CO2 Release Research Articles

New evidence of syn-eruptive magma-carbonate interaction: the case study of the Pomici di Avellino eruption at Somma-Vesuvius (Italy)

Calcareous lithics are commonly found within the products of some explosive eruptions of Somma-Vesuvius. The pumice fragments from the final phase of the Plinian fallout event of the Pomici di Avellino eruption contain abundant calcareous xenoliths. Previous work on that eruption, including numerical simulations, suggested that the release of CO2 from the entrapment of carbonates may have prolonged the magmatic phase of the eruption by maintaining sufficient driving pressure in the feeding dike. The texture and thermo-metamorphic reactions of carbonate xenolith-bearing pumice fragments of the Pomici di Avellino eruption are analyzed through petrography, scanning electron microscope images, energy dispersive spectrometer analyses, and micro-computed X-ray tomography to deduce the behavior of short-term carbonate-magma interaction and its contribution to the eruption dynamics. Results show that calcareous xenoliths experienced short-term magma-carbonate interaction, which took place in three steps: (i) entrainment, i.e., the mechanical process of carbonate xenoliths entrapment into a magma; (ii) decarbonation, related to high-temperature decomposition reaction of the xenoliths; and (iii) digestion or dissolution of the incorporated calcareous xenoliths into the melt with diffusion of Ca and Mg. The CO2 released during the syn-eruptive decarbonation process thus provided extra volatiles to the rising magma, which may have maintained magma buoyancy longer than expected if only magmatic volatiles were involved in the eruption.

Modified biochar affects CO2 and N2O emissions from coastal saline soil by altering soil pH and elemental stoichiometry

The application of biochar in degraded farmland improves soil productivity while achieving the recycling of agricultural waste. The collapse of the physical structure of coastal saline soils will greatly reduce the carbon sequestration potential of biochar. Phosphorus- and magnesium-modified biochar greatly improve the stability of biochar, which endows them with the potential to greatly improve the organic carbon pool of coastal saline soil. However, changes in the properties of modified biochar increase the uncertainty of microbial driven CO2 and N2O release by affecting soil chemistry properties. In this study, through laboratory soil microcosmic experiment, we investigated the effects of magnesium-modified biochar (BCMg) and phosphorus-modified biochar (BCP) on CO2 and N2O releases from coastal saline soils, and further uncovered their potential mechanisms. Compared with unapplied biochar (CK) and unmodified biochar (BC) treatment, BCMg reduced both the releases of CO2 and N2O, and BCP decreased N2O release but enhanced CO2 release. pH is the medium through which BCMg affects the release of CO2 and N2O. Specifically, BCMg increased soil pH above 8.5, which reduced the metabolic activity of the microbial community, and the abundance of bacteria directly or indirectly involved in N2O production, thereby decreasing the releases of CO2 and N2O. The amendment of BCP changed soil elemental stoichiometry causing microbial N-limitation. Increasing CO2 release and decreasing N2O release were strategies for microorganisms to cope with N-limitation. These findings suggested that BCMg is superior to BCP in mitigating greenhouse gas emissions, providing a basis for the application of modified biochar to improve the carbon pool and reduce greenhouse gas emissions of coastal saline soil.

Natural light driven plastic leaching effects on carbon chemistry in the tropical coastal waters of eastern Arabian sea: An experimental study

This study examined the effects of solar light driven plastic degradation on carbon chemistry in the coastal waters of eastern Arabian Sea along the west coast of India. The research was conducted through experimental incubations exposed to natural sunlight at multiple locations between December 2023–February 2024. Photodegradation induced a significant pH decrease (up to 0.38 ± 0.02) between controls and plastic incubations ranging from 8.17 ± 0.01 to 7.54 ± 0.02 with the highest variation in the Mumbai coast ranging from 8.13 ± 0.01 to 7.75 ± 0.03. pH variations are primarily caused by the leaching of organic acids and CO2 release during solar irradiated incubation. Plastic leaching due to natural light irradiation and subsequent changes in the water chemistry is of prime significance with dissolved organic carbon (DOC) leaching of 0.002–0.03% of plastic weight into the coastal waters. Our estimations suggest 15–75 metric tonnes (MT) of DOC release per year by plastic pollution in the eastern Arabian Sea coastal waters. Further, the fluorescent dissolved organic matter (FDOM) fragmentation, a part of DOC, may act as an organic source of synthetic contaminants and would promote heterotrophic microbial action in the coastal waters. Photodegradation of plastic and the interaction of natural DOC and plastic-derived DOC resulted in longer wavelengths FDOM, which may affect the penetration of photosynthetically active radiation in the water column, thereby impacting primary production. Finally, future research work focussing on the role of plastic pollution in coastal ocean acidification and vice-versa is essential and will be increasingly intense in the upcoming decades.

Photostimulated Anticancer Activity of Mitochondria Localized Rhenium(I) Tricarbonyl Complexes Bearing 1H-imidazo[4,5-f][1,10]phenanthroline Ligands Against MDA-MB-231 Cancer Cells.

We have introduced Re(I) tricarbonyl complexes (ReL1 - ReL6) [Re(CO)3(N^N)Cl] where N^N = extensive π conjugated imidazo-[4,5-f]1,10-phenanthroline derivatives that helps in strong DNA intercalation, enhanced photophysical behavior, increase the 3π-π* character of T1 state for PDT and high value of lipophilicity for cell membrane penetration. These complexes exhibited prominent intraligand/ligand-centered (π - π*/ 1LC) absorption bands at λ 260 - 350 nm and relatively weak metal-to-ligand charge-transfer (1MLCT) bands within the λ 350 - 550 nm range. Among the six synthesized complexes, [(CO)3ReICl(K2-N,N-2-(4-(1-benzyl-1H-tetrazol-5-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline] (ReL6) exhibited outstanding potency (IC50 ~ 6 µM, PI > 9) under yellow light irradiation compared to dark conditions. Importantly, extremely lipophilic complex ReL6 showed effective penetration through the cell membrane and localized primarily in mitochondria (Pearson's correlation coefficient, PCC = 0.918) of MDA-MB-231 cells. Complex ReL6 exhibited more than 9 times higher photo-toxicity in normoxic and hypoxic environment of tumor by inducing 1O2 generation (type II PDT), radical generation triggered by NADH oxidation (type I PDT). This complex is a promising candidate for TNBC treatment in hypoxic tumors, with efficacy comparable to photofrin and have demonstrated CO release ability under UV light irradiation.

Half substitution of mineral N with fish protein hydrolysate enhancing microbial residue C and N storage and climate benefits under high straw residue return

The widespread utilization of straw return was a popular practice straw disposal for highly intensive agriculture in China, which has brought about some negative impacts such as less time for straw complete biodegradation, aggravation of greenhouse gas evolution, and lower efficient of carbon accumulation. It was urgent to find an eco-friendly N-rich organic fertilizer instead of mineral N as activator to solve the above problems and lead a carbon accumulation in long tern management. Besides, microbial necromass was considered as a crucial contributor to persistent soil carbon (C) and nitrogen (N) pool. How organic fertilizer activators influence microbial residue under different amount of crop residues input remained unclear. Thus, soils incorporating moderate and high rate of rice straw residue with additions of half and full of organic activators (fish protein hydrolysates vs. manure) were incubated for measuring carbon dioxide (CO2) and nitrous oxide (N2O) emission, microbial community and necromass. It was found that soil CO2 emission was rapidest during the first 13 days of straw decomposition but remained lowest in the treatments of 50% mineral N substituted by fish protein hydrolysate. There were that 81%–89% of total CO2 release and 59%–65% of total N2O emission occurred within 60 days of incubation period, and bacterial community and nitrate positively affected soil CO2 and N2O release respectively. Straw incorporation amount and organic activator application interactively influenced soil CO2 emission but not affected soil N2O emission. After 360 days of incubation, the difference of bacterial necromass was noticeable but fungal necromass remained almost unaltered across all treatments. All treatments showed generally comparable contribution of microbial necromass N to the total N pool. The treatment of 50% mineral N substituted by fish protein hydrolysate under high rate of straw input (HSF50) promoted the highest proportion of microbial necromass C in soil organic C because of alleviating N limitation for microorganisms. Finally, HSF50 was recommended as an eco-friendly strategy for enhancing microbial necromass C and N storage and climate benefits in agroecosystems.

Spatiotemporal evolution of air-sea CO2 flux in the Northwest Pacific and its response to ENSO

Global warming, driven by human activities since the Industrial Revolution, has significantly elevated atmospheric carbon dioxide (CO2) levels, leading to higher global temperatures and a rise in extreme weather events. The ocean, as a major carbon sink, has absorbed about 30% of human-induced carbon emissions, helping mitigate global warming’s impacts. This study examines the spatiotemporal distribution of air-sea CO2 flux in the Northwest Pacific from 1982 to 2021 and its response to El Niño-Southern Oscillation, using Empirical Orthogonal Function and composite analysis. The seasonal patterns of air-sea CO2 flux and the influence of environmental factors were further evaluated. The results show that air-sea CO2 flux in the Northwest Pacific exhibits clear seasonal fluctuations. In winter, high-latitude areas act as significant carbon sources. Strong winds deepen the mixed layer, promoting CO2 release from the ocean into the atmosphere. In contrast, in summer, longer daylight hours, rising SST, and melting sea ice lead to upwelling, which brings nutrients to the surface and stimulates phytoplankton growth. This process turns the region into a carbon sink as phytoplankton growth, driven by intense sunlight, enhances the ocean’s CO2 absorption. The mid-latitude region consistently acts as a carbon sink year-round. During El Niño events, more negative air-sea CO2 flux anomalies appear in the eastern Northwest Pacific, enhancing carbon uptake. La Niña events have the opposite effect in the eastern regions. These findings highlight the Northwest Pacific’s critical role in modulating regional and global carbon cycles under varying climatic conditions. Understanding these dynamics is crucial for improving predictions of future climate impacts and for developing effective strategies to mitigate global warming.

"Evaluation of spinel ferrites magnetic nanoparticles based hyperthermia: in-vitro study"

This study is an attempt to compare the hyperthermia and antimicrobial activity of three members of the family of spinel ferrite magnetic nanoparticles (XFe2O4, where X = Mg, Cu, and CO) MNPs. Spinell ferrite of MgFe2O4, CuFe2O4, and CoFe2O4 were prepared via sol–gel method. Structural and morphological shapes were investigated by different techniques X-ray diffraction X-ray powder diffractometer (XRD), Fourier transformed infrared spectroscopy (FTIR), and (Transmission electron microscope) TEM. Magnetic properties were examined by vibrating sample magnetometer (VSM). The in vitro test was conducted on cervical Hela cells using an MTT assay. Finally, the antimicrobial activity was tested on Staphylococcus aureus, Bacillus subtlus, and Escherichia coli using a clearing inhibition zone. XRD results confirmed the crystalline nature of MgFe2O4, CuFe2O4, and CoFe2O4. VSM results showed a high maximum saturation (Ms = 44.87 emu/g) of CuFe2O4 which is greater than that of CoFe2O4 and MgFe2O4 (18.221 and 18.669) emu/g, respectively. MTT assay revealed that high cell death was detected on Hela cells of CuFe2O4 compared to that of MgFe2O4 and CoFe2O4. The anti-microbial study showed that the prepared spinel magnetic nanoparticles possessed antimicrobial activity due to the release of Mg, Cu, Co, and Fe ions. Results showed that the CuFe2O4 could be a good spinel ferrite for medical application with antimicrobial activity and generate heat (hyperthermia, anti-cancer material).

Upcycling of nutrients from kitchen waste: Integration of anaerobic digestion system and microbial protein production system

To upcycle the nutrients from kitchen waste (KW), an integrated system consisting of anaerobic digestion (AD) reactor and microbial protein (MP) production reactor was established in this study. The subsystem I (AD system) demonstrated an efficient bio-energy production (282.37 mL CH4/g VS), with 553.54 mg/L of NH4+-N remained in the digestate. The subsystem II (MP production system) utilized the nitrogenous constituents of the digestate, with 2.04 g/L MP production. In order to further enhance the recovery efficiency, C/N ratio in the subsystem II was studied. NH4+-N recovery efficiency was 23.08% higher after C/N ratio optimization along with 0.24 g/L increment on MP production. Over 0.7 g/L of essential amino acids was obtained, according with the qualitative necessary for the feeds. Also, the key enzyme abundance of CO2 releasing and amino acid biosynthesis was obviously increased with max. 55.21%. Meanwhile, the integrated system was profitable via a simplified economic assessment.

Decarbonization of siderite in the water-rich upper mantle

The aqueous fluids within subducted slabs have the potential to influence the form of carbonate presence and the carbon cycling process. Experiments were performed on resistive heating diamond anvil cell using siderite crystals and grains with water under conditions of pressure as high as 11.4 GPa and temperatures reaching up to 530 °C. These experiments aimed to simulate geological reactions that may occur within a depth range of 340 km in subducted slabs. Raman spectroscopy was employed to monitor the reactions and microscale phenomena within the sample chamber as pressure and temperature increase. The recovered products were analyzed using scanning electron microscopy and transmission electron microscopy. The results indicate that at 0.8 GPa and 108°C, a Fischer-Tropsch Type (FTT) reaction occurred on the sample surface, resulting in the formation of organic compound formaldehyde, followed by the observation of formic acid. At higher pressures and temperatures (3.5 GPa, 420°C), the formation of γ-Fe2O3 and γ-FeOOH was observed on the sample surface, accompanied by the release of CO2 and H2. Transmission electron microscope analysis of the quenched product powders indicated that the generated iron oxides were consistent with the phases observed at high pressure and temperature conditions. High pressure and temperature dissolution experiments of siderite in water reveal that carbon may be released into the mantle wedge entirely in the form of CO2 in warm subducted slabs and cold subducted slabs that subduct to depths of 75 km. The released CO2 participates in the carbon cycle of the island arc volcanic systems in the upper mantle at depths of 70–120 km and accelerates the transfer of subducted carbon to the Earth’s surface.

Study on K-modified Ca-based dual-functional materials for carbon capture and in-situ methane dry reforming

Integrated carbon capture and in-situ methane dry reforming (ICCU-DRM) is a promising technology for chemical looping transformation, this process involves the sequential switching of feedstocks within a single reactor, allowing CO2 capture to occur before methane dry reforming without direct CO2-CH4 contact. However, a significant challenge in the ICCU-DRM process is the disparity between the optimal temperatures required for carbon capture and dry reforming, with the latter necessitating considerably higher temperatures. This could lead to substantial CO2 losses when the reaction temperature is elevated to the optimal level for dry reforming. To address this issue and improve CO2 conversion efficiency, this study explores K doping in synthesizing a dual-functional material, NiCa1.6K0.4@Al2O3, through extrusion-spheronization. The synthesized material exhibits a stable pore structure and a large internal surface area, crucial for enhancing CO2 capture. The optimum temperature for DRM is around 800 °C. Notably, the formation of 1K2Ca(CO3)2 during the calcination of NiCa1.6K0.4@Al2O3, with a thermal decomposition temperature of approximately 800°C, plays a crucial role in minimizing CO2 release during the heating process, thereby significantly improving the CO2 conversion. To evaluate the impact of K doping on the material, the samples were subjected to carbon capture at 650 °C and dry reforming of methane at 750 °C. The results showed that the CO2 conversion rate of NiCa1.6K0.4@Al2O3 reached 52.8%, compared to only 18.9% for NiCa2@Al2O3 under the same conditions. Moreover, this study also investigates the impact of carbon capture temperature, dry reforming temperature, and catalytic metal loading on the performance of the ICCU-DRM process.

High frequency monitoring of carbon (iv) oxide evolution from a tropical soil amended with organomineral fertilizer in a screenhouse Ile-Ife, Nigeria

The study compared responses of carbon (iv) oxide evolved from an Ultisol sampled at different time scales and the soil properties when amended with organomineral fertilizer (OMF); thus tracking the carbon footprint of the amendment in ambient air. The carbon (iv) oxide efflux was measured titrimetrically in a static chamber set up in a screenhouse at sub-daily, daily and weekly time scales. At the same time, the antecedent soil properties were determined using standard methods. The treatments involved OMF addition at three rates (0 kg OMF, 40 kg Urea-N + 2.5 tons/ha organic fertilizer and 40 kg Urea-N + 5 tons/ha organic fertilizer) based on some Nigerian indigenous vegetable nutrient requirements. The result showed that a more detailed and accurate understanding of CO2 evolution processes was revealed at daily sampling resolution while sub-daily variation occurred in response to sub-daily variation in ambient temperature. Organomineral fertilizer at 40 kg/ha Urea + 2.5 tons/ha OF rate was comparatively safer in C management through the reduction in the CO2 released thus constituting a better alternative in terms of the greenhouse effect. Thus, the study recommends at least daily monitoring for a detailed understanding of CO2 evolution dynamics and management and identifies OMF rate with less CO2 release as a comparatively better alternative in the production of those vegetables in the environmental context.

Three-dimensional alkaline earth metal-organic framework poly[[μ-aqua-aqua-bis-(μ3-carba-moyl-cyano-nitro-somethanido)barium] monohydrate] and its thermal decomposition.

In the structure of the title salt, {[Ba(μ3-C3H2N3O2)2(μ-H2O)(H2O)]·H2O} n , the barium ion and all three oxygen atoms of the water mol-ecules reside on a mirror plane. The hydrogen atoms of the bridging water and the solvate water mol-ecules are arranged across a mirror plane whereas all atoms of the monodentate aqua ligand are situated on this mirror plane. The distorted ninefold coord-ination of the Ba ions is completed with four nitroso-, two carbonyl- and three aqua-O atoms at the distances of 2.763 (3)-2.961 (4) Å and it is best described as tricapped trigonal prism. The three-dimensional framework structure is formed by face-sharing of the trigonal prisms, via μ-nitroso- and μ-aqua-O atoms, and also by the bridging coordination of the anions via carbonyl-O atoms occupying two out of the three cap positions. The solvate water mol-ecules populate the crystal channels and facilitate a set of four directional hydrogen bonds. The principal Ba-carbamoyl-cyano-nitro-somethanido linkage reveals a rare example of the inherently polar binodal six- and three-coordinated bipartite topology (three-letter notation sit). It suggests that small resonance-stabilized cyano-nitroso anions can be utilized as bridging ligands for the supra-molecular synthesis of MOF solids. Such an outcome may be anti-cipated for a broader range of hard Lewis acidic alkaline earth metal ions, which perfectly match the coordination preferences of highly nucleophilic nitroso-O atoms. Thermal analysis reveals two-stage dehydration of the title compound (383 and 473 K) followed by decomposition with release of CO2, HCN and H2O at 558 K.

The impact of different batter mixing atmospheres on the quality of reduced sucrose sponge and cream cakes

Cakes are chemically-leavened sugar-rich bakery products. Depending on the cake type, air is incorporated differently during mixing. Sponge cake batter is a gas bubble rich foam, while cream cake batter is an emulsion containing less gas cells. Given the consumer interest in reduced sucrose food systems, we here examined the potential of using altered mixing atmospheres [pure nitrogen (N2) or carbon dioxide (CO2)] to improve reduced sucrose cake quality. The use of poorly soluble N2 resulted in voluminous, stable batter. This was especially the case for foam-type sponge cake batters. During baking of sponge and cream cake batters, leavening was similar for batters prepared either under air or N2, resulting in similar cake qualities. Use of the highly soluble CO2 as mixing atmosphere negatively affected batter density, but positively leavening during baking due to temperature-induced release of previously solubilized CO2. In foam-type sponge cake making, the significant negative effect of CO2 on batter density was not overruled by the positive effect of CO2 release during leavening/baking. In contrast, the CO2 mixing atmosphere during batter-type cream cake making had only a limited negative effect on batter density while greatly affecting leavening, and resulting in high-quality, voluminous (reduced sucrose) cakes.

Constructing sodium alginate/carboxymethyl chitosan coating capable of catalytically releasing NO or CO for improving the hemocompatibility and endothelialization of magnesium alloys

Although significant progress in developing biodegradable magnesium alloy materials in cardiovascular stents has been achieved recently, they still face challenges such as rapid in vivo corrosion degradation, inferior blood compatibility, and limited re-endothelialization after the implantation. Hydrogel coating that can catalyze the liberation of gas signal molecules offers a good solution to alleviate the corrosion rate and enhance the biocompatibility of magnesium and its alloys. In this study, based on alkaline heat treatment and construction of polydopamine coating on the surface of magnesium alloy, sodium alginate/carboxymethyl chitosan (SA/CMCS) gel was simultaneously covalently grafted onto the surface to build a natural polymer hydrogel coating, and selenocystamine (SeCA) and CO release molecules (CORM-401) were respectively immobilized on the surface of the hydrogel coating to ameliorate the anticoagulant performance and accelerate endothelial cells (ECs) growth by catalyzing the release of endogenous gas signal molecules (NO or CO). The findings verified that the as-prepared hydrogel coating can catalyze the liberation of CO or NO and significantly improve the corrosion resistance of magnesium alloy. At the same time, owing to the excellent hydrophilicity of the hydrogel coating, the good anticoagulant property of sodium alginate, and the ability of CMCS to promote the ECs growth, the modified magnesium alloy could significantly improve the albumin adsorption while preventing the adsorption of fibrinogen, hence significantly augmenting the anticoagulant properties and promoting the ECs growth. Under the catalytic release of NO or CO, the released gas molecules further enhanced hemocompatibility and promoted endothelial cell (EC) growth and the expression of vascular endothelial growth factor (VEGF) and NO of ECs. Therefore, the bioactive coatings that can catalyze the release of NO or CO have potential applications in constructing surface bioactive coatings for magnesium alloy materials used for intravascular stents.

Understanding the heat release fluctuations and combustion noise characteristics of non-premixed co/counter-swirl syngas flames at MILD conditions

The heat release fluctuations and combustion noise of co/counter-swirl non-premixed syngas (mixture of CO and H2) and air flames at moderate or intense low-oxygen dilution (MILD) conditions has been investigated experimentally using simultaneous OH∗-chemiluminescence (5 kHz) and microphone measurements (50 kHz). Furthermore, the similarities and differences between co and counter-swirl flames are elucidated using proper orthogonal decomposition (POD), spectrogram, and frequency distributions. At a high O2 concentration (21% by volume), noise measurements for both co/counter-swirl flames comprise both high-amplitude periodic and low-amplitude aperiodic oscillations, revealing signatures of intermittency. Interestingly, for periodic oscillations, the global luminosity (Ifluc) obtained from OH∗-chemiluminescence and noise (Pfluc) are found to be in phase, indicating a strong coupling between noise and heat-release rate. Moreover, POD modes indicate that the global heat release fluctuation occurring in the central region of the combustor is the source of these periodic fluctuations. Besides global fluctuation, the heat release region undergoes rotation around the combustor axis with differing frequencies for co and counter-swirl flames. Furthermore, the global fluctuation is found to be prominent for co-swirl flames, while precession motion is more pronounced in counter-swirl flames. When O2 is reduced to 13.13%, the combustion becomes stable, as suggested by low-amplitude aperiodic oscillations in the noise measurement. Heat release of co and counter-swirl flames respond differently to this reduction in O2 concentration. The precession motion remains unaffected for co-swirl flames upon O2 reduction. In contrast, precession motion alters significantly for counter-swirl. Regarding global fluctuations, low oxygen concentration suppresses all periodic fluctuations, mitigates noise, and Pfluc and Ifluc become entirely decoupled for both flames. Hence, the present study demonstrates for the first time the applicability of a low-oxygen dilution strategy in the context of co/counter-swirl flames for decoupling heat release and noise measurements. Furthermore, the study also indicates the varied response of complex co and counter-swirl flames to different oxygen concentrations.

Examination of the use of binderless zeolite blend as backfill materials to enhance CO2 adsorption in coal mine working face

The release and accumulation of CO2 in the working face of the coal mine is a major safety concern and requires an effective means to avoid the incidence of the mine. This present study therefore sought to develop a self-CO2 adsorbing backfill (SCAB) material to remove CO2 from the working environment, and simultaneously mitigate the movements of the surrounding rock layers. SCAB was formulated using coal mine solid waste activated with an alkali activator, and binderless 4 A zeolite was embedded in the backfill body. The total CO2 adsorption capacity was investigated using a CO2 flow-through method under ambient pressure and temperature conditions. The adsorption plateau was found in stages II and III respecting the predetermined curing time and zeolite contents. The maximum adsorption capacity was 143.8 mg-CO2/g-SCAB, resulting in an increase of up to 82 % in UCS compared to reference samples. The underlying mechanism was discovered in morphological analyses.1) The well distribution of zeolite in the SCAB body provided as diffusive pathways and adsorption sites for CO2 after standard curing. 2) The adsorbed CO2 underwent a desorption stage when the CO2 concentration decreased and reacted to the cementitious matrix of the SCAB body. 3) More CaCO3 crystals were generated and filled in the micro spaces of the SCAB body, which contributed to an increase in compressive strength. This study developed an effective approach to remove CO2 gas from the working face of the coal mine during backfilling. Adsorbed CO2 improved the strength of the material, provided as a novel multi-function backfill mining for sustainable green coal mining technology.

Assessment of carbon flux gradients and dominant processes in a subtropical highly urbanized coastal ecosystem

Highly urbanized coastal ecosystems are vital in the global carbon budget. However, there are limited researches on carbon flux gradients in these nearshore areas, considering both natural and anthropogenic influences. Through on-site measurements and field samplings during wet-to-dry season in 2023, this study investigated spatial variations and factors affecting carbon fluxes, focusing on the impacts of salinity and eutrophic status in five geographically connected coastal waters of the Guangdong-Hong Kong-Macau Greater Bay Area (GBA). By estimating carbon exchange at land-sea-air interface, dominant processes in carbon dynamics were identified as well. Results showed that partial pressure of CO2 (pCO2) varied from 391 to 2290 μatm, and sea-air CO2 exchange fluxes (FCO2) ranged from -3.07 to 70.07 mmol m–2 d–1, indicating significant geographical distinctions among five coastal waters of the GBA. The total carbon transport from rivers to these nearshore waters was approximated at 6.44 Tg C yr-1, with the Pearl River (PR) contributing 99.7%, primarily in dissolved forms. Atmospheric CO2 release was calculated at 0.29 Tg C yr-1 for studied five coastal waters, primarily as carbon sources, except for Dapeng Bay (DPB) as a sink. CO2 emissions inversely correlated with salinity, yet positively with eutrophication status, particularly in river-dominated estuaries. Moreover, CO2 flux decreased 23 times as eco-status shift from eutrophic to non-eutrophic. River plumes, terrestrial pollutant inputs, and economic structure were underlying drivers, influencing carbon species concentrations and fluxes. Elevated CO2 concentrations in eutrophic coastal waters were mainly attributed to terrestrial carbon and nutrients inputs, supporting active biological respiration and microbial decomposition. Conversely, carbon dynamics potentially depend on the balance of respiration and photosynthesis in non-eutrophic coastal waters. This study offers high geographic precision and specificity of carbon species, and provides land-sea integration insight to understand carbon dynamic mechanisms, promoting advancements in water quality management and climate mitigation.

Enhanced CO₂ Detection Using Potentiometric Sensors Based on PIM‐1/DBU Imidazolate Membranes

AbstractA novel potentiometric sensor for carbon dioxide (CO2) detection utilizing a composite membrane of Polymer of Intrinsic Microporosity (PIM‐1) and 18‐diazabicyclo[5.4.0]undec‐7‐ene imidazolate (DBU‐imidazolate) is presented. The high surface area and gas permeability of PIM‐1, combined with the chemical affinity and ion‐exchange properties of DBU‐imidazolate, contribute to enhanced CO2 sensitivity and selectivity. The research objectives included the synthesis of PIM‐1 and DBU‐imidazolate, the preparation of composite membranes, and the evaluation of their performance as CO2 sensors. Solvent casting and impregnation methods are employed to prepare the membranes, which are characterized using Thermal Gravimetric Analysis (TGA), and Field Emission Scanning Electron Microscopy (FESEM). CO₂ absorption tests and Electrochemical Impedance Spectroscopy (EIS) are conducted to assess the sensors' performance. The PIM‐1/DBU‐imidazolate membrane exhibited high efficiency in CO₂ capture and release. Open circuit voltage (OCV) measurements are performed under varying concentrations of CO2 exposure and cycles of adsorption/desorption. Results show that the membrane achieves steady state faster at higher CO2 concentrations, with a logarithmic relationship between CO2 concentration and voltage variation, indicating potential for CO2 detection in human environments. These results confirm the sensor's ability to detect varying CO2 concentrations, highlighting its potential for reliable and efficient CO2 monitoring in environmental and industrial applications.

Understanding the Catalytic Effect on the CO2 Regeneration Performance of Amine Aqueous Solutions

To address the high energy consumption of the carbon capture and storage process in the shipping industry, the effects of several commonly used commercial catalysts, such as HZSM-5-25, γ-Al2O3, and SiO2, as well as a self-prepared catalyst, Zr-HZSM-5-25, on the regeneration of MEA solution and MEA + MDEA mixed solution were investigated in this paper. The results showed that Zr-HZSM-5-25 had the best catalytic effect on the regeneration process of the MEA aqueous solution, which could increase the instantaneous maximum CO2 regeneration rate of the MEA-rich solution by about 8.25% and the average regeneration rate by about 5.28%. For the MEA + MDEA mixed solution, the reaction between tertiary amine MDEA and CO2 produced a large amount of HCO3− in the reaction system, which could accelerate the release of CO2 to a large extent, which resulted in the catalytic effect of the Zr-HZSM-5-25 catalyst on the regeneration process of the mixed amine solution being significantly lower than that on the single MEA solution, with an increase of 4.91% in the instantaneous maximum regeneration rate. This instantaneous maximum regeneration rate was only increased by 4.91%. While Zr-HZSM-5-25 showed a better performance in the bench-scale test, it reduced CO2 regeneration energy consumption by 7.3%.

Increase in gross primary production of boreal forests balanced out by increase in ecosystem respiration

Changes in the net carbon sink of boreal forests constitute a major source of uncertainty in the future global carbon budget and, hence, climate change projections. The annual net ecosystem exchange of carbon dioxide (CO2) controlling the terrestrial carbon stock results from the small difference between respiratory CO2 release and the photosynthetic CO2 uptake by vegetation. The boreal forest, and the boreal biome in general, is regarded as a persistent and even increasing net carbon sink. However, decreases in photosynthetic CO2 uptake and/or concurrent increases in respiratory CO2 release under a changing climate may turn boreal forests from a net sink to a net source of CO2. Here, we assessed the interannual variability of the boreal forest net CO2 sink-source strength and its two component fluxes from 1981 to 2018. Our remote sensing approach - trained by net CO2 flux observations at eddy covariance sites across the circumpolar boreal forests - employs satellite-derived retrievals of snowmelt timing, landscape freeze-thaw status, and yearly maximum estimates of the normalized difference vegetation index as a proxy for peak vegetation productivity. Our results suggest that for the period 2000–2018, the mean annual evergreen boreal forest CO2 photosynthetic uptake (gross primary productivity) was 2.8±0.2 Pg C y−1 (1.6±0.1 Pg C y−1 for Eurasia and 1.2±0.1 Pg C y−1 for North America). In contrast to earlier studies results obtained here do not indicate a clear increasing trend in the circumpolar evergreen boreal forest CO2 sink. The increase in photosynthetic CO2 uptake is compensated by increasing respiratory releases with both component fluxes showing considerable interannual variabilities.