Search Results (626)

Soil organic carbon (SOC) responds rapidly to vegetation changes, and exploring SOC sequestration mechanisms under different vegetation types is critical for optimizing wetland carbon sink functions. This study investigated the abiotic and biotic mechanisms driving SOC stability across four typical vegetation types (reed marsh, woodland, farmland, and wasteland) in the 0–10 cm and 10–20 cm soil layers of Hengshui Lake wetland. Results showed that reed marshes exhibited the highest total organic carbon (TOC) and particulate organic carbon (POC), owing to anaerobic soil conditions and stable macroaggregate physical protection. Woodlands accumulated higher dissolved organic carbon (DOC) and microbial biomass carbon (MBC) via an efficient microbial carbon pump, despite weaker aggregate stability. In contrast, farmlands and wastelands presented intense labile organic carbon (LOC) turnover and enzymatic decomposition, accelerating SOC mineralization and carbon dissipation with poor carbon sequestration capacity. Proteobacteria and Acidobacteriota dominated bacterial communities, while Ascomycota prevailed in fungi. Soil water content (SWC) and bulk density (BD) were the core drivers of microbial community succession, and fungi were more sensitive to vegetation changes. Conclusively, distinct vegetation types shape divergent SOC sequestration pathways. This work provides a theoretical basis for wetland restoration and regional carbon sink enhancement. Full article

Ophicarbonates provide an important natural record of mineral carbonation during serpentinization of ultramafic rocks and therefore offer insight into the mechanisms and limits of CO₂ fixation in low-temperature geological environments. This paper presents a synthesis and process-oriented reinterpretation of stable-isotope published and previously unpublished data, petrographic, and mineralogical evidence for carbonate formation under fluid-limited serpentinization conditions. Using mineralogical constraints together with a compiled δ¹³C–δ¹⁸O dataset that includes legacy measurements from the 1980s–1990s, we evaluate how multi-stage carbonate precipitation reflects evolving water–rock ratio, redox state, transport limitation, and deformation-controlled permeability. Particular attention is given to systematic differences between vein-hosted carbonates and dispersed intergranular or scattered-grain ophicarbonates, as these textural–isotopic relationships help identify fluid flux, carbon source, and reaction progress in ultramafic systems. The analysis shows that carbonation does not proceed uniformly but is restricted to overlapping reactive windows controlled by fluid availability, nucleation kinetics, and permeability evolution. These constraints help explain why carbonation may either intensify or stall during progressive serpentinization. The Author further discuss why kinetic barriers and Mg–Ca partitioning may redirect carbonate mineralogy toward calcite or metastable Mg-rich phases even where dolomite or magnesite may be thermodynamically favored. The results highlight the importance of coupling isotopic signatures with petrographic context in reconstructing carbonation pathways and provide a broader framework for understanding natural mineral sequestration of carbon in heterogeneous serpentinite systems. Full article

Currently, research that quantitatively disentangles the relative importance of these effects in terms of carbon balance and clarifies its independent mechanisms, particularly in ecologically sensitive urban agglomerations, is lacking. To address this gap, this study took the Guanzhong Plain Urban Agglomeration as a case study and used remote sensing imagery as the primary data source with the XGBoost–SHAP framework as the main analytical approach to quantitatively assess the importance and mechanisms of forest and grassland cover on carbon balance. The results indicate that forest and grassland cover in the Guanzhong Plain Urban Agglomeration slightly increased from 2000 to 2020, with a spatial pattern characterized by “more in the west and south, less in the east and north”. Forest and grassland cover contributes approximately 9.36% to carbon emissions, while it plays a dominant role in carbon sequestration, with an estimated contribution of approximately 79.07%. At the carbon balance level, its contribution reaches 9.55%. Furthermore, the results reveal significant spatial heterogeneity in the influence of forest and grassland cover on the carbon balance. The results of this study can provide important scientific basis for achieving the dual-carbon goal and formulating policies for the sustainable development of forest and grassland ecosystems. Full article

Nanobubbles (NBs) are emerging as a promising area of research across multiple scientific and industrial domains due to their unique physicochemical characteristics. NBs exhibit distinctive properties compared to normal bubbles, including high internal pressure, a large specific surface area, high interfacial activity, and long-term stability in liquids. Therefore, NBs have gained increasing attention as a novel enhanced oil recovery (EOR) technique, offering potential advantages over traditional gas flooding and chemical flooding. CO₂-NB specifically represents a particularly promising approach as an intersection of EOR and carbon capture, utilization, and storage (CCUS), as CO₂-NB enables hydrocarbon recovery and in situ CO₂ utilization and storage at reservoir conditions. This paper presents a structured comparative discussion of currently identified experimental EOR studies that employ CO₂-NBs. Based on the observations of these experiments, this paper discusses the proposed mechanisms in those experiments or other studies that could scientifically play a role in achieving incremental recovery. The main mechanisms discussed include interfacial tension reduction, wettability alteration, CO₂ transfer from NBs into the oil liquid phase, and suppression of gravity segregation. Other possible contributors discussed in the literature include buoyancy-assisted mobilization, induced shock waves, and drag force reduction. These mechanisms are examined in relation to the distinctive properties of CO₂-NBs, showing how these properties contribute to the occurrence of the proposed mechanisms, showcasing the potential of CO₂-NBs as an emergent EOR–CCUS technology. A preliminary probabilistic assessment was performed to estimate CO₂ storage potential during CO₂-NBs EOR injection. The results suggest that the majority of the injected CO₂ is dissolved in the saturated liquid phase, while the amount of free NBs is negligible, indicating that CO₂-NB injection may provide secure storage through solubility trapping, but with lower storage capacity compared to conventional geological sequestration in saline aquifers. Full article

Mangrove ecosystems in coastal wetland restoration areas are experiencing escalating nitrogen stress, yet the microbial metabolic mechanisms underlying soil carbon sequestration in Kandelia obovata systems under exogenous nitrogen input remain unclear. In this laboratory tidal simulation experiment, five nitrogen addition levels (N0–N4) were applied to two treatments, namely the planted group and the unplanted group. Results showed that total carbon (TC), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) were all higher under nitrogen addition than in the N0 control. TC showed a unimodal response to nitrogen addition, with the highest values observed at N2, while the planted group exhibited the greatest relative increase in TC over the unplanted group at N3 (53.49%). MBC and MBN contents initially increased and then decreased with elevated nitrogen addition, peaking at the N3 treatment. Compared with the N0 control, MBC and MBN contents under N3 increased by 31.83% and 206.24% in the planted group, and by 23.46% and 279.03% in the unplanted group, respectively. Microbial carbon source utilization was stronger in the planted group, where microorganisms preferred amino acid and lipid carbon sources. Microbial communities in the unplanted group fluctuated markedly under nitrogen input, whereas those in the planted group were more stable with higher evenness. In the planted group, nitrogen addition promoted carbon sequestration by enhancing microbial activity and biomass accumulation, while in the unplanted group, nitrogen input exerted complex effects and directly suppressed soil carbon sequestration. These findings suggest that the introduction of Kandelia obovata may enhance microbial biomass, stabilize microbial carbon-use strategies, and promote short-term soil carbon accumulation under moderate nitrogen addition in a laboratory tidal simulation system. Overall, the N3 treatment (20 g N m⁻² a⁻¹) serves as a key nitrogen threshold, and exceeding this addition level may weaken the beneficial effects on microbial biomass, metabolic activity, and the relative carbon accumulation advantage of the planting system. Full article

Agricultural crop residue burning is a major driver of seasonal PM2.5 pollution and greenhouse gas (GHG) emissions in Northern Thailand. This study quantified GHG emissions from the open burning of rice, maize, and sugarcane residues across six provinces (Chiang Mai, Mae Hong Son, Lampang, Uttaradit, Nakhon Sawan, and Kamphaeng Phet) from 2019 to 2024 using the 2006 IPCC emission methodology. Spatiotemporal patterns of fire hotspots were characterized using MODIS and VIIRS satellite data, combined with kernel density estimation (KDE) and land-use classification in ArcGIS Pro. Total non-CO₂ GHG emissions (CH₄ and N₂O, expressed as CO₂-eq using GWP100 from IPCC AR5) over the six years totaled 2,599,551 tCO₂-eq, with major rice contributing the largest share (35%), followed by sugarcane (24%), second rice (21%), and maize (20%). Nakhon Sawan was the leading emitter (41%), reflecting its extensive rice and sugarcane cultivation. Pearson correlation analysis revealed consistently positive relationships between daily fire hotspot counts and PM2.5 concentrations (r = 0.30–0.84), with the strongest correlations observed in Mae Hong Son, where basin topography traps pollutants. Time-series analysis confirmed pronounced seasonal PM2.5 peaks that exceeded Thailand’s 24-h NAAQS limit (37.5 μg/m³) by 7–9 times in severe years. Biochar production via pyrolysis was evaluated as a zero-burning alternative, with an estimated annual carbon sequestration potential of 2.3–3.5 million tCO₂-eq, substantially exceeding emissions from open burning. These findings indicate that crop-residue valorization options—including biochar production, composting, and biochar co-compost—could theoretically offset agricultural GHG emissions and reduce field-burning PM2.5 emissions in Northern Thailand. However, the realized mitigation will depend on (i) verification of biochar long-term stability in tropical Thai soils through dedicated in situ trials, (ii) economic incentives that offset biochar production costs of approximately 1500–3500 THB per tonne, and (iii) integration within a policy mix that combines burning bans, mechanization support, and farmer extension services. Without these enabling conditions, biochar should be regarded as a future-perspective option rather than an immediately deployable solution. Full article

Monoethanolamine (MEA) remains the predominant solvent for carbon dioxide (CO₂) capture due to its rapid reaction kinetics, substantial absorption capacity, and demonstrated industrial effectiveness. Despite its established status, MEA-based systems are undergoing continuous development to lower energy requirements, enhance solvent stability, and expand operational adaptability. This review provides a critical assessment of recent progress in MEA-based CO₂ capture, encompassing molecular-level understanding, advancements in reactor and process design, solvent modification strategies, and system-wide optimization. Recent theoretical and experimental research has improved the understanding of CO₂ absorption mechanisms in MEA, highlighting the effects of reaction-product buildup, interfacial phenomena, and free amine availability on mass-transfer efficiency. Reboiler duty and comparable work have significantly decreased as a result of advances in process intensification, improved regeneration systems, and energy-integration techniques. New hybrid strategies that partially decouple capture from thermal regeneration, such as combined absorption–mineralization pathways, show promise for long-term CO₂ sequestration. To address regeneration energy, corrosion, degradation, and cyclic stability, this review examines advances in MEA-based solvents, including aqueous blends, non-aqueous and biphasic systems, ionic liquids, and deep eutectic solvent hybrids. It also critically assesses the trade-offs of developments in intensified contactors, surfactants, nanomaterials, and catalysts. The growing role of digital optimization, machine learning, and computational modeling in MEA process design and control is highlighted. Overall, this analysis underscores MEA’s continued importance as a versatile platform for next-generation carbon capture, utilization, and storage. Full article

Soil organic carbon (SOC) is pivotal to the terrestrial carbon cycle and climate regulation, yet its spatiotemporal dynamics and future climate responses across soil layers remain insufficiently understood in mountainous ecosystems. Taking the Qinling Mountains, a typical mountainous ecological barrier in central China with a total area of approximately 38.18 × 10⁴ km², as the study area, we analyzed historical SOC changes (1980s–2010s) and projected its future dynamics under different scenarios using a validated Random Forest model (R² = 0.81 for 0–20 cm, SOC₂₀; 0.73 for 0–100 cm, SOC₁₀₀), and further disentangled dominant drivers. Results showed historical mean SOC density increased, with higher storage in western/central high-elevation zones and lower values in southern/eastern low-elevation areas. Climate was the primary driver of SOC₂₀ dynamics, while SOC₁₀₀ was jointly regulated by climate, vegetation, and environmental factors, indicating weakened climatic control with increasing soil depth. Precipitation increases partially offset warming-induced SOC loss, leading to small changes in regional mean SOC density, but strong spatial heterogeneity resulted in substantial total SOC stock losses (SOC₂₀: −1.41 to −6.59 Tg C; SOC₁₀₀: −6.86 to −28.76 Tg C), with net losses in high-elevation zones and gains in low-elevation areas. SOC within the whole 1 m soil profile exhibited larger climate-driven changes than topsoil. These findings advance understanding of SOC dynamics in complex mountainous ecosystems and provide key scientific insights for regional carbon cycle assessments under climate change. Full article

Faced with the dual challenges of intensifying global climate change and tightening food security, achieving a balance between food security and agricultural carbon sequestration and emissions reduction has become a focal point of academic inquiry. This study quantifies agricultural carbon intensity and food security levels in Hunan Province from 2002 to 2023. By employing the Tapio decoupling model, the Logarithmic Mean Divisa Index (LMDI) method, and spatial analysis techniques, it systematically examines the decoupling relationship and driving mechanisms between agricultural carbon intensity and food security in Hunan Province. The results indicate that agricultural carbon intensity exhibits a spatial pattern of “high in the east, low in the west,” while food security levels decline from the eastern plains to the western mountainous regions. The decoupling trajectory is broadly characterized by a transition from predominantly weak decoupling toward strong decoupling; since 2016, prefecture-level cities exhibiting strong decoupling have accounted for 92.9% of all cases, displaying spatial characteristics of “overall improvement, an uneven process, and regional asynchrony.” Agricultural energy intensity, energy structure, and rural labor force size serve as positive drivers of decoupling between agricultural carbon intensity and food security, whereas agricultural economic development and per capita cultivated area exert a restraining effect. Developing differentiated emissions reduction strategies to target these key factors is essential for advancing the coordinated development of low-carbon agriculture and food security. Full article

As a rapidly developing extreme drought event, flash drought poses an increasingly serious threat to agricultural production, ecosystem carbon sequestration, and regional ecological security. However, systematic understanding remains limited regarding the occurrence characteristics of flash drought across different cropland types and the mechanisms by which it affects gross primary productivity (GPP). Using root-zone soil moisture, meteorological variables, and GPP data for China from 2000 to 2020, this study characterized flash drought events across different cropland ecosystems, quantified the response frequency and intensity of GPP, and further explored the dominant driving factors using eXtreme Gradient Boosting and SHapley Additive exPlanations. The results showed that flash drought occurred more frequently in cropland than in non-cropland areas, and that rainfed cropland experienced flash drought more frequently and developed more rapidly than irrigated cropland. The mean GPP response frequency in cropland was 0.43, indicating that nearly half of flash drought events suppressed GPP. Regions with high sensitivity were mainly concentrated in northwestern and northeastern China, with northwestern China showing the lowest resistance to flash drought. Climatic background and hydro-meteorological anomalies were the dominant factors controlling GPP responses in cropland, and the dominant driving factors differed significantly among cropland types, exhibiting pronounced nonlinear and threshold effects. This study reveals the spatial heterogeneity and driving mechanisms of flash drought impacts across different cropland ecosystems in China and provides a scientific basis for agricultural drought-risk assessment and differentiated adaptive management. Full article

In recent years, the application of fly ash concrete (FAC) has witnessed a remarkable expansion worldwide. Compared with ordinary Portland cement (OPC), the incorporation of fly ash (FA) reduces the consumption of cement, realizes solid waste resource utilization, and concurrently cuts down carbon emissions from cement production, thus yielding notable environmental benefits. With the gradual popularization of concrete carbon sequestration technology, the research focus of academic circles on concrete carbonation behavior has shifted from the traditional orientation of “optimizing carbonation resistance” to the new direction of “enhancing carbon sequestration efficiency”. Nevertheless, current research on the mechanical properties, durability, and other behaviors of FAC after carbonation remains scarce, lacking systematic and in-depth exploration, and the mechanism underlying the impacts of carbonation on material properties still requires further systematic collation and generalization. Consequently, research on the carbonation behavior of FAC holds profound academic significance and promising application value. This paper reviews the microscopic mechanisms and influencing factors of FAC carbonation; summarizes and analyzes the effects of FAC carbonation on its various properties and microscopic pore structure; introduces the innovative breakthroughs in FAC technology in recent years; and finally, prospects future research directions. It is anticipated to provide a valuable reference for subsequent relevant studies. Full article

This review synthesizes recent advances in the characterization of eco-friendly cement composites, focusing on hydration kinetics, microstructural evolution, and mechanical durability. Advanced techniques—from isothermal calorimetry to nanoindentation—enable decoding of reaction pathways, mix optimization, and long-term performance prediction. The analysis covers supplementary cementitious materials (fly ash, slag, silica fume), geopolymers, bio-based additives (SNSs, biochar, CNCs, lignosulfonates), and microbially induced calcite precipitation (MICP). For each category, key mechanisms are identified, property effects quantified, and microstructural correlations established. SCMs achieve pore refinement and enhanced durability through long-term pozzolanic reactions. Geopolymers exhibit exceptional thermal stability (800–1000 °C) and acid resistance. Fly ash-based geopolymers exhibit chloride diffusion coefficients 1–2 orders of magnitude lower than ordinary Portland cement (OPC), though slag-based systems show more moderate improvements due to their different pore structure and higher calcium content. Bio-based additives enable accelerated hydration (SNSs), internal curing and CO₂ sequestration (biochar), pore refinement (CNCs), workability enhancement (lignosulfonates), and autonomous crack healing (MICP). Multi-scale characterization is essential for establishing robust structure–property relationships. The review concludes that properly optimized eco-friendly cement composites offer viable pathways toward sustainable construction with reduced carbon footprint, enhanced durability, and extended service life. This review is novel in its systematic comparison of hydration kinetics, microstructural evolution, and mechanical performance across three distinct classes of eco-friendly additives (SCMs, geopolymers, and bio-based materials), with particular emphasis on the complementarity of advanced characterization techniques—an aspect that has received limited attention in previous reviews. Full article

Differential enrichment of shale oil hydrocarbon fractions exerts a fundamental control on the spatial distribution of “sweet spots” and the efficiency of unconventional resource recovery. This study investigates the continental shales of the Upper Es4 Member in the Dongying Sag, Bohai Bay Basin, through an integrated analytical framework combining Laser Scanning Confocal Microscopy (LSCM), Scanning Electron Microscopy (SEM), and high-pressure mercury intrusion. By moving beyond qualitative observations, we characterize the micro-scale partitioning of light and heavy fractions and establish a deterministic hierarchy of controlling factors. Our results indicate the following. (1) Mineral composition functions as a “primary geochemical filter,” where carbonate minerals exhibit a preferential adsorption affinity for light fractions (≤ C₁₈), while clay minerals facilitate the selective retention of heavy components (> C₁₈). (2) Pore–throat architecture acts as a “secondary mobility modulator.” A statistically significant linear correlation (R² = 0.72, p < 0.05) was identified between mean pore diameter and the light-to-heavy fluorescence ratio, suggesting that interconnected macropores in carbonate laminae provide low-resistance conduits for light oil accumulation, whereas isolated mesopores in argillaceous matrices promote heavy-component sequestration. (3) Thermal maturity (Ro) drives a progressive shift in the light-to-heavy ratio, enhancing oil fluidity and regulating the transition from adsorption-dominated to migration-dominated enrichment. This study clarifies the lithofacies-dependent coupling mechanisms between mineral diagenesis and pore-scale fractionation, providing a semi-quantitative conceptual model for shale oil sweet-spot prediction in complex lacustrine basins. Full article

Straw and no-tillage management, as important practices in conservation agriculture, have the potential to improve soil structure. However, their effects on the aggregate stability of soil and on active organic carbon pools in paddy fields are unclear. To investigate how different tillage and straw management practices affect soil properties, this study drew on a 15-year long-term experiment conducted in a double-cropped rice region in South China. It systematically compared four treatments: no-tillage (NT), conventional tillage (CT), conventional tillage with incorporated straw (CT-SR), and no-tillage with straw mulch (NT-SMR)—in terms of their effects on the distribution and stability of mechanical and water-stable aggregates, as well as the distribution of particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) across various aggregate size fractions. The results showed that: (1) Relative to the CT, NT, and CT-SR treatments, NT-SMR significantly enhanced soil structure, as evidenced by a higher percentage of large aggregates (>0.25 mm) and improved aggregate stability. (2) NT-SMR consistently increased soil organic carbon pools, raising SOC, POC, and MAOC contents by 2.0–14.2%, 5.7–24.3%, and 1.0–11.9%, respectively, compared to other treatments. (3) In this study, stability of soil aggregates parameters (R_>0.25, MWD and GMD) increased combined with higher levels of bulk SOC and >0.053 mm MAOC, but decreased with higher fractal dimension, indicating a direct causal link between organic carbon accumulation and the betterment of soil structure. Overall, NT-SMR promotes aggregate stability through an optimized particle-size distribution and increased SOC, particularly in the >0.053 mm MAOC fraction. This practice is a sustainable long-term strategy for enhancing SOC sequestration and structural stability in paddy. Full article

Air–sea CO₂ flux (FCO₂) in the estuary–coastal continuum plays a vital role in global carbon sequestration; however, the mechanisms governing FCO₂ spatial heterogeneity during early spring remain poorly understood, particularly the roles of distinct dissolved inorganic carbon (DIC) sources. In March 2025, we investigated the FCO₂ spatial variability and DIC sources across the Yangtze River estuary and adjacent coastal areas using DIC concentration, pH, and δ¹³C_DIC analyses. The study area was a net CO₂ source (7.3 ± 8.7 mmol m⁻² d⁻¹), with the intensity declining progressively from the inner estuary to offshore areas. Physical mixing of three principal water masses established the following pattern: high-pCO₂ Changjiang Diluted Water and Yellow Sea Coastal Current drove CO₂ outgassing, while low-pCO₂ East China Sea Shelf Water weakened it. Quantitative apportionment revealed atmospheric CO₂ invasion as the dominant DIC source, followed by carbonate dissolution and organic matter degradation, with the latter declining from the inner estuary to offshore areas. The spatial variation in DIC source contributions further confirms that, superimposed on the physical mixing, biogeochemical processes—particularly biological activity—modulated reginal source intensities. This early-spring case captures a critical transitional window and highlights the necessity of integrating multi-factor regulation with DIC source partitioning to resolve carbon dynamics in the estuarine–coastal continuum. Full article