CO2 Migration Research Articles

Heterogeneous Carbonylation of Alcohols on Charge‐Density‐Distinct Mo−Ni Dual Sites Localized at Edge Sulfur Vacancies

AbstractAlcohols carbonylation is of great importance in industry but remains a challenge to abandon the usage of the halide additives and noble metals. Here we report the realization of direct alcohols heterogeneous carbonylation to carbonyl‐containing chemicals, especially in methanol carbonylation, with a remarkable space‐time‐yield (STY) of 4.74 molacetyl/kgcat./h and a durable stability as long as 100 h on Ni@MoS2 catalyst. Mechanistic analysis reveals that the Mo−Ni dual sites localized at edge sulfur vacancies of Ni@MoS2 exhibit distinct charge density, which strongly activate CH3OH to break its C−O bond and non‐dissociatively activate CO. Density functional theory calculations further suggest that the low charge density in Mo−Ni, the Ni site, could significantly lower the barrier for CO migration and nucleophilic attack of methoxy species, and finally leads to the rapid formation of acetyl products. Ni@MoS2 catalyst could also effectively realize the carbonylation of ethanol, n‐propanol and n‐butanol to their acyl products, which may demonstrate its universal application for alcohols carbonylation.

Genesis of an Inorganic CO2 Gas Reservoir in the Dehui–Wangfu Fault Depression, Songliao Basin, China

This study systematically examines the origins and formation mechanisms of inorganic CO2 gas reservoirs located within the Dehui–Wangfu Fault in the southeastern uplift region of the Songliao Basin. The research aims to clarify the primary sources of inorganic CO2, along with its migration and accumulation processes. The identification of the Wanjinta gas reservoir within the Dehui–Wangfu Fault Zone, abundant in inorganic CO2, has sparked significant interest in the pivotal roles of volcanism and tectonic activity in gas generation and concentration. To analyze the release characteristics of CO2, this study conducted degassing experiments on volcanic and volcaniclastic rock samples from various boreholes within the fault trap. It evaluated CO2 release behaviors and controlling factors across varying temperatures (150 °C to 600 °C) and particle sizes (20, 40, and 100 µm). The findings indicated a negative correlation between CO2 release and particle size, with a notable transition at 300 °C—marking this temperature as critical for the release of adsorbed and lattice gases. Moreover, volcaniclastic rocks exhibited higher CO2 release compared to volcanic rocks, attributable to their larger specific surface area and higher porosity. At 600 °C, the decomposition of the rock crystal structure results in substantial gas escape. These observations suggest that the inorganic CO2 in this area derives not only from mantle sources but is also influenced by crustal components. Elevated temperatures prompted by tectonic activity and magmatic intrusion facilitated the degassing of the surrounding rocks, allowing released CO2 to migrate upwards through the fracture system and accumulate in the shallow crust, ultimately forming a gas reservoir. This study enhances the understanding of volcanic rock’s roles in inorganic CO2 gas generation and migration, highlighting the fracture system’s critical controlling influence on gas transport and aggregation. The findings indicate that inorganic CO2 gas reservoirs in the Dehui–Wangfu Fault Zone primarily originate from mantle sources with a mixture of crustal gases. This discovery offers new theoretical insights and practical guidance for the exploration and development of gas reservoirs in the Songliao Basin and similar regions.

New insights into sustainable in-situ fixation of heavy metals in disturbed seafloor sediments

To address the issues of plume formation and heavy metal ion release during deep-sea mining operations, this study employed multi-sourced mineral composite roasting materials (MMCCM) of varying sizes. An in-situ capping technique was applied within a simulated system to immobilize heavy metals in contaminated sediments. The results demonstrated that capping with MMCCM of different sizes significantly suppressed the upward migration of Cu, Co, and Ni from sediments into the overlying seawater following disturbance. Ion diffusion was identified as a key mechanism driving heavy metal migration. By calculating the release rates of heavy metals during both the disturbed and undisturbed phases, it was found that the application of MMCCM induced a negative diffusion of heavy metals, indicating that the MMCCM-sediment layer functioned as a "sink" for heavy metals. FTIR and XPS analysis showed that the primary mechanisms for heavy metal removal by MMCCM were electrostatic attraction and complexation-precipitation. Additionally, capping with MMCCM facilitated the transition of heavy metals from labile to stable forms within the sediments. Through comprehensive evaluation, the long-term effectiveness of the fixed effects was demonstrated as follows: large MMCCM (L@MCM) > medium MMCCM (M@MCM) > small MMCCM (S@MCM) > powder MMCCM (P@MCM). Finally, we proposed future research directions and introduced the DQSE framework for the sustainable application of MMCCM. Based on the above findings, this study provides new insights and research references for the in-situ immobilization of heavy metals and plume reduction during future deep-sea mining processes.

Risk assessment and management strategy of geologic carbon storage in multi-well site

Many oil and gas production areas may serve as potential geologic carbon storage(GCS) sites, but large-scale CO2 injection in these sites with multiple legacy wells poses a leakage risk. Therefore, it is crucial to analyze the well leakage risk of these GCS sites and develop effective risk management strategies to minimize CO2 and brine leakage. In this study, we hypothesized a GCS site based on the Jingbian area in the Ordos Basin, which has 177 legacy wells. We conducted a three-dimensional geological modeling of the site and simulated the injection and migration of CO2. Using the National Risk Assessment Partnership’s open-source Integrated Assessment toolkit, we outlined a workflow for assessing the risk of CO2 and brine leakage in multi-well site. Simulations of CO2 and brine leakage through 177 existing wells into the USDW or the atmosphere are used as an indicator of potential risk. Finally, we proposed risk management strategies based on well integrity, injection rate, and pollution range, verifying their effectiveness. The results of the 95th percentile (P95) model implementation showed that the leakage risk of GCS sites was low over 150 years, with a CO2 leakage of 15,996.4 tonnes(0.16 % of the 107 t injected). The risk-based strategy outperformed both distance-based strategy and hybrid strategy overall. Reducing injection rates alone proved ineffective as a risk management strategy. Only high-risk wells near the injection zone may cause pollution to USDW. Meanwhile, legacy wells have negligible impact on atmospheric pollution. The management strategy based on pollution range can be used as a supplement to the risk-based strategy in practical engineering.

The Why, What, Who, When, and Where of Carbon Capture and Storage in Southern Ontario

This paper reviews the five Ws (Why, What, Who, When, and Where) of carbon capture and storage in southwestern Ontario. This area is home to nearly one quarter of Canada’s population and approximately three-quarters of one million people work in the manufacturing sector. Fifteen of the province’s top 20 CO2 emission point sources are in this area. The industries responsible for these emissions include steel mills, refineries and petrochemical plants, and cement plants. These industries are part of the hard-to-abate sector, in that CO2 is used or generated as an integral part of the industrial process. As such, eliminating or even reducing emissions from these industries is a difficult task. Carbon capture and storage (CCS) projects aim to sequester that gas in sedimentary basins over periods exceeding several thousand years. To this end, deeply buried (> 800 m) porous and permeable rocks (a repository) must be overlain by impermeable rocks that act as a seal, preventing the upward migration of CO2 into the atmosphere. The possibility that injection activities could trigger seismicity is but one of the additional considerations. When operational, CCS projects have a negative carbon footprint and the desirability of developing and using this technology has been established for over 20 years. True CCS projects differ from carbon capture, utilization, and storage (CCUS) projects in that the former are only designed with sequestration in mind. One type of CCUS project involves using CO2 for enhanced oil recovery (EOR) and this technology has been employed for several decades. Cambrian sandstones are the most suitable injection targets for CCS in southwestern Ontario because previous oil and gas drilling has shown the rocks to have the necessary characteristics. They are buried below 800 m, can be tens of metres thick, and have adequate porosity and permeability. However, the Cambrian section is lithologically and stratigraphically heterogeneous and oil, gas, and brine can all be present in the pore space. The extent to which this complexity will affect CO2 injection has not yet been evaluated.

A Leakage Safety Discrimination Model and Method for Saline Aquifer CCS Based on Pressure Dynamics

The saline aquifer CCS is a crucial site for carbon storage. Safety monitoring is a key technology for saline aquifer CCS. Current CO2 leakage detection methods include microseismic, electromagnetic, and well-logging techniques. However, these methods face challenges, such as difficulties in determining CO2 migration fronts and predicting potential leakage events; as a result, the formulation of test timing and methods for these safety monitoring techniques are somewhat arbitrary. This study establishes a gas–water two-phase seepage model and solves it using a semi-analytical method to obtain the injection pressure and the derivative curve characteristics of the injection well. The pressure derivative curve can reflect the physical properties of the reservoir through which CO2 flows underground, and it can also be used to determine whether CO2 leakage has occurred, as well as the timing and amount of leakage, based on boundary responses. This study conducted sensitivity analyses on eight parameters to determine the impact of each parameter on the bottom-hole pressure and its derivatives, thereby obtaining the influence of its parameters on different flow stages. The research indicates that, when a steady-state flow characteristic appears at the outer boundary, CO2 leakage will occur. Additionally, the leakage location can be determined by calculating the distance from the injection well. This can guide the placement and measurement of safety monitoring methods for saline aquifer CCS. The method proposed in this paper can effectively monitor the timing, location, and amount of leakage, providing a technical safeguard for promoting CCS technology.

The effects of formation inclination on the operational performance of compressed carbon dioxide energy storage in aquifers

Compressed CO2 energy storage in aquifers (CAESA) is a net-zero energy storage technology. Due to the widespread existence of inclined aquifers in nature, it is of practical significance to study the influence of inclined reservoirs on CO2 migration, safety and energy efficiency of the storage system. We build 3D numerical models with different dips (0°–16°), analyze the hydrodynamic and thermodynamic behavior of the system, and discuss the effects of injection schemes (temperature and pressure) on wellbore pressure, temperature, and energy efficiency. The results show that formation dip affects the energy storage characteristics of the system mainly by affecting the migration and distribution of CO2 in the aquifer. The greater the formation dip, the greater the difference in CO2 distribution, and the farther the CO2 diffuses upward along the dip direction. The farthest migration distances in the low- and high-pressure aquifers, occurring in the case of 16° formation dip, increase by 100 and 53 m, respectively, compared with those of the flat formation. The average daily energy storage efficiency decreases with the increase in formation dip angle. The dip angle of aquifer which is selected for compressed CO2 energy storage should not exceed 8°.

Simulation of bench-scale CO2 injection using a coupled continuum-discrete approach

Unintended releases of CO2 from carbon capture and storage operations presents the risk of atmospheric emissions and groundwater or surface water quality impacts. Given the potential impacts, it is valuable to have tools capable of predicting groundwater concentrations and likely pathways of CO2 migration in the subsurface. Traditional multiphase flow models struggle to simulate the discontinuous flow expected at leakage sites. This work applied a coupled continuum-discrete model, ET-MIP, to simulate a bench-scale injection of CO2. Results demonstrate the capability of ET-MIP to accurately capture gas fingering behaviour, and the complexity of multicomponent mass transfer observed in the experiment. Simulations were computationally efficient, allowing for the use of multiple displacement pressure realizations. CO2 migration in the subsurface was shown to be sensitive to mass transfer, as i) increased groundwater velocity can dissolve leaked CO2 prior to reaching the surface and ii) background dissolved gases in the subsurface can impact the rate of upwards gas movement, gas distribution, and the composition and persistence of the gas phase. The sensitivity to mass transfer suggests it may be preferable to monitor for low-solubility gases in the source mixture rather than CO2. These findings are applicable to other gases in the subsurface, such as hydrogen or methane migrating from geoenergy wells.

Caprock Safety Evaluation Method in CCUS Based on Latin Hypercube Sampling: A case study of a block reservoir

Abstract CO2 geological sequestration is one of the essential means to achieve carbon neutrality goals. However, substantial CO2 sequestration in formations can lead to leakage issues, primarily through the caprock, involving caprock rupture, leakage along caprock fractures/faults, and capillary leakage. Therefore, establishing a method to assess the safety of the caprock during CO2 storage processes is crucial. Firstly, a numerical simulation model is constructed based on parameters from the target block to study the influences of reservoir property, development parameters, and caprock parameters on CO2 flooding, gas injection, and CO2 storage. Latin hypercube sampling is employed for scheme design and subsequent result analysis, applying Spearman’s method to analyze the controlling factors in each CO2 storage. Secondly, using continuous gas flooding as an example, the migration pattern of CO2 in the formation is investigated, and the influence of the formation pressure distribution on caprock safety is analyzed. Finally, considering the comprehensive impact of different parameters on caprock safety, a fuzzy comprehensive evaluation of caprock safety in the target block is conducted. The study indicates that caprock permeability is the most critical factor affecting safety operation across all storage stages, with respective highest positive correlation coefficients of 0.413, 0.356, and 0.221 in different stages. The migration of CO2 in the formation is primarily influenced by the distribution of injection wells and gas migration channels. The established quantitative evaluation standard for caprock safety in the target block calculates a suitability degree of 3.43, suggesting a relatively secure caprock in the block suitable for achieving long-term stable CO2 storage. This research provides theoretical support for the safety analysis of caprock in different stages of CO2 flooding and storage, offering a scientific basis for the safety operation of CCUS schemes.

A New Methodology for Quantitative Risk Assessment of CO2 Leakage in CCS Projects

Summary Assessing risks during carbon dioxide (CO2) sequestration involves a systematic process to identify them (risk assessment), analyze, prioritize, score them (risk analysis), develop mitigation strategies, and plan for measurement, monitoring, and verification (MMV) activities. In this context, risk assessment and analysis are often conducted involving qualitative approaches and/or subjective evaluations based on experts judgments. In this paper, we propose to use numerical results of dynamic subsurface modeling to assess risks in a more precise, less subjective, and quantitative manner, enabling a comprehensive definition of effective MMV plans. In this context, MMV evolves into modeling, measurements, monitoring, and verification [(M)MMV]. The conceptual model used for this study integrates flow and geomechanical-coupled behavior to assess caprock integrity, faults reactivation, and ultimately the risk of CO2 leakage. Uncertainty analysis and a 4D probabilistic workflow are used to quantify the likelihood and consequences of CO2 leakage and to score risks. The proposed approach offers a general framework to enable subsurface-modeling-based quantitative risk assessment (QRA) for the definition of successful (M)MMV plans. In this study, we have focused on the QRA of leakage risks through the fault and intact caprock. Other applications are possible, such as: (1) leakage risks through the caprock resulting from caprock failure; (2) lateral CO2 migration leading to permit limits violation or inducing interferences with neighboring activities; (3) leakage risks resulting from loss of well integrity; (4) risks of faults reactivation; (5) risks of surface heave; and (6) risks of induced seismicity. All these results can be used to formulate effective (M)MMV strategies for an optimized and cost-effective risk mitigation.

Mechanism of Minerals Action in Reservoir During CCS

Abstract The carbon capture and storage (CCS) is one of the most effective ways to control greenhouse gases emissions and mitigate greenhouse effects. There will be a series of effects on the physical properties and chemical composition of the reservoir after CO2 injection. It is of great significance to study the effect of CO2 injection on reservoir for better CO2 storage. In this paper, Through the mechanism model established by numerical simulation technology and the phase permeability hysteresis simulation method, the whole process of reservoir pH, mineral dissolution and precipitation and porosity change during CO2 storage was accurately described. The results indicate that CO2 firstly dissolves in water to form carbonic acid after injection into the reservoir, which will cause a drastic change acid-base properties of reservoir, manifesting as a significant decrease in pH value. Under the effect of H +, Partia mineral components(for example: anorthite) in the reservoir) are dissolved, however, some other minerals (for example: kaolinite and calcite) are precipitated, which significantly change the composition of underground aqueous solution. The reaction rate of CO2-water-rock is very slow. After stopping CO2 injection, the mineralization of all kinds of minerals still goes on for a long time. In addition, due to the effect of CO2-water-rock reaction, a certain increase of reservoir porosity is more conducive to CO2 migration in the reservoir.

Engineering nanoparticle structure at synergistic Ru-Na interface for integrated CO2 capture and hydrogenation

The development of dual functional material for cyclic CO2 capture and hydrogenation is of great significance for converting diluted CO2 into valuable fuels, but suffers from kinetic limitation and deactivation of adsorbent and catalyst. Herein, we engineered a series of RuNa/γ-Al2O3 materials, varying the size of ruthenium from single atoms to clusters/nanoparticles. The coordination environment and structure sensitivity of ruthenium were quantitatively investigated at atomic scale. Our findings reveal that the reduced Ru nanoparticles, approximately 7.1 nm in diameter with a Ru-Ru coordination number of 5.9, exhibit high methane formation activity and selectivity at 340 °C. The Ru-Na interfacial sites facilitate CO2 migration through a deoxygenation pathway, involving carbonate dissociation, carbonyl formation, and hydrogenation. In-situ experiments and theoretical calculations show that stable carbonyl intermediates on metallic Ru nanoparticles facilitate heterolytic C–O scission and C–H bonding, significantly lowering the energy barrier for activating stored CO2.

Exploring the influences of salinity on CO2 plume migration and storage capacity in sloping formations: A numerical investigation

Accurate evaluation of CO2 plume migration, potential leakage, and storage capacity are the main challenges for CO2 geological storage (CGS). This study develops a suite of numerical models, focusing on the Shiqianfeng Formation of the Shenhua-Carbon Capture and Storage (CCS) demonstration project in the Ordos Basin, China, aiming to numerically evaluate the influence of combining salinity, dip angle, and faulting factors on CO2 plume migration, storage amount, conversion of gas and dissolved phase states. Simulation results show that lower salinity and larger dip angles result in earlier CO2 leakage. Increasing salinity from 0.00 to S in a 10° sloping formation causes later CO2 leakage (205–260 years). Lower salinity enhances CO2 plume migration, injection amount, and dissolved-phase CO2. As the salinity decreased from S to 0.00 in a 3° sloping formation over 120 years of CO2 migration, the dissolved CO2 plume migration increased by 9.1 %, the total CO2 amount increased by 70.0 %, and the proportion of dissolved CO2 increased by 13.07 %. Compared to formation dip angle, salinity has a more significant impact on the plume migration of dissolved CO2. However, CO2 storage safety decreases with increasing dip angle. The conversion proportion (1.88 %–9.75 %) of gas-phase to dissolved CO2 increased with an increasing dip angle and decreasing salinity for the first 100 years after injection ceased. Thus, we conclude that salinity, dip angle and faulting are important factors during CGS, and this study may provide a practical reference for further studies for evaluating CO2 storage potential.

CO2 trapping dynamics in tight sandstone: Insights into trapping mechanisms in Mae Moh's reservoir

The reliance on fossil fuels is a major contributor to increased anthropogenic CO2 emissions, driving global challenges such as climate change through the greenhouse effect. Carbon capture and storage (CCS) is a promising interdisciplinary technology aimed at mitigating these emissions by securely sequestering gigatons of CO2. This study focuses on the feasibility of storing point-source CO2 emissions in saline formations, with a particular emphasis on the Mae Moh coal-fired power plant in Lampang, Thailand, which is located near its associated coal mine. The region presents challenges due to tight sandstone reservoirs buried over 2000 m deep. With reservoir simulation, this study evaluates the impact of various factors on CO2 containment and trapping in these geological settings. Results show that elevated temperatures decrease structural trapping of 43.0%–28.9% and increase solubility trapping of 28.55%–46.5%, at 40 °C and 80 °C respectively. Hysteresis is found to enhance residual trapping by immobilizing up to 31.1% of CO2 within pore spaces at 0.5. Permeability heterogeneity has a minimal impact on overall trapping efficiency due to the less heterogeneity of the tight sandstone. However, the kV/kH ratio significantly influences vertical CO2 migration which resulted in residual trapping at its highest at the ratio of 0.1, while lower ratios support lateral dispersion. Moderate rock compressibility values are identified as optimal for structural and residual trapping, while extreme compressibility enhances solubility trapping by up to 30%. These findings emphasize the complexity of CO2 trapping mechanisms in tight sandstone formations, emphasizing the need for careful consideration of key factors in CCS projects.

Numerical optimisation of microbially induced calcite precipitation (MICP) injection strategies for sealing the aquifer's leakage paths for CO2 geosequestration application

Carbon capture and storage (CCS) in deep geological aquifers has shown to be the most viable option for mitigating the greenhouse gas effect of carbon dioxide (CO2) at a large scale. However, the underground formations often possess discontinuities in the caprocks, leaking the stored CO2. Potential leakage paths, such as abandoned wells, have been growing due to excessively unplugged oil and gas exploration wells. The leakage of CO2 from these wells is a major concern, considering their negative impact on the environment and compromising CO2 storage efficiency. Recently, microbially induced calcite precipitation (MICP) technology has proven to be an effective and sustainable method for reducing the permeability of geomaterials. Nevertheless, the MICP process involves intricate interactions among bio-chemo-hydraulics (BCH) domains to comprehend the reactive transport of biochemicals. The complex nature of the MICP process poses difficulties in setting the biochemical injection durations for a particular target distance at the given injection rate. Given this, the present study developed a coupled numerical model and employed it as a workable tool for optimising MICP injections to plug the abandoned well connecting two deep geological aquifers. Following that, the study evaluated the leakage of CO2 using flow migration rates in the untreated and MICP-treated leaky aquifer. The study proposed a novel optimisation strategy for biochemical injections under near and far-field leakage conditions. The sensitivity of biochemical injection durations on the attached bacterial amount and permeability in the leak was also determined. The observations from the present study indicated a complete reduction in the CO2 migration rates from the abandoned well due to a reduced permeability after MICP, thereby indicating the efficacy of the proposed optimisation methodology. Further, a cost analysis of the MICP treatment indicated a rational application cost with the target distance compared to the detrimental effects of CO2 leakage.

Numerical investigations on the performance of sc-CO2 sequestration in heterogeneous deep saline aquifers under non-isothermal conditions

CO2 sequestration in geological formations is an efficient step towards mitigating climate change by reducing global warming. The CO2 emitted from natural sources and anthropogenic activities is injected into geological formations. The flow and transport of CO2 during sequestration operations require in-depth knowledge of the effects of the type of geological formation. The present work analyses the CO2 migration and storage in a heterogeneous deep saline aquifer with variable porosity and evolving permeability under non-isothermal flow conditions while upscaling the capillary pressure using the Leverett J-function. The developed numerical model is history-matched with CO2 gas saturation profiles reported using analytical and numerical approaches. The novelty of the present work lies in its ability to capture fine-scale heterogeneities in the aquifer, which is modelled through variation in the porosity (ϕ) distribution and the permeability (k). The thermal-hydraulic numerical analysis projected a pronounced effect of the degree of heterogeneity arising from the variation in porosity and permeability on pressure buildup along the top of the formation decreasing from a maximum of about 6.41 MPa at the injection well to about 0.933 MPa at 1200 m and affecting gas characteristics and transmission. The thermal front could only propagate to a maximum extent of about 142 m from the injection well in aquifers, while gas plume lengths migrated to a maximum plume length of about 1010 m. The permeability and porosity of the aquifer are critically observed to vary during the sequestration by a ratio (k/k0) of about 1.07 to 1.01 and a percentage of about 0.791 % – 3.136 % in the low permeable conditions. Maximum effective storage of CO2 by a factor of 0.95 observed in low-permeable heterogeneous aquifers with normally distributed porosity affirms maintenance of optimum gas injection rates below the fracture gradient in these formations to sequester the CO2 economically.

A review of CO2-injection projects in the Brazilian Pre-Salt — Storage capacity and geomechanical constraints

This review describes the main geological and geomechanical aspects of CO2-injection projects in the Brazilian Pre-Salt reservoirs, focusing on the storage potential and geomechanical aspects of CO2 injection. The Pre-Salt reservoirs in the Santos Basin offer favorable conditions for CCS due to their geological characteristics and existing infrastructure. The thick evaporite caprock, primarily composed of halite, acts as an efficient seal against CO2 migration. The CO2-injection in the Pre-Salt has been active since 2010, with significant amounts of CO2 already stored in the reservoirs. The volumetric assessment estimates the static storage capacity of the Pre-Salt reservoirs to be over 3.3 Gt of CO2, considering only the four fields currently undergoing injection. Geomechanical constraints, including the maximum injection pressure and caprock integrity, are crucial considerations for safe CCS operations. The high stress regime and the hydrostatic state of the caprock minimize the risk of fracturing during injection. Furthermore, dynamic storage capacity calculations indicate the feasibility of injecting CO2 into Pre-Salt reservoirs. This review provides insights into the current state and future prospects of CO2-injection projects in the Brazilian Pre-Salt, contributing to the development of sustainable carbon mitigation strategies in the region.

Generation and migration of CO in CO2 DBD glow plasma under Martian pressure

AbstractDielectric barrier discharge (DBD) plasma is a potential tool in the field of in situ CO2 conversion with the low‐pressure environment of Mars. CO is an important intermediate product in the conversion process of CO2. Understanding the pathways and dynamics that govern the generation of CO in CO2 plasmas establishes the foundation for effective regulation. In this work, parallel‐plate DBD structure was employed in our experiment and one‐dimensional fluid simulation model. The findings indicate that CO primarily originates at the boundary of the cathode potential fall region, and it subsequently migrates toward the surface of instantaneous cathode where it accumulates. The thickness of CO‐enriched region is approximately 0.8 mm. During this process, CO migration speed reaches about 2000 m/s. It is worth noting that surface reactions at the instantaneous cathode and anode surfaces contribute only 0.24% to CO generation, in contrast to the predominant influence of impact dissociation reaction between CO2 and electrons (e + CO2 → 2e + CO + O+) at 53.21%, and two‐body decomposition reaction between O+ and CO2 (O+ + CO2 → O +2 + CO) at 35.88%. Finally, the primary factors influencing the migration of CO from production sites to enrichment regions are determined to be particle collisions and momentum exchange between ions and CO, followed by electro‐hydro dynamics force, while dielectrophoresis forces have minimal effect.

Microstructural evolution and diffusion mechanism of MCrAlY coated nickel-based superalloy turbine blades after serviced for 47,000 h

The large-sized industrial gas turbine blades exhibit non-uniform microstructural degradation in various parts due to ultra-long term service in high-temperature and high-pressure environments. Determination of degradation behavior at critical locations is important for the safety of gas turbine and blades refurbishment program. The microstructure characterization on the surface and interface of MCrAlY coated Ni-based superalloy blades have been studied. The microstructure evolution near the coating/ substrate interface was studied by scanning electron microscope (SEM) and the difference in degradation of the main precipitates at several locations were quantified. Surface oxidation and interfacial diffusion were analyzed through energy dispersive spectrum (EDS) and electron probe microanalyzer (EPMA) to clarify the influence of elemental diffusion on microstructure. The results indicated that regional microstructure evolution influenced by the spatial structural characteristics of the blades. The migration of Ni, Al, Cr, and Co dominated the diffusion mechanism during service, and reconstructed the microstructure of the coating/substrate interface and surface.

Cyanobacteria decay alters CH4 and CO2 produced hotspots along vertical sediment profiles in eutrophic lakes

Cyanobacteria-derived organic carbon has been reported to intensify greenhouse gas emissions from lacustrine sediments. However, the specific processes of CH4 and CO2 production and release from sediments into the atmosphere remain unclear, especially in eutrophic lakes. To investigate the influence of severe cyanobacteria accumulation on the production and migration of sedimentary CH4 and CO2, this study examined the different trophic level lakes along the middle and lower reaches of the Yangtze River. The results demonstrated that eutrophication amplified CH4 and CO2 emissions, notably in Lake Taihu, where fluxes peaked at 929.9 and 7222.5 μmol/m2·h, mirroring dissolved gas levels in overlying waters. Increased sedimentary organic carbon raised dissolved CH4 and CO2 concentrations in pore-water, with isotopic tracking showing cyanobacteria-derived carbon specifically elevated CH4 and CO2 in surface sediment pore-water more than in deeper layers. Cyanobacteria-derived carbon deposition on surface sediment boosted organic carbon and moisture levels, fostering an anaerobic microenvironment conducive to enhanced biogenic CH4 and CO2 production in surface sediments. In the microcosm systems with the most severe cyanobacteria accumulation, average CH4 and CO2 concentrations in surface sediments reached 6.9 and 2.3 mol/L, respectively, surpassing the 4.7 and 1.4 mol/L observed in bottom sediments, indicating upward migration of CH4 and CO2 hotspots from deeper to surface layers. These findings enhance our understanding of the mechanisms underlying lake sediment carbon emissions induced by eutrophication and provide a more accurate assessment of lake carbon emissions.