Environmental Earth Sciences最新文献

Soil salinization is a major threat to agricultural sustainability in arid and semi-arid regions, leading to the progressive loss of fertile land. The irrigated El Habibia–Mansoura zone in the Mejerda low valley (NE Tunisia) is highly affected by salinity due to drought, dam construction, poor irrigation water quality, and insufficient drainage. This study employed Google Earth Engine (GEE) machine-learning algorithms to map and monitor soil salinity over a 24-year period (2000–2023). Landsat imagery was processed using positively correlated salinity indices (SI), Shuttle Radar Topography Mission (SRTM) data, negatively correlated indices such as NDVI and Iron Index (IIn), MODIS-derived climatic features, and ground control measurements. A Support Vector Machine (SVM) model achieved robust predictive performance (R² = 0.82; RMSE = 1.34). Results reveal strong spatio-temporal variability in salinity, with the most pronounced peak between 2010 and 2015, when 46.72% of the area was moderately saline and 1.92% highly saline, reflecting high evapotranspiration and low precipitation. Extremely saline soils, although limited in extent, showed a gradual but consistent increase from 0.03% in 2000–2005 to 0.12% in 2020–2023. Iron nutrient availability sharply declined after 2013, correlating negatively with salinity, while alkaline pH (> 7) and high Na⁺ and Cl⁻ contents further constrained soil fertility. These findings confirm that salinity dynamics are driven by both climatic and anthropogenic factors, including irrigation practices, groundwater salinity, and land management. Remote sensing integrated with machine learning offers reliable monitoring tools, providing essential decision-support for sustainable land management and food security in Tunisia and worldwide.

With the increase of coal mining depth, high gas pressure, high ground temperature, and high osmotic pressure have significantly changed the characteristics of coal and rock, promoting the evolution of low-gas non-spontaneous combustion coal seams to high-gas spontaneous combustion-prone coal seams. In this paper, through building a physical simulation experimental platform, conducting low-temperature liquid nitrogen and scanning electron microscope experiments, the influence law of adsorbed gas on the pore structure and oxidation characteristics of coal under the coupling effect of temperature and pressure was systematically studied. The research shows that: (1) The increase of pre-adsorption temperature inhibits adsorption, while the increase of pre-adsorption pressure promotes adsorption, and the two have a synergistic effect on the adsorption performance of coal. (2) The adsorption isotherms of raw coal samples and coal samples pre-adsorbed with gas belong to type Ⅱ, and the adsorption hysteresis loops belong to type H3. Adsorbed gas regulates the structural evolution by occupying pore space and supporting. The increase of temperature promotes desorption and softening of the pore wall, and the increase of pressure causes coal compression or fracture. Gas temperature, pressure and adsorbed gas jointly control the dynamic evolution of the pore structure. (3) Adsorbed gas significantly inhibits the spontaneous combustion process of coal through diluting the oxygen concentration and endothermic effect. At the same time, during the heating and oxidation process of coal with low adsorbed gas content, the concentrations of CO and C₂H₄ are higher, and the risk of spontaneous combustion is greater. This study innovatively reveals the variation laws of the pore structure and oxidation characteristic parameters of coal samples in different temperature and pressure gas environments, providing an optimization direction for the prevention and control measures of the combined disasters of gas and coal spontaneous combustion in goafs.

The development of shale oil and gas resources has emerged as a pivotal trend in the global energy sector. Among the advanced reservoir stimulation techniques,the injection of carbon dioxide (CO₂) has gained prominence for its potential to optimize fracturing treatment and enhance oil and gas recovery. This study investigates the effects of CO₂, slickwater, guar gum, and their composite fracturing fluids on the mechanical and fracture properties of bedding-developed shale and laminated shale. Among the fluids tested, CO₂ caused the smallest reduction in tensile strength, by 12.42% in bedding-developed shale and 29.38% in laminated shale, compared to slickwater and guar gum, which cause reductions of 42.21%–45.63%. When combined with water-based fluids, CO₂ mitigates tensile strength reductions to 16.94%–32.51%. CO₂ treatment reduces compressive strength by 28.84%, less than the 52.55% reduction caused by slickwater. Laminated shale treated with CO₂ and slickwater achieves higher fracture complexity, with a fractal dimension of 2.5. Fractal dimension analysis underscores the capacity of CO₂, both as a standalone treatment and in combination with guar gum, to enhance fracture complexity, with increases of 4% to 8.7% compared to water-based fracturing fluids. Fracture energy analysis demonstrates CO₂’s high energy efficiency, making it suitable for low-permeability reservoirs. A comprehensive evaluation indicates that CO₂ fracturing is optimal for bedding-developed shale, while laminated shale benefits more from CO₂ combined with slickwater. These findings offer valuable insights for optimizing fracturing designs in shale oil reservoirs, advancing the efficacy and sustainability of resource exploration technologies.

When the PIM (Probability Integration Method) was applied to predicting surface subsidence for grouted backfill mining with overlying thick loose layers, it resulted in reduced accuracy, and the predicted values converged too rapidly at the edge of the subsidence basin. As a case study, this paper focuses on surface subsidence in grouted backfill mining at working face 1076 of Yangliu Coal Mine in the Huaibei Mining District. According to the principle of transferring the subsidence of grouted backfill mining, this study treated the bed separation cavity in the overburden strata as a semi-ellipsoid. It proposed an improved method for calculating the subsidence coefficient q in the PIM prediction model and established the surface subsidence dynamics prediction model called SEDC-Boltzmann (Semi-Ellipsoid Delamination Cavity-Boltzmann). The model was used for the dynamic prediction of surface subsidence in the grouting working face 1076 during the mining and grouting period. The prediction results were consistent with the monitored values from SBAS-InSAR (Small Baseline Subsets Interferometric Synthetic Aperture Radar) technology and leveling measurements. This model overcomes the flaw of predicted values converging too rapidly at the edge of the subsidence basin. Its prediction accuracy improved by 16.5% compared to the IDPIM (Improved Dynamic Probability Integral Method) model and by 33.1% compared to the PIM model. Therefore, the SEDC-Boltzmann model proposed in this paper holds significant potential for predicting and evaluating geological hazards in mining areas.

The Stampriet Transboundary Aquifer System (STAS) is one of the well-investigated shared watercourses on the continent of Africa, located in the most arid region of southern Africa. It is the only permanent water source in the Stampriet Basin shared between Namibia, Botswana, and South Africa. However, in recent years, mineral resources exploration in the Stampriet basin has intensified, resulting in the discovery of an economic uranium ore body located in the second aquifer of the STAS called the Auob Aquifer. Uranium extractions will be conducted using the in situ leach mining technology, which is amenable to low-grade uranium deposits in saturated aquifers. In situ leaching for uranium will be the first of its kind in Namibia and has raised major concerns about possible groundwater contamination. This study will use mathematical models to simulate the spread of the contamination plume resulting from the kinetic reaction of the sulfuric acid with the uranium ore. For this, a mathematical model replicating the kinetic reaction between the UO₃ and the sulfuric acid was suggested and solved numerically using the Runge–Kutta method. The numerical solutions were depicted for 8 h. The condition of the existence of a unique 3-solution was presented. Partial differential equations for the transport of the uranyl sulfate, with linear and nonlinear iron exchange and multiple reactions, taking into account a fault, were proposed. These equations were solved numerically using the upwind numerical scheme. Suitable initial and boundary conditions were selected for the fault’s position to perform simulations. The numerical simulations suggest a possible rapid spread of uranyl under the condition that the solution escapes via the extraction boreholes. To our readers, we stress the fact that this study presents a scenario-based modeling framework, using hypothetical yet realistic assumptions, to evaluate potential risks of ISL operations under a range of plausible but unverified conditions.

The occurrence of mine floor water inrush accidents is mostly related to faults, i.e., water inrush accidents occur in impermeable faults in the natural state under the influence of factors such as mining and water pressure. Under the action of high water pressure in a fault fractured rock mass, the characteristics of the fault activation are not clear and definite, and the system of evaluating tectonic water inrush hazards under deep geological conditions has not yet been perfected. A typical reverse fault was used as the research background to conduct in situ water injection tests in two sites of this fault to explore the in situ hydraulics and permeability properties of the rock mass. During the testing of the fault rock’s permeability during three stages of change, the high-pressure fluid caused fracture expansion, resulting in a significant increase in the permeability of the rock mass. In addition, in different locations in the same fault, in the difference in the permeability is large.The research results show that the fault is a broken fracture rock type characterized by obvious anisotropy and heterogeneity. The results of this study increase our understanding of the permeability changes in tectonically fractured rocks under high water pressure and have guiding significance to practical coal mine production.

Understanding regional hydroclimatic patterns is essential for managing water resources and ensuring agricultural sustainability in rain-fed areas under changing climate conditions. The intensifying effects of climate change on rain-fed agriculture in India necessitate a comprehensive understanding of the precipitation dynamics and groundwater recharge patterns. This study strives to evaluate the relationship in 11 districts of Jharkhand between 2001 and 2020 using rainfall and ground water level data collected from Indian Meteorological Department (IMD) and Central Ground Water Board (CGWB), Ranchi respectively. Rainfall data analysis reveals significantly positive and negative trends in pre-monsoon, monsoon, and post-monsoon across districts. Pre-monsoon rainfall ranged from 25 to 175 mm, monsoon from 650 to 1250 mm, and post-monsoon from 20 to 120 mm, with higher values in Simdega, Lohardaga, and Latehar, and lower values in Garhwa and Palamu. The Mann-Kendall test indicated negative rainfall trends in 7 out of 11 districts, with Sen’s slope values declining up to − 6.8 mm/year, especially in eastern and northern Jharkhand. Pre-monsoon groundwater levels varied between 2 and 18 m, with declining trends in Palamu, East Singhbhum, and Khunti, while positive trends (Sen’s slope up to 0.21 m/year) were observed in Simdega and Ranchi. In the post-monsoon period, six districts such as Simdega, Latehar, Gumla, Ranchi, West Singhbhum, and Saraikela Kharsawan, exhibited positive trends, whereas Garhwa and East Singhbhum showed declines of − 0.12 to − 0.17 m/year. Addressing these hydroclimatic challenges in Jharkhand requires region-specific strategies, such as rainwater harvesting, efficient irrigation methods, and localized groundwater management to mitigate water stress, sustain agriculture, and enhance resilience to climate variability.

This study presents a risk-based approach for mapping gully erosion susceptibility in the Jhang-Ping and Ping-Lin River watersheds of Taiwan. The study used six key conditioning indicators: rainfall, curve number, slope, topographic wetness index, distance to rivers, and distance to roads. Unlike the majority of recent studies that have relied on machine learning, this study used a simplified hazard–vulnerability framework, aiming to provide a transparent, interpretable, and cost-effective assessment tool. The model’s performance was validated on data from 21 field-surveyed gully sites. The model achieved an overall accuracy of 85.71%, a Kappa coefficient of 0.67, and an area under the receiver operating characteristic curve of 0.85. These results confirm the model’s robustness and practical applicability in terrain-based gully risk identification. Moreover, the proposed model offers straightforward management implications: high-risk zones (Levels 1 and 2) are recommended for engineering interventions, and lower-risk zones (Levels 3 and 4) may benefit from ecological stabilization measures. The proposed framework provides a valuable alternative to black-box algorithms, especially for regions with limited data availability or field resources, and contributes to bridging the gap between empirical erosion modeling and land management planning.

The chemical corrosion environment significantly affects the mechanical properties and fissure evolution of fissured rocks, which is vital for understanding rock mass instability and ensuring the safety of underground engineering projects. Uniaxial compression tests on double-fissured rocks with varying fissure thicknesses under chemical corrosion were conducted to analyze mechanical behavior in different chemical environments. Particle flow simulation software (PFC2D) and acoustic emission technology were used to study fissure evolution, acoustic emission, and damage characteristics. The results show that, for a given fissure thickness, higher acid concentrations reduce peak stress and compressive strength. At constant pH values, smaller fissure thicknesses lead to higher peak stress and compressive strength. The elastic modulus follows a “V”-shaped trend with changes in chemical environment and fissure thickness. Tensile failure is the primary failure mode, with shear failure occurring secondarily. As fissure thickness increases, failure shifts from tensile wing cracks to reverse tensile wing cracks. In acidic environments, the damage variable (D) increases with factors such as acid concentration, exposure time, and mineral composition. Larger fissure thicknesses intensify stress concentration, accelerating crack propagation and reducing strength and modulus. This study provides insights for mitigating safety risks in underground rock mass engineering.