Gas Dissolution Research Articles

Cryptosporidium parvum inactivation from short durations of treatment with ozonated water produced by an electrolytic generation system.

Cryptosporidium is a waterborne pathogen that causes diarrhea in vertebrates and humans (mainly C. hominis and C. parvum). Ozone (O3) is a powerful disinfectant due to its high oxidative characteristics, and it is used to inactivate microorganisms in drinking water. As an alternative to the gas dissolution system for producing ozone from oxygen, a simpler electrolytic ozone generation system has recently been developed. In the present study, the efficacy of the ozonated water produced by this system in inactivating Cryptosporidium parasites (C. parvum) was evaluated at different current intensities (which change the ozone concentrations) and short exposure times (15-60s). Oocyst viability and integrity was assessed using vital dye staining, excystation assays, and scanning electron microscopy (SEM). SEM data revealed that oocyst walls were damaged by exposure to ozone molecules even at low concentrations (< 0.01mg/l for 1min) (current intensity 0.2 A), but that the excystation assay could not differentiate between deformed oocysts (dead) and partially excysted oocysts (alive). Exposure to ozonated water produced with a low current intensity (0.3 A) for 15 and 120s resulted in the inactivation of 96.2% (CT value < 0.003) and 99.4% (CT value < 0.020) of the oocysts, respectively. Thus, it was estimated that a CT value more than 0.020 was required to inactivate > 99% of the C. parvum oocysts. These results suggested that the electrolytic ozone generation system may be more effective than gas dissolution ozone generation; however, further studies using additional approaches are needed to obtain clearer evidence.

Multiphase flow and reactive transport benchmark for radioactive waste disposal

AbstractCompacted bentonite is part of the multi-barrier system of radioactive waste repositories. The assessment of the long-term performance of the barrier requires using reactive transport models. Here we present a multiphase flow and reactive transport benchmark for radioactive waste disposal. The numerical model deals with a 1D column of unsaturated bentonite through which water, dry air and $${\hbox {CO}_{2{(g)}}}$$ CO 2 ( g ) may flow and with the following reactions; aqueous complexation, calcite and gypsum dissolution/precipitation, cation exchange and gas dissolution. INVERSE-FADES-CORE V2, $$\hbox {DuMu}^X$$ DuMu X , TOUGHREACT and iCP were benchmarked with 6 test cases of increasing complexity, starting with conservative tracer transport under variably unsaturated conditions and ending with water flow, gas diffusion, minerals and cation exchange. The solutions of all codes exhibit similar trends. Small discrepancies are found in conservative tracer transport due to differences in hydrodynamic dispersion. Computed $${\hbox {CO}_{2{(g)}}}$$ CO 2 ( g ) pressures agree when a sufficiently refined grid is used. Small discrepancies in $${\hbox {CO}_{2{(g)}}}$$ CO 2 ( g ) and pH are found near the no-flow boundary at early times which vanish later. Discrepancies are due differences in the formulations used for gas flow at nearly water-saturated conditions. Computed $${\hbox {CO}_{2{(g)}}}$$ CO 2 ( g ) pressures show a fluctuation between $$10^{-4}$$ 10 - 4 and $$10^{-3}$$ 10 - 3 years which slows down the in-diffusion of $${\hbox {CO}_{2{(g)}}}$$ CO 2 ( g ) . This fluctuation is associated with chemical reactions involving $${\hbox {CO}_{2}}$$ CO 2 . There are discrepancies in solute concentrations due to differences in the Debye–Hückel (DH) formulation. They are overcome when all codes use the same DH formulation. The results of this benchmark will contribute to increase the confidence on multiphase reactive transport models for radioactive waste disposal.

Computational evaluation of phosphonium ILs as CO2 absorbents for electrochemistry

Since phosphonium-based ionic liquids (ILs) are suitable electrolytes for electrochemical reduction, a computationally informed analysis of these ILs was conducted to assess their ability to absorb CO2. In this work, theoretical and experimental approaches were mixed with a focus on gas solubility, transport properties, and structural characterization. The calculations included free energy of solvation (ΔG), the Henry constant (Kh), and short-range energies (Coulomb plus Lennard–Jones). Two ILs, [P1444][TFSI] and [P1444][FSI], were selected for further evaluation because of their lower Kh values. The enthalpy and entropy of the solvation process for these selected ILs were computationally determined; both ILs were found to have a favourable enthalpy of solvation for gas dissolution, and [P1444][TFSI] had a lower penalty for solvation (less negative entropy). Moreover, the analysis revealed competition among the ions interacting with the gas. The structural characterization of the [P1444][TFSI] and [P1444][FSI] with the CO2 systems involved radial and spatial distribution functions. The gas was likely enveloped by an anion cage, and oxygen and fluorine exhibited greater interactions with the carbon atom of CO2 than nitrogen. The viscosity and density were also calculated for the two systems, and the addition of CO2 only caused a slight change on these values. Experiments on viscosity and density confirmed the computational results; here, compared with those of neat ionic liquids, an approximate 4 % decrease in the viscosity of CO2-saturated systems was observed. Finally, the actual CO2 solubility in [P1444][TFSI] was experimentally determined to be 120 mM; this value was nearly four times greater than those of typical aqueous bicarbonate solutions.

Diffusive solubility of nitrogen in Propane: Measurement from 96 K to 227 K at 0.1 MPa

The burgeoning demand for large-scale energy storage has catalyzed the advancement of Liquid Air Energy Storage (LAES) technology. However, the liquid-phase propane cold storage process in LAES systems encounters a significant challenge: the dissolution of nitrogen protection gas in propane poses a substantial risk to both operational safety and performance. Given the dearth of data on the diffusive solubility of nitrogen in propane under constant atmospheric pressure and low-temperature conditions, this study constructed a testbench and conducted experiments within a temperature range of 96–227 K at a pressure of 0.1 MPa. The molar diffusive solubilities at 227 K, 176 K, 139 K, and 96 K are 0.030 %, 0.177 %, 0.297 %, and 0.962 %, respectively. Besides, this study also fits a calculation equation for the diffusive solubility of nitrogen in propane, which applies to the propane cold storage process in LAES systems.

Study on the gas dissolution performance and bubble generation characteristics of a jet flow type pressurized tubular microbubble generator

Microbubble generation technology has the potential to significantly enhance the separation efficiency of offshore oilfield produced water flotation treatment devices, which currently display unstable performance. In this study, we developed a jet flow type pressurized tubular microbubble generator, comprising a jet-dissolved gas tube (JDGT) and a standard ball valve. The JDGT was designed based on the principle of intensifying bubble breakup through jet nozzles and enhancing gas dissolution via up-down circulation vortex. We proposed an innovative Computational Fluid Dynamics (CFD) model that utilizes User Defined Functions (UDF) to predict the flow pattern and dissolved oxygen (DO) distribution within the tube. The relative error between numerical simulations and experimental results was 5.25 %. Under identical operating conditions, the JDGT can efficiently produce gas-dissolved water in 3.5 s, achieving a dissolved gas efficiency of 80.24 %, compared to 58.31 % for a conventional jet vertical vessel with a hydraulic retention time of 30 s. High-quality microbubbles can be generated through decompression via a standard ball valve. The oxygen volumetric mass transfer coefficient increases with the inlet water flow rate, the gas–liquid volume ratio, and increased dissolved pressure. As the inlet water flow rate increases, the Sauter mean bubble diameter initially increases before decreasing. Both the gas–liquid volume ratio and dissolved gas pressure are exponentially related to the Sauter mean bubble diameter. An engineering prototype with a treatment capacity of 35 m3/h was successfully field-tested on a platform in the South China Sea. The test results indicated that when the microbubble generator was connected to a vertical air flotation unit with a 10 % reflux flow system, the average oil concentration at the unit’s outlet was 13 mg/L. The calculated average oil removal efficiency was 72.38 %, which is 12.8 % higher than that achieved without a tubular microbubble generator.

Enhancing Zn-MnO2 Battery Performance with Hydrogen-Bonded MnO2 Interfaces in Wet Nonaqueous Electrolytes

The quest for sustainable and high-performing battery technologies has directed attention towards Zinc (Zn)-manganese dioxide (MnO2) based rechargeable batteries. These batteries emerge as a viable alternative to lithium-ion systems, particularly due to their advantageous raw material supply, cost, and performance parameters. Despite their potential, Zn-MnO2 batteries face operational challenges, including gas evolution, Zn self-corrosion, and dissolution of the host material when utilized in mild acid aqueous electrolytes. Addressing these issues, our research explores the efficacy of wet nonaqueous electrolytes as a solution. Previously, we demonstrated a substantial enhancement in battery performance (~200 mAh/g of MnO2) by incorporating a specific proportion of water into the nonaqueous electrolyte. Building on this foundation, our current study investigates the role of hydrogen-bonded pillars, particularly proton and ammonium cations, in augmenting the interfacial properties of MnO2. This modification aims to bolster surface kinetics, thereby elevating battery performance closer to that of aqueous systems. Employing a suite of material characterization techniques, including in-situ X-ray absorption spectroscopy (XAS), Raman spectroscopy, and synchrotron X-ray diffraction (XRD), we observed a notable performance improvement (~270 mAh/g), while maintaining stability. These findings hold significant promise for advancing the practical application of MnO2-based hosts in Zn-MnO2 batteries, marking a stride towards next-generation energy storage solutions.

Effects of non-equilibrium phase behavior in nanopores on multi-component transport during CO2 injection into shale oil reservoir

Injecting CO2 into shale oil reservoirs is one of the most effective methods for enhancing oil recovery (EOR) while simultaneously facilitating CO2 capture, utilization, and storage (CCUS). However, it is not always that gas dissolution or condensate evaporation reaches equilibrium instantaneously during the CO2 injection process. In cases where equilibrium is not attained instantaneously, conventional vapor-liquid equilibrium models will have certain limitations in characterizing phase transition hysteresis. These limitations will affect the accuracy of simulating multi-component transport in porous media. In this paper, a robust and generic vapor-liquid non-equilibrium thermodynamic model considering nano-confinement effects (NC) was established by introducing component mass transfer rates proportional to the chemical potential difference. The established model was then used to modify the fully-compositional, projection-based embedded discrete fracture model (pEDFM). Furthermore, C++ hybrid programming and the Graphics Processing Unit (GPU) parallel method were both used to accelerate both the nonlinear and linear solvers. By comparing with results from MATLAB Reservoir Simulation Tools (MRST), Eclipse, and tNavigator, the accuracy and advantages of our solver were demonstrated. The results show that if the underground fluid undergoes a phase transition from a vapor-liquid two-phase state to a single-phase state, non-equilibrium thermodynamic effects need to be considered, and the simulation results show a larger two-phase zone, higher bottom hole pressure, and lower cumulative liquid production. But the nano-confinement effects will weaken the non-equilibrium thermodynamic effects.

Modeling hydrogeological conditions of noble gases in water and aqueous electrolyte solutions

Dissolved noble gases in water hold significant potential as tracers and precursors in various hydrogeological and geological applications, particularly in understanding surface water-groundwater interactions. These applications necessitate precise solubility predictions. Employing the fugacity-fugacity approach, our study models the solubilities of Neon, Argon, Krypton, Xenon, and Radon in both pure water and electrolyte solutions. Leveraging the Cubic-Plus-Association Equation of State, we achieve remarkable accuracy, with average deviations below 2.5 % for vapor pressure, liquid, and vapor-phase densities. Additionally, in water–gas binary systems, deviations in gas solubilities within pure water remain under 5.0 %. Extending our analysis to water–gas-salt ternary systems, our model demonstrates deviations smaller than 5.6 %. Alongside discussing the gas dissolution mechanism, this work emphasizes the adaptability of the model, informed by robust experimental and modeling data. The interpretations derived from modeling hydrogeological conditions are poised to enhance our understanding of hydrological processes, thereby assisting planners and water managers in achieving sustainable development and management of water resources.

Differential enrichment mechanism of helium in the Jinqiu gas field of Sichuan Basin, China

Helium is extensively utilized in aerospace, healthcare, electronics, semiconductors, advanced science, and renewable energy sectors, playing a pivotal role in the advancement of human technology. Presently, helium is primarily extracted from natural gas as an associated resource. The cost of extraction decreases with an increase in the helium concentration within the gases. Therefore, understanding the mechanisms involved in helium generation, migration, and accumulation underground is vital. This article delves into the differential enrichment mechanism of helium in the Jinqiu gas field, situated in the Sichuan Basin of China, by analyzing the molecular and isotopic composition characteristics of the major gases and noble gases, employing gas dissolution and diffusion models. Compared with other Jurassic gas reservoirs in the Sichuan Basin, the Jinqiu gas field contains a significantly higher helium concentration, displaying unique enrichment patterns within its area. The majority of hydrocarbon gases originate from the local underlying Triassic Xujiahe Formation source rocks. Specifically, the western section of the Jinqiu field is primarily supplied by the higher maturity Xujiahe Formation source rocks located in the western Sichuan Basin. Notably, there is no significant contribution of mantle-derived volatile components in the Jinqiu field. Helium and argon are primarily radiogenic, whereas neon primarily originates from atmosphere. The good linear correlation between 4He and 20Ne suggests that their transfer is primarily facilitated through groundwater. The solubility calculation reveals that the helium exsolved from the in-situ pore water of the reservoir, due to stratigraphic uplift during the Himalayan movement, comprises only 0.04%–0.11% of the existing reserves. This suggests that gas desolvation plays a relatively minor role in helium enrichment in the Jinqiu field. Additionally, the calculation results of gas diffusion indicate that diffusion's contribution to helium enrichment in the Jinqiu gas field remains minimal. Finally, our analysis of methane reserve changes suggests that the combined effect of differential loss and dilution of hydrocarbon gases is the primary mechanism for helium's differential enrichment in the Jinqiu field. Notably, methane and carbon dioxide depletion may be a significant factor in helium enrichment within the crustal natural gas system.

New insight into groundwater 4He ages based on Ne isotopic equilibrium in Jianghan Plain, Central China

The change of hydrostatic pressure caused by the fluctuation of groundwater table in the aquifer will lead to the partial dissolution of excess 4He gas, resulting in the isotope imbalance of 3He/4He-4He. The dissolved Ne in groundwater is mainly derived from the atmosphere, and its isotopic composition can correct the isotopic imbalance of 3He/4He-4He. We collected thirty-eight groundwater samples from the second aquifer of the Jianghan Plain, and the isotopic concentrations and ratios of He and Ne were measured. 21Ne/22Ne-20Ne/22Ne illustration is proposed to estimate the shares of atmospheric and mantle components. The 21Ne content and isotopic ratios of atmospheric and mantle components are used to estimate a calculated Ne content. The difference between the calculated Ne content and the measured Ne content (∆Ne) is used to evaluate the percentage of error estimated“excess air”. The accumulation of crustal 4He is corrected with the measured 4He content and the percentage of error estimated “excess air”. We found the maximum percentage of error estimated “excess air” was 7.57 % occurring in the groundwater samples from the second aquifer of Jianghan Plain, and the disequilibrium of 3He/4He-4He led to overestimation of the share of mantle He. The percentage of mantle He in total dissolved components is reassessed and range from 0.03 % to 0.74 %, indicating the mantle component is minor. The reassessed 4He ages (1.79 ka to 21.90 ka) were uniformly older than those estimated by traditional method which only use the measured 3He/4He ratio to distinguish the crust 4He (1.28 ka to 18.74 ka). 4He age is significantly underestimated up to 47.05 %.

Mechanistic analysis of acid gas storage and oil recovery in naturally fractured reservoirs using single matrix block approach

AbstractThe objective of this study is to assess the storage of acid gas, containing CO2 and H2S, in a depleted naturally fractured reservoir (NFR) using single matrix block (SMB) approach. The acid gas dissolution in oil is considered by Peng‐Robinson equation of state and compositional simulation. The PHREEQC package is used to determine acid gas solubility in formation brine. Three types of acid gases with different compositions are used for this study and their swelling behavior and miscibility in relation to the reservoir oil are analyzed. An SMB model, with a matrix block surrounded by fractures, is constructed, and validated for simulation of a real experiment. The simulation is conducted for synthetic and real reservoir fluids when the oil is in its residual saturation. A sensitivity analysis is performed to study the effects of key parameters, such as acid gas composition, reservoir pressure, permeability, porosity and matrix height on the storage capacity and oil recovery factor. The matrix has a volume of 27 m3 and about half of acid gas storage is achieved in the first 5 years while the simulations are run for 30 years. The results show that up to 90% of remained oil is recoverable, and more than 0.67 kmol of acid gas per cubic meter of matrix is stored whether matrix contains a real oil or a synthetic one. Higher storage is achieved for higher matrix porosities and heights and large H2S proportion in acid gas. In all cases about 10% of acid gas is trapped in water and the remaining 90% is dissolved in oil. The mineral trapping was more active in CO2‐rich acid gases. While about 10 kg of the matrix rock was dissolved in the acidic brine when the acid gas contained H2S, the amount of the dissolved minerals in acidic brine resulted from the injection of CO2‐rich acid gas was more than 16 kg. Finally, this study gives a comparative analysis of the storage performance of acid gas mixture and pure CO2. © 2024 Society of Chemical Industry and John Wiley &amp; Sons, Ltd.

Triggering and evolution of static liquefaction in submarine slopes with quasi-saturated sand

Liquefaction flow slides of submarine slopes with quasi-saturated sand have been frequently observed in engineering practice. That instability can be attributed to a decrease in resistant shear strength caused by static liquefaction. However, the triggering of static liquefaction in submarine slopes has received limited attention. To address this gap, a state-dependent constitutive model for quasi-saturated sand with entrapped air is employed that can represent the effects of compression and dissolution of gas accurately. Moreover, the soil model enables the evaluation of the triggering of static liquefaction based on second-order work. To study the triggering mechanism of static liquefaction, a submarine slope model is established using the material point method. The static liquefaction area is detected by the vanish of second-order work. Results indicate that static liquefaction initially arises at the slope surface and gradually expands towards the interior of the slope as the rapid loading at the top of the slope increases. Furthermore, the presence of entrapped gas within the slope can effectively enhance the resistance to slope instability caused by static liquefaction. It significantly alters both the location where static liquefaction is initially triggered and the subsequent evolution pattern, in comparison with saturated submarine slopes.

Analysis on degassing at microgravity condition

For the future diversity and sustainability of the International Space Station, the manned flight time will be greatly increased, and the water required will be greatly increased as well. It is particularly important to deal with resources in more detail. In the process of treating drinking water, tiny air bubbles may be created. Bubbles can form in the Water Recovery and Management System (WRMS) on the ISS due to gas dissolution, microgravity environment, chemical reactions, and microbial metabolism. Water under pressure can dissolve gases. In the ISS, if water comes from a high-pressure environment to a lower one, gas may come out of solution, forming bubbles. Also, in the microgravity environment of the ISS, bubbles can remain suspended in the water, interfering with the systems sensors and pumps. Some processes in the water recovery system can produce gases as byproducts, such as electrolysis used in the Oxygen Generation System of the ISS. Finally, some microbial metabolic processes generate gases which can form bubbles in the water. According to four reasons given above, the passage will first introduce the current situation about dealing with bubbles in ISS, then providing some future directions of the development of the bubble-remove techniques.

Dissolution of gas in a stationary liquid layer: A diffusion-kinetic model and experimental studies

An analytic model of gas dissolution in a stationary liquid layer is presented. This model considers for the first time the intrinsic kinetics of the process of gas dissolution in a liquid characterized by the rate of gas absorption/desorption reaction at the gas–liquid interface. Within the framework of the presented model, it is shown that the process of gas dissolution in a stationary liquid layer occurs either in the diffusion-kinetic regime or in the diffusion regime. In the diffusion-kinetic regime, the rate of gas dissolution in a stationary liquid layer is affected by both the intensity of gas diffusion through the liquid layer and the intrinsic kinetics of the gas dissolution process in the liquid; in the diffusion regime, the rate of gas dissolution in a stationary liquid layer is limited only by the intensity of gas diffusion through the liquid layer. Experiments were carried out to study the kinetics of methane dissolution in a stationary layer of water at different temperatures. From the comparison of calculated and experimental data, the values of the diffusion coefficient of methane in water were determined, and it was also established that the process of methane dissolution in a stationary layer of water occurs in the diffusion regime. A new empirical correlation for calculating the diffusion coefficient of methane in water in the temperature range from 273 to 323.15 K was obtained based on our and available data points: D[m2/s]=exp(−12.64−2250.5/T[K]).

Tracing of natural gas migration by light hydrocarbons: A case study of the Dongsheng gas field in the Ordos Basin, NW China

Based on the analysis of light hydrocarbon compositions of natural gas and regional comparison in combination with the chemical components and carbon isotopic compositions of methane, the indication of geochemical characteristics of light hydrocarbons on the migration features, dissolution and escape of natural gas from the Dongsheng gas field in the Ordos Basin is revealed, and the effect of migration on specific light hydrocarbon indexes is further discussed. The study indicates that, natural gas from the Lower Shihezi Formation (P1x) in the Dongsheng gas field displays higher iso-C5−7 contents than n-C5−7 contents, and the C6−7 light hydrocarbons are composed of paraffins with extremely low aromatic contents (<0.4%), whereas the C7 light hydrocarbons are dominated by methylcyclohexane, suggesting the characteristics of coal-derived gas with the influence by secondary alterations such as dissolution. The natural gas from the Dongsheng gas field has experienced free-phase migration from south to north and different degrees of dissolution after charging, and the gas in the Shiguhao area to the north of the Borjianghaizi fault has experienced apparent diffusion loss after accumulation. Long-distance migration in free phase results in the decrease of the relative contents of the methylcyclohexane in C7 light hydrocarbons and the toluene/n-heptane ratio, as well as the increase of the n-heptane/methylcyclohexane ratio and heptane values. The dissolution causes the increase of isoheptane values of the light hydrocarbons, whereas the diffusion loss of natural gas in the Shiguhao area results in the increase of n-C5−7 contents compared to the iso-C5−7 contents.

Experimental Study on Carbon Dioxide Displacement by Coal Seam Water Injection.

Using water to displace carbon dioxide adsorbed in coal can prevent coal and gas outbursts. However, the mechanism of continuous water injection replacing adsorbed gases in coal has not been well studied. An experiment with the same water injection pressure and different adsorption equilibrium pressures for displacing carbon dioxide was conducted. The variation patterns of the amount of displaced carbon dioxide, time, and water displacement rate, displacement ratio, and water action ratio were analyzed. The modes of water injection displacing carbon dioxide are discussed. The results show that the change in the amount of displaced carbon dioxide consists of three stages: rapid, slow, and stop growth stages. For the same displacement time, as the adsorption equilibrium pressure rises, more carbon dioxide is displaced. The time displacement rate and water displacement rate can be divided into three stages: rising, peak, and dropping stages. As the adsorption equilibrium pressure increases, the duration of the peak stage decreases, while the time and water displacement rates increase. At different adsorption equilibrium pressures, the carbon dioxide displacement ratio ranged from 45% to 54%, less than the natural desorption ratio. But the water action ratio containing the gas dissolution amount was close to or greater than the natural desorption ratio. Thus, the displacement effect of flowing water accelerated the desorption of carbon dioxide in coal. The modes of carbon dioxide displacement by water injection include water-displacement, gas-dissolution displacement, and gas-diffusion-dissolution displacement. The findings of this study provide novel suggestions for preventing and controlling coal and gas outbursts.

Metal-facilitated, sustainable nitroarene hydrogenation under ambient conditions

Hydrogenation is a critical reaction in the chemical industry, yielding a range of important compounds such as fine chemicals, pharmachemicals and agrochemicals. However, conventional hydrogenation typically requires pressurized hydrogen, high temperatures and involves noble metal catalysts. We proposed a two-step hydrogenation process, utilizing water as the hydrogen source for the industrially important reduction of nitroarenes to anilines. A metal or reduced metal oxide, which can be obtained from solar thermal or electrochemical reduction, acts as the active site for nitrobenzene adsorption, H2O dissociation and in-situ hydrogen generation. Among the 15 metal and reduced metal oxides investigated, Zn and Sn emerged as highly efficient catalysts for the reduction of a broad range of organic nitro compounds under mild conditions, with H2 utilization efficiency 1–2 orders of magnitude above the state-of-the-art. The presented protocol provides extra dimensions for designing and optimizing conventional hydrogenation process with an alternative pathway. The reactive hydrogen atoms generated in-situ effectively overcome the barriers associated with hydrogen gas dissolution and its subsequent dissociation on the catalyst surface, thereby greatly enhancing the overall effectiveness for the hydrogenation reaction. This research potentially establishes a sustainable, generally applicable alternative to conventional hydrogenation methods, simultaneously presenting a viable solution for renewable energy storage.

Measuring changes in background dissolved gases to evaluate multi-component gas dissolution: Laboratory experiments and implications for stray gas monitoring

Gas emitted from leaking wells is a concern for natural gas production as well as the underground storage of carbon dioxide and hydrogen. Stray gas migration through heterogeneous layers, and its subsequent dissolution, controls the fraction emitted to the atmosphere rather than dissolved in groundwater. Understanding the effects of multiple gas components on gas dissolution is important for risk prediction, and measuring changes in background dissolved gas concentrations may provide a complementary tool to support site investigation. A series of two-dimensional laboratory experiments were performed to measure transient gas saturations and background dissolved gas concentrations during and after gas injection into heterogeneous sand packs. Mass transfer was influenced by both source architecture and groundwater velocity, and steady-state modelling was used to estimate mass transfer coefficients at the scale of the flow cell. The results demonstrate the potential of using background dissolved gases as part of gas migration monitoring strategies.

Irrigation of Sand-based Creeping Bentgrass Putting Greens with Nanobubble-oxygenated Water

Cultural and environmental factors can place creeping bentgrass (Agrostis stolonifera) under extreme stress during the summer months. This stress, coupled with the growth adaptation of creeping bentgrass, can result in shallow, poorly rooted stands of turf. To enhance root zone oxygen and rooting of creeping bentgrass, golf courses use methods such as core and solid-tine aerification, and sand topdressing. An additional method of delivering oxygen to the soil could be irrigation with nanobubble-oxygenated water. The properties of nanobubbles (NBs) allow for high gas dissolution rates in water. Irrigating with NB-oxygenated water sources may promote increased rooting of creeping bentgrass putting greens during high-temperature periods and lead to a more resilient playing surface. The objectives of this study include comparing the effects of irrigation with NB-oxygenated water sources with untreated water sources on creeping bentgrass putting green root zone and plant health characteristics using field and controlled environment experiments. Treatments included NB-oxygenated potable water and irrigation pond water, and untreated potable and irrigation pond water. In the field, NB-oxygenated water did not enhance plant health characteristics of creeping bentgrass. In 1 year, NB-oxygenated water increased the daily mean partial pressure of soil oxygen from 17.48 kPa to 18.21 kPa but soil oxygen was unaffected in the other 2 years of the trial. Subsurface irrigation with NB-oxygenated water did not affect measured plant health characteristics in the greenhouse. NB-oxygenation of irrigation water remains an excellent means of efficiently oxygenating large volumes of water. However, plant health benefits from NB-oxygenated irrigation water were not observed in this research.

Mechanistic Basis of Conductivity in Carbon Dioxide-Expanded Electrolytes: A Joint Experimental-Theoretical Study.

Electrolyte conductivity contributes to the efficiency of devices for electrochemical conversion of carbon dioxide (CO2) into useful chemicals, but the effect of the dissolution of CO2 gas on conductivity has received little attention. Here, we report a joint experimental-theoretical study of the properties of acetonitrile-based CO2-expanded electrolytes (CXEs) that contain high concentrations of CO2 (up to 12 M), achieved by CO2 pressurization. Cyclic voltammetry data and paired simulations show that high concentrations of dissolved CO2 do not impede the kinetics of outer-sphere electron transfer but decrease the solution conductivity at higher pressures. In contrast with conventional behaviors, Jones reactor-based measurements of conductivity show a nonmonotonic dependence on CO2 pressure: a plateau region of constant conductivity up to ca. 4 M CO2 and a region showing reduced conductivity at higher [CO2]. Molecular dynamics simulations reveal that while the intrinsic ionic strength decreases as [CO2] increases, there is a concomitant increase in ionic mobility upon CO2 addition that contributes to stable solution conductivities up to 4 M CO2. Taken together, these results shed light on the mechanisms underpinning electrolyte conductivity in the presence of CO2 and reveal that the dissolution of CO2, although nonpolar by nature, can be leveraged to improve mass transport rates, a result of fundamental and practical significance that could impact the design of next-generation systems for CO2 conversion. Additionally, these results show that conditions in which ample CO2 is available at the electrode surface are achievable without sacrificing the conductivity needed to reach high electrocatalytic currents.