Environmental Earth Sciences最新文献

In the field of landslide susceptibility, the utilization of data driven methodologies has seen a significant breakthrough. However, the performance of the models depends on the geo-environmental factors, and the selection of factors vary from one location to another, and this leads to a persistent lacuna for the present exploration. This study was aimed to assess landslide susceptibility for Darjeeling hills in Eastern Himalayan region with sixteen causative geo-environmental factors. The selection of causal factors was performed through a two-stage procedure, namely Pearson’s correlation coefficient (PCC) and Boruta algorithm (PCC-BA). The dataset associated with the research was split randomly into 70:30 ratio for train and test data. In addition, 30% of the training data was taken as validation dataset. Four advanced data-driven models namely K-nearest neighbour (KNN), Boosted Tree (BT), Gradient Boosting Machines (GBM) and ensembled Neural Network with Principal Component Analysis (PCA-NN) were taken up and four advanced novel ensembles namely KNN-BT, PCA-NN-BT, GBM-KNN and GBM-PCA-NN were constructed. The susceptibility maps were grouped into five divisions, viz., very low (VL), low (L), medium (M), high (H), and very high (VH) susceptibility. Through area under receiver operation characteristics curve, the accomplishment of constructed susceptibility models was substantiated with training, testing and validation dataset, where KNN-BT attained 0.943, 0.889 and 0.944 respectively, PCA-NN-BT attained 0.934, 0.876 and 0.943 respectively; GBM-KNN attained 0.959, 0.897 and 0.957 respectively; and GBM-PCA-NN attained 0.956, 0.889 and 0.962 respectively. The researchers have utilized an extensive explainable artificial intelligence (ex-AI) method, partial dependence profile (PDP) to quantify the effect of causal factors on all the four ensembled models. The study was aimed to demonstrate a significant capacity to substantially optimize disaster mitigation policies with a constituent endeavour to bridge the chasm between contemporary machine learning approaches and geo-spatial applications, and thereby paving the way to enhance the resilience of inhabitants in landslide prone areas of hilly portion of Darjeeling district.

The salt lakes in arid deserts serve as crucial ecological resources and tourist attractions. However, due to the limitations of aeolian sand cover, it is challenging to directly investigate the underground contact relationship between lake water and groundwater. In the Badain Jaran Desert (BJD) of China, the fresh groundwater near salt lakes is the sole source of drinking water. Consequently, a pressing concern arises regarding how groundwater exploitation impacts the intrusion of salt water into groundwater. In this study, Lake Cherigele (CRG) was chosen as a case to investigate the characteristics and migration mechanisms of the saltwater-freshwater interface using numerical simulation methods. The results reveal that: (1) The saltwater-freshwater mixing zone exhibits a wedge-shaped morphology, with a length of 250 to 290 m and a depth ranging from 50 to 70 m within the model. (2) The hydrodynamic conductivity coefficient (K) of the sand layer and molecular diffusion coefficient (D_m) in the desert are identified as the primary parameters influencing the characteristics of the interface. (3) The annual fluctuations in the current groundwater level have a limited impact on the saltwater-freshwater interface; however, excessive groundwater exploitation can lead to the intrusion of salt water into freshwater body. (4) The density difference between groundwater and lake water results in the concentration of groundwater flow lines around the lake, giving rise to the numerous springs observed in the field.

This paper presents a statistical analysis of water table depth fluctuations in the Ghahavand plain of Hamedan province, western Iran. The study is based on 49,232 water table depth records collected by the Hamedan regional water authority between October 1988 and March 2016. The data were processed to improve their quality and construct a monthly time series of water table depth. Singular Spectrum Analysis (SSA), a non-parametric technique for time series analysis, was used to analyze the time series. Exponentially Weighted Moving Average (EWMA) was applied to the residuals of the SSA model to monitor management policies and institutions. The EWMA control chart is an effective alternative to the Shewhart control chart when the goal is to detect smaller shifts in the process. One of the key advantages of using EWMA is its robustness to non-normality, making it suitable for real-world applications where data often deviates from the normal distribution. The results indicate that the SSA model fits the data very well. Using EWMA control chart on the residuals of the SSA model revealed three statistically unusual points that need to be examined by water resource management systems. The findings of this study can assist water resource managers in making informed decisions regarding groundwater management policies and practices.

To enhance existing theoretical frameworks previously confined to predicting surface subsidence for individual salt caverns, this study introduces an advanced model based on the stochastic medium theory. This innovative approach integrates the principle of displacement superposition and formulates equations for estimating surface settlements of twin salt caverns with varied cross-sectional geometries. Comparative analysis of numerical data reveals a high congruence between surface settlements derived from our model and those predicted by numerical results for twin salt caverns. Distinct from the conventional symmetrical 'single valley' subsidence profile associated with a solitary salt cavern, this model adeptly depicts the asymmetric 'double valley' topography characterizing twin salt caverns with diverse cross-sectional shapes. The burial depth and horizontal spacing of twin caverns significantly affect both the maximum influence radius and maximum settlement value. Conversely, the vertical spacing and dimensions of the twin caverns predominantly impact the surface settlement of each individual cavern. Critically, the inter-cavern center distance emerges as a pivotal factor in transitioning the subsidence profile from a 'double valley' to a 'single valley' configuration. This study provides scientific decision-making support for the long-term safe operation of energy storage salt caverns and the conservation of land resources.

Greenspaces are crucial in enhancing the standard of living, environmental sustainability, and overall well-being of urban populations. It serves the goal of providing thermal comfort, restoring the environment’s ecological balance, and climatic modification within the urban fabric. However, allocating and distributing these valuable resources often involve complex environmental, social, economic, and spatial considerations. Factors like built-up density, land use, land cover, slope, and distance from roads, greenspaces and water bodies have been adopted as the criterion for the site suitability of green space. This paper proposes a structured approach using these factors that integrates quantitative analyses and advanced spatial modelling to guide informed decisions, foster inclusivity, and optimize the benefits of greenspace provisioning and distribution. The study employed a geographic information system (GIS) based Analytical Hierarchy Process (AHP) approach to determine the optimal locations for allocating greenspaces within urban planning. The study deeply analyzed the existing land use of Sikar city and found 47.23 ha of land parcels suitable for allocating greenspace based on the six factors mentioned above. The analysis reveals that, among the 49.23 hectares of suitable areas, 48% of the land parcels are less than 0.5 hectares in size. These parcels are predominantly unplanned and situated away from the city centre. There’s also a lack of the possibility of large green spaces in the city’s central area due to the non-availiability of vacant land. By synthesizing empirical data, case studies, and existing literature, this research paper outlines a robust methodology to support urban planners, policymakers, and stakeholders in making informed choices that promote sustainable urban development and a higher quality of life.

Water and mud inrush disasters are common disasters in tunnel engineering in karst areas. To study the evolution mechanism of seepage-stress field in tunnels when passing through karst caves, on-site investigation and numerical simulation methods are applied to analyze the evolution characteristics of water inflow, deformation of surrounding rock and lining mechanical performance during tunnel construction and operation. The results show that: As the excavation face of the tunnel approaches the karst area, the water inflow of the tunnel, the horizontal extrusion displacement of the excavation face and the range of the plastic zone rapidly increase, leading to a significant increase in the risk of water and mud inrush. Full section curtain grouting can effectively reduce the water inflow of karst tunnels and improve the stress environment of surrounding rock. As the thickness of the grouting circle increases, the deformation and plastic zone range of the surrounding rock decrease, the reduction ratio of the grouting circle to water pressure increases, and the tensile stress of the lining decreases. As the thickness of the waterproof rock slab in front of the excavation face gradually decreases, its waterproof effect gradually weakens, leading to an increase in water inflow, deformation and plastic zone. The maximum water inflow of the excavation face is 2.41 m³/h and the maximum horizontal extrusion displacement is only 2.6 mm when the thickness of waterproof rock slab is 6 m, which can effectively prevent water and mud inrush disasters. Increasing the density of drainage blind pipes can effectively reduce the water pressure of the lining. Compared with the blind pipe spacing of 10 m, the average water pressure of the lining decreases by 39.3%, and the maximum tensile stress of the lining decreases by more than 30% when the blind pipe spacing is 2 m. The research results can not only provide support for the study of the mechanism of water and mud inrush disasters in tunnels, but also provide useful references for tunnel construction in karst areas.

Humidity could significantly affect the failure morphology and characteristics of rock joints. This study experimentally investigated the effects of humidity on the mechanical behavior of saw-toothed sandstone joints. Various humidity conditions were created using the chemical thermodynamic vapor–liquid equilibrium principle, which is a non-contact and non-destructive humidity curing method. The rock joints were maintained under these humidity conditions for up to two months, followed by joint shear tests to assess the impact of water vapor on shear performance. The results show that rock joints are relatively more sensitive to humidity under higher normal stress. The second peak shear stress phenomenon occurs in saw-toothed joint samples with large asperity angle. For rock joints under the same normal stress, the greater the humidity the smaller the second peak shear stress. High humidity significantly influences the deformation behavior of sandstone joints by shortening the peak shear displacement and reducing joint dilation. Furthermore, under low and medium humidity, spalling occurs around asperities and cracks are not generated within the body of rock samples. In contrast, for rock joints subjected to high humidity, cracks are generated and extended within the joint body.

Microbial induced calcite precipitation is a commonly used technique for the application of biocementation. The metabolism of urea by ureolytic active bacteria leads, among other metabolic products such as ammonium, to carbonate ions. In the presence of calcium ions, calcium carbonate formation occurs. It was investigated whether the addition of different additives (Ca-bentonite, Na-bentonite, clinoptilolite, natrolite, limestone, marl clay, concresol, secursol, and activated carbon powder) can optimize this process. First, the influence of these additives on the adsorption rates and distribution of the ureolytic active organism Sporosarcina pasteurii in quartz sand columns was tested. Moreover, an investigation was conducted on the impact of various additives on ammonium immobilization to mitigate its leaching from soils subjected to the biocementation process. For eight additives uniaxial compressive strength tests in quartz sand columns and a storage method according to DIN EN 12390–2 were carried out. Each additive showed a characteristic adsorption and localisation progression. Furthermore, each additive was able to enhance the immobilization behavior of the present ammonium, with a maximum immobilization capacity of 10.76 (frac{mg (NH^+_4)}{g (additive)}). The uniaxial compressive strength of biocemented columns out of quartz sand could sectionally be increased by the addition of each additive. However, the storage methodology shows a much greater influence on column strength. Overall, the best results were achieved with the two additives, Ca-bentonite and clinoptilolite, resulting in strength increases in sand columns of up to 4.64 and 3.22 (frac{N}{mm^2}), respectively.

Groundwater resources are vital for human development, particularly in arid and semi-arid regions with limited water availability. This study examines the evolution of aquifer vulnerability in the Miranda basin by addressing the critical interaction between land use and water quality amidst increasing pressures on water resources, with a focus on the impact of historical land use changes and agricultural practices on groundwater quality in the Campo de Cartagena aquifer, which drains into the degraded Mar Menor coastal lagoon in southern Spain. To evaluate aquifer vulnerability, this research employs the DRASTIC vulnerability assessment method, which is based on seven hydrogeological parameters. This theoretical framework allows for a comprehensive analysis of the interactions between land use changes, water management, and aquifer health, which deepens the understanding of the factors driving vulnerability over time. A key component of the methodology is the use of the Soil and Water Assessment Tool (SWAT) to estimate aquifer recharge and generate reliable maps that depict this essential parameter. The study reveals significant results through an extensive analysis of vulnerability changes over the past 70 years, which shows that high vulnerability areas have increased from 11%, prior to the Tagus-Segura water transfer in 1979, to 53% today. In contrast, low and moderate vulnerability areas have decreased by 15% and 28%, respectively. This shift is primarily attributed to intensified agricultural practices, which lead to enhanced aquifer recharge and elevated piezometric levels, which increase contamination risks, as demonstrated by the severe eutrophication observed in the Mar Menor. Moreover, the accuracy of the vulnerability maps is validated by comparing them with observed nitrate concentrations in groundwater, which reveals a strong correlation (R² = 0.86). The methodology provides essential insights for policymakers and supports the implementation of land use restrictions to mitigate groundwater contamination risks. The findings ultimately underscore the necessity for integrated water management strategies that balance agricultural productivity with ecological sustainability in water-scarce environments.

Impact loading and exposure acidic mine water considerably influence the safety and stability of rock masses in coal mines during blasting and excavation. To investigate these effects, three different levels of impact tests were carried out on sandstone specimens exposed to five varying acidic drying-wetting cycles, utilizing a split Hopkinson pressure bar (SHPB) device. The pore structure of the sandstone specimens was analyzed by employing Image Pro Plus (IPP) software to segment Scanning Electron Microscope (SEM) images. The findings revealed that, under the same impact air pressure, the energy reflectivity and fractal dimension of the sandstone specimens increased as the frequency of acidic drying-wetting cycles increased. Conversely, the transmissivity, dissipation rate, dissipation energy density, and average fragment size decreased. Furthermore, as the impact air pressure increased, sandstone specimens exposed to identical acidic drying-wetting cycles showed an increased in energy reflectivity, dissipation rate, dissipation energy density, and fractal dimension, while transmissivity and average fragment size decreased. The primary failure modes observed in the sandstone specimens were splitting and crushing. The main pore types identified were micropores and mesopores, whose size and area increased with the frequency of acidic drying-wetting cycles increased.