Ionic Composition Research Articles

Major Ion Chemistry of Surface Water and Its Controlling Factors in Ebinur Lake Basin

The sustainable development of arid regions is significantly constrained by the availability of water resources, which play a crucial role in this context. It is necessary to deeply investigate and analyze the hydrochemical characteristics and major ion sources. This study, which was based on data from 183 water samples collected from the Jinghe River Basin, provided a comprehensive analysis of the river water hydrochemistry. The results show that the average TDSs (total dissolved solids) was measured at 49.8 mg·L−1. HCO3− (82.4%) and Ca2+ (77.1%) were the ions present in the highest abundances. The river water was classified as the HCO3−-Ca2+ hydrochemical type. The Gibbs diagrams indicated that the ion composition was primarily influenced by rock weathering. Additionally, the Na-normalized molar ratio diagrams suggested that the chemical composition was primarily governed by the weathering and dissolution of silicate rocks, while the carbonate rock dissolution played a lesser role. This study demonstrates a critical aspect of water resources quality evaluation, which is of great significance for the sustainable development, utilization and environmental protection of regional water resources.

Influence of the ionic composition of water on the efficiency of dissolving milk powder

Influence of the ionic composition of water on the efficiency of dissolving milk powder

Seasonal changes in the physicochemical characteristics of atmospheric aerosol at the research station “Ice Base Baranova Cape” (Severnaya Zemlya archipelago)

Since 2017 we have carried out aerosol sampling at the research station “Ice Base Baranova Cape” (Novaya Zemlya Archipelago) with the purpose of studying the variations in aerosol physicochemical characteristics: the concentrations of ions, microelements, organic and elemental carbon (ОС and ЕС), as well as the isotopic composition of carbon δ13C in the aerosol. The average summed concentrations of ions throughout the period of measurements were 1,99 μg/m3, the concentrations of elements were 51,1 ng/m3; and those of ОС and ЕС were 398 and 25 ng/m3, respectively; the isotopic composition of carbon δ13C was–27.6 ‰. The main contribution (73 %) to the ion composition of atmospheric aerosol is due to “marine” ions Na+ and Cl-, and the contribution to the elemental composition is due to terrogenic Fe and Al (71 %). The large enrichment coefficients (with respect to Na+ in sea water) were manifested for ions SO 2-, K+, and Ca2+. Aerosol enrichment by these ions is the largest in the warm period. In the aerosol elemental composition, we identified large enrichment coefficients (with respect to Al in the Earth’s crust) in elements Se, Sn, Sb, Mo, As, Zn, Cu, Cr, Pb, and Cd, indicating their technogenic origin. The nearest sources of aerosol enrichment by technogenic elements are plants for mining and processing mineral resources in the Taymyr Autonomous Okrug. The statistical generalization of the multiyear data allowed us to calculate for the first time the annual average behavior of the chemical composition of aerosol in the study region. With respect to the seasonal variations, the ions and elements can be divided into three groups: 1) with winter maximum (Na+, Cl-, Mg2+, Br-; Se, Cd, V, Co, As); 2) with summer (PO 3-, NH +, CH SO3-, F-) or autumn (Al, Ti, Li, Sr, Fe, Zn, Ba, Ni) maximum; 3) with poorly defined or indefinite variations in other ions (NO -, K+, SO 2-, Ca2+) and elements (Cu, Pb, Mo, W, Sn, Cr, Sb, Mn). As most of the other characteristics, the annual behaviors of the ОС and ЕС concentrations are characterized by the general maximum in the winter-spring period. In addition, a second maximum is manifested in the ОС content in the summer-autumn period. The average monthly carbon isotopic composition in the aerosol varies in the range from –28.3 ‰ (February) to –27.3 ‰ (May).

Structure-activity relationship, adsorption, and fenton-like catalytic oxidation capacity of iron-oxide nano-confined materials

In this study, iron-oxide was loaded into polystyrene macroporous microspheres containing sulfonate groups to prepare an environmental purification material with adsorption and Fenton-like oxidizing abilities. Iron-oxide is prone to inactivation due to reunion in the process of preparation and application, and this modification aimed to mitigate this problem. Subsequently, based on the microscopic characterization results and the effect on the treatment of methylene blue (MB) simulated wastewater, the structure-activity relationship of two key (OH− concentrations in precipitation solution and iron ion compositions in the impregnation solution) factors with the adsorption and catalytic oxidation ability of the iron-oxide nano-confined materials were explored. The results indicated that the samples both exhibited adsorption and catalytic oxidation capabilities. The removal efficiency of MB simulated wastewater can reached 95.3% after adsorption for 9 h, reaching 99.98% after catalytic oxidation for 6 h. In addition, the removal efficiency of the MB simulated wastewater exceeded 95% after 6 cycles. The concentration of OH− in precipitation solution could affect the volume of iron crystals on the carrier which affected the pore size of the sample and the adsorption capacity. It also influenced whether iron ions could be stably loaded inside the carrier, determining the conducting homogeneous or heterogeneous Fenton-like reactions and the stability of the samples. The composition of iron ions in the impregnating solution regulated the volume of the crystals and adsorption sites, which influenced the adsorption ability of the samples. In addition, the presence of Fe2+ could promote the progress of Fenton-like reactions. The identification results of the ROSs showed that •OH was the main free radical. The quenching experiment results showed that the contribution rate of •OH toward MB degradation reached 99.81%. In addition, the possible degradation pathways of MB were analyzed.

Plasma opacity induced by laser-driven movement of background ions

Abstract The transition threshold from relativistically transparent regime to opaque regime in the interaction of an ultra-intense laser pulse and a bulk plasma with mobile background ions is investigated. The threshold corresponds to the onset of laser hole-boring. We show that for an ultra-intense laser, the threshold depends on the ion composition of the plasma, and the corresponding plasma density is significantly lower than that with ion immobile plasma. These are supported by 1D PIC simulations by using hydrogen plasma and fully ionized carbon plasma. The movement of background ions modifies the dynamics and distribution of electrons in the plasma, which results in the Doppler-red-shift of the incident laser and the increase of the effective plasma density. An intuitive model, which gives the dependence of the transparency-opaqueness threshold on laser intensity and frequency, as well as the ion composition, is established. It is tested by multi-dimensional PIC simulations with hydrogen plasma.

Controls on the stable Mo isotopic composition of inner-continental precipitation

The molybdenum (Mo) isotope budget of the surface environment has been well characterized in recent decades, facilitating accurate mass balance modeling of the ancient redox-driven Mo cycle. One yet unresolved component is the range of possible processes and sources that result in isotopically heavy river waters relative to continental sources. Following a recent hypothesis that isotopically heavy δ98Mo of precipitation may control the final δ98Mo of river water relative to its continental source bedrock, we investigated the δ98Mo composition of 19 snow samples from three locations in Central Europe: the Swiss Alps (“Alpine” samples) from the Hochalpine Forschungsstation Jungfraujoch (HFSJ) in both summer and winter, the Swiss Jura Mountains in winter and the French Vosges Mountains in winter. Stream waters from two snowmelt-fed streams were additionally collected from the Alpine site. Snow sample δ98Mo compositions were highly variable, ranging from −0.03 to +1.93 ‰, with no clear mixing trends indicating complex sources, source pathways, or post-depositional processing. Only the winter snow samples from the high-altitude HFSJ site had δ98Mo values consistently heavier than typical continental crust. The δ98Mo results were coupled with radiogenic Sr isotopic, major ion, and trace element compositions as tracers for three major sources of airborne ion inputs: sea salt, mineral dust, and anthropogenic aerosols. We found that the most likely source of Mo to precipitation in the lower elevation Vosges and Jura Mountains samples was isotopically light soil mineral dust, which reflected the underlying bedrock sources, with a likely additional anthropogenic component. The isotopically heavy winter snow samples at the elevated HFSJ site were attributed to a higher input of carbonate mineral dust from long-distance transport of carbonate-rich Saharan dust, which was overwritten in the summer by an influx of low elevation sources transported upwards during higher vertical thermal mixing. Finally, we concluded that precipitation has a negligible direct effect on the overall Mo content and isotopic composition of inner continental European streams and rivers relative to other sources, such as bedrock weathering. Future time-series studies may augment these conclusions to show possible heterogeneity of precipitation as well as the addition of sample sites closer to marine sources, where a larger flux of isotopically heavy marine aerosols to streams might be expected.

Reducing the Sodium Adsorption Ratio Improves the Soil Aggregates and Organic Matter in Brackish-Water-Irrigated Cotton Fields

The assessment of soil health relies on key parameters such as soil aggregates and organic matter content. Therefore, examining the impact of irrigation water ion composition and variations in salinity on soil aggregates and organic matter is imperative, which is key to developing a theoretical basis for the sustainable utilization of saline water resources, particularly in extremely arid regions. This experiment was conducted to investigate the impact of different irrigation water salinity treatments (T3: 3 g/L, T5: 5 g/L, and T7: 7 g/L) on the root zone soil of cotton fields. Each salinity treatment included three variations of the sodium adsorption ratio (SAR) at S10: 10 (mmol/L)1/2, S15: 15 (mmol/L)1/2, and S20: 20 (mmol/L)1/2. Local freshwater irrigation served as the control, resulting in a total of 10 treatments. Our findings show that the soil Ca2+ and Mg2+ content increased with higher irrigation water salinity but decreased with increasing irrigation water SAR. The relative macroaggregate stability and the content of water-stable macroaggregates and soil organic matter (SOM) decreased as the irrigation water salinity and SAR increased. In comparison to T3S20, T5S10 did not improve the soil Na+ content but significantly increased the soil Ca2+ content by 147.76%, while the water-stable aggregate and SOM saw a notable increase of 7.66% and 9.86%, respectively. Reducing the SAR in brackish water lessens its negative impact on soil aggregates in cotton fields. This is primarily because Ca2+ counteracts the dispersive effect of high Na+ concentrations and promotes aggregate formation. Irrigation water with a salinity of 3 g/L and an SAR of 10 (mmol/L)1/2 positively affected the stabilization of soil aggregates and organic matter.

Numerical simulations of a low-pressure electrodeless ion source intended for air-breathing electric propulsion

Abstract Air breathing electric propulsion (ABEP) systems offer a promising solution to extend the lifetime of very low earth orbit (VLEO) missions by using residual atmospheric particles as propellants. Such systems would operate in very low-pressure environments where plasma ignition and confinement prove challenging. In this contribution, we present results of a global plasma model (GPM) of a plasma ignited in a very low-pressure air mixture. The results are validated against experimental measurements acquired using a laboratory electrodeless ion source utilizing a resonator for plasma ignition. The device is specifically designed to operate within low-pressure environments as it holds potential applications in ABEP systems for VLEO missions. Parametric studies are carried out via GPM to investigate the resonant behavior and its implications. The potential of the model serving as a predictive tool is assessed through experimental validation against measured data, mainly investigating the extracted ion current dependency on operational pressure and external magnetic field strength. The verified model is further utilized to extrapolate additional information about the resonant plasma such as ion composition or a degree of ionization.

Structural bases for blockade and activation of BK channels by Ba2+ ions.

We studied the impact of Ba2+ ions on the function and structure of large conductance potassium (BK) channels. Ion composition has played a crucial role in the physiological studies of BK channels due to their ability to couple ion composition and membrane voltage signaling. Unlike Ca2+, which activates BK channels through all Regulator of K + Conductance (RCK) domains, Ba2+ has been described as specifically interacting with the RCK2 domain. It has been shown that Ba2+ also blocks potassium permeation by binding to the channel's selectivity filter. The Cryo-EM structure of the Aplysia BK channel in the presence of high concentration Ba2+ here presented (PDBID: 7RJT) revealed that Ba2+ occupies the K+ S3 site in the selectivity filter. Densities attributed to K+ ions were observed at sites S2 and S4. Ba2+ ions were also found bound to the high-affinity Ca2+ binding sites RCK1 and RCK2, which agrees with functional work suggesting that the Ba2+ increases open probability through the Ca2+ bowl site (RCK2). A comparative analysis with a second structure here presented (PDBID: 7RK6), obtained without additional Ba2+, shows localized changes between the RCK1 and RCK2 domains, suggestive of coordinated dynamics between the RCK ion binding sites with possible relevance for the activation/blockade of the channel. The observed densities attributed to Ba2+ at RCK1 and RCK2 sites and the selectivity filter contribute to a deeper understanding of the structural basis for Ba2+'s dual role in BK channel modulation, adding to the existing knowledge in this field.

Dynamic interactions of negatively charged gold nanoparticles (AuNPs) in aqueous environments with different ionic compositions

This study provides a comprehensive analysis of the interactions between negatively charged gold nanoparticles (Au)144(SRCOO1−)60 and both divalent (Mg2+, Ca2+) and monovalent (Na+, K+) ions in aqueous solution, employing molecular dynamics simulations. The investigation focuses on elucidating the energetics, hydrogen bond patterns and radial distribution of ions surrounding gold nanoparticles. Our results reveal distinct differences in the Coulombic and van der Waals energies between gold nanoparticles and ions, as well as between gold nanoparticles and water, which exert influence on hydrogen bond patterns and lifetimes, as even as ion and water mobility. These findings have important implications for potential applications in nanotechnology and materials science. This research contributes to a deeper understanding of ion-nanoparticle interactions and provides valuable insights for the design and development of new nanomaterials with properties and functionalities.

Trace element distribution, sources, toxicity risk characteristics associated with lacustrine groundwater discharge in boreal lakes: Implications for the eco-environmental security in the Yellow River Basin, China

Although the pollution of trace elements has been extensively studied, there is still a lack of comprehensive understanding regarding accumulation of these elements in lake ecosystems within the Yellow River basin, specifically the effects of lacustrine groundwater discharge (LGD) on trace elements. This study investigated the distribution, sources, and toxicity risks associated with 20 target trace elements (i.e., Li, Sc, Ti, V, Mn, Cr, Co, Ni, Cu, Zn, Rb, Y, Mo, Sb, Ba, W, Tl, Pb, U and Sr) in lake water (LW), groundwater (GW), and river water (RW) influenced by the LGD process in lake Ulansuhai and lake Daihai. The natural source is the primary contributor of trace elements in both LW and GW within the two lake basins, while industrial discharge plays a secondary role. The average LGD fluxes in lake Ulansuhai and Daihai basins were 6.39 × 105 m3/d and 1.07 × 105 m3/d, respectively. Additionally, the trace element fluxes from LGD in lake Ulansuhai (mean of 106,659.37 g/d) exceeded those observed in lake Daihai (mean of 3236.57 g/d). The overall toxicity risk was found to be higher in lake Ulansuhai (LW (17.36) > RW (16.81) > GW (12.76)) compared to lake Daihai (GW (10.43) > LW (9.10) > RW (4.63)). As well as the toxicity levels of trace elements in lake Ulansuhai were elevated compared to Daihai, which can be attributed to the influenced of ion compositions and water nutrients. Among them, Ca2+, Mg2+, and SO42+ were identified as key ions impacting the toxicity of trace elements in lake Ulansuhai. These findings provide crucial insights for targeted monitoring and mitigation of trace element pollution in the Yellow River basin’s lake ecosystems.

Neutrophil Extracellular Traps Affect Human Inner Ear Vascular Permeability.

The integrity of the blood-labyrinth barrier (BLB) is essential for inner ear homeostasis, regulating the ionic composition of endolymph and perilymph and preventing harmful substance entry. Endothelial hyperpermeability, central in inflammatory and immune responses, is managed through complex intercellular communication and molecular signaling pathways. Recent studies link BLB permeability dysregulation to auditory pathologies like acoustic trauma, autoimmune inner ear diseases, and presbycusis. Polymorphonuclear granulocytes (PMNs), or neutrophils, significantly modulate vascular permeability, impacting endothelial barrier properties. Neutrophil extracellular traps (NETs) are involved in diseases with autoimmune and autoinflammatory bases. The present study evaluated the impact of NETs on a BLB cellular model using a Transwell® setup. Our findings revealed a concentration-dependent impact of NETs on human inner ear-derived endothelial cells. In particular, endothelial permeability markers increased, as indicated by reduced transepithelial electrical resistance, enhanced dextran permeability, and downregulated junctional gene expression (ZO1, OCL, and CDH5). Changes in cytoskeletal architecture were also observed. These preliminary results pave the way for further research into the potential involvement of NETs in BLB impairment and implications for auditory disorders.

Exploring the Distribution of Low Molecular Weight Compounds in Water-Based Two-Phase Systems with Various Salt Additives

The partition coefficients of seven low molecular weight compounds were tested in different aqueous two-phase systems. The ionic composition of each system included specific salt additives, and it was found that there is a linear relationship between the solute partition coefficients and the presence of different salt additives. The study suggests that the solute structure and the type of ions influence the solute response to the ionic environment. Additionally, it was observed that the solutes’ polar surface area and the solvent-accessible surface area are the essential structural features governing partitioning in aqueous two-phase systems.

Counterion Loss from Charged Surface-Bound Complexes Drives the Formation of Loosely Packed Monolayers.

The functionality of multicomponent self-assembled monolayers (SAMs) can be severely diminished by the segregation of like components into nanoscale domains, a process that maximizes favorable short-range intermolecular interactions. Here, we explore the use of a modular family of sulfur-functionalized metal bis(terpyridine) complexes ([M(tpy-R)2]2+(PF6-)2) to prepare mixed SAMs, considering that the comparable structure, dimensions, and ionic composition of these species should render them interchangeable within the adsorbed surface layer. While surface voltammetry experiments show that these SAMs do exhibit compositions representative of their assembly solutions, they also suggest, in line with previous reports, that adjacent complexes in the monolayer are separated by a gap of ∼ 1 nm. Remarkably, X-ray photoelectron spectroscopy studies reveal no F 1s peak features that would confirm the proliferation of PF6- counterions on the surface. We propose that the loosely packed structure of these SAMs results from the loss or exchange of PF6- counterions, which introduces significant repulsive Coulomb interactions between the adsorbed 2+ charged complexes. The hypothesis is supported by an electrostatic model which indicates that these complexes should form close-packed SAMs if mobile counterions are present. First-principles calculations demonstrate that complex-counterion binding interactions are weakened by charge transfer to the gold substrate, suggesting that this may play an important role in the formation of such low-coverage SAMs. Together, this study raises important questions regarding the assembly, organization, and composition of charged SAMs and highlights new opportunities in the design of multicomponent monolayer assemblies with free volume, for example, to facilitate surface-based reactions or support molecular switches.

Особливості перебігу хронічної хвороби нирок у пацієнтів з артеріальною гіпертензією, цукровим діабетом та хронічним гломерулонефритом

Chronic kidney disease (CKD), especially its terminal stage, is a serious problem in modern medicine. There are certain features of the course of CKD in patients with arterial hypertension (AH), diabetes mellitus (DM), and chronic glomerulonephritis (CGN). The purpose of the study was to study the course of CKD against the background of hypertension, diabetes and chronic hypertension based on clinical and laboratory examination data to assess the severity of the patients' condition. Materials and methods. 86 patients with stage V chronic renal failure (CKD) were examined, who were divided into 3 groups depending on the existing concomitant disease. Group 1 (n – 35) included patients with CKD and hypertension, group 2 (n – 28) – patients with CKD and diabetes, and group 3 (n – 23) – patients with CKD and CGN. Anthropometric, general clinical, laboratory and instrumental research methods were performed on all patients. Research results and their discussion. Analyzing the data of a general blood test, 100 % of patients in all three groups had a decrease in hemoglobin and erythrocyte levels. A significant decrease in the level of albumin (p < 0.05) and an increase in the levels of urea (p < 0.001) and creatinine (p < 0.001) were also found, which indicated a pronounced decrease in kidney function and significant kidney damage. Analyzing the results of the ionic composition of the blood, a significant increase in the levels of phosphorus and parathyroid hormone was found in patients of the III group (CNN and CGN). Conclusions: 1. In all groups of patients with CKD of the V degree in combination with concomitant hypertension, diabetes mellitus or CGN, persistent anemia was noted, which was manifested by a progressive drop in hemoglobin to the levels of 86.22 ± 3.61 g/l, 83.89 ± 3.06 g/l and 83.22 ± 3.49 g/l, respectively. 2. In such patients, a pronounced decrease in kidney function was noted, which was manifested by a delay in the release of the products of protein metabolism from the blood due to a decrease in the levels of albumin (p < 0.05), a significant increase in the levels of urea (p < 0.001), creatinine (p < 0.001) and a decrease glomerular filtration rate. 3. In the group of patients with a combination of CKD stage V and CGN, a significant increase in phosphorus and parathyroid hormone levels was found (p < 0.01). Such an increase in the level of parathyroid hormone in blood serum may be associated with a drop in the level of calcium in the blood of such patients and the subsequent progressive increase in the level of inorganic phosphate and the development of hyperphosphatemia.

EXPERIMENTAL STUDY OF HYDRATE FORMATION PECULIARITIES FOR CONDITIONS OF THE TURNO AND CENOMANIAN DEPOSITS: Part II

This paper is the second part of the research devoted to the study of hydrate formation features for the conditions of Turonian and Cenomanian deposits. The launch of new gas projects at the Turon and Senoman production facilities in Western Siberia provided a good opportunity to critically analyze the known methods of protecting production, gathering and transportation facilities of the gas field from the formation of solid gas hydrates. The paper presents the experience of implementing a program of laboratory studies of conditions of gas hydrate formation with their subsequent processing and in-depth analysis. The research program covered the area of thermobaric parameters typical for the conditions of Turon-Senoman deposits exploitation with localization of hydrate-hazardous areas in the conditions of Technological Regimes for full development. The description of laboratory studies is given, in which two gas compositions of Senoman and Turon objects, different variants of mineralization and ionic composition corresponding to formation and condensation water, as well as hydrate formation conditions under changing dosages of basic inhibitor on the basis of methanol were considered. The details of the experiment based on the method of swinging cells and the subsequent analysis of the results of the completed experiments to determine the thermobaric conditions of formation and decomposition of hydrates are given. The main features of the experiment are specified, estimates of the rate of change of the influencing parameters of the experiment on its quality are given. In the process of implementation of the experimental program, the optimal values of these parameters were selected, which allowed us to significantly reduce the variation of experimental results to determine the thermobaric conditions of hydrate formation. It is experimentally established that the temperature of hydrate decomposition is higher than the temperature of its formation at all investigated gas compositions and water mineralization.

Spectral decomposition for collective Thomson scattering based on an improved genetic algorithm.

Collective Thomson scattering (CTS) is a diagnostic technique that obtains ion temperature and ion composition of plasma by spectral decomposition from scattering spectra. Bayesian estimation and least squares fitting are usually applied in this spectral decomposition process. Nevertheless, these spectral decomposition methods strongly rely on measurements of other diagnostic systems, and the measurement errors of other systems would influence the spectral decomposition results. In this article, an improved genetic algorithm is applied to decompose the scattering spectra of CTS. By analyzing the sensitivity of plasma parameters, the width and slope of the scattering spectrum are found to be strongly associated with ion temperature. Based on this correlation relation, a new fitness function is designed to provide a more precise estimation of ion temperature. Meanwhile, adaptive crossover and mutation operators are introduced to solve the premature convergence problem. This improved genetic algorithm with the new fitness function can obtain a more precise ion temperature from scattering spectra of CTS and does not rely on the measurement of other diagnostic systems, which has an extensive application prospect in data processing of CTS.

The role of the thermal properties of electrons on the dispersion properties of Alfvén waves in space plasmas

Context. The transition from left-hand to right-hand polarised Alfvén waves depends on the wavenumber, the ratio of kinetic to magnetic pressure, β, the temperature anisotropy, and the ion composition of the plasma. Along with the temperature anisotropy, the electron-to-proton temperature ratio, Te/Tp, is of great relevance for the characterisation of the thermal properties of a plasma. This ratio varies significantly between different space plasma environments. Thus, studying how variations in this ratio affect the polarisation properties of electromagnetic waves becomes highly relevant for our understanding of the dynamics of space plasmas. Aims. We present an extensive study on the effect of the thermal properties of electrons on the behaviour and characteristics of Alfvénic waves in fully kinetic linear theory, as well as on the transition from the electromagnetic ion-cyclotron wave to the kinetic Alfvén wave. Methods. We solved the fully kinetic dispersion relation for oblique electromagnetic waves of the Alfvén branch in a homogenous Maxwellian electron-proton plasma. We quantified the effect of the thermal properties of electrons by varying the electron-to-proton temperature ratio for different configurations of the propagation angle, βp = 8πnkTp/B2, and wavenumber. Results. We show that the temperature ratio, Te/Tp, has strong and non-trivial effects on the polarisation of the Alfvénic modes, especially at kinetic scales (k⊥ρL > 1, where k⊥ = k sin θ, θ is the propagation angle, and ρL = cs/Ωp, with cs the plasma sound speed and Ωp the proton’s gyrofrequency) and βe + βp > 0.5. We conclude that electron inertia plays an important role in the kinetic scale physics of the kinetic Alfvén wave in the warm plasma regime, and thus cannot be excluded in hybrid models for computer simulations.

Induced carbonate dissolution: Impact of brine chemistry in CO2 foam

Foam CO2might be considered an efficient alternative to reduce gas mobility and produce favorable mobility ratios. It offers significant advantages, particularly in heterogeneous or fractured reservoirs due to its ability to block highly permeable layers or divert the injected fluid from fractures into the matrix. In the present work, a surfactant solution made of different ionic compositions was co-injected into outcrop Edwards Limestone to determine the impact of brine chemistry on carbonate dissolution upon CO2foam injection. The development in differential pressures (DP) during continuous co-injection of sc-CO2 and different surfactant solutions (NaCl, NFB, CB) shows that unwanted chemical reactions (dissolution/precipitation) compromise the rock integrity by more acid formation and wormholing. Rock-fluid-foam interactions indicate that the total heat in the rock-fluid-foam systems is 6.9 mJ NaClfoam, 19.3 mJ NFBfoam, and 37.8 mJ CBfoam systems. On the other hand, the total heat for the fluid-foam interactions is 11.5 mJ NaClfoam, 12.5 NFBfoam, and 20.4 mJ CBfoam. The demicellization of the foam formulations could have led to calcite dissolution. The synergy between ITC and core flooding experiments elucidates the impact of the brine chemistry on calcite dissolution during foam-assisted CO2sequestration at both microscopic and macroscopic scales.

Advancing CO2 Solubility Prediction in Brine Solutions with Explainable Artificial Intelligence for Sustainable Subsurface Storage

Underground CO2 storage is crucial for sustainability as it reduces greenhouse gas (GHG) emissions, helping mitigate climate change and protect the environment. This research explores the use of Explainable Artificial Intelligence (XAI) to enhance the predictive modelling of CO2 solubility in brine solutions. Employing Random Forest (RF) models, the study integrates Shapley Additive exPlanations (SHAP) analysis to uncover the complex relationships between key variables, including pressure (P), temperature (T), salinity, and ionic composition. Our findings indicate that while P and T are primary factors, the contributions of salinity and specific ions, notably chloride ions (Cl−), are essential for accurate predictions. The RF model exhibited high accuracy, precision, and stability, effectively predicting CO2 solubility even for brines not included during the model training as evidenced by R2 values greater than 0.96 for the validation and testing samples. Additionally, the stability assessment showed that the Root Mean Squared Error (RMSE) spans between 8.4 and 9.0 for 100 different randomness, which shows good stability. SHAP analysis provided valuable insights into feature contributions and interactions, revealing complex dependencies, particularly between P and ionic strength. These insights offer practical guidelines for optimising CO2 storage and mitigating associated risks. By improving the accuracy and transparency of CO2 solubility predictions, this research supports more effective and sustainable CO2 storage strategies, contributing to the overall goal of reducing greenhouse gas emissions and combating climate change.