CO2 Diffusion Research Articles

Study of Carbonation-depth Prediction of Unsaturated Concrete Considering Carbonation-produced Water

Carbon dioxide can react with alkaline carbonate substances in cement-based materials, which harms the durability of the concrete structure. The carbonation reaction is a process of releasing water, resulting in an increase in pore water saturation, which was always neglected by previous studies. In this paper, a transient pore water saturation equation is proposed and introduced into the classical carbonation reaction kinetic model, which is simulated by finite-element software with a typical ordinary Portland cement. The model was verified by two classical empirical equations for carbonation-depth prediction. The simulation results indicated that the increment of pore water saturation originated by carbonation-produced water will weaken the CO2 diffusivity and enhance the carbonation resistance. Besides, the growth rate of carbonation depth is slightly faster without considering the produced water and with higher initial saturation, the difference will be more significant. If the influence of carbonation water is ignored, the predicted carbonation depth of unsaturated concrete may be less accurate. This study can provide some reference for theoretical and experimental studies on concrete carbonation. However, future work is still needed including more realistic effects in the model such as the mesoscale modeling of concrete and the integration of stress states. KEYWORDS: Ordinary Portland concrete, Carbonization reaction, Carbon-dioxide transport, Finite-element method, Pore saturation.

Why surface hydrophobicity promotes CO2 electroreduction: a case study of hydrophobic polymer N-heterocyclic carbenes.

We report the use of polymer N-heterocyclic carbenes (NHCs) to control the microenvironment surrounding metal nanocatalysts, thereby enhancing their catalytic performance in CO2 electroreduction. Three polymer NHC ligands were designed with different hydrophobicity: hydrophilic poly(ethylene oxide) (PEO-NHC), hydrophobic polystyrene (PS-NHC), and amphiphilic block copolymer (BCP) (PEO-b-PS-NHC). All three polymer NHCs exhibited enhanced reactivity of gold nanoparticles (AuNPs) during CO2 electroreduction by suppressing proton reduction. Notably, the incorporation of hydrophobic PS segments in both PS-NHC and PEO-b-PS-NHC led to a twofold increase in the partial current density for CO formation, as compared to the hydrophilic PEO-NHC. While polymer ligands did not hinder ion diffusion, their hydrophobicity altered the localized hydrogen bonding structures of water. This was confirmed experimentally and theoretically through attenuated total reflectance surface-enhanced infrared absorption spectroscopy and molecular dynamics simulation, demonstrating improved CO2 diffusion and subsequent reduction in the presence of hydrophobic polymers. Furthermore, NHCs exhibited reasonable stability under reductive conditions, preserving the structural integrity of AuNPs, unlike thiol-ended polymers. The combination of NHC binding motifs with hydrophobic polymers provides valuable insights into controlling the microenvironment of metal nanocatalysts, offering a bioinspired strategy for the design of artificial metalloenzymes.

Kapacitet izmjene plinova graha (Phaseolus vulgaris L.) u uvjetima nedostatka hranjiva

The lack of plant nutrients is a major problem for agriculture. Because of their essential role in the most important metabolic processes of plants, their deficiency depresses photosynthesis and disrupts the efficient operation of the photosynthetic apparatus. In this study, we investigated the gas exchange of common beans bean under the N, P, K, Mg, and Fe deficiency. The experiment was set up as a hydroponic, fully aerated, floating system in 6 hydroponic tubs. Each hydroponic tub contained 10 plants and was filled with a modified Hoagland nutrient solution. One group of plants was grown in a complete nutrient solution (control), while the other treatments lacked one of the following nutrients: N, P, K, Mg and Fe. During the experiment, gas exchange parameters: net photosynthetic rate (A), transpiration rate (E), stomatal conductance (gs) and intercellular CO2 concentration (Ci) were measured. At the end of the experiment, the nutrient content of the plant tissue was determined. Nutrient deficiency significantly affected all measured photosynthetic parameters and visual symptoms indicated that a lack of different nutrients affected the photosynthetic machinery at different points. Potassium deficiency lower stomatal conductance and increased mesophyll resistance to CO2 diffusion and/or RubisCO activity. Nitrogen and Mg deficiency affected chlorophyll synthesis and accelerated leaf senescence. Phosphorus deficiency caused less damage to gas exchange parameters probably due to protective mechanisms of reduced leaf area. Seed Fe content was surplus to sustain photosynthetic machinery during the early developmental phase.

CO<sub>2</sub> Demand-Supply Coordination in Photosynthesis Reflecting the Plant-Environment Interaction: Extension and Parameterization of Demand Function and Supply Function

Photosynthesis consists of a biochemical process named demand and a CO2 diffusion process named supply function. The intersection (Ci, An) at equal to the demand function and the supply function reflects a steady state of the plant subjected to the environment. The intersections of these demand-supply functions under different photosynthetically active radiation (PAR) can be fitted to a regression line (names DSF) in which slope (ΔAn/ΔCi) can be defined as dsf. We found that DSF information was embedded in both Laisk method (CO2 response curve (A/Ci) measured at three sub-saturated PARs, and their intersections were used to estimate daytime respiration (Rd), and CO2 compensation point (Ci*) and light response curve measurements, which could be used to estimate dsf values. This study investigated the relationship between dsf and the parameters related to the biochemical process and the CO2 diffusion process of photosynthesis. The results showed that dsf was negatively correlated with gs, apparent carboxylation efficiency, and apparent quantum yield. This suggests that DSF may coordinate the influence of environmental conditions (light, CO2 and water) on photosynthesis in the biochemical and CO2 diffusion process. Moreover, dsf was independent of gas exchange measurement conditions and showed species specificity. In conclusion, we speculated that dsf seems to be a comprehensive parameter that might be related to the intrinsic adaptation mechanism of plants to environmental conditions. We proposed an auxiliary line perpendicular to the DSF and used it to improve the stability of Ci* and Rd estimated from the Laisk dataset.

Capturing CO2 by ceria and ceria-zirconia nanomaterials of different origin.

Ceria and ceria-zirconia nanomaterials of different origin were studied in order to elucidate the role of their structural and textural characteristics in controlling the performance towards CO2 capture. Two commercial cerias and two home-prepared samples, CeO2 and CeO2-ZrO2 (75% CeO2) mixed oxide, were investigated. The samples were characterized by a number of analytical techniques including XRD, TEM, N2-adsorption, XPS, H2-TPR, Raman and FTIR spectroscopy. Static and dynamic CO2 adsorption experiments were applied to assess the CO2 capture performance. The type of surface species formed and their thermal stability were evaluated by in situ FTIR spectroscopy and CO2-TPD analysis. The two commercial ceria samples possessed similar structural and textural characteristics, formed the same types of carbonate-like surface species upon CO2 adsorption and, consequently, demonstrated almost identical CO2 capture performance under both static and dynamic conditions. The thermal stability of the adsorbed species increased in the order bidentate (B) carbonates, hydrogen carbonates (HC) and tridentate carbonates (T-III, T-II, T-I). Reduction of CeO2 increased the relative amount of the most strongly bonded T-I tridentate carbonates. Preadsorbed water led to hydroxylation and enhanced formation of hydrogen carbonates. Although the synthesized CeO2 sample had a higher surface area (by 30%) it showed a disadvantageous long mass transfer zone in the CO2-adsorption breakthrough curves. Because of its complex pore structure, this sample probably experiences severe intraparticle CO2 diffusion resistance. Having the same surface area as the synthesized CeO2, the mixed CeO2-ZrO2 oxide exhibited the highest CO2 capture capacity of 136 μmol g-1 under dynamic conditions. This was related to the highest concentration of CO2 adsorption sites (including defects) on this sample. The CeO2-ZrO2 system showed the lowest sensitivity to the presence of water vapor in the gas stream due to the lack of dissociative water adsorption on this material.

Enhancing MgO efficiency in CO2 capture: engineered MgO/Mg(OH)2 composites with Cl-, SO42-, and PO43- additives.

The formation of a MgCO3 shell hampers CO2 capture efficiency in MgO. Our previous studies developed MgO/Mg(OH)2 composites to facilitate CO2 diffusion, improving capture efficiency. However, MgCO3 still formed along the interfaces. To tackle this issue, we engineered the MgO/Mg(OH)2 interfaces by incorporating Cl-, SO42-, and PO43- additives. Novel MgO-H2O-MgX (X = Cl-, SO42-, and PO43-) composites were synthesized to explore the role of additives in preventing MgCO3 formation. MgO-Mg(OH)2-MgCl2 nano-composites displayed enhanced CO2 adsorption and stability. This breakthrough paves the way for effective bio-inspired strategies in overcoming CO2 transport barriers in MgO-based adsorbents.

CO2 Reaction-Diffusion Experiments in Shales and Carbonates

The evaluation of caprock integrity and reservoir efficiency is critical for safe CO2 geological storage management. It is therefore important to investigate geochemical reactions between CO2-rich fluids and host rocks and their contribution in retaining CO2 at depth. This study deals with diffusive reaction experiments on shales and carbonate samples cored from an offshore structure in the Malaysian basin, a potential target for CO2-enhanced gas recovery. The aim is to evaluate the CO2 reaction front velocity in a typical shaly caprock and the mineral response of the reservoir. Rock samples were characterized in terms of texture, chemistry, and mineralogy by X-ray diffraction, electron microscopy (SEM), microanalysis (EDS), infrared spectroscopy (FT-IR), rock geochemistry (XRF), and mercury injection capillary permeability (MICP). Performed analyses show mineralogical alteration induced by CO2 as it penetrated into the samples. Carbonate dissolution and weathering of pyrite to form secondary carbonates belonging to siderite-ankerite series were observed along two reaction fronts. Estimated diffusion coefficients of CO2 are two orders of magnitude lower than CO2(aq) molecular diffusion in pure water and from half to an order of magnitude lower than diffusivity computed on unaltered sample, highlighting the important effect of gas–water–rock reactions on the CO2(aq) diffusivities in shales and carbonates. Results obtained in this study provide an insight regarding the effect of geochemical reactions on CO2 transport and represent a further discussion point on the diffusion coefficients.

Polyaniline anchoring environment facilitates highly efficient CO2 electroreduction of cobalt phthalocyanine over a wide potential window

Metallophthalocyanines (MPcs) with the especially active metal-N4 catalytic sites have the great potential for the electrocatalytic CO2-to-CO conversion. However, the masking of metal-N4 catalytic sites attributed to the strong π-π interaction and the difficulty in capturing CO2 severely limits their catalytic efficiency. Herein, we designed a self-supported electrode that tetra-β-carboxy phthalocyanine cobalt(II) (TcPcCo) was anchored into polyaniline (PANI) chain in isolation using the carbon paper (CP) as a support. The PANI with unique porous structure provides large surface area, rapid electron transfer, and unimpeded pathways for CO2 diffusion. More importantly, sufficient CO2 captured by PANI can continuously spill over to metal-N4 active sites and be reduced into CO. The synthesized electrode for CO2 reduction reaction (CO2RR) could maintain a high CO Faraday efficiency of over 95% (maximum 99.3%) at an extraordinary wide potential range of 450 mV (from -0.50 V to -0.95 V vs. RHE), ranking foremost among the previously reported phthalocyanine-based electrocatalysts. Furthermore, relative to TcPcCo, the CO turnover frequency (TOF) of PANI-TcPcCo/CP significantly improves, especially at the more negative operating potential (about 7 ∼ 68 times). Theoretical calculations further reveal that the introduce of PANI optimizes the free energy barrier of CO2RR intermediate at Co-N4 site, thus accommodating the*COOH formation, and also suppresses the competition of hydrogen evolution reaction. This work presents a new perspective on advancing the catalytic CO2RR capability of molecular materials by regulating the chemical environment surrounding a catalytically active site.

Does the Interaction Between ICT Diffusion and Economic Growth Reduce CO2 Emissions? An ARDL Approach

Does the Interaction Between ICT Diffusion and Economic Growth Reduce CO2 Emissions? An ARDL Approach

Uncertainty quantification for CO2 storage during intermittent CO2-EOR in oil reservoirs

CO2 enhanced oil recovery (CO2-EOR) process is considered the most feasible option for a secure storage of CO2 in underground formations. However, predicting amounts of CO2 stored and the oil recovered is associated with high risks due to data uncertainty. Sources of uncertainty lie in the challenges of accurately characterizing reservoir properties. Hence, the main objective of this study is to quantify the uncertainty of CO2 storage and oil recovery during intermittent CO2-assisted gravity drainage (CO2-GAGD) EOR process with a focus on key uncertain parameters including reservoir properties (permeability heterogeneity, porosity, and compressibility); fluid properties (CO2 diffusion coefficient and Henry's constant); and rock-fluid properties (gas-oil relative permeability data). Additionally, we aim to generate a rapid tool that reduces the computational expenses of the compositional reservoir simulation process by employing artificial neural network (ANN) as a machine learning (ML) tool. ANN was applied to generate predictive models that accurately predicted oil recovery and gas storage during the intermittent CO2-GAGD process. A total of 173 numerical samples were simulated and the objective functions were obtained. From the defined ranges of input variables and simulation results, cumulative distribution functions (CDFs) were obtained and uncertainty bounds, i.e., P10, P50, and P90, were estimated. Additionally, the generated ANN model showed excellent predictions of the objective functions with high correlation coefficients, higher than 0.98 in most of the cases, and with an absolute average percentage error (AAPE) range from 2.6 to 9%. Finally, the results of sensitivity analysis, conducted using the developed ML models with generating 10,000 realizations from the input and output parameters, showed the most influential input parameters on the performance of the CO2 storage and oil recovery factor. Reservoir porosity was found to have a significant impact on oil recovery and CO2 storage. A response surface analysis showed that the main independent input parameters contributing to the total uncertainty of oil recovery were horizontal permeability, oil relative permeability, and formation porosity. This study highlights the significant impact of uncertainties of input parameters on simulating the performance of CO2 storage and oil recovery in underground reservoirs.

Promoting CH4/CO2 replacement from hydrate with warm brine injection for synergistic energy harvest and carbon sequestration

CH4/CO2 replacement for natural gas hydrates (NGHs) exploitation is a promising method for CO2 geological sequestration and energy recovery simultaneously. However, the puzzles of low replacement efficiency and slow reaction rate caused by the mass transfer obstacle of gas exchange are fatal bottlenecks for field application of gas replacement method. Therefore, we propose a method that uses warm brine injection during CH4/CO2 replacement process to break the barrier of CO2 diffusion and enhance CH4 recovery as well as CO2 storage. Benefiting from the synergistic influence of salt effect and thermal stimulation as well as water flow erosion, warm brine injection provides three dimensionally connected channels in hydrate for subsequent mass transfer, improving CH4/CO2 replacement in the deep layer of hydrate. CO2 sequestration efficiency of the newly proposed method reaches 76.46%, and the maximum amounts of CH4 recovery is nearly treble than that achieved by single CO2 replacement method. Notably, a potential risk of secondary hydrate formation could occur upon the pressure surge and fluid migration attached to warm brine injection, which could be effectively alleviated by increasing salinity to destabilize hydrate lattices by reducing water activity. The gas production is insensitive to the injected heat as the significant heat loss during the transportation of injected brine in pipelines and thermal diffusion through boundaries. The introduction of free water increases the complexity of the reactions in hydrate reservoirs, and the formulation of brine injection regimes should be synergistically optimized based on energy harvest, energy efficiency and CO2 sequestration. This work extends the previous knowledge on CH4/CO2 replacement and shows important practical significance for future field studies of NGHs exploitation and CO2 geological sequestration.

Microstructure and properties of WC–Co cemented carbide/40Cr steel joints brazed at low–temperature with Ag–Cu–In–Ti filler alloy

WC–Co cemented carbide/steel brazed at low–temperature is of significant scientific and technical interest. In this study, the interface microstructure between the filler alloy and WC–Co and 40Cr steel, the formation process of the joint microstructure, and the effect of brazing temperature on the microstructure and properties of joints were systematically studied. The filler alloy was bonded by forming a TiC reaction layer with WC–Co and 40Cr steel, which enhanced the retention of the filler layer on the joint. The microstructure of the joint was a WC–Co/TiC reaction layer/TiCo reaction layer/Cu2InTi + eutectic structure (Ag [s, s] + Ag–doped Cu7In3 + Cu4In) + Cu [s, s]/TiC reaction layer/40Cr steel. Moreover, the maximum average shear strength of the joint (brazed at 740 °C) reached 258 MPa, which is approximately 60% higher than those reported in the literature. The fracture behavior of the joint was mainly affected by the distribution of the Cu2InTi intermetallic compounds in the filler layer and the diffusion of Co from the cemented carbide.

A mathematical model of CO2 miscible front migration in tight reservoirs with injection-production coupling technology

The CO2 front migration law and the CO2 breakthrough are of great significance to both of the CO2 flooding and CO2 sequestration. Currently, the numerical simulation study on CO2 front migration mainly focused on the continuous CO2 miscible flooding, is time-consuming, and requires many experimental results, such as the crude oil composition obtained by PVT analyses and the minimum miscibility pressure (MMP) get by slim tube experiments. Besides, there is a little study on the CO2 miscible front migration of tight reservoirs with the injection-production coupling technology (IPCT) and few attentions are paid to build a correlation between the threshold pressure gradient (TPG) and CO2 concentration. In this paper, a correlation between the TPG and CO2 concentration is built firstly, and then a mathematical model of CO2 miscible front migration in tight reservoirs with IPCTs is proposed. The effects of parameters, such as the reservoir property, injection rate, CO2 adsorption, and injection-production cycle, on front migrations or CO2 breakthrough are analyzed, and the effects of continuous CO2 injection and IPCTs on the CO2 breakthrough is presented. From this work, it is concluded that the CO2 miscible flooding of IPCTs can alleviate the CO2 breakthrough when comparing with the continuous CO2 miscible flooding. The CO2 diffusion accelerates the CO2 breakthrough. The most important parameter that affects the CO2 breakthrough is the injection rate, followed by the adsorption effect, injection-production cycle time, and diffusion effect. When the injection volume in a cycle is a constant, a small injection-production cycle time can alleviate the CO2 breakthrough.

Deep soil CO2 flux with strong temperature dependence contributes considerably to soil-atmosphere carbon flux

The diffusion of CO2 produced by carbon mineralization in vertical profiles is an important CO2 emission process. However, because of the relatively slow rate of change in the subsoil environment compared with the surface soil, carbon mineralization and diffusion are often ignored, and the mechanisms that transfer deep carbon to the soil-atmosphere interface are still unclear. We studied vertical differences in CO2 flux and its driving mechanism in layers situated from 0 to 200 cm in Robinia pseudoacacia plantations with different stand ages on the Loess Plateau under a typical temperate continental semi-arid monsoon climate. The results showed that (1) in the 0–200 cm layer, CO2 flux showed a bimodal seasonal trend, and total CO2 flux of Robinia pseudoacacia forests with a 10 years stand age fluctuated more actively among the months (Standard Deviation: 3.28%–9.57%). (2) Dynamic evaluation of contribution rate showed a stable (21.81–24.42%) contribution of deep CO2 flux to soil atmosphere interface. (3) Temperature sensitivity of CO2 flux (expressed as Q10) significantly increased with soil depth, moisture and soil CO2 flux presented stronger quadratic function relation in deep layers than shallow layers. There was a significant positive correlation between deep CO2 flux and soil organic carbon (SOC), but there was a weak negative correlation in the shallow layers. The CO2 flux in the shallow layers was mainly regulated by soil organic carbon, whereas that in the deep layers was more regulated by soil temperature.(4) Compared with the traditional hydrothermal two-factor model, the new T&M&C (temperature & moisture & organic carbon) model can improve the model precision by 20–25%, especially in the prediction of CO2 flux in deep layers. Overall, this study is significant for understanding the stability and dynamic changes in the soil carbon pool, and the mechanism of deep organic carbon diffusion to the soil-atmosphere interface in the Loess Plateau.

Supercritical Carbon Dioxide in Presence of Water for the Valorization of Spent Coffee Grounds: Optimization by Response Surface Methodology and Investigation of Caffeine Extraction Mechanism.

Spent coffee grounds are a promising bioresource that naturally contain around 50 wt% moisture which requires, for a valorization, a drying step of high energy and economic costs. However, the natural water in spent coffee grounds could bring new benefits as a co-solvent during the supercritical CO2 extraction (SC-CO2). This work reports the influence and optimization of pressure (115.9-284.1 bars), temperature (33.2-66.8 °C), and moisture content (6.4-73.6 wt%) on simultaneous extraction of lipids and polar molecules contained in spent coffee grounds by supercritical CO2 (SC-CO2) using Central Composite Rotatable Design and Response Surface Methodology. The results show that for lipids extraction, pressure is the most influent parameter, although the influence of moisture content is statistically negligible. This suggests that water does not act as barrier to CO2 diffusion in the studied area. However, moisture content is the most influent parameter for polar molecules extraction, composed of 99 wt% of caffeine. Mechanism investigations highlight that H2O mainly act by (i) breaking caffeine interactions with chlorogenic acids present in spent coffee grounds matrix and (ii) transferring selectively caffeine without chlorogenic acid by liquid/liquid extraction with SC-CO2. Thus, the experiment for the optimization of lipids and polar molecules extraction is performed at a pressure of 265 bars, a temperature of 55 °C, and a moisture content of 55 wt%.

Ultrasound-assisted synthesis of copper-based catalysts for the electrocatalytic CO2 reduction: Effect of ultrasound irradiation, precursor concentration and calcination temperature

The reduction of high CO2 concentrations in the atmosphere is an imperative task to reduce the consequences of the greenhouse effect on our planet. Developing active and selective materials for electrochemical CO2 reduction towards value-added products is mandatory to bring this technology to a practical application. This work studied the effect of assisting Cu and Zn oxides co-precipitation with sonochemistry. Different factors were investigated: the ultrasounds (US) amplitude, the effect of US irradiation time during either precipitation or ageing processes, the precursor concentration and calcination temperature. The synthesised catalysts were tested for the electrocatalytic CO2 reduction reaction in a Rotating Disk Electrode (RDE) system. Faradaic efficiencies >14% towards alcohols were obtained using US-assisted synthesised Cu-based catalysts. Instead, with the US-prepared Cupper-Zinc-based catalysts, the selectivity towards H2 and C1 products (CO and formate) was improved, and the syngas productivity was increased by > ⁓1.4-fold compared to the non-sonicated one. The alcohols production of the best Cu-catalyst was also confirmed on scalable electrodes. Controlling the synthesis conditions allowed to tune the physicochemical properties of the nanoparticles, including specific surface area, porosity, crystallite size and phases. Mesoporous materials with a mean pores size of around 25 nm were found to induce a better CO2 diffusion and CO retention time in the porous network, improving the *CO intermediate adsorption at active sites, promoting its dimerisation and thus enhancing the selectivity towards C2+ alcohols. The here reported results open the way for new electrocatalysts designs with properly tuned porosity for the selective CO2 conversion to different valuable products.

Microscopic Insights and Optimization of the CH4-CO2 Replacement in Natural Gas Hydrates.

Using the CO2 replacement method to exploit natural gas hydrates and store CO2 has great significance in energy access and environmental protection. Herein, the molecular dynamic method is utilized to analyze and evaluate the CH4-CO2 replacement at different constant temperatures and pressures. For optimization, various temperature oscillations are introduced in the CH4-CO2 replacement. It illustrates that increasing the temperature can improve the amounts of CH4 escape and CO2 capture but is unfavorable to the long-term CO2 storage and hydrate stability. The effects of pressure are not as significant and definite as those of temperature. Appropriate temperature oscillations can achieve comprehensive improvements, which benefit from both the deep diffusion of CO2 in the higher temperature stage and the rapid rebuilding of CO2 hydrate within just nanoseconds caused by the memory effects in the lower temperature stage. The results also reveal that the optimal lower temperature duration and frequency should be moderate. Decreasing the lower temperature value can distinctly enhance CO2 capture and hydrate stability. This study can help understand the mechanisms of CH4-CO2 replacement under different temperature and pressure conditions, especially at temperature transitions, and proposes a potentially effective method to achieve large-scale carbon sequestration in the hydrate.

Radon-rich waters of the Tulinka aquifers, Novosibirsk, Russia

The first integrated isotope and chemical data on radon-rich waters of the Tulinka aquifers (Novosibirsk, West Siberia) are presented. The Tulinka radon waters are fresh, with neutral to moderately alkaline рН (7.3–7.7), SO4–HCO3 Na–Mg–Ca major-ion chemistry. The amount of total dissolved solids is 720–910 mg/L, Si content 6.41–9.02 mg/L. Eh is within +169.1 – +250.0 mV, corresponding to oxidized conditions. The concentration of dissolved oxygen is 2.86–7.37 mg/L. Radon activity (222Rn) varies from 173 to 276 Bq/L. The concentrations of U, Th, and Ra isotopes are 0.015–0.017 mg/L238U, 9.59∙10−7 to 1.58∙10−5232Th, and up to 4.93∙10−10226Ra; the 232Th/238U ratio is in the range 5.81∙10−5 to 9.42∙10−4. Total α activity is not higher than 891 mBq/L, and β activity is 80 mBq/L. The compositions of stable isotopes are −15.4 to −15.1‰ δ18O, −114.2 to −112.8‰ δD, and −13.9 to −9.9‰ δ13C. The isotope signatures and recharge patterns of the Tulinka waters are insensitive to seasonal effects, which suggests the slow water exchange. Substantial seasonal variations of the content of dissolved inorganic carbon (DIC) are detected. The range of δ13CDIC in the analyzed samples (from −14.3 to −9.0‰) corresponds to a mixed CO2 origin: diffusion of soil CO2 approaching the atmospheric δ13CCO2 values, and biogenic CO2 released by decaying plant residues. The measured isotope characteristics provide evidence that the waters recharge by infiltration from meteoric sources. The approximate radiocarbon age of DIC in the Tulinka waters, determined for the first time, is 2663 ± 144 years. However, this age may be underestimated due to groundwater mixing with the present-day surface waters.

Surface engineering of γ-Al2O3 nanosheets with highly dispersed poly(ionic liquids) for selective CO2 adsorption

An efficient CO2 adsorbent (γ-Al2O3 @PAVIMBr) was constructed by means of graft copolymerization with mesoporous γ-Al2O3 nanosheets served as the host material and amino-functionalized imidazolium based poly(ionic liquids) (PAVIMBr) as the guest material. Thereinto, mesoporous γ-Al2O3 could provided abundant hydroxyl groups for loading PAVIMBr uniformly via chemical bonding interaction, while PAVIMBr was able to tailor suitable pore size and expose amino-groups adsorption active sites that was contributed to chemisorb with CO2. It was observed that the general topography of γ-Al2O3 @PAVIMBr composite was almost unchanged after PAVIMBr loaded, and its mesoporous structure and crystalline form was still maintained. Moreover, the content of PAVIMBr in our composite could be calculated from the TGA results before and after its grafting. The obtained γ-Al2O3 @PAVIMBr presented a good CO2 adsorption performance, its CO2 adsorption capacity increased obviously. Meanwhile, the CO2/N2 selectivity of γ-Al2O3 @PAVIMBr was 15.3 times higher than that of γ-Al2O3 at room temperature and the pressure of 100 kPa, while the CO2 uptake of γ-Al2O3 @PAVIMBr was almost 13 and 3 times higher than that of PAVIMBr and γ-Al2O3 at 10 kPa and 25 °C, respectively. It was mainly attributed to that the maintaining mesoporous channels in γ-Al2O3 @PAVIMBr could accelerate the CO2 diffusion, while chemisorption of those exposed adsorption active sites from loaded PAVIMBr could improve the adsorption performance at lower CO2 partial pressure and CO2/N2 selectivity of our composite. Furthermore, the excellent CO2/N2 selectivity, renewability and physicochemical stability of γ-Al2O3 @PAVIMBr might employ it as one of the potential CO2 adsorbents.

Simulated Analysis of Influence of Changes in H+-ATPase Activity and Membrane CO2 Conductance on Parameters of Photosynthetic Assimilation in Leaves.

Photosynthesis is an important process in plants which influences their development and productivity. Many factors can control the efficiency of photosynthesis, including CO2 conductance of leaf mesophyll, which affects the CO2 availability for Rubisco. It is known that electrical stress signals can decrease this conductance, and the response is probably caused by inactivation of H+-ATPase in the plasma membrane. In the current work, we analyzed the influence of both CO2 conductance in the plasma membrane, and chloroplast envelopes and H+-ATPase activity on photosynthetic CO2 assimilation, using a two-dimensional mathematical model of photosynthesis in leaves. The model included a description of assimilation on the basis of the Farquhar-von Caemmerer-Berry model, ion transport through the plasma membrane, diffusion of CO2 in the apoplast, and transport of CO2 through the plasma membrane and chloroplast envelope. The model showed that the photosynthetic CO2 assimilation rate was mainly dependent on the plasma membrane and chloroplast envelope conductance; direct influence of the H+-ATPase activity (through changes in pH and CO2/HCO3- concentration ratio) on this rate was weak. In contrast, both changes in CO2 conductance of the plasma membrane and chloroplast envelopes and changes in the H+-ATPase activity influenced spatial heterogeneity of the CO2 assimilation on the leaf surface in the simulated two-dimensional system. These effects were also observed under simultaneous changes in the CO2 conductance of the plasma membrane and H+-ATPase activity. Qualitatively similar influence of changes in the CO2 conductance of the plasma membrane and chloroplast envelopes, and changes in the H+-ATPase activity on photosynthesis were shown for two different densities of stomata in the simulated leaf; however, lowering the density of stomata decreased the assimilation rate and increased the heterogeneity of assimilation. The results of the model analysis clarify the potential influence of H+-ATPase inactivation on photosynthesis, and can be the basis for development of new methods for remote sensing of the influence of electrical signals.