Search Results (809)

Climate change is increasing the drought frequency and severity, so projecting spatiotemporal drought evolution across climate zones is critical for drought mitigation. Model biases, the choice of drought index, and neglecting CO₂ effects on potential evapotranspiration (PET) add large uncertainties to future drought projections. We selected 10 global climate models (GCMs) that participated in the Coupled Model Intercomparison Project Phase 6 and downscaled model outputs using the bias correction and spatial downscaling (BCSD) method. We then developed a CO₂-aware standardized moisture anomaly index (SZI[CO₂]) and used a three-dimensional drought identification method to extract the duration, area, and severity; we then analyzed their spatiotemporal dynamics. To account for nonstationarity, Copula-based approaches were used to estimate joint drought probabilities with time-varying parameters. Projections indicate wetting in Southern Northwest China, Inner Mongolia, and the Western Tibetan Plateau (reduced drought frequency, duration, intensity), while Central and Southern China show a drying trend in the 21st century. Three-dimensional drought metrics exhibit strong nonstationarity; nonstationary log-normal and generalized extreme value distributions fit most regions best. Under equal drought characteristic values, co-occurrence probabilities are higher under SSP5-8.5 scenarios than SSP2-4.5 scenarios, with the largest scenario differences over the Tibetan Plateau and Central and Southern China. Full article

As a critical ecological barrier in the arid and semi-arid regions of northwestern China, the spatio-temporal evolution of vegetation carbon sequestration in the Hexi Corridor is of great significance to the ecological security of this region. Based on multi-source remote sensing and meteorological data, this study integrated second-order partial correlation analysis, ridge regression, and other methods to reveal the spatio-temporal evolution patterns of Gross Primary Productivity (GPP) in the Hexi Corridor from 2003 to 2022, as well as the response characteristics of GPP to air temperature, precipitation, and Vapor Pressure Deficit (VPD). From 2003 to 2022, GPP in the Hexi Corridor showed an overall increasing trend, the spatial distribution of GPP showed a pattern of being higher in the east and lower in the west. In the central oasis region, intensive irrigation agriculture supported consistently high GPP values with sustained growth. Elevated air temperatures extended the growing season, further promoting GPP growth. Due to irrigation and sufficient soil moisture, the contributions of precipitation and VPD were relatively low. In contrast, desert and high-altitude permafrost areas, constrained by water and heat limitations, exhibited consistently low GPP values, which further declined due to climate fluctuations. In desert regions, high air temperatures intensified evaporation, suppressing GPP, while precipitation and VPD played more significant roles. This study provides a detailed analysis of the spatio-temporal change patterns of GPP in the Hexi Corridor and its response to climatic factors. In the future, the Hexi Corridor needs to adopt dual approaches of natural restoration and precise regulation, coordinate ecological security, food security, and economic development, and provide a scientific paradigm for carbon neutrality and ecological barrier construction in arid areas of Northwest China. Full article

Early-age cracking remains a major durability challenge for concrete. It is primarily caused by internal restraint stresses induced by humidity and temperature gradients during hydration. Conventional approaches often fail to capture the coupled and non-uniform nature of heat and moisture transport, limiting their ability to predict cracking risk and evaluate mitigation strategies. To address this limitation, we characterize the spatiotemporal evolution of internal humidity and temperature using a spatial coefficient of variation. From a numerical standpoint, the influence of polypropylene fibers (PPFs) on internal relative humidity is elucidated by adopting an unconditionally stable backward-Euler finite-difference scheme to resolve multiple coupled physicochemical processes—hydration, heat release, self-desiccation, heat and moisture diffusion to the environment—and their mutual interactions. Furthermore, a one-dimensional homogeneous random-field model is proposed to quantify the spatial non-uniformity of humidity in PPF concrete. On this basis, the effects of polypropylene fibers (PPFs) in mitigating internal humidity is quantitatively revealed. Good agreement is achieved between simulations and tests, with standard deviations of 0.0119 for normal concrete and 0.0041 for PPF concrete, thereby validating the model’s predictive capability for the spatiotemporal distribution of internal relative humidity (RH) in PPF concrete. According to the numerical analysis, owing to the moisture-sorption characteristics of PPFs, at a depth of 25 mm, the internal RH in PPF concrete has decreased by 16% at 28 days, whereas normal concrete exhibits a 28% decrease. With increasing depth, the RH reduction at 28 days is approximately 13% for both PPF concrete and plain concrete, and the time-dependent evolution of RH in PPF concrete is broadly similar to that of normal concrete. Furthermore, the mitigating influence of PPFs decreases with hydration age and distance from the surface, reflecting the gradual decline of diffusion heterogeneity over time and depth. These findings provide new numerical evidence for the effectiveness of PPFs in reducing the early-age cracking risk in concrete. Full article

This study utilizes ambient air quality monitoring data from 13 prefecture-level cities in Heilongjiang Province to systematically analyze the pollution characteristics and dynamic evolution of ozone (O₃) and non-methane hydrocarbons (NMHCs). The findings reveal that overall air quality in Heilongjiang Province has improved substantially in recent years. The concentrations of SO₂, NO₂, PM₁₀, PM_2.5 and CO in 2023 decreased significantly compared with 2015, with an average reduction of 38.7%. However, O₃ concentrations have continued to rise, indicating that O₃ pollution has become an increasingly pressing environmental concern. On an annual scale, the monthly average O₃ concentration in 2023 displayed a “clear single-peak” pattern, reaching its maximum in June, at a concentration of 139 μg/m³. In contrast, the monthly average NMHC concentration exhibited a “distinct double-peak” pattern, with elevated levels in January and December, at 59.4 and 48.35 μg/m³, respectively. From an hourly perspective, the highest O₃ concentrations across the 13 cities occurred between 11:00 and 17:00, while NMHC concentrations showed an opposite trend. Furthermore, during the heating season (October to April of the following year), O₃ and NMHC concentrations increased by 0.78 and 1.56 times, respectively, compared with the non-heating season. In terms of ambient air quality levels, both O₃ and NMHC concentrations exhibited a gradual upward trend under conditions of “excellent”, “good”, and “light pollution”. However, under “moderate pollution”, “heavy pollution”, and “severe pollution” levels, O₃ and NMHC concentrations exhibited irregular patterns, likely due to the interaction of multiple complex factors. O₃ pollution follows a “central concentration and peripheral diffusion” pattern, reflecting the combined influence of human activities and natural conditions. In contrast, NMHC concentrations display pronounced spatial heterogeneity, with low levels in the west and high levels in the east, primarily driven by regional differences in industrial structure and environmental conditions. In summary, this study aims to elucidate the spatiotemporal distribution characteristics of O₃ and NMHC pollution in Heilongjiang Province and their complex relationship with air quality levels, providing a scientific basis for future pollution prevention and control strategies. Subsequent research should focus on identifying the underlying causes of pollution to develop more precise and effective mitigation measures, thereby continuously improving ambient air quality in the province. Full article

Land surface temperature (LST) is a key indicator reflecting the ecological environmental disturbance caused by open-pit coal mining activities and determining the ecological status in alpine permafrost regions. Thus, it is crucial to study the spatiotemporal variations and influencing mechanisms of LST throughout all stages of small-scale mining–large-scale land surface damage–ecological restoration. Landsat imagery over nine periods was extracted from the growing seasons between 1990 and 2024. This study retrieved LST while simultaneously calculating albedo, soil moisture, and normalized difference vegetation index (NDVI) for each time phase. By integrating land use/cover (LUCC) data, the spatiotemporal evolution patterns of LST in the mining area throughout all stages were revealed. Based on the Geodetector method, an identification approach for factors influencing LST spatial differentiation was established. This approach was applicable to the entire process characterized by significant land type transitions. The results indicate that the spatiotemporal variations in LST were significantly correlated with land surface damage and restoration caused by human activities in the mining area. With the implementation of ecological restoration, high and ultra-high temperatures decreased by about 25.98% compared to the period when the surface damage was the most severe. The main influencing factors of LST differentiation were identified for different land use types, i.e., natural and restored meadows (soil wetness, albedo, and NDVI), mine pits (albedo, aspect, and elevation), and mining waste dumps (aspect and albedo before restoration; aspect and NDVI after restoration). This study can provide a reference for monitoring the ecological environment changes and ecological restoration of global coalfields with the same climatic characteristics. Full article

From the perspective of “dynamic supply–demand coordination,” this study evaluates the development level of China’s economic “dual circulation” across 30 provinces during 2001–2020. Employing Kernel density estimation, natural breakpoint method, and exploratory spatial–temporal data analysis (ESTDA), we provide a comprehensive examination of the spatiotemporal evolution and developmental dynamics of China’s “dual circulation” economy. Furthermore, a nested matrix linking the quantile response types of driving factors with spatiotemporal transition types is constructed to uncover the mechanisms underlying these transitions, in order to form a unified understanding of the significance of China’s implementation of the economic “dual circulation” strategy against the background of high-quality development and lay a solid theoretical foundation for the empirical measurement of China’s economic “double circulation”. The results reveal the following: (1) Despite the “dual circulation” development level of Chinese provinces steadily improving over time, a marked east-to-west gradient of regional imbalance remains; (2) The spatial correlation of the “dual circulation” development level across provinces is significant, with changing trends influenced by neighboring provinces, showing both “concentration” and “differentiation” characteristics; (3) The spatial agglomeration trend of China’s “dual circulation” economy continues to strengthen, with distinct characteristics of “high rigidity + low mobility.” The low mobility of provinces locked in low-level spatial patterns will become a key limiting factor for their overall transition; (4) The quantile response types of the driving factors for the “dual circulation” development level in each province exhibit nest ability with their spatiotemporal transition types. The driving and constraining patterns of various driving factors coexist and interact. Full article

Against the backdrop of global warming and intensified anthropogenic activities, groundwater reserves are rapidly depleting and facing unprecedented threats to their long-term sustainability. Consequently, investigating groundwater reserves is of critical importance for ensuring water security and promoting sustainable development. This study takes the Heilongjiang (Amur) River Basin as the research area. Groundwater storage was estimated using data from the Gravity Recovery and Climate Experiment (GRACE) satellite and the Global Land Data Assimilation System (GLDAS) covering the period from 2002 to 2024. A combination of Random Forest (RF), SHapley Additive exPlanation (SHAP) models, and Pearson partial correlation coefficients was employed to analyze the spatiotemporal evolution characteristics, driving mechanisms, and spatial linear correlations of the primary influencing factors. The results indicate that the basin’s groundwater storage anomaly (GWSA) exhibits an overall declining trend. GWSA is influenced by multiple factors, including climatic and anthropogenic drivers, with temperature (TEM) and precipitation (PRE) identified as the primary controlling variables. Spatiotemporal analysis reveals significant spatial heterogeneity in the relationship between GWSA evolution and its primary drivers. This study adopts a “retrieval–attribution–spatial analysis” framework to provide a scientific basis for enhancing regional groundwater security and supporting sustainable development goals. Full article

The Cretaceous marks the peak of magmatic activity in southeastern (SE) China, which is attributed to the subduction of the paleo-Pacific plate beneath the South China Block. This region constitutes a significant igneous belt along the active continental margin of the western Pacific. Despite extensive research, the origin and evolution of Cretaceous felsic volcanic rocks are still debated. This study investigates the characteristics of zircon U-Pb-Hf isotopes and trace elements, and whole-rock geochemistry of Cretaceous volcanic rocks from the Wenzhou–Taizhou region in SE Zhejiang, and discusses their spatio-temporal patterns and petrogenesis. The results indicate that rhyolitic volcanic rocks formed during the period ca. 114 Ma and 95 Ma, representing two distinct magmatic episodes spanning the transition from the late Early to early Late Cretaceous. The late Early Cretaceous and early Late Cretaceous volcanic rocks are of a hybrid crust–mantle origin, as evidenced by their distinct Nb/Ta ratios, zircon ε_Hf(t) values, and variable trace element enrichments (Ti, Hf, U, Nb, and Yb). These compositional signatures suggest partial melting of late Paleoproterozoic to early Mesoproterozoic basement materials, with increasing mantle contributions over time. Both volcanic phases exhibit elevated Nb/Yb, Th/Nb, and U/Yb ratios, indicating a subduction-modified source akin to arc magmas. Together with calculated initial melt temperatures (<800 °C for Early Cretaceous, >800 °C for Late Cretaceous) and whole-rock rare-earth elements (REEs) distribution patterns (U-shaped with δEu = 0.37–0.65, seagull-shaped with δEu = 0.19–0.62, respectively), it is suggested that both phases of the volcanic magmas were generated through water-assisted (hydrous) melting, whereas the later phase formed at relatively higher temperatures and with a diminished water contribution via dehydration melting under extensional conditions. The generation of voluminous high-silica magmas in the SE China coastal region is probably linked to the rollback and retreat of the paleo-Pacific plate. Full article

Amid the global energy transition, geothermal energy, as a clean, stable, and renewable energy source, serves as a core direction for energy structure optimization. The development of medium-deep geothermal reservoirs is dominated by thermo–hydro–mechanical (THM) multi-physics coupling effects, yet the quantitative regulation laws of their operational parameters remain unclear. In this study, a numerical model for geothermal extraction considering THM multi-physics coupling was established. Using the single-factor variable method, simulations were conducted within the set parameter ranges of injection–production pressure difference, well spacing, and injection temperature. The spatiotemporal evolution characteristics of the temperature field, the dynamic temperature–pressure responses at the midpoint of injection–production wells and production wells, and efficiency indicators, such as instantaneous heat extraction power and cumulative heat extraction, were analyzed and quantified. The results show that a larger pressure difference accelerates the expansion of the cold zone in the reservoir, which improves short-term heat extraction efficiency but increases the risk of long-term thermal depletion; a smaller well spacing leads to higher initial heat production power but results in lower long-term cumulative heat extraction due to rapid heat consumption; within the normal temperature range of 16–24 °C, the injection temperature has a negligible impact on heat extraction efficiency. This study clarifies the regulatory laws of operational parameters and provides theoretical support for well pattern design and injection–production process optimization in medium-deep geothermal development. Full article

Long-term positioning tests can systematically reveal the evolution characteristics of soil fertility and crop productivity, and reflect the spatiotemporal changes in soil quality and their driving factors. While soil microorganisms mediating nutrient cycling are crucial for maintaining crop productivity and the long-term resilience of agricultural ecosystems, how prolonged use of different fertilization strategies affects their functional capacity remains insufficiently understood. In this study, we applied metagenomic sequencing to investigate how three fertilization treatments, namely (i) N0 receiving only phosphorus (P) and potassium (K) fertilizers, (ii) N250 receiving conventional urea + P and K, and (iii) F250 receiving humic acid urea + P and K, influence soil microbial communities, functional genes related to C and N cycling, and associated soil properties in a long-term field experiment. The F250 treatment significantly increased average annual yields of wheat and maize to 7166.21 kg hm⁻² and 8309.96 kg hm⁻², respectively. These values were 148.66% and 73.47% higher than those under N0, and 8.22% and 11.64% higher than those under N250. Compared with N0, both N250 and F250 signally augmented soil nitrate, ammonium, total nitrogen (TN), and soil organic carbon (SOC), altered microbial community composition, and enhanced the relative abundance of genes engaged in C fixation and methane oxidation. Both treatments also promoted denitrification and dissimilatory nitrate reduction to ammonium (DNRA). Relative to N250, F250 specifically enriched the beneficial bacterial genus Pedobacter, further increased the abundance of the C fixation gene pccA, and markedly upregulated the DNRA gene nrfA. Soil TN and SOC were identified as the key environmental factors regulating microbial community structure and the functional potential of C and N cycling pathways. Collectively, our findings provide a mechanistic understanding of how long-term application of humic acid urea enhances crop productivity by modulating the genetic potential of soil microorganisms in biogeochemical cycles, offering a biological foundation for optimizing fertilization strategies in sustainable agriculture. Full article

Partial discharge serves as a typical indicator of insulation defects in high-voltage electrical equipment and is often accompanied by acoustic emission. The online monitoring of partial discharge via acoustic signals makes it essential to investigate the underlying mechanism of acoustic wave excitation by partial discharge. However, experimental investigation is often prohibitively expensive and struggles to capture key discharge parameters. Numerical simulation thus provides a valuable alternative for microscopic analysis. In this study, a typical needle-plane corona discharge model is employed. Based on the theory that acoustic waves are generated by gas disturbances caused by collisions between charged and neutral particles in weakly ionized gases, a numerical model for acoustic wave excitation by positive corona discharge is developed. Simulations and analyses are performed on the acoustic source characteristics and the acoustic field distribution. The results demonstrate that the spatiotemporal evolution of electron density plays a dominant role in the generation of acoustic waves during positive DC corona discharge. The characteristics of the simulated acoustic field agree well with experimental results from relevant studies, validating the effectiveness of the proposed electroacoustic coupling numerical model and providing a new tool for further research into the acoustic features of partial discharge. Full article

Understanding the interactions among ecosystem services (ESs) and their spatiotemporal dynamics is pivotal for sustainable ecosystem management, particularly in arid regions where water scarcity imposes significant constraints. This study focuses on the Ili River Valley, a representative arid region, to investigate the evolution of ESs, their trade-offs and synergies, and the underlying driving mechanisms from a water-resource-constrained perspective. We assessed five key ESs—soil retention (SR), habitat quality (HQ), water purification (WP), carbon sequestration (CS), and water yield (WY)—utilizing multi-source remote sensing and statistical data spanning 2000 to 2020. Employing the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model, Spearman correlation analysis, Geographically Weighted Regression (GWR), and the Geodetector method, we conducted a comprehensive analysis at both sub-watershed and 500 m grid scales. Our findings reveal that, except for SR and WP, the remaining three ESs exhibited an overall increasing trend over the two-decade period. Trade-off relationships predominantly characterize the ESs in the Ili River Valley; however, these interactions vary temporally and across spatial scales. Natural factors, including precipitation, temperature, and soil moisture, primarily drive WY, CS, and SR, whereas anthropogenic factors significantly influence HQ and WP. Moreover, the impact of these driving factors exhibits notable differences across spatial scales. The study underscores the necessity for ES management strategies tailored to specific regional characteristics, accounting for scale-dependent variations and the dual influences of natural and human factors. Such strategies are essential for formulating region-specific conservation and restoration policies, providing a scientific foundation for sustainable development in ecologically vulnerable arid regions. Full article

High-resolution meteorological satellite cloud imagery plays a crucial role in diagnosing and forecasting severe convective weather phenomena characterized by suddenness and locality, such as tropical cyclones. However, constrained by imaging principles and various internal/external interferences during satellite data acquisition, current satellite imagery often fails to meet the spatiotemporal resolution requirements for fine-scale monitoring of these weather systems. Particularly for real-time tracking of tropical cyclone genesis-evolution dynamics and capturing detailed cloud structure variations within cyclone cores, existing spatial resolutions remain insufficient. Therefore, developing super-resolution techniques for meteorological satellite cloud imagery through software-based approaches holds significant application potential. This paper proposes a Multi-scale Residual Deformable Attention Model (MRDAM) based on Generative Adversarial Networks (GANs), specifically designed for satellite cloud image super-resolution tasks considering their morphological diversity and non-rigid deformation characteristics. The generator architecture incorporates two key components: a Multi-scale Feature Progressive Fusion Module (MFPFM), which enhances texture detail preservation and spectral consistency in reconstructed images, and a Deformable Attention Additive Fusion Module (DAAFM), which captures irregular cloud pattern features through adaptive spatial-attention mechanisms. Comparative experiments against multiple GAN-based super-resolution baselines demonstrate that MRDAM achieves superior performance in both objective evaluation metrics (PSNR/SSIM) and subjective visual quality, proving its superior performance for satellite cloud image super-resolution tasks. Full article

Population mobility links cities, propelling the spatiotemporal spread of urban pandemics and adding complexity to disease dynamics. It also closely shapes, and is shaped by, the selection and intensity of intervention measures. Revealing the multistage spatial-temporal dynamics of cross-regional epidemic continuity under this interaction is often overlooked but critically important. This study innovatively applies a self-organizing map (SOM) neural network to classify cities into six distinct types based on population mobility characteristics: high-inflow core (HIC), low-inflow core (LIC), low-inflow sub-core (LISC), high-outflow semi-peripheral (HOSP), equilibrious semi-peripheral (ESP), and low-outflow peripheral (LOP). Building on this, we propose a novel SEIR-AHQ theoretical framework and construct an epidemiological model using network-coupled ordinary differential equations (ODEs). This model captures the dynamic interplay between inter-city population mobility and intervention measures, and quantifies how heterogeneous city types shape the evolution of epidemic transmission across the coupled mobility network. The results show that: (1) Cities with stronger population mobility face significantly higher infection risks and longer epidemic durations, characterized by “higher peaks and longer tails” in infection curves. HIC cities experience the greatest challenges, and LOP cities experience the least. (2) Both higher transmission rates and delayed intervention timings lead to exponential growth in infections, with nonlinear effects amplifying small changes disproportionately. (3) Intervention efficacy follows a “diminishing marginal returns” pattern, where the incremental benefits of increasing intervention intensity gradually decrease. This study offers a novel perspective on managing interregional epidemics, providing actionable insights for crafting tailored and effective epidemic response strategies. Full article

Water and soil resources (WSRs) determine the healthy development of the socio-economic systems. This research seeks to clarify the spatiotemporal evolution characteristics, spatial spillover effects, and key constraint factors influencing the comprehensive carrying capacity (CCC) of WSR in the Yellow River (YR) Basin from 2012 to 2023, thereby supporting the healthy development of the river basin. Based on the structural relationships among the internal elements of this system, the entropy method and an extensible cloud model are employed in this study to evaluate the WSR-CCC. Based on the estimation theory and spatial econometrics methods, the temporal and spatial evolution process of WSR-CCC was explored, and the obstructive factors were analyzed. We made the following discoveries: (1) The WSR-CCC demonstrates a fluctuating upward tendency, gradually moving from critical overload level IV to sustainable level II, but inter-provincial disparities expand. (2) The spatial pattern exhibits a gradient of higher levels in the western region, lower levels in the eastern region, stronger intensity in the northern region, and weaker intensity in the southern region, with weak spatial correlation. However, the spatial spillover effect is significant, with club convergence and the Matthew effect coexisting. (3) The obstacle factors exhibit a drive–influence–state three-stage dominant characteristic. The findings provide actionable insights for coordinating WSR optimization and ecological conservation. Full article