Gas Cycling Research Articles

Greenhouse gas emissions from the Tubul-Raqui estuary (central Chile 36°S)

The Tubul-Raqui estuary is a coastal system off central Chile at 37°S, adjacent to an active coastal upwelling area, which undergoes rapid changes associated with natural and anthropogenic perturbations. Biogenic greenhouse gas cycling and the gas saturation levels are good indicators of microbial metabolism and trophic status in estuaries. The dissolved greenhouse gases CO2, CH4 and N2O and other biological and chemical variables were spatially recorded in this estuary over two seasons (summer and winter) and over one-half of one tidal cycle. Tidal and spatial variability of these gases indicated they had different origins within the system. Surface waters were always oversaturated in CO2 (up to 578%) and CH4 (up to 6200%) with respect to the atmosphere. But while CO2 seems to come from marine and in situ metabolism, CH4 appears to be more influenced by fluvial and adjacent salt marsh areas. In contrast, N2O was mostly undersaturated and sediments seem to be largely responsible for its consumption. Strong seasonal variability was also observed in CO2 and CH4 fluxes, being tenfold (from −319 to 714 mmol m−2 d-1) and fivefold (from 0.33 to 2.5 mmol m−2 d-1) higher, respectively, in the austral summer compared to winter. In contrast, only small seasonal differences in N2O fluxes were found ranging from −59 to 28 µmol m−2 d−1. These temporal patterns can be explained not only in terms of hydrological and nutrient balances within the system, but also by the influence of wind-driven upwelling processes. Additionally, potential effects of changes in nutrient load and freshwater discharge on net ecosystem metabolism (i.e., autotrophy or heterotrophy) and therefore, on the production/removal of greenhouse gases in this system were explored.

Poly-Use Multi-Level Sampling System for Soil-Gas Transport Analysis in the Vadose Zone

Soil-gas turnover is important in the global cycling of greenhouse gases. The analysis of soil-gas profiles provides quantitative information on below-ground turnover and fluxes. We developed a poly-use multi-level sampling system (PMLS) for soil-gas sampling, water-content and temperature measurement with high depth resolution and minimal soil disturbance. It is based on perforated access tubes (ATs) permanently installed in the soil. A multi-level sampler allows extraction of soil-gas samples from 20 locations within 1 m depth, while a capacitance probe is used to measure volumetric water contents. During idle times, the ATs are sealed and can be equipped with temperature sensors. Proof-of-concept experiments in a field lysimeter showed good agreement of soil-gas samples and water-content measurements compared with conventional techniques, while a successfully performed gas-tracer test demonstrated the feasibility of the PMLS to determine soil-gas diffusion coefficients in situ. A field application of the PMLS to quantify oxidation of atmospheric CH4 in a field lysimeter and in the forefield of a receding glacier yielded activity coefficients and soil-atmosphere fluxes well in agreement with previous studies. With numerous options for customization, the presented tool extends the methodological choices to investigate soil-gas transport in the vadose zone.

A Comparative Review of North American Tundra Delineations

Recent profound changes have been observed in the Arctic environment, including record low sea ice extents and high latitude greening. Studying the Arctic and how it is changing is an important element of climate change science. The Tundra, an ecoregion of the Arctic, is directly related to climate change due to its effects on the snow ice feedback mechanism and greenhouse gas cycling. Like all ecoregions, the Tundra border is shifting, yet studies and policies require clear delineation of boundaries. There are many options for ecoregion classification systems, as well as resources for creating custom maps. To help decision makers identify the best classification system possible, we present a review of North American Tundra ecoregion delineations and further explore the methodologies, purposes, limitations, and physical properties of five common ecoregion classification systems. We quantitatively compare the corresponding maps by area using a geographic information system.

Numerical Simulation of Cyclic Gas Injection in Condensate Gas Reservoir with Aquifer by Horizontal Vertical Composed Well Pattern

Pressure maintenance such as gas cycling which re-injection of produced lean gas into the reservoir are common practices and effective measures to improve the development performance of gas condensate reservoir. However, effectively control of gas channeling and control water cut of horizontal well in gas reservoir with aquifer both the keys to improve the development effectiveness. There are many factors that respond for gas channeling and water cresting, single factor experiment is difficult to obtain reliable result. Orthogonal experimental design, also called Taguchi experimental design, is widely used in various fields of scientific research. This paper applied Taguchi experimental design, an L9 orthogonal was used to the X gas reservoir numerical simulation to carry out sensitivity analysis among four factors which are the well pattern, gas cycle time, gas offtake, recirculating ratio.

TS-1 zeolite as an effective diffusion barrier for highly stable Pd membrane supported on macroporous α-Al2O3 tube

Thin and defect-free supported palladium membranes were prepared on macroporous α-alumina ceramic tubes using TS-1 zeolite as the intermediate and diffusion barrier layer. It is necessary to modify the pore size of the substrate and form an effective diffusion barrier between the palladium membrane and the support in order to obtain a continuous and thin Pd layer. The detailed microstructure of the composite membranes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy. Pd membranes supported on a TS-1 layer with a thickness of 2–5 μm showed high H2 flux and ideal selectivity of H2/N2 in the working temperature range. The result reveals that the palladium penetrated into the TS-1 films through the nonzeolitic pores existing in the zeolite films. The resultant Pd-TS-1 membrane displays very high stability due to the excellent anchorage of Pd layer inside the zeolite barrier grown on the support. This membrane could be able to tolerate rapid and repeated cycling of gases, temperature and pressure without sacrificing its good permeance and selectivity, even below the Pd embrittlement temperature (<573 K). These results suggest that TS-1 zeolite is an effective intermediate substrate modifier to bridge the large pore size of the support for the synthesis of a thin Pd layer.

Gas Consumption Reactions and Cycling Characteristics of Improved Sealed Ni-Cd Batteries

Gas Consumption Reactions and Cycling Characteristics of Improved Sealed Ni-Cd Batteries

Effect of oxygen minimum zone formation on communities of marine protists

Changes in ocean temperature and circulation patterns compounded by human activities are leading to oxygen minimum zone (OMZ) expansion with concomitant alteration in nutrient and climate active trace gas cycling. Here, we report the response of microbial eukaryote populations to seasonal changes in water column oxygen-deficiency using Saanich Inlet, a seasonally anoxic fjord on the coast of Vancouver Island British Columbia, as a model ecosystem. We combine small subunit ribosomal RNA gene sequencing approaches with multivariate statistical methods to reveal shifts in operational taxonomic units during successive stages of seasonal stratification and renewal. A meta-analysis is used to identify common and unique patterns of community composition between Saanich Inlet and the anoxic/sulfidic Cariaco Basin (Venezuela) and Framvaren Fjord (Norway) to show shared and unique responses of microbial eukaryotes to oxygen and sulfide in these three environments. Our analyses also reveal temporal fluctuations in rare populations of microbial eukaryotes, particularly anaerobic ciliates, that may be of significant importance to the biogeochemical cycling of methane in OMZs. Eukaryotic 18S rRNA gene sequences recovered from the Saanich Inlet water column on were deposited in Genbank under accession numbers HQ864863–HQ871151.

Model Integration and Data Optimization Software Enables Integrated Project Modeling

Technology Update Integrated asset modeling and optimization is an underserved niche in an industry where its demand is increasing because of the growing complexity of operating environments. Software called Pipe-It, which falls under the category of “integrated asset management tools,” and specifically “model integration and optimization,” was unveiled in December by Petrostreamz of Norway. It is designed for building integrated model-based tools for oil and gas asset optimization. Petrostreamz is a software spinoff of PERA, a consultancy firm in global pressure, volume, and temperature (PVT) modeling and gas enhanced oil recovery modeling. Curtis H. Whitson, a professor at the Norwegian University of Science and Technology (NTNU) and the chief technical officer of Petrostreamz, said the software addresses a much needed, underserved segment. Although it is a commercial product, it is made available to university students and research institutes in order to cultivate a data stream translation user community in the oil and gas industry. The company has published two Pipe-It integrated asset management (IAM) technical papers: the first in 2009 with paper SPE 121252, “Model-Based Integration and Optimization—Gas Cycling Benchmark,” and the second in 2010 with paper SPE 130768, “Multi-Field Asset Integrated Optimization Benchmark.” In both, all model data sets are made avail-able to the public, including the Pipe-It project itself, for those who wish to test their IAM solution against the company’s published results. The second benchmark is a complex integrated model publicly documented from NTNU’s Center for Integrated Operations (www.ntnu.edu/iocenter), with specific attention to the paper SPE 130768 benchmark (www.ipt.ntnu. no/~io-opt/wiki/doku.php). “If the application runs from a command line, you can integrate it in Pipe-It. In the past, model integration was more limited, as market solutions were sold in packages from a single vendor,” said Petrobras production engineer Sthener Campos. “It was used as a commercial strategy to tie the client. This scenario goes against a smooth implementation as it clashes with the profile of final users. Preset integration packages require users to change the software they used to develop engineering, and the knowledge they already own.” Streamz Technology The software performs four main functions: data stream translation, the orchestration of multiple processes, parametric analysis, and project optimization. The data stream translation is based on a technology for translating data streams for oil, gas, and water, from one description to another, with each description being needed as input for different software applications.

Application of ground‐penetrating radar to measure near‐saturation soil water content in peat soils

The presence and flux of biogenic methane‐rich free phase gas that is eventually released to the atmosphere influence water content (θ) of peat soils below the water table. Small variations in gas content in peat soils at near‐saturation θ could be inferred by changes in dielectric permittivity, but detailed measurements in that range of θ needed to develop calibration functions are lacking. Our experiment uses a new method for varying θ in the sample using elevated pressure to reduce the naturally occurring volumetric gas content in a manner similar to what occurs in situ under atmospheric pressure change, which relevant to understanding carbon gas cycling in peatlands. We recorded dielectric permittivity using a 1.6 MHz ground‐penetrating radar antenna at multiple water contents between 0.87 and 0.95 m3 m−3 on four peat monoliths with varying levels of humification and with &lt;5% gas content as is commonly observed in the field. We identified empirical equations that were linear over the range of θ investigated and optimized a dielectric mixing model for estimating θ from GPR. These results indicate that there are differences in the permittivity‐θ relationships developed between peat samples and suggest that variability in dielectric relationships may be attributed to peat structure and particle orientation. The empirical relationships developed in this study confirm the utility of previously applied multiphase mixing models for estimating peat properties using methods sensitive to dielectric permittivity. This work is relevant to studies of gas content in peat and the role of peatlands in the carbon cycle.

Durability Analysis of Nafion/Hydrophilic Pretreated PTFE Membranes for PEMFCs

The durability of a novel Nafion/poly(tetrafluoroethylene) (PTFE) composite membrane was evaluated using an accelerated stress test. The composite membrane was embedded with a porous PTFE layer and was prepared by the solution-casting method using 5% Nafion solution. The porous PTFE layer was treated chemically to improve its hydrophilicity before incorporating it within the membrane. The goal of the hydrophilic treatment was to improve the interfacial bonding between the Nafion polymer and the PTFE fibers resulting in improved strength and durability. The accelerated degradation testing was performed by the wet/dry gas cycling method. The chemical and mechanical stability of the membrane was evaluated by measuring the polarization curve, hydrogen crossover, and proton resistance during wet/dry cycles. Cross-sections of the composite membrane were examined after failure by a scanning electron microscope. The results show that the degradation rate of the composite fuel cell membrane incorporating the PTFE layer with hydrophilic pretreatment was lower than the degradation rate of the membrane with untreated PTFE. Tensile testing revealed that the composite membrane with pretreated PTFE has higher mechanical strength compared to both the composite membrane with untreated PTFE, and a commercial Nafion membrane.

Experimental Research on a New Vaporization of LNG using Flue Gas to Impact Underwater Umbrella Rotor to Enhance Heat Transfer

A new LNG heat vaporization technology is developed and experimental researched. The LNG vaporizer use flue gas jet to impact underwater umbrella rotor at high speed, and form rotating air flow including steam and water drop. When wet flue gas flow through heat exchanger, heat transfer is enhanced because of water phase change. The vaporizer also uses flue gas cycling system to enhance heat transfer of LNG, efficiently reduce exit temperature of flue gas and increase heat efficiency. The vaporizer is designed as upper and lower coils to vaporize and reheat LNG. Thermal efficiency and convection heat transfer coefficients of LNG inside upper and lower coils, wet flue gas outside upper coils and water outside lower coils are experimental obtained.

Hydrological Dynamics are Critical to Greenhouse Gas Cycling

Hydrological Dynamics are Critical to Greenhouse Gas Cycling

THE H I MASS DENSITY IN GALACTIC HALOS, WINDS, AND COLD ACCRETION AS TRACED BY Mg II ABSORPTION

It is well established that MgII absorption lines detected in background quasar spectra arise from gas structures associated with foreground galaxies. The degree to which galaxy evolution is driven by the gas cycling through halos is highly uncertain because their gas mass density is poorly constrained. Fitting the MgII equivalent width (W) distribution with a Schechter function and applying the N(HI)-W correlation of Menard & Chelouche, we computed Omega(HI)_MgII ~ Omega(HI)_halo =(1.41 +0.75 -0.44)x10^-4 for 0.4<z<1.4. We exclude DLAs from our calculations so that Omega(HI)_halo comprises accreting and/or outflowing halo gas not locked up in cold neutral clouds. We deduce the cosmic HI gas mass density fraction in galactic halos traced by MgII absorption is Omega(HI)_halo/Omega(HI)_DLA=15% and Omega(HI)_halo/Omega_b=0.3%. Citing several lines of evidence, we propose infall/accretion material is sampled by small W whereas outflow/winds are sampled by large W, and find Omega(HI)_infall is consistent with Omega(HI)_outflow for bifurcation at W=1.23^{+0.15}_{-0.28}\AA; cold accretion would then comprise no more than ~7% of of the total HI mass density. We discuss evidence that (1) the total HI mass cycling through halos remains fairly constant with cosmic time and that the accretion of HI gas sustains galaxy winds, and (2) evolution in the cosmic star formation rate depends primarily on the rate at which cool HI gas cycles through halos.

Spatiotemporal variations of dissolved organic carbon and carbon monoxide in first-year sea ice in the western Canadian Arctic

We monitored the spatiotemporal progression of dissolved organic carbon (DOC) and carbon monoxide (CO), along with general meteorological, hydrographic, and biological variables, in first-year sea ice in the western Canadian Arctic between mid-March and early July 2008. DOC and CO concentrations fluctuated irregularly in surface ice, but followed the concentration of ice algae in bottom ice, i.e., low at the start of ice algal accumulation, highly enriched during the peak-bloom and early post-bloom, and depleted again during sea ice melt. Vertical profiles of DOC and CO typically decreased downward in early spring and were variable in the melting season. In the presence of high bottom ice algal biomass in mid-spring, DOC and CO exhibited high concentrations in the bottom (DOC: 563 +/- 434 mu mol L(-1); CO: 82.9 +/- 84 nmol L(-1)) relative to the surface (DOC: 56 +/- 26 mu mol L(-1); CO: 16.8 +/- 7 nmol L(-1)). Landfast ice contained higher levels of DOC and CO than drifting ice. Cruise-mean DOC and CO inventories in sea ice were 87 +/- 51 mu mol m(-2) and 13.9 +/- 10 mu mol m(-2), respectively. Net productions of DOC and CO linked to the ice algal bloom were assessed to be 75 mu mol m(-2) and 13.2 mu mol m(-2). Sea ice in the study area was estimated to contribute 7.4 x 10(7) moles of CO a(-1) to the atmosphere. This study suggests that sea ice plays important roles in the cycling of organic carbon and trace gases.

The Performance of Various Injecting Gases into Fractured Retrograde Gas Reservoirs for Revaporization of Liquid Drop-Out

Lean gas cycling and gas injection scenarios are widely used to avoid liquid formation and to revaporize the liquid drop-out in gas condensate reservoirs. In this study, the performance of methane, carbon dioxide, and nitrogen as injecting gases into fractured retrograde gas reservoirs for revaporization of condensates is discussed. The investigation is performed from two perspectives: comparison of the condensate revaporization potency of injecting gases and comparison of the mixing performance of injecting gases. The results show that carbon dioxide has the best performance for condensate revaporization, whereas nitrogen has a greater diffusion coefficient (i.e., the best mixing performance).

Estimating UK methane and nitrous oxide emissions from 1990 to 2007 using an inversion modeling approach

[1] Methane (CH4) and nitrous oxide (N2O) have strong radiative properties in the Earth's atmosphere and both are regulated through the United Nations Framework Convention on Climate Change. Through this convention the United Kingdom is obliged to report an inventory of annual emission estimates from 1990. This paper describes a methodology that estimates emissions of CH4 and N2O completely independent of the inventory values. Emissions have been estimated for each year 1990–2007 for the United Kingdom and for NW Europe. The methodology combines high-frequency observations from Mace Head, a monitoring site on the west coast of Ireland, with an atmospheric dispersion model and an inversion system. The sensitivities of the inversion method to the modeling assumptions are reported. The 20 year Northern Hemisphere midlatitude baseline mixing ratios, growth rates, and seasonal cycles of both gases are also presented. The results indicate reasonable agreement between the inventory and inversion results for the United Kingdom for N2O over the entire period. For CH4 the agreement is poor in the 1990s but good in the 2000s. The UK CH4 inventory reported reduction from 1990–1992 to 2005–2007 (over 50%) is dominated by changes to landfill and coal mine emissions and is more than double the corresponding drop in the inversion estimated emissions (24%). The inversion results suggest that the United Kingdom has met its Kyoto commitment (−12.5%) but by a smaller margin (−14.3%) than reported (−17.3%). The results for NW Europe with the United Kingdom removed show reasonable agreement in trend, on average the inversion results for N2O are 25% lower and for CH4 21% higher.

Hydrogen Generation and Coke Formation over a Diesel Oxidation Catalyst under Fuel Rich Conditions

Hydrogen production via hydrocarbon steam reforming and water gas shift reactions was investigated over a monolith-supported Pt-based diesel oxidation catalyst. The evaluation included comparison between constantly rich gas composition conditions and cycling between rich gas conditions and an inert stream. Analysis was performed along the catalyst length at temperatures ranging from 200 to 500 °C. During the constant inlet composition experiments, C3H6 steam reforming started at 375 °C, while dodecane steam reforming began at 450 °C, and resulted in less hydrogen produced. With a mixture of C3H6 and dodecane, hydrogen production originated solely from C3H6 steam reforming and, under otherwise identical conditions, was less than that observed with only C3H6, but higher than that with only dodecane. Hydrogen production from the water gas shift reaction was higher than that observed with hydrocarbon steam reforming and started at 225 °C. During cycling experiments, hydrogen production via hydrocarbon steam r...

Slow-mode gas/liquid-induced periodic hydrodynamics in trickling packed beds derived from direct measurement of cross-sectional distributed local capacitances

Hydrodynamics of a periodically operated trickling packed bed was studied with a high-speed wire-mesh sensor technique based on direct measurement of cross-sectional distributed local capacitances. Liquid cycles in the alumina packing were generated by periodic induction of gas and/or liquid phase in distinctive slow-mode. Hydrodynamics were characterized with respect to liquid saturation and liquid saturation distribution varying period length, split and time-averaged superficial gas and liquid velocities. The sensors technique allows direct access to local phenomena during liquid pulse breakthrough, to distribution patterns and their reproducibility at different cycle positions that were studied based on transient liquid saturation distribution data of different periodicity variables. Due to simultaneous measurement at four different axial reactor positions, pulse attenuation along the reactor and pulse velocity could be analyzed. Furthermore, hydrodynamics of different modes of gas-induced periodic cycling, e.g. gas cycling only, asynchronous and synchronous cycling of gas and liquid flow rate and alternating gas–liquid cycling, were studied.

A novel approach for the preparation of highly stable Pd membrane on macroporous α-Al 2O 3 tube

Pd membrane with excellent stability was prepared on macroporous α-Al 2O 3 tubes using a nanoporous Sil-1 zeolite as an intermediate support and diffusion barrier layer. The detailed microstructure of the composite membrane was examined by scanning electron microscopy and mapped by EDXS and EPMA to reveal a palladium membrane anchored by multi-legs Pd protrutions that penetrates through the interstices of the zeolite grains into the seed layer. This membrane architecture allowed the membrane to tolerate rapid and repeated cycling of gases, temperature and pressure over 300 h without lost of permeance and selectivity. The zeolite layer contributed up to 25% of the transport resistance across the Pd–Sil-1 composite membrane and has a significant effect on the hydrogen permeance.

Blood Oxygen Level-Dependent Magnetic Resonance Imaging of the Human Liver

To investigate blood oxygen level-dependent (BOLD) response of human liver to hyperoxic exposure under fasting and postprandial conditions. Twelve healthy volunteers and 1 patient with chronic liver disease underwent liver BOLD magnetic resonance imaging at 3.0T. The BOLD images of a single slice were collected (1 image per second) during 3 breathing cycles of hyperoxia (3 minutes, 100% oxygen) with 5 minutes medical air (20.8% oxygen) in both preprandial and postprandial states. The BOLD signal time courses were correlated with a predefined stimulus paradigm. Eight healthy subjects showed increased BOLD signal within 44.6% +/- 21.1% liver area in the fasting state with gas cycling. Two showed slightly reduced BOLD signal within 23.4% +/- 14.9% liver area in the fasting state with gas cycling. In the postprandial state, the degree of change in BOLD signal with gas cycling was reduced for both the subjects having increased and those having decreased signal with gas cycling (13.4% +/- 12.6% positive, 10.9% +/- 10.1% negative; P < 0.05). Chronic liver disease also demonstrated increased BOLD signal with gas cycling, but the correlation decreased postprandially. The proposed physiological challenges induce certain BOLD signal response patterns in healthy and diseased livers, which may be useful for assessing liver function.