth in Asian natural gas market

    SciTech Connect

    O'Driscoll, M.

    1993-06-03

    Power capacity additions in Asia will at least triple by 2010, and Arthur D. Little Inc. predicts natural gas can pick up a good 15 percent of that market. The study predicts Asia potentially will need 720 gigawatts of new power generation by 2010, of which 15 percent may be gas-based. This represents a market three times the size of the US market in the same period, and would require more than $1 trillion in investment to finance the power generation projects alone. Six forces are driving new market opportunities for natural gas in Asia, and have set the stage for major investments in Asian gas-based power generation. They are: New technologies; growing environmental pressures; privatization; alternative energy pricing; gas availability; and continued economic growth. Japan, South Korea and Taiwan already have large, well-established markets for both gas and power that provide minimal opportunities for foreign investment. But the rest of Asia - specifically, India, Pakistan, the Philippines, Vietnam, Indonesia, Malaysia, the People's Republic of China, Thailand, Bangladesh and Myanmar - is still relatively undeveloped, the study said, and gas is emerging as an energy import substitute or export earner. The study found those countries will turn increased environmental awareness and concern into legislation as their economic prosperity grows, leading to a higher future value for natural gas relative to other fuels. Stricter emissions standards will favor gas over diesel, fuel oil and coal.

  6. Analysis of multicomopnent groundwater flow in karst aquifer by CFC, tritium, tracer test and modelling, case study at Skaistkalnes vicinity, Latvia

    NASA Astrophysics Data System (ADS)

    Bikshe, Janis; Babre, Alise; Delina, Aija; Popovs, Konrads

    2014-05-01

    Groundwater in karst environments tends to have difficulties to distinguish multiple flows if several sources of water are present. Skaistkalne vicinity faces with such situation where old groundwater, fresh groundwater and inflow from river Iecava occurs. Attempts were made to distinguish groundwater residence time of multiple components of water applying CFC and tritium dating techniques supplied by tracer test and numerical model of study area. Study area covers territory between two rivers Iecava and Memele with water level difference of 7 meters and horizontal distance of 2.2 kilometres between both. Study area consists of karst affected Devonian gypsum and carbonaceous rocks covered by Quaternary low to high permeable deposits. Confined groundwater at depth of 10-25 meters where analysed by CFC's and tritium. At this depth groundwater exhibits anoxic reducing environment that has caused degradation of CFC's at similar degree in all samples. Taking it into account, mean residence time based on CFC piston flow model is 22 - 42 years and 28 - 34 years based on binary mixing model. Tritium results show signs of incensement of groundwater residence time towards discharge area. CFC combined with tritium proved increased vertical velocity in middle part between the rivers likely caused by hydrogeological window in Quaternary deposits created by karst processes. Numerical model (Delina et al. 2012) was applied and calculations yielded groundwater flow velocity rate at 0.3 - 1 m/day in area between the rivers. Investigation of CFC data resulted in possible groundwater flow rate of at a minimum of 0.2 m/day although it's not applicable to all sampled wells due to specific hydrogeological conditions. Tracer test was made between the rivers in order to distinguish main water flow paths and flow velocity. Results showed that very high permeable conduits connect rivers and karst lakes with velocity rates of 800 - 1300 m/day. Complex investigation leads to conclude that

  7. Numerical study of a helicon gas discharge

    NASA Astrophysics Data System (ADS)

    Batishchev, Oleg; Molvig, Kim

    2001-06-01

    Plasma sources based on the helicon gas discharge are widely used in industry [1] due to their high efficiency. We investigate performance of a particular helicon plasma sources designed for the VASIMR [2] plasma thruster. Specifically we are interested in the VX-10 configuration [3] operating with hydrogen or helium plasmas. Firstly, we use our zero-dimensional model to characterize plasma condition and composition [4]. Next we couple it to one-dimensional hybrid model [5] for a rarified gas flow in the system feeding pipe - quartz tube of the helicon. We perform numerical analysis of plasma source operation in different regimes. Results are compared and used to explain experimental data [3]. Finally, we'll discuss more detailed fully kinetic models for the gas and plasma species evolution in the helicon discharge with parameters typical to that of the VASIMR plasma thruster. [1] M.A. Lieberman and A.J.Lihtenberg, , 'Principles of plasma discharges and materials processing', Wiley, NY, 1994; [2] F.Chang-Diaz et al, Bull. APS 45 (7) 129, 2000; [3] J. Squire et al., Bull. APS 45 (7) 130, 2000; [4] O.Batishchev and Kim Molvig, AIAA technical paper 2000-3754, 2000; [5] O.Batishchev and Kim Molvig, AIAA technical paper 2001-0963, 2001.

  8. Multiphase, multicomponent parameter estimation for liquid and vapor fluxes in deep arid systems using hydrologic data and natural environmental tracers

    USGS Publications Warehouse

    Kwicklis, E.M.; Wolfsberg, A.V.; Stauffer, P.H.; Walvoord, M.A.; Sully, M.J.

    2006-01-01

    Multiphase, multicomponent numerical models of long-term unsaturated-zone liquid and vapor movement were created for a thick alluvial basin at the Nevada Test Site to predict present-day liquid and vapor fluxes. The numerical models are based on recently developed conceptual models of unsaturated-zone moisture movement in thick alluvium that explain present-day water potential and tracer profiles in terms of major climate and vegetation transitions that have occurred during the past 10 000 yr or more. The numerical models were calibrated using borehole hydrologic and environmental tracer data available from a low-level radioactive waste management site located in a former nuclear weapons testing area. The environmental tracer data used in the model calibration includes tracers that migrate in both the liquid and vapor phases (??D, ??18O) and tracers that migrate solely as dissolved solutes (Cl), thus enabling the estimation of some gas-phase as well as liquid-phase transport parameters. Parameter uncertainties and correlations identified during model calibration were used to generate parameter combinations for a set of Monte Carlo simulations to more fully characterize the uncertainty in liquid and vapor fluxes. The calculated background liquid and vapor fluxes decrease as the estimated time since the transition to the present-day arid climate increases. However, on the whole, the estimated fluxes display relatively little variability because correlations among parameters tend to create parameter sets for which changes in some parameters offset the effects of others in the set. Independent estimates on the timing since the climate transition established from packrat midden data were essential for constraining the model calibration results. The study demonstrates the utility of environmental tracer data in developing numerical models of liquid- and gas-phase moisture movement and the importance of considering parameter correlations when using Monte Carlo analysis to

  9. The random walk of tracers through river catchments

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Atreyee

    2012-08-01

    River catchments play critical roles in regional economies and in the global economy. In addition, rivers carry large volumes of nutrients, pollutants, and several other forms of tracers into the ocean. An intricate system of pathways and channels, both on the surface and in the subsurface of catchments, allows rivers to carry large volumes of tracers. However, scientists do not yet fully understand how pollutants and other tracers travel through the intricate web of channels in the catchment areas of rivers. In a new study, Cvetkovic et al show that the travel path of tracers through channels can be modeled as a random walk, which is mathematically similar to the path an animal would trace when foraging. Previous studies have applied the random walk approach to understand the behavior of fluids flowing through aquifers and soils but not to model the transport mechanism of tracers that travel passively with water flowing through catchments.

  10. Evaluation of groundwater residence time in a high mountain aquifer system (Sacramento Mountains, USA): insights gained from use of multiple environmental tracers

    NASA Astrophysics Data System (ADS)

    Land, Lewis; Timmons, Stacy

    2016-06-01

    The New Mexico Bureau of Geology and Mineral Resources (USA) has conducted a regional investigation of groundwater residence time within the southern Sacramento Mountains aquifer system using multiple environmental tracers. Results of the tracer surveys indicate that groundwater in the southern Sacramento Mountains ranges in age from less than 1 year to greater than 50 years, although the calculated ages contain uncertainties and vary significantly depending on which tracer is used. A distinctive feature of the results is discordance among the methods used to date groundwater in the study area. This apparent ambiguity results from the effects of a thick unsaturated zone, which produces non-conservative behavior among the dissolved gas tracers, and the heterogeneous character and semi-karstic nature of the aquifer system, which may yield water from matrix porosity, fractures, solution-enlarged conduits, or a combination of the three. The data also indicate mixing of groundwater from two or more sources, including recent recharge originating from precipitation at high elevations, old groundwater stored in the matrix, and pre-modern groundwater upwelling along fault zones. The tracer data have also been influenced by surface-water/groundwater exchange via losing streams and lower elevation springs (groundwater recycling). This study highlights the importance of using multiple tracers when conducting large-scale investigations of a heterogeneous aquifer system, and sheds light on characteristics of groundwater flow systems that can produce discrepancies in calculations of groundwater age.

  11. Quantification of methane and nitrous oxide emissions from various waste treatment facilities by tracer dilution method

    NASA Astrophysics Data System (ADS)

    Mønster, Jacob; Rella, Chris; Jacobson, Gloria; Kjeldsen, Peter; Scheutz, Charlotte

    2013-04-01

    tracer gas concentrations while another measured the nitrous oxide concentration. We present the performance of these instruments at different waste treatment facilities (waste water treatment plants, composting facilities, sludge mineralization beds, anaerobic digesters and landfills) in Denmark, and discuss the strengths and limitations of the method of the method for quantifying methane and nitrous oxide emissions from the different sources. Furthermore, we have measured the methane emissions from 10 landfills with emission rates ranging from 5 to 135 kg/h depending on the age, state, content and aftercare of the landfill. In addition, we have studied 3 waste water treatment plants, and found nitrous oxide emission of 200 to 700 g/h from the aeration tanks and a total methane emission ranging from 2 to 15 kg/h, with the primary emission coming from the sludge treatment. References Galle, B., Samuelsson, J., Svensson, B.H., and Börjesson, G. (2001). Measurements of methane emissions from landfills using a time correlation tracer method based on FTIR absorption spectroscopy. Environmental Science & Technology 35 (1), 21-25 Scheutz, C., Samuelsson, J., Fredenslund, A. M., and Kjeldsen, P. (2011). Quantification of multiple methane emission sources at landfills using a double tracer technique. Waste Management, 31(5), 1009-17 Solomon, S., D. Qin, M. Manning, R.B. Alley, T. Berntsen, N.L. Bindoff, Z. Chen, A. Chidthaisong, J.M. Gregory, G.C. Hegerl, M. Heimann, B. Hewitson, B.J. Hoskins, F. Joos, J. Jouzel, V. Kattsov, U. Lohmann, T.Matsuno, M. Molina, N. Nicholls, J.Overpeck, G. Raga, V. Ramaswamy, J. Ren, M. Rusticucci, R. Somerville, T.F. Stocker, P. Whetton, R.A.Wood and D. Wratt, 2007: Technical Summary. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

  12. The effect of ram pressure on the molecular gas of galaxies: three case studies in the Virgo cluster

    NASA Astrophysics Data System (ADS)

    Lee, Bumhyun; Chung, Aeree; Tonnesen, Stephanie; Kenney, Jeffrey D. P.; Wong, O. Ivy; Vollmer, B.; Petitpas, Glen R.; Crowl, Hugh H.; van Gorkom, Jacqueline

    2017-04-01

    We present 12CO (2-1) data of three Virgo spirals - NGC 4330, NGC 4402 and NGC 4522 obtained using the Submillimeter Array. These three galaxies show clear evidence of ram pressure stripping due to the cluster medium as found in previous H I imaging studies. Using the high-resolution CO data, we investigate how the properties of the inner molecular gas disc change while a galaxy is undergoing H I stripping in the cluster. At given sensitivity limits, we do not find any clear signs of molecular gas stripping. However, both its morphology and kinematics appear to be quite disturbed as those of H I. Morphological peculiarities present in the molecular and atomic gas are closely related with each other, suggesting that the molecular gas can be also affected by strong intracluster medium (ICM) pressure even if it is not stripped. CO is found to be modestly enhanced along the upstream sides in these galaxies, which may change the local star formation activity in the disc. Indeed, the distribution of Hα emission, a tracer of recent star formation, well coincides with that of the molecular gas, revealing enhancements near the local CO peak or along the CO compression. FUV and Hα share some properties in common, but FUV is always more extended than CO/Hα in the three galaxies, implying that the star-forming disc is rapidly shrinking as the molecular gas properties have changed. We discuss how ICM pressure affects dense molecular gas and hence star formation properties while diffuse atomic gas is being removed from a galaxy.

  13. Urban Pollutant Transport and Infiltration into Buildings Using Perfluorocarbon Tracers

    PubMed Central

    Matthews, James C.; Bacak, Asan; Khan, M. Anwar H.; Wright, Matthew D.; Priestley, Michael; Martin, Damien; Percival, Carl J.; Shallcross, Dudley E.

    2017-01-01

    People spend the majority of their time indoors and therefore the quality of indoor air is worthy of investigation; indoor air quality is affected by indoor sources of pollutants and from pollutants entering buildings from outdoors. In this study, unique perfluorocarbon tracers were released in five experiments at a 100 m and ~2 km distance from a large university building in Manchester, UK and tracer was also released inside the building to measure the amount of outdoor material penetrating into buildings and the flow of material within the building itself. Air samples of the tracer were taken in several rooms within the building, and a CO2 tracer was used within the building to estimate air-exchange rates. Air-exchange rates were found to vary between 0.57 and 10.90 per hour. Indoor perfluorocarbon tracer concentrations were paired to outdoor tracer concentrations, and in-out ratios were found to vary between 0.01 and 3.6. The largest room with the lowest air-exchange rate exhibited elevated tracer concentrations for over 60 min after the release had finished, but generally had the lowest concentrations, the room with the highest ventilation rates had the highest concentration over 30 min, but the peak decayed more rapidly. Tracer concentrations indoors compared to outdoors imply that pollutants remain within buildings after they have cleared outside, which must be considered when evaluating human exposure to outdoor pollutants. PMID:28230812

  14. Urban Pollutant Transport and Infiltration into Buildings Using Perfluorocarbon Tracers.

    PubMed

    Matthews, James C; Bacak, Asan; Khan, M Anwar H; Wright, Matthew D; Priestley, Michael; Martin, Damien; Percival, Carl J; Shallcross, Dudley E

    2017-02-21

    People spend the majority of their time indoors and therefore the quality of indoor air is worthy of investigation; indoor air quality is affected by indoor sources of pollutants and from pollutants entering buildings from outdoors. In this study, unique perfluorocarbon tracers were released in five experiments at a 100 m and ~2 km distance from a large university building in Manchester, UK and tracer was also released inside the building to measure the amount of outdoor material penetrating into buildings and the flow of material within the building itself. Air samples of the tracer were taken in several rooms within the building, and a CO₂ tracer was used within the building to estimate air-exchange rates. Air-exchange rates were found to vary between 0.57 and 10.90 per hour. Indoor perfluorocarbon tracer concentrations were paired to outdoor tracer concentrations, and in-out ratios were found to vary between 0.01 and 3.6. The largest room with the lowest air-exchange rate exhibited elevated tracer concentrations for over 60 min after the release had finished, but generally had the lowest concentrations, the room with the highest ventilation rates had the highest concentration over 30 min, but the peak decayed more rapidly. Tracer concentrations indoors compared to outdoors imply that pollutants remain within buildings after they have cleared outside, which must be considered when evaluating human exposure to outdoor pollutants.

  15. Using predictive uncertainty analysis to optimise tracer test design and data acquisition

    NASA Astrophysics Data System (ADS)

    Wallis, Ilka; Moore, Catherine; Post, Vincent; Wolf, Leif; Martens, Evelien; Prommer, Henning

    2014-07-01

    Tracer injection tests are regularly-used tools to identify and characterise flow and transport mechanisms in aquifers. Examples of practical applications are manifold and include, among others, managed aquifer recharge schemes, aquifer thermal energy storage systems and, increasingly important, the disposal of produced water from oil and shale gas wells. The hydrogeological and geochemical data collected during the injection tests are often employed to assess the potential impacts of injection on receptors such as drinking water wells and regularly serve as a basis for the development of conceptual and numerical models that underpin the prediction of potential impacts. As all field tracer injection tests impose substantial logistical and financial efforts, it is crucial to develop a solid a-priori understanding of the value of the various monitoring data to select monitoring strategies which provide the greatest return on investment. In this study, we demonstrate the ability of linear predictive uncertainty analysis (i.e. “data worth analysis”) to quantify the usefulness of different tracer types (bromide, temperature, methane and chloride as examples) and head measurements in the context of a field-scale aquifer injection trial of coal seam gas (CSG) co-produced water. Data worth was evaluated in terms of tracer type, in terms of tracer test design (e.g., injection rate, duration of test and the applied measurement frequency) and monitoring disposition to increase the reliability of injection impact assessments. This was followed by an uncertainty targeted Pareto analysis, which allowed the interdependencies of cost and predictive reliability for alternative monitoring campaigns to be compared directly. For the evaluated injection test, the data worth analysis assessed bromide as superior to head data and all other tracers during early sampling times. However, with time, chloride became a more suitable tracer to constrain simulations of physical transport

  16. [A microbiological study of an underground gas storage in the process of gas injection].

    PubMed

    Ivanova, A E; Borzenkov, I A; Tarasov, A L; Milekhina, E I; Beliaev, S S

    2007-01-01

    The liquid phase of different units of an underground gas storage (UGS) in the period of gas injection was studied with respect to its hydrochemical composition and characterized microbiologically. The presence of viable aerobic and anaerobic bacteria was revealed in the UGS stratal and associated waters. An important source of microorganisms and biogenic elements in the ecosystem studied is water and various technogenic admixtures contained in trace amounts in the gas entering from the gas main in the period of gas injection into the storage. Owing to this fact, the bacterial functional diversity, number, and activity are maximal in the system of gas treatment and purification and considerably lower in the observation well zone. At the terminal stages, the anaerobic transformation of organic matter in the UGS aqueous media occurs via sulfate reduction and methanogenesis; exceptionally high rates of these processes (up to 4.9 x 10(5) ng S(2-)l(-1) day(-1) and 2.8 x 10(6) nl CH4 l(-1) day(-1), respectively) were recorded for above-ground technological equipment.

  17. Dating of shallow groundwater--Comparison of the transient tracers 3H/3He chlorofluorocarbons and 85Kr

    USGS Publications Warehouse

    Ekwurzel, Brenda; Schlosser, Peter; Smethie, William M.; Plummer, L. Niel; Busenberg, Eurybiades; Michel, Robert L.; Weppernig, Ralf; Stute, Martin

    1994-01-01

    This paper describes a direct comparison of apparent ages derived from 3H/3He, chlorofluorocarbons (CCl3F and CCl2F2), and 85Kr measurements in shallow groundwater. Wells chosen for this study are completed in the unconfined surficial aquifers in late Cenozoic Atlantic Coastal Plain sediments of the Delmarva Peninsula, on the east coast of the United States. Most of the apparent tracer ages agree within 2 years of each other for recharge dates between 1965 and 1990. Discrepancies in apparent tracer ages usually can be explained by hydrological processes such as mixing in a discharge area. Recharge rate calculations based on apparent tracer age gradients at multilevel well locations agree with previous recharge estimates. High recharge rates on the Delmarva Peninsula result in nearly complete dissolved-gas confinement in the groundwater. The remarkable agreement between the different tracer ages indicates negligible mixing of waters of different ages, insignificant dispersion, minimal gas loss to the atmosphere, and insignificant sorption-desorption processes at this location.

  18. Fluid dynamic studies on scattering aerosol and its generation for application as tracer particles in supersonic flow measurements utilizing laser Doppler velocimeter

    NASA Technical Reports Server (NTRS)

    Mazumder, M. K.; Hoyle, B. D.; Kirsch, K. J.

    1974-01-01

    An experimental study on the particle-fluid interactions of scattering aerosols was performed using monodisperse aerosols of different particle sizes for the application of laser Doppler velocimeters in subsonic turbulence measurements. Particle response was measured by subjecting the particles to an acoustically excited oscillatory fluid velocity field and by comparing the ratio of particle velocity amplitude to the fluid velocity amplitude as a function of particle size and the frequency of oscillation. Particle velocity was measured by using a differential laser Doppler velocimeter. The test aerosols were fairly monodisperse with a mean diameter that could be controlled over the size range from 0.1 to 1.0 micron. Experimental results on the generation of a fairly monodisperse aerosol of solid particles and liquid droplets and on the aerosol response in the frequency range 100 Hz to 100 kHz are presented. It is indicated that a unit density spherical scatterer of 0.3 micron-diameter would be an optimum choice as tracer particles for subsonic air turbulence measurements.

  19. Impacts of Wood Additions on Dissolved and Particulate Nutrient Retention in an Agriculturally Impacted Stream: A Multi-Tracer Injection Study at Whatawhata, New Zealand

    NASA Astrophysics Data System (ADS)

    Drummond, J. D.; Wright-Stow, A.; Nagels, J.; Quinn, J.; Franklin, P.; Packman, A. I.

    2014-12-01

    Wood is a key component in forested streams, playing an important ecological and physical role in creating step-pool profiles, enhancing habitat heterogeneity, retaining organic matter, and changing water velocity. Wood additions can increase surface water-groundwater exchange, increasing in-stream residence times by slowing water velocities and providing high depositional areas for fine particles (i.e. particulate nutrients C, N, P). Thus, wood additions may create biogeochemical hotspots in streams that allow greater potential for local nutrient cycling and processing. The objectives of this research were to determine if added wood enhances in-stream heterogeneity, results in more complex flow paths, increases natural retention of further organic matter and changes geomorphic characteristics of the stream reach. We conducted a conservative solute and fluorescent fine particle tracer injection study in an agriculturally impacted stream with emplaced wood additions to estimate in-stream retention times in the Whatawhata catchment, North Island of New Zealand. Although similar solute peak concentrations were observed at the different in-stream sampling sites, increased retention was observed near to the wood. Both fine particle deposition and retention time was increased near the emplaced log. Fine particles were also analyzed in situ in sediment and biofilms on cobbles throughout the stream reach following the injection. A direct positive correlation was observed between cobble biofilm biomass and particle accumulation within this retention area. In general, the addition of wood to these agriculturally impacted streams enhanced hydraulic complexity and increased the retention of solute and fine particles.

  20. Use of rubidium, manganese, and zinc as tracers to measure intestinal permeability by PIXE analysis: basal study in an experimental enteritis model.

    PubMed

    Nakao, Keitaro; Suzuki, Yasuo; Imaseki, Hitoshi; Joshima, Hisamasa; Tamanoi, Itsuro; Saito, Yasushi

    2004-04-01

    Intestinal permeability has been suggested to be closely linked with the etiology or activity of Crohn's disease. However, current methods for measurement of intestinal permeability are too laborious for routine examination, as they require urine collection and/or use of radioisotopes. The present study was performed to develop a more convenient and safer method for assessing intestinal permeability using blood samples rather than urine. Rats with indomethacin-induced enteritis were orally administered Rb, Mn, and Zn as tracers. Intestinal permeability was determined by assaying the levels of Rb, Mn, and Zn in blood samples by particle-induced X-ray emission (PIXE). The distributions of Rb, Mn, and Zn in the small intestine after administration were analyzed by micro-PIXE. The conventional PIXE analysis showed that the levels of Rb and Zn in the blood in the enteritis group were correlated with the grade of enteritis. The micro-PIXE analysis showed that Rb, Mn, and Zn were translocated into the wall of the proximal small intestine 5 min after administration, and this effect was more conspicuous in the enteritis group than in controls. Analysis of blood or small intestine tissue samples using the PIXE allows determination of both intestinal permeability and the route of permeation.

  1. Using Neural Networks to Describe Tracer Correlations

    NASA Technical Reports Server (NTRS)

    Lary, D. J.; Mueller, M. D.; Mussa, H. Y.

    2003-01-01

    Neural networks are ideally suited to describe the spatial and temporal dependence of tracer-tracer correlations. The neural network performs well even in regions where the correlations are less compact and normally a family of correlation curves would be required. For example, the CH4-N2O correlation can be well described using a neural network trained with the latitude, pressure, time of year, and CH4 volume mixing ratio (v.m.r.). In this study a neural network using Quickprop learning and one hidden layer with eight nodes was able to reproduce the CH4-N2O correlation with a correlation co- efficient of 0.9995. Such an accurate representation of tracer-tracer correlations allows more use to be made of long-term datasets to constrain chemical models. Such as the dataset from the Halogen Occultation Experiment (HALOE) which has continuously observed CH4, (but not N2O) from 1991 till the present. The neural network Fortran code used is available for download.

  2. Isotope tracer studies of diffusion in silicates and of geological transport processes using actinide elements. Progress report

    SciTech Connect

    Wasserburg, G.J.

    1992-12-31

    The following are reported: high abundance sensitivity mass spectrometer for U-Th studies; {sup 238}U-{sup 230}Th disequilibrium in recent lavas from Iceland; water-rock interaction from U-Th studies; resonance ionization mass spectrometry of Os and Ti isotopes; and self-diffusion of Mg.

  3. Simple Spreadsheet Models For Interpretation Of Fractured Media Tracer Tests

    EPA Science Inventory

    An analysis of a gas-phase partitioning tracer test conducted through fractured media is discussed within this paper. The analysis employed matching eight simple mathematical models to the experimental data to determine transport parameters. All of the models tested; two porous...

  4. North American Natural Gas Markets: Selected technical studies

    SciTech Connect

    Huntington, H.G.; Schuler, G.E.

    1989-04-01

    The Energy Modeling Forum (EMF) was established in 1976 at Stanford University to provide a structural framework within which energy experts, analysts, and policymakers could meet to improve their understanding of critical energy problems. The ninth EMF study, North American Natural Gas Markets, was conducted by a working group comprised of leading natural gas analysts and decision-makers from government, private companies, universities, and research and consulting organizations. The EMF 9 working group met five times from October 1986 through June 1988 to discuss key issues and analyze natural gas markets. This third volume includes technical papers that support many of the conclusions discussed in the EMF 9 summary report (Volume 1) and full working group report (Volume 2). These papers discuss the results from the individual models as well as some nonmodeling analysis related to US natural gas imports and industrial natural gas demand. Individual papers have been processed separately for inclusion in the Energy Science and Technology Database.

  5. North American Natural Gas Markets: Selected technical studies. Volume 3

    SciTech Connect

    Huntington, H.G.; Schuler, G.E.

    1989-04-01

    The Energy Modeling Forum (EMF) was established in 1976 at Stanford University to provide a structural framework within which energy experts, analysts, and policymakers could meet to improve their understanding of critical energy problems. The ninth EMF study, North American Natural Gas Markets, was conducted by a working group comprised of leading natural gas analysts and decision-makers from government, private companies, universities, and research and consulting organizations. The EMF 9 working group met five times from October 1986 through June 1988 to discuss key issues and analyze natural gas markets. This third volume includes technical papers that support many of the conclusions discussed in the EMF 9 summary report (Volume 1) and full working group report (Volume 2). These papers discuss the results from the individual models as well as some nonmodeling analysis related to US natural gas imports and industrial natural gas demand. Individual papers have been processed separately for inclusion in the Energy Science and Technology Database.

  6. Study on alkali removal technology from coal gasification gas

    SciTech Connect

    Inai, Motoko; Kajibata, Yoshihiro; Takao, Shoichi; Suda, Masamitsu

    1999-07-01

    The authors have proposed a new coal based combined cycle power plant concept. However, there are certain technical problems that must be overcome to establish this system. Major technical problem of the system is hot corrosion of gas turbine blades caused by sulfur and alkali vapor, because of high temperature dust removal without sulfur removal from the coal gas. So the authors have conducted several fundamental studies on dry type alkali removal sorbents for the purposed of reducing the corrosion on gas turbine blades. Based on the fundamental studies the authors found preferable alkali removal sorbents, and made clear their alkali removal performance.

  7. Studying the Variation in Gas Permeability of Porous Building Substrates

    NASA Astrophysics Data System (ADS)

    Townsend, L.; Savidge, C. R.; Hu, L.; Rizzo, D. M.; Hayden, N. J.; Dewoolkar, M.

    2009-12-01

    Understanding permeability of building materials is important for problems involving studies of contaminant transport. Examples include contamination from fire, acid rain, and chemical and biological weapons. Our research investigates the gas permeability of porous building substrates such as concretes, limestones, sandstones, and bricks. Each sample was cored to produce 70 mm (2.75”) diameter cores approximately 75-130 mm (3-5”) tall. The surface gas permeability was measured on the top surface of these specimens using the AutoScan II device manufactured by New England Research, Inc. The measurements were taken along a 3 mm grid producing a map of surface gas permeability. An example map is shown in Figure 1. The macroscopic measurements were performed along the entire cored specimen. A second set of measurements were made on a 5 mm thick slice cut from the top of each specimen to examine whether these measurements compare better with the surface measurements. The macroscopic gas permeability was measured for all specimens using ASTM D 4525. The results are summarized in Table 1. In general, the surface and macroscopic gas permeability measurements (Table 1) compare reasonably well (within one order of magnitude). The permeability of the 5 mm slices is not significantly different from the entire core for the specimens tested. Figure 1. Results of surface permeability mappingof Ohio Sandstone using the AutoScan II device. a) Map of gas permeability b) Range of gas permeability c) Density function of permeability. Table 1. Gas permeability values (mD)

  8. Reevaluation of the Reservoir Gas Sands of Rashidpur Gas Field: A Case Study

    NASA Astrophysics Data System (ADS)

    Eahsanul Haque, Akm; Ahmed, Nur

    2010-05-01

    Rashidpur Gas Field is located in the west of Srimongal in East Central Bangladesh. The accumulation associated with the Miocene Bhuban-Boka Bil Sandstone Reservoirs in a structural trap. The structure is about 35 km long and 7 km wide with amplitude of some 4900 ft. Rashidpur anticline is a sub-meriodinal axis, elongated, asymmetrical doubly plunging anticline which has two pay sands namely Upper Gas Sand (UGS) and Lower Gas Sand (LGS) indicated in all four wells drilled in the structure. After penetrating the shalebsection beneath LGS, drilling plan was rescheduled to a depth of 9200 ft in order to investigate the deeper sands of potential hydrocarbon accumulation. On reaching a depth of 10073 ft a sudden kick occurred, which halted the drilling operation and forced to kill the well. An immediate sidetrack well (4521 ft) was drilled at Well-4 and an existence of a sealing fault was drawn on the final report. But mud logs of Well-3 and Well-4 based on the hydrocarbon component of UGS and LGS clearly indicate the absence of any fault between Well-3 and Well-4. Recent geological investigation in the study area reveals the updated facts on the two wells of Rashidpur Gas Field. The paper analyses mud logs and other geological data and reevaluates the reservoir gas sands of Rashidpur Gas Field.

  9. Leakage detection of Marcellus Shale natural gas at an Upper Devonian gas monitoring well: a 3-d numerical modeling approach.

    PubMed

    Zhang, Liwei; Anderson, Nicole; Dilmore, Robert; Soeder, Daniel J; Bromhal, Grant

    2014-09-16

    Potential natural gas leakage into shallow, overlying formations and aquifers from Marcellus Shale gas drilling operations is a public concern. However, before natural gas could reach underground sources of drinking water (USDW), it must pass through several geologic formations. Tracer and pressure monitoring in formations overlying the Marcellus could help detect natural gas leakage at hydraulic fracturing sites before it reaches USDW. In this study, a numerical simulation code (TOUGH 2) was used to investigate the potential for detecting leaking natural gas in such an overlying geologic formation. The modeled zone was based on a gas field in Greene County, Pennsylvania, undergoing production activities. The model assumed, hypothetically, that methane (CH4), the primary component of natural gas, with some tracer, was leaking around an existing well between the Marcellus Shale and the shallower and lower-pressure Bradford Formation. The leaky well was located 170 m away from a monitoring well, in the Bradford Formation. A simulation study was performed to determine how quickly the tracer monitoring could detect a leak of a known size. Using some typical parameters for the Bradford Formation, model results showed that a detectable tracer volume fraction of 2.0 × 10(-15) would be noted at the monitoring well in 9.8 years. The most rapid detection of tracer for the leak rates simulated was 81 days, but this scenario required that the leakage release point was at the same depth as the perforation zone of the monitoring well and the zones above and below the perforation zone had low permeability, which created a preferred tracer migration pathway along the perforation zone. Sensitivity analysis indicated that the time needed to detect CH4 leakage at the monitoring well was very sensitive to changes in the thickness of the high-permeability zone, CH4 leaking rate, and production rate of the monitoring well.

  10. Gas-filled hohlraum study on Shenguang-III prototype

    NASA Astrophysics Data System (ADS)

    Yang, Dong; Li, Sanwei; Li, Zhichao; Yi, Rongqing; Guo, Liang; Jiang, Xiaohua; Liu, Shenye; Yang, Jiamin; Jiang, Shaoen; Ding, Yongkun; Hao, Liang; Zhang, Huasen; Zhao, Yiqing; Zou, Shiyang; Huo, Wenyi; Li, Xin

    2015-11-01

    Experimental studies on gas-filled hohlraum were performed extensively in recent years on Shenguang-III prototype laser facility. These experiments employed Au hohlraums within C5H12 gas fill heated by smoothing beams. In the first round of experiments, although the low-Z gas fill impeded the blow-off plasma ablated from hohlraum wall, the x-ray flux from the LEH decreased dramatically compared with the vacuum hohlraum. Further analysis of several ways of energy deposition including heating the gas-fill, extra scattered light and ablating the LEH membrane, revealed that too much laser energy were wasted in exploding the LEH membrane if we use a 1 ns square pulse. After we introduced a low power prepulse to intentionally exploding the membrane, the behavior of the x-ray flux from the gas-filled hohlraum is identical with the vacuum hohlraum. In subsequent studies, the motion of x-ray spot and corona plasma has also been studied using the gas-filled hohlraum. We obtained high quality data of the gas/wall interface and the boundary of the ablated wall near the LEH. The result agrees with that in simulation. However, there is a discrepancy between the experiment and the simulation in the spatial feature of the ablated wall near the LEH extracted from M-band x-ray image.

  11. Effects of Submesoscale Ocean Turbulence on Buoyant and Passive Tracers

    NASA Astrophysics Data System (ADS)

    Smith, K.; Fox-Kemper, B.; Hamlington, P.

    2015-12-01

    Recent studies have shown that submesoscale processes greatly influence the dynamics and structure of the oceanic mixed layer. These processes have a substantial impact, in particular, on the transport of momentum, buoyancy, and passive tracers such as carbonate chemical species, nutrients, and plankton. It has been suggested that the vertical transfer of both active buoyancy and passive tracers can be described by the same vertical flux profile, thus permitting the use of one flux profile when parameterizing the effects of submoescale processes on tracer transport. Within the submesoscale range, however, both partly geostrophic fronts and eddies, which act to restratify the mixed layer, and small-scale three-dimensional turbulence, which acts to enhance vertical mixing, are simultaneously active, thus giving rise to complex multiscale interactions between turbulence and tracer dynamics. In this talk, large eddy simulations spanning the range of scales from 20km down to 5m are used to examine the role of multiscale turbulent mixing on both an active buoyancy tracer and several nonreactive passive ocean tracers from interior and sea-surface sources. The simulations include the effects of both small-scale wave-driven Langmuir turbulence and larger submesoscale eddies. Tracer properties are characterized using spatial fields and statistics, multiscale fluxes, and spectra. Results show that while submesoscale eddies transport buoyancy upward to extract potential energy, the same is not true of passive tracers. Instead, the suppression of turbulent vertical mixing in active submesoscale regions leads to suppressed entrainment of tracers, implying weaker transport by submesoscale activity. These results along with implications for the development of reduced order tracer models will be discussed.

  12. Small Gas Turbine Combustor Primary Zone Study

    NASA Technical Reports Server (NTRS)

    Sullivan, R. E.; Young, E. R.; Miles, G. A.; Williams, J. R.

    1983-01-01

    A development process is described which consists of design, fabrication, and preliminary test evaluations of three approaches to internal aerodynamic primary zone flow patterns: (1) conventional double vortex swirl stabilization; (2) reverse flow swirl stabilization; and (3) large single vortex flow system. Each concept incorporates special design features aimed at extending the performance capability of the small engine combustor. Since inherent geometry of these combustors result in small combustion zone height and high surface area to volume ratio, design features focus on internal aerodynamics, fuel placement, and advanced cooling. The combustors are evaluated on a full scale annular combustor rig. A correlation of the primary zone performance with the overall performance is accomplished using three intrusion type gas sampling probes located at the exit of the primary zone section. Empirical and numerical methods are used for designing and predicting the performance of the three combustor concepts and their subsequent modifications. The calibration of analytical procedures with actual test results permits an updating of the analytical design techniques applicable to small reverse flow annular combustors.

  13. USE OF PERFLUOROCARBON TRACER (PFT) TECHNOLOGY FOR SUBSURFACE BARRIER INTEGRITY VERIFICATION AT THE WALDO TEST SITE.

    SciTech Connect

    SULLIVAN,T.

    1999-06-01

    Testing of perfluorocarbon gas tracers (PFT) on a subsurface barrier with known flaws was conducted at the Waldo Test Site operated by Science and Engineering Associates, Inc (SEA). The tests involved the use of five unique PFTs with a different tracer injected along the interior of each wall of the barrier. A fifth tracer was injected exterior to the barrier to examine the validity of diffusion controlled transport of the PFTs. The PFTs were injected for three days at a nominal flow rate of 15 cm{sup 3}/min and concentrations in the range of a few hundred ppm. Approximately 65 liters of air laced with tracer was injected for each tracer. The tracers were able to accurately detect the presence of the engineered flaws. Two flaws were detected on the north and east walls, and one flaw was detected on the south and west walls. In addition, one non-engineered flaw at the seam between the north and east walls was also detected. The use of multiple tracers provided independent confirmation of the flaws and permitted a distinction between tracers arriving at a monitoring port after being released from a nearby flaw and non-engineered flaws. The PFTs detected the smallest flaw, 0.5 inches in diameter. Visual inspection of the data showed excellent agreement with the known flaw locations and the relative size of the flaws was accurately estimated. Simultaneous with the PFT tests, SEA conducted tests with another gas tracer sulfur hexafluoride (SF{sub 6}).

  14. Single-scan dual-tracer FLT+FDG PET tumor characterization

    NASA Astrophysics Data System (ADS)

    Kadrmas, Dan J.; Rust, Thomas C.; Hoffman, John M.

    2013-02-01

    Rapid multi-tracer PET aims to image two or more tracers in a single scan, simultaneously characterizing multiple aspects of physiology and function without the need for repeat imaging visits. Using dynamic imaging with staggered injections, constraints on the kinetic behavior of each tracer are applied to recover individual-tracer measures from the multi-tracer PET signal. The ability to rapidly and reliably image both 18F-fluorodeoxyglucose (FDG) and 18F-fluorothymidine (FLT) would provide complementary measures of tumor metabolism and proliferative activity, with important applications in guiding oncologic treatment decisions and assessing response. However, this tracer combination presents one of the most challenging dual-tracer signal-separation problems—both tracers have the same radioactive half-life, and the injection delay is short relative to the half-life and tracer kinetics. This work investigates techniques for single-scan dual-tracer FLT+FDG PET tumor imaging, characterizing the performance of recovering static and dynamic imaging measures for each tracer from dual-tracer datasets. Simulation studies were performed to characterize dual-tracer signal-separation performance for imaging protocols with both injection orders and injection delays of 10-60 min. Better performance was observed when FLT was administered first, and longer delays before administration of FDG provided more robust signal-separation and recovery of the single-tracer imaging measures. An injection delay of 30 min led to good recovery (R > 0.96) of static image values (e.g. SUV), Knet, and K1 as compared to values from separate, single-tracer time-activity curves. Recovery of higher order rate parameters (k2, k3) was less robust, indicating that information regarding these parameters was harder to recover in the presence of statistical noise and dual-tracer effects. Performance of the dual-tracer FLT(0 min)+FDG(32 min) technique was further evaluated using PET/CT imaging studies in

  15. Integrating Source Apportionment Tracers into a Bottom-up Inventory of Methane Emissions in the Barnett Shale Hydraulic Fracturing Region.

    PubMed

    Townsend-Small, Amy; Marrero, Josette E; Lyon, David R; Simpson, Isobel J; Meinardi, Simone; Blake, Donald R

    2015-07-07

    A growing dependence on natural gas for energy may exacerbate emissions of the greenhouse gas methane (CH4). Identifying fingerprints of these emissions is critical to our understanding of potential impacts. Here, we compare stable isotopic and alkane ratio tracers of natural gas, agricultural, and urban CH4 sources in the Barnett Shale hydraulic fracturing region near Fort Worth, Texas. Thermogenic and biogenic sources were compositionally distinct, and emissions from oil wells were enriched in alkanes and isotopically depleted relative to natural gas wells. Emissions from natural gas production varied in δ(13)C and alkane ratio composition, with δD-CH4 representing the most consistent tracer of natural gas sources. We integrated our data into a bottom-up inventory of CH4 for the region, resulting in an inventory of ethane (C2H6) sources for comparison to top-down estimates of CH4 and C2H6 emissions. Methane emissions in the Barnett are a complex mixture of urban, agricultural, and fossil fuel sources, which makes source apportionment challenging. For example, spatial heterogeneity in gas composition and high C2H6/CH4 ratios in emissions from conventional oil production add uncertainty to top-down models of source apportionment. Future top-down studies may benefit from the addition of δD-CH4 to distinguish thermogenic and biogenic sources.

  16. AtSUC2 has a role for sucrose retrieval along the phloem pathway: evidence from carbon-11 tracer studies.

    PubMed

    Gould, N; Thorpe, M R; Pritchard, J; Christeller, J T; Williams, L E; Roeb, G; Schurr, U; Minchin, P E H

    2012-06-01

    The location of the phloem within a plant, and its vulnerability to disruption, make it a difficult tissue to study and therefore non-invasive studies of phloem functionality are important. Here we compare, phloem transport, measured non-invasively, in wild type Arabidopsis thaliana, and transposon-insertion mutants for AtSUC1 or AtSUC2, giving in vivo information on the importance of these sucrose transporters for phloem transport. The suc2 mutant showed an increase in both phloem leakage and transport time, consistent with reduced sucrose uptake into both transport and collection phloem. The results are consistent with the AtSUC2 transporter being important for retrieval of leaked sucrose in the transport phloem of Arabidopsis. There was no difference in phloem transport properties between the wild type and the suc1 mutants, implying that the AtSUC1 transporter does not play a significant role within the transport phloem of Arabidopsis under the conditions of our study.

  17. Pulmonary complications of mustard gas exposure: a study on cadavers.

    PubMed

    Taghaddosinejad, Fakhreddin; Fayyaz, Amir Farshid; Behnoush, Behnam

    2011-01-01

    Sulfur mustard gas is one of the chemical warfare gases that roughly about 45000 soldiers continue to suffer long-lasting consequences of exposure during the Iran-Iraq war between 1980 and 1988. According to the common pulmonary lesions due to this gas exposure, we studied gross and microscopic pulmonary lesions in cadavers and also assessed the main causes of mortality caused by mustard gas exposure. A case-series study was performed on hospital record files of 100 cadavers that were exposed with documented sulfur mustard gas during the Iran-Iraq war from 1979 to 1988 and autopsied in legal medicine organization In Tehran between 2005 and 2007 and gross and microscopic pathological findings of autopsied organs such as hematological, pulmonary, hepatic, and renal changes were evaluated. All cases were male with the mean age of 43 years. The time interval between the gas exposure and death was almost 20years. The most frequent pulmonary complication was chronic bronchitis in 81% of autopsied cadavers. Other pulmonary findings were progressive pulmonary fibrosis (9%), pulmonary infections and tuberculosis (29%), malignant cellular infiltration (4%), and aspergilloma (1%). According to the chronic progressive lesions caused by mustard gas exposure such as pulmonary lesions and also its high mortality rate, suitable programming for protection of the gas exposed persons and prohibiting chemical warfare are recommended.

  18. Comparative dual-tracer studies of carbon-14 tryptophan and iodine-131 HIPDM in animal models of pancreatic diseases

    SciTech Connect

    Kubota, K.; Som, P.; Brill, A.B.; Sacker, D.F.; Meinken, G.E.; Srivastava, S.C.; Atkins, H.L. )

    1989-11-01

    Our previous studies have shown that a significant amount of the diamine derivative {sup 131}I-N,N,N'-trimethyl-N'-(2-hydroxy-3-methyl-5-iodobenzyl)-1,3- propanediamine (HIPDM) is taken up and retained by the normal pancreas. Therefore, we studied the uptake of ({sup 13}1I)HIPDM in various pathophysiological models in mice (chronic alcoholism, diabetes with beta-cell atrophy and obesity with beta-cell hypertrophy) and compared to {sup 14}C-L-Tryptophan (TRY) distribution in order to determine the factors influencing their pancreatic uptake. In normal animals, the pancreas uptake of TRY was generally higher than HIPDM. In diabetes, the relative concentration of both compounds was higher over the controls; however, in obesity, TRY showed lower accumulation than in controls while HIPDM showed no significant difference. Chronic ethanol (20%) ingestion increased TRY uptake in the pancreas compared to controls (36.88 {plus minus} 3.21 vs. 30.03 {plus minus} 4.17% ID/g; p less than 0.01) after 5 wk study period, but it decreased by 10 wk (22.36 {plus minus} 0.95% ID/g; p less than 0.005). There were no significant changes in ({sup 131}I)HIPDM distribution in alcoholics as compared to the controls. Radioiodinated HIPDM has potential advantages over ({sup 11}C)TRY for pancreatic imaging since conventional imaging techniques can be employed. Our data, however, suggest that {sup 11}C-L-TRY is a more sensitive indicator of various pancreatic disorders.

  19. Comparison of different tracers for PIV measurements in EHD airflow

    NASA Astrophysics Data System (ADS)

    Hamdi, M.; Havet, M.; Rouaud, O.; Tarlet, D.

    2014-04-01

    In this study, a proposed method for selecting a tracer for particle imaging velocimetry (PIV) measurement in electrohydrodynamics flows was developed. To begin with, several published studies were identified that exploit different tracers, such as oil smoke, cigarette smoke and titanium dioxide (TiO2). An assortment of tracers was then selected based on comparisons with conventional dimensionless numbers; Stokes number ( St), Archimedes number ( Ar) and electrical mobility ratio ( M). Subsequently, an experimental study for testing tracers was developed, which enabled the velocity profile of an ionic wind generated by a needle/ring configuration to be measured. Air velocity measurements carried out with a Pitot tube, considered as the reference measurements, were compared to PIV measurements for each tracer. In addition, the current-voltage curves and the evolution of the current during seeding were measured. All the experimental results show that TiO2, SiO2 microballoons and incense smoke are the ideal tracers in the series of tracers investigated.

  20. Feasibility study of full-reactor gas core demonstration test

    NASA Technical Reports Server (NTRS)

    Kunze, J. F.; Lofthouse, J. H.; Shaffer, C. J.; Macbeth, P. J.

    1973-01-01

    Separate studies of nuclear criticality, flow patterns, and thermodynamics for the gas core reactor concept have all given positive indications of its feasibility. However, before serious design for a full scale gas core application can be made, feasibility must be shown for operation with full interaction of the nuclear, thermal, and hydraulic effects. A minimum sized, and hence minimum expense, test arrangement is considered for a full gas core configuration. It is shown that the hydrogen coolant scattering effects dominate the nuclear considerations at elevated temperatures. A cavity diameter of somewhat larger than 4 ft (122 cm) will be needed if temperatures high enough to vaporize uranium are to be achieved.

  1. A study of gas mixtures for the ATLAS MDT

    SciTech Connect

    Zhao, T.; He, L.

    1996-06-01

    Results of a gas study for the ATLAS Monitored Drift Tubes (MDT) are reported. The electron drift velocity, Lorentz angle and tube radius to drift time relations are calculated for selected gas mixtures by using the CERN drift chamber simulation code GARFIELD/MAGBOLTZ. The drift tube efficiency, gas gain, avalanche size and self-quenching streamer (SQS) mode fraction as functions of anode voltage are measured by using radioactive sources. Discussions of the results, including effects of nitrogen and water vapor, are presented.

  2. Study on propane-butane gas storage by hydrate technology

    NASA Astrophysics Data System (ADS)

    Hamidi, Nurkholis; Wijayanti, Widya; Widhiyanuriyawan, Denny

    2016-03-01

    Different technology has been applied to store and transport gas fuel. In this work the storage of gas mixture of propane-butane by hydrate technology was studied. The investigation was done on the effect of crystallizer rotation speed on the formation of propane-butane hydrate. The hydrates were formed using crystallizer with rotation speed of 100, 200, and 300 rpm. The formation of gas hydrates was done at initial pressure of 3 bar and temperature of 274K. The results indicated that the higher rotation speed was found to increase the formation rate of propane-butane hydrate and improve the hydrates stability.

  3. In vitro study of gas effects on alveolar macrophages.

    PubMed

    Wallaert, B; Voisin, C

    1992-01-01

    To evaluate the biological effects of gas pollutants on alveolar macrophages several in vitro systems have been developed. We described here an original method of cell culture in aerobiosis, which permitted direct contact between the atmosphere and the target cells. We studied the long term (24 h) and short term (30 min) effects of NO2 on alveolar macrophages. Our results demonstrated that exposure of alveolar macrophages to gas pollutants may be responsible for either cell injury or cell activation associated with the release of various bioactive mediators (superoxide anion, neutrophil chemotactic activity). Cell culture in aerobiosis opens new ways for the research on the biological effects of gas pollutants.

  4. Differential allocation of carbon in mosses and grasses governs ecosystem sequestration: a 13C tracer study in the high Arctic.

    PubMed

    Woodin, S J; van der Wal, R; Sommerkorn, M; Gornall, J L

    2009-12-01

    *This study investigates the influence of vegetation composition on carbon (C) sequestration in a moss-dominated ecosystem in the Arctic. *A (13)C labelling study in an arctic wet meadow was used to trace assimilate into C pools of differing recalcitrance within grasses and mosses and to determine the retention of C by these plant groups. *Moss retained 70% of assimilated (13)C over the month following labelling, which represented half the growing season. By contrast, the vascular plants, comprising mostly grasses, retained only 40%. The mechanism underlying this was that moss allocated 80% of the (13)C to recalcitrant C pools, a much higher proportion than in grasses (56%). *This method enabled elucidation of a plant trait that will influence decomposition and hence persistence of assimilated C in the ecosystem. We predict that moss-dominated vegetation will retain sequestered C more strongly than a grass-dominated community. Given the strong environmental drivers that are causing a shift from moss to grass dominance, this is likely to result in a reduction in future ecosystem C sink strength.

  5. Radioactive tracers as a tool for the study of in situ meiofaunal-microbial trophic interactions in marine sediments

    SciTech Connect

    Carman, K.R.

    1989-01-01

    Three methods of delivering labeled substrates to natural cores of sediments were compared. Slurried sediments disrupted the sedimentary structure and significantly altered uptake of labeled substrates by copepod species. Thus, disruption of sedimentary structure can significantly alter microbial-meiofaunal interactions and influence the results of grazing studies. The ({sup 3}H)-thymidine technique for measuring bacterial production was evaluated. The metabolic fate of labeled thymidine in a coastal marine sediment was not consistent with assumptions necessary for measuring bacterial production or its consumption by meiofauna. Microautoradiography was used to demonstrate the sedimentary microalgae and heterotrophic bacteria can be selectively labeled with ({sup 14}C)bicarbonate and labeled organic substrates, respectively. A study was performed to determine if radioactivity measured in copepods from grazing experiments was the result of ingestion of labeled microorganisms or the result of uptake by non-feeding processes. Uptake of label by copepods from ({sup 14}C)-bicarbonate was due almost exclusively to grazing on microalgae. Uptake of label by copepods from ({sup 14}C)-acetate, however, resulted from activity by epicuticular bacteria and was not due to ingestion of labeled bacteria.

  6. Assessment of surface water resources availability using catchment modelling and the results of tracer studies in the mesoscale Migina Catchment, Rwanda

    NASA Astrophysics Data System (ADS)

    Munyaneza, O.; Mukubwa, A.; Maskey, S.; Uhlenbrook, S.; Wenninger, J.

    2014-12-01

    In the present study, we developed a catchment hydrological model which can be used to inform water resources planning and decision making for better management of the Migina Catchment (257.4 km2). The semi-distributed hydrological model HEC-HMS (Hydrologic Engineering Center - the Hydrologic Modelling System) (version 3.5) was used with its soil moisture accounting, unit hydrograph, liner reservoir (for baseflow) and Muskingum-Cunge (river routing) methods. We used rainfall data from 12 stations and streamflow data from 5 stations, which were collected as part of this study over a period of 2 years (May 2009 and June 2011). The catchment was divided into five sub-catchments. The model parameters were calibrated separately for each sub-catchment using the observed streamflow data. Calibration results obtained were found acceptable at four stations with a Nash-Sutcliffe model efficiency index (NS) of 0.65 on daily runoff at the catchment outlet. Due to the lack of sufficient and reliable data for longer periods, a model validation was not undertaken. However, we used results from tracer-based hydrograph separation from a previous study to compare our model results in terms of the runoff components. The model performed reasonably well in simulating the total flow volume, peak flow and timing as well as the portion of direct runoff and baseflow. We observed considerable disparities in the parameters (e.g. groundwater storage) and runoff components across the five sub-catchments, which provided insights into the different hydrological processes on a sub-catchment scale. We conclude that such disparities justify the need to consider catchment subdivisions if such parameters and components of the water cycle are to form the base for decision making in water resources planning in the catchment.

  7. Isotope tracer studies of diffusion in silicates and of geological transport processes in aqueous systems using actinide elements

    SciTech Connect

    Wasserburg, G.J.

    1999-02-01

    This research program has moved ahead with success in several areas. The isotopic composition of osmium in seawater and in some rivers was directly determined for the first time. The concentration of osmium was first estimated in both seawater and rivers. A major effort was directed toward the transport of the U,Th series nuclides in a watershed in Sweden. A serious effort was directed at developing a transport model for the U,Th series nuclides in aquifers. A detailed study of {sup 238}U-{sup 230}Th dating of a cave in Israel was carried out collaboratively. The Os-Re fractionation between silicate and sulfide melts were determined in MORB basalts and glasses and the isotopic composition of Os was measured in sulfide samples.

  8. {Use of isotopic tracers for the study of the interaction of surface water and groundwater in a karst environment.}

    NASA Astrophysics Data System (ADS)

    Cuomo, A.

    2009-04-01

    Domenico Guida1, Michele Guida2, Albina Cuomo1, Davide Guadagnuolo2, Antonia Longobardi1, Vincenzo Siervo3 1 Dipartimento di Ingegneria Civile dell'Università di Salerno 2 Dipartimento di Fisica dell'Università di Salerno 3 C.U.G. RI., Salerno Groundwater and surface water resources management represents a present key issue, both in the hydrogeological and the hydrological fields. An integrated approach, accounting for hydrogeological, hydrological, geochemical and biological features can be a valuable tool, being fundamental in karstic landscape because of the great system variability and because of the frequently complex anthropic interaction. In this study we focus on a particular case study, the Bussento river basin, located in the Campania region, Southern Italy, which is well known to hydrogeology and geomorphology scientists for its karstic features, as summit highland with dolines and poljes, lowland with blind valleys, disappearing streams into sinkholes and cave systems. The catchment groundwater circulation is very complex and frequently groundwater inflows from the outside of the hydrological watershed and groundwater outflows toward surrounding drainage systems occur. We aim at propose a validation of a conceptual hydro-geological model (Guida D. et al., 1980; Iaccarino G., et al., 1986; e Guida D. et al.,1988, Guida D. et al., 2005) and to this purpose a measurements campaign, of about one year, has been undertaken along the Bussento for the acquisition of data about the Rn222 concentration in the waters, using a Rad7 water probe and a Rad7H2O (Durridge Inc., South Australia). Besides radon concentration, more chemical and physical variables have been measured, such as pH, water temperature, dissolved oxygen, atmospheric pressure, water conductivity, water resistivity. The preliminary results enable us to consider this as an useful methodology for the localization of the contributions of the groundwaters, diffused along the riverbed, and for their

  9. Characterization of thermal tracer tests and heat exchanges in fractured media

    NASA Astrophysics Data System (ADS)

    de La Bernardie, Jérôme; Bour, Olivier; Guihéneuf, Nicolas; Chatton, Eliot; Labasque, Thierry; Longuevergne, Laurent; Le Lay, Hugo; Koch, Florian; Gerard, Marie-Françoise; Lavenant, Nicolas; Le Borgne, Tanguy

    2016-04-01

    Geothermal energy is a renewable energy source particularly attractive due to associated low greenhouse gas emission rates. Crystalline rocks are in general considered of poor interest for geothermal applications at shallow depths (< 100m), because of the low permeability of the medium. In some cases, fractures may enhance permeability, but thermal energy storage at these shallow depths is still remaining very challenging because of the low storativity of the medium. Within this framework, the purpose of this study is to test the possibility of efficient thermal energy storage in shallow fractured rocks with a single well semi open loop heat exchanger (standing column well). For doing so, several heat tracer tests have been achieved along a borehole between two connected fractures. The heat tracer tests have been achieved at the experimental site of Ploemeur (H+ observatory network). The tracer tests consist in monitoring the temperature in the upper fracture while injecting hot water in the deeper one thanks to a field boiler. For such an experimental setup, the main difficulty to interpret the data comes from the requirement for separating the temperature advective signal of the tracer test (temperature recovery) from the heat increase due to injection of hot water through the borehole which induces heat losses all along the injection tube in the water column. For doing so, in addition to a double straddle packer used for isolating the injection chamber, the particularity of the experimental set up is the use of fiber optic distributed temperature sensing (FO-DTS); an innovative technology which allows spatial and temporal monitoring of the temperature all along the well. Thanks to this tool, we were able to estimate heat increases coming from diffusion along the injection tube which is found much lower than localized temperature increases resulting from tracer test recovery. With local temperatures probes, separating both effects would not have been feasible. We

  10. Quantifying Methane Fluxes Simply and Accurately: The Tracer Dilution Method

    NASA Astrophysics Data System (ADS)

    Rella, Christopher; Crosson, Eric; Green, Roger; Hater, Gary; Dayton, Dave; Lafleur, Rick; Merrill, Ray; Tan, Sze; Thoma, Eben

    2010-05-01

    Methane is an important atmospheric constituent with a wide variety of sources, both natural and anthropogenic, including wetlands and other water bodies, permafrost, farms, landfills, and areas with significant petrochemical exploration, drilling, transport, or processing, or refining occurs. Despite its importance to the carbon cycle, its significant impact as a greenhouse gas, and its ubiquity in modern life as a source of energy, its sources and sinks in marine and terrestrial ecosystems are only poorly understood. This is largely because high quality, quantitative measurements of methane fluxes in these different environments have not been available, due both to the lack of robust field-deployable instrumentation as well as to the fact that most significant sources of methane extend over large areas (from 10's to 1,000,000's of square meters) and are heterogeneous emitters - i.e., the methane is not emitted evenly over the area in question. Quantifying the total methane emissions from such sources becomes a tremendous challenge, compounded by the fact that atmospheric transport from emission point to detection point can be highly variable. In this presentation we describe a robust, accurate, and easy-to-deploy technique called the tracer dilution method, in which a known gas (such as acetylene, nitrous oxide, or sulfur hexafluoride) is released in the same vicinity of the methane emissions. Measurements of methane and the tracer gas are then made downwind of the release point, in the so-called far-field, where the area of methane emissions cannot be distinguished from a point source (i.e., the two gas plumes are well-mixed). In this regime, the methane emissions are given by the ratio of the two measured concentrations, multiplied by the known tracer emission rate. The challenges associated with atmospheric variability and heterogeneous methane emissions are handled automatically by the transport and dispersion of the tracer. We present detailed methane flux

  11. /sup 18/F-2-deoxy-2-fluoro-D-glucose as a tracer in the positron emission tomographic study of senile dementia

    SciTech Connect

    Farkas, T.; Ferris, S.H.; Wolf, A.P.; De Leon, M.J.; Christman, D.R.; Reisberg, B.; Alavi, A.; Fowler, J.S.; George, A.E.; Reivich, M.

    1982-03-01

    Using /sup 18/F-2-deoxy-2-fluoro-D-glucose as a tracer, the authors obtained positron emission tomographic scans of 11 patients with senile dementia and 6 age-matched controls. The rate of glucose metabolism was significantly lower in the patients with senile dementia and significantly correlated with the degree of cognitive impairment.

  12. Nitrogen isotope tracers of high-temperature fluid-rock interactions: Case study of the Catalina Schist, California

    NASA Astrophysics Data System (ADS)

    Bebout, Gray E.

    1997-09-01

    Nitrogen isotope data for metasomatized rocks, veins, and pegmatites in the Catalina Schist subduction zone metamorphic complex allow futher characterization of complex, high-P/T metasomatic proceses and evaluation of the scales of isotopic equilibration and fluid transport during subduction-zone metamorphism. Throughout the Catalina Schist, N resides predominantly as NH 4+ in white mica, which occurs in nearly all bulk compositions (i.e., metasedimentary, metamafic and, to a lesser extent, metaultramafic mélange) at all grades. Within each metamorphic unit of the Catalina Schist (ranging in grade from lawsonite-albite to amphibolite facies), δ 15N values of mica in metasomatized metamafic and metaultramafic rocks are consistent with the metasomatic addition of N from nearby, devolatilizing metasedimentary rocks into the initially N-poor mafic and ultramafic rocks. Within each unit, uniformity of mica δ 15N in metasomatized rocks relative to the δ 15N of metasedimentary rocks in the same unit implies mixing of N from nearby, heterogeneous metasedimentary sources, perhaps producing fluids with unifrom δ 15N at up to the kilometer scale. However, the trend in δ 15N of metasedimentary sources, with increasing metamorphic grade is inconsistent with larger scale up-temperature transfer of fluid (in this case, N 2-bearing) in the Catalina Schist paleosubduction zone; such flow (at scales of up to tens of kilometers) has been inferred through previous oxygen isotope study. Nitrogen isotope compositions are instead believed to have been controlled at a more local scale than the O isotope systematics, due to the more rock-dominated fluid-rock mass balance for N. The δ 15N of muscovite in leucosomes and pegmatites in amphibolite-grade metasedimentary exposures matches that of muscovite in metasedimentary hosts, implying minimal N-isotope fractionation during migmatization processes and possible transfer of metasedimentary N-isotope signatures in silicate melts. These

  13. Measuring air-water interfacial areas with X-ray microtomography and interfacial partitioning tracer tests.

    PubMed

    Brusseau, Mark L; Peng, Sheng; Schnaar, Gregory; Murao, Asami

    2007-03-15

    Air-water interfacial areas as a function of water saturation were measured for a sandy, natural porous medium using two methods, aqueous-phase interfacial partitioning tracer tests and synchrotron X-ray microtomography. In addition, interfacial areas measured in a prior study with the gas-phase interfacial partitioning tracer-test method for the same porous medium were included for comparison. For all three methods, total air-water interfacial areas increased with decreasing water saturation. The interfacial areas measured with the tracer-test methods were generally larger than those obtained from microtomography, and the disparity increased as water saturation decreased. The interfacial areas measured by microtomography extrapolated to a value (147 cm(-1)) very similar to the specific solid surface area (151 cm(-1)) calculated using the smooth-sphere assumption, indicating that the method does not characterize the area associated with microscopic surface heterogeneity (surface roughness, microporosity). This is consistent with the method resolution of approximately 12 microm. In contrast, the interfacial areas measured with the gas-phase tracer tests approached the N2/BET measured specific solid surface area (56000 cm(-1)), indicating that this method does characterize the interfacial area associated with microscopic surface heterogeneity. The largest interfacial area measured with the aqueous-phase tracer tests was 224 cm(-1), while the extrapolated maximum interfacial area was approximately 1100 cm(-1). Both of these values are larger than the smooth-sphere specific solid surface area but much smaller than the N2/BET specific solid surface area, which suggests that the method measures a limited portion of the interfacial area associated with microscopic surface heterogeneity. All three methods provide measures of total (capillary + film) interfacial area, a primary difference being that the film-associated area is a smooth-surface equivalent for the

  14. A Hundred Volatile Years Of Hawaiian Volcanic Gas Studies

    NASA Astrophysics Data System (ADS)

    Sutton, A. J.; Elias, T.

    2011-12-01

    As Thomas Jaggar, HVO's founder, stated "The observatory worker, who has lived a quarter of a century with Hawaiian lavas frothing in action, cannot fail to realize that gas chemistry is the heart of the volcano magma problem". Despite the fervor of this statement, hazardous field conditions associated with sampling volcanic vents and the modest evolutionary state of analytical techniques applied to gas samples conspired to produce only modest progress in the understanding of gas release processes for many years. Still, principal volatile constituents were identified and what were once invisible gases suddenly became visible at least in the scientific literature. Much has changed regarding volcanic gas studies at HVO since the time of Jaggar and other early observers of the 20th century. The careful sampling and analytical work of these studies allowed more recent follow-on researchers, notably T. Gerlach, to reinterpret Jaggar's partial analyses through the lens of modern chemical thermodynamics. Field-based UV and IR spectroscopic techniques make it possible to acquire bulk emission data of several principle volcanic volatile constituents. Spurred by a long-running eruption in Kilauea volcano's east rift zone and more recently at Kilauea's summit caldera, along with comparatively easy access to summit and rift emission sources, it became practical to link measured emission rates with ratioed chemical abundance data to test idealized models for how Kilauea and other volcanoes like it, work. Gas analyses, and solubility data, coupled with emission rate studies allow routine estimation of lava effusion rates. Modern gas measurement techniques, such as in-situ gas sensing instruments and spectroscopic methods facilitate time series comparisons of gas and real-time geophysical measurements such as tilt and seismicity, in order to help elucidate short duration processes.

  15. Hydroxy fatty acids in remote marine aerosols as microbial tracers: Long term study on β-hydroxy fatty acids from the remote marine Island, Chichi-Jima

    NASA Astrophysics Data System (ADS)

    Tyagi, P.

    2014-12-01

    To better understand the long-range atmospheric transport of microbial aerosols from Southeast Asia to the western North Pacific, marine aerosols were collected at a remote Island, Chichi-Jima on a biweekly basis during 1990-1993. These samples were investigated for the atmospheric abundances of hydroxy fatty acids (OH FAs). β-OH FAs are the major structural components of endotoxins in the outer membrane of Gram-negative bacteria (GNB) whereas w-OH FAs are present in cell walls of higher plants. Thus, we tested the applicability of the β-OH FAs (C10-C18) and ω-OH FAs (C16-C26) to assess the Gram-negative bacteria (GNB) and contribution of terrestrial higher plants, respectively. The average concentrations of β- and ω-OH FAs show pronounced seasonal variability with spring maximum (~301 ng/m-3 and ~ 272 ng/m-3, respectively). The concentrations of total OH FAs increased in winter/spring and decreased in summer/autumn, except for 1992-93. This seasonal trend can be interpreted by the atmospheric transport of microbial soil dust and higher plant metabolites from the Asian continent during winter/spring, when westerly winds dominate over the western North Pacific. The even carbon predominance of β- and ω-OH FAs (80 and 74 % of total) in marine aerosols could be explained by their significant contribution from GNB and terrestrial higher plants. These results have implications towards assessing the bacterial transport in the continental outflows. This study also confirms that β-OH FAs can be used as bacterial tracers in ambient aerosol samples.Keywords: β- and ω-hydroxy fatty acids, terrestrial biomarkers, marine aerosols, GC-MS

  16. [Study on drawing aseptic gas in diluting drugs].

    PubMed

    Fan, Z C; Yu, F Y; Zou, F S

    1996-07-01

    In this study, the gas was drawn from sealed aseptic bottles, the blue flame of an alcohol lamp, and the air of the same treatment room. And the gas was put into aseptic solutions of 10% glucose separately and dripped. Then the samples were taken for bacteriaculture at appointed time-points. Meanwhile, the gases were drawn and put into aseptic solutions of 10% glucose separately. Then deactived penicillines were diluted with the solutions separately. Finally, the penicillines were mixed with 10% glucose and dripped. The samples were taken for bacteria-culture in the same way. The results showed that there was no colony existed in the gas from the sealed aseptic bottles and the flame of the alcohol lamp. However, colonies existed in the samples from the air of the treatment room. It is suggested that sealed aseptic gas should be drawn and kept for use in diluting drugs.

  17. Some design considerations for the proposed Dixie Valley tracer test

    SciTech Connect

    Doughty, C.; Bodvarsson, G.S.

    1988-06-01

    A tracer test for the Dixie Valley, Nevada, geothermal resource is planned for the summer of 1988, in order to study the fluid flow paths that will develop under typical operating conditions. During the test six production wells will provide the power plant with steam sufficient for generation of 60 MWe, requiring fluid production at a rate of approximately 600 kg/sec. Up to 75% by mass of the extracted fluid will be reinjected into the reservoir, using four injection wells. Tracer will be added to the injected fluid for a twenty-minute period, and subsequently the produced fluid will be monitored for the tracer. 5 refs., 9 figs., 5 tabs.

  18. Tracer transport by the diabatic circulation deduced from satellite observations

    NASA Technical Reports Server (NTRS)

    Solomon, S.; Kiehl, J. T.; Garcia, R. R.; Grose, W.

    1986-01-01

    Nimbus-7 sensor data were used to track the diabatic circulation in the stratosphere to study the advective transport of CH4 and N2O as tracer species. Advective transport by the mean circulation was found to be a function of the temperature field and associated deviations from radiative equilibrium. A photochemical model was applied to account for the disappearance of the tracer species from the stratosphere. Comparisons between the SAMS data and modeling on the basis of the chemical loss rates of the tracers and the LIMS circulation data showed that the model predictions underestimated the resident abundances, although the global distributions and circulations exhibited a good match.

  19. Dispersion of a tracer in the deep Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Ledwell, James R.; He, Ruoying; Xue, Zuo; DiMarco, Steven F.; Spencer, Laura J.; Chapman, Piers

    2016-02-01

    A 25 km streak of CF3SF5 was released on an isopycnal surface approximately 1100 m deep, and 150 m above the bottom, along the continental slope of the northern Gulf of Mexico, to study stirring and mixing of a passive tracer. The location and depth of the release were near those of the deep hydrocarbon plume resulting from the 2010 Deepwater Horizon oil well rupture. The tracer was sampled between 5 and 12 days after release, and again 4 and 12 months after release. The tracer moved along the slope at first but gradually moved into the interior of the Gulf. Diapycnal spreading of the patch during the first 4 months was much faster than it was between 4 and 12 months, indicating that mixing was greatly enhanced over the slope. The rate of lateral homogenization of the tracer was much greater than observed in similar experiments in the open ocean, again possibly enhanced near the slope. Maximum concentrations found in the surveys had fallen by factors of 104, 107, and 108, at 1 week, 4 months, and 12 months, respectively, compared with those estimated for the initial tracer streak. A regional ocean model was used to simulate the tracer field and help interpret its dispersion and temporal evolution. Model-data comparisons show that the model simulation was able to replicate statistics of the observed tracer distribution that would