Environmental Earth Sciences最新文献

The Karst groundwater system affected by coal-mining activities is complicated, hampering the sustainable management of groundwater resources. In this study, hydrochemical methods, multivariate statistical methods, and multi-isotope tracing techniques were integrated to clarify the genesis of the karst groundwater system in the Sichuan Basin, southwestern China. Three clusters of groundwater samples were identified in the study area. The hydrochemical type of Cluster I and Cluster II waters was mainly HCO₃-Ca type, and hydrochemical type of Cluster III water was dominated by HCO₃·SO₄-Ca type. The main processes dominating hydrochemical compositions consist of sulfide oxidative dissolution, carbonate dissolution, positive cation exchange, and human activities. The oxidation of sulfides exposed to air and water during coal mining is the primary source of the elevated SO₄²⁻ concentrations. Positive cation exchange resulted in higher Na⁺ concentrations, and agricultural activities added NO₃⁻, Cl⁻, and K⁺ ions to the aquifers. Atmospheric precipitation was the major recharge source. Groundwater is also influenced by evaporation and mineral dissolution. This study developed a hydrogeological conceptual model for the basin karst groundwater system within coal-mining activities. These findings provide valuable information for the sustainable development of karst groundwater resources.

Understanding long-term changes in Eco-Environment Quality (EEQ) is vital for managing arid ecosystems under increasing anthropogenic pressure and climate variability. This study investigated the spatio-temporal dynamics of EEQ in the Akarçay Closed Basin from 1985 to 2020. We utilized Landsat-5 TM and Landsat-8 OLI images processed on the Google Earth Engine (GEE) platform. To assess EEQ of the basin, The Remote Sensing Ecological Index (RSEI), constructed from greenness, wetness, heat (LST), and dryness (NDBSI) indicators, was computed at five-year intervals. Principal Component Analysis (PCA) was applied to derive RSEI, and Geographical Detector analysis was used to identify key natural and anthropogenic drivers. Results indicated that NDBSI and LST had the strongest influence on RSEI, with NDBSI emerging as the dominant indicator. RSEI values were lowest in 1990 (0.267) and 2000 (0.303), and highest in 2010 (0.417). A transition was observed from fair to moderate and good ecological classes between 1985 and 2020. Spatial heterogeneity in EEQ was largely shaped by temperature, land use/land cover, and population density. Furthermore, Hotspot analysis and the Mann-Kendall trend test were employed to examine the spatio-temporal consistency of the RSEI results, revealing persistent patterns of degradation and improvement. This study demonstrates the effectiveness of RSEI for long-term environmental monitoring and provides a comprehensive scientific basis for developing sustainable management strategies in arid basins.

Strong seismic events can induce co-seismic slope instability, and the subsequent rainfall can further aggravate the damage within accumulation landslides, posing compounded hazards. Understanding the multi-stage failure mechanisms and assessing the associated risks under sequential earthquake–rainfall conditions are vital for disaster prevention in seismic regions. This study focuses on the K3-H05 landslide along the Hailuogou Scenic Road, triggered by the 2022 Luding Earthquake. A simplified pre- and post-event landslide model was constructed based on UAV imagery, and the dynamic damage to the slope induced by seismic shaking was analyzed through the Limit Equilibrium Method (LEM) and the Newmark permanent displacement analysis. Coupled stress–seepage simulations, incorporating regional rainfall data, were employed to evaluate slope stability under post-seismic precipitation conditions. Moreover, the secondary instability process was simulated using the Finite Volume Method (FVM) incorporating (mu left( I right)) rheological constitutive model. The results indicate that seismic acceleration is amplified significantly at slope crests and the interface between loose accumulation layer and bedrock, with permanent displacement corresponding to “super high” risk level, consistent with field observations. The post-earthquake degradation of the soil structure, combined with sustained rainfall, reduced the slope safety factor below unity, substantially elevating the likelihood of secondary failure. The landslide subsequently destroyed portions of the scenic road and deposited substantial material at the slope toe. Based on the findings, post-disaster reconstruction strategies such as elevated bridges and piled slab walls are proposed to mitigate future risks. This research provides technical references for slope risk prevention and control in high-intensity seismic zones.

This study aimed to assess the impact of land use land cover (LULC) changes on soil loss (SL) and sediment yield (SY) using the Revised Universal Soil Loss Equation (RUSLE) model in the Angereb watershed. The 1991, 2001, 2011, and 2021 Landsat TM and OLI images were used for classification. Cover management (C) and conservation practice (P) factors of the RUSLE model were prepared for each LULC map. The other three RUSLE factors, such as slope length and steepness (LS), erosivity (R), and erodibility (K) factors, were prepared from digital elevation model (DEM), rainfall, and soil data, respectively. The sediment delivery ratio (SDR) and the SL maps were used to calculate the mean annual SY of the watershed. Results indicated that cultivated land expanded from 29.6% in 1991 to 42.6% in 2021 at the expense of forest and bush/shrubland. The change in LULC from 1991 to 2021 increased the mean annual SL and SY by 57% and 39%, respectively. The erosion rate increased from 107 t ha⁻¹ yr⁻¹to 134.3 t ha⁻¹ yr⁻¹ on cultivated land between 1991 and 2021. In the Angereb watershed, areas classified under very severe erosion (> 50 t ha⁻¹ yr⁻¹) cover 23.1% of the total area but contribute approximately 99.4% of the overall soil loss, predominantly occurring on steep slopes. These steeply sloped regions represent critical erosion risk zones and should be prioritized for targeted soil and water conservation interventions. The study’s findings offer valuable insights for evidence-based policymaking and the development of effective watershed management strategies.

The degradation of groundwater quality due to human activities and environmental changes has become a global challenge, especially in semi-arid regions that are highly dependent on these resources. This study presented a comprehensive mapping of Groundwater Quality (GQ) distribution in Northwest Iran, utilizing a combination of Deep Learning (DL) and Machine Learning (ML) algorithms alongside the Borda scoring method for validation. Based on research methodology, the study focused on a range of WQ parameters, including potassium (K⁺), sodium (Na⁺), magnesium (Mg²⁺), calcium (Ca²⁺), sulfate (SO₄²⁻), chloride (Cl⁻), bicarbonate (HCO₃⁻), pH levels, Total Dissolved Solids (TDS), and Electrical Conductivity (EC). After creating raster maps of the chemical parameters of GQ, critical and non-critical quality points were identified using the Borda scoring algorithm based on Game Theory (GT). Once these points were established, DL and ML algorithms were employed in Python to spatially map GQ. Finally, water quality classes were categorized into five levels—very low, low, moderate, high, and very high—using ArcGIS software. Key quantitative findings included Total Hardness (TH) values ranging from 2.06 mg/L in Abgharm to 31.92 mg/L in Hamid Bolaghi, and Sodium Adsorption Ratio (SAR) values between 0.1 and 1.89, indicating varying soil sodicity risks. Strong correlations were observed among specific ions, notably a correlation of 0.93 between Na⁺ and Cl⁻. Borda scoring highlighted significant groundwater concerns, with the highest score of 260 at sampling point 26, while points 21, 25, and 33 showed lower scores of 32, 39, and 70, respectively. Based on the results, LSTM emerged as the most effective model among the DL algorithms, exhibiting the lowest MAE (0.12) and MSE (0.02), along with a high R² value of 0.89 and an AUC of 0.94. Spatial zoning identified areas of very low GQ, particularly in the central and eastern regions, which necessitated targeted management interventions. This research underscored the effectiveness of combining ML and DL methodologies with scoring systems to enhance GQ assessments, thereby fostering improved water management practices in the region.

The hyporheic zone is an active ecotone between surface water and groundwater where strong biogeochemical reactions occur, and it underpins various ecosystem functions. In the 21st century, the hyporheic zone has become a research hotspot due to its important role in biogeochemical activities; however, no comprehensive and systematic review of the current literature on the hyporheic zone has been conducted. In this study, we conducted scientometric analysis of 2,308 articles related to the hyporheic zone in the Web of Science Core Collection database using CiteSpace. This article summarizes the literature on the hyporheic zone in the 21st century based on scientometric visualization, thoroughly capturing the recent developments in this field. In addition, we identified and quantitatively analyzed the top authors, publications, references, institutions, countries, and relevant disciplines. Based on the results, we clarify the current developments, research hotspots, and frontiers of research on the hyporheic zone. We also predict the future research trends in this field. This review provides a comprehensive knowledge framework that can provide a detailed and broad perspective on the status and future trends of this interdisciplinary field.

Lake Jackson in Florida, USA has experienced multiple lake dry-downs, in which the lake partially drained through sinkholes within the lakebed into the karstic Upper Floridan aquifer. This study focused on the lake dry-downs in 2021–2022 and investigated their impacts on groundwater geochemistry at a groundwater monitoring well about 9 km downgradient of the lake and at Wakulla Spring, a first-magnitude spring about 32 km downgradient of the lake. Major ion concentrations were measured for water samples collected at the lake, the monitoring well, and the spring throughout the dry-down occurrences to monitor hydrochemical changes over these events. Following the dry-down events, the hydrochemical facies at the monitoring well shifted from a calcium magnesium bicarbonate hydrochemical facies to a mixed type hydrochemical facies, followed by a return to the original hydrochemical facies within eight days. A three end-member mixing model between meteoric water, water reacting with minerals in the lakebed formation, and aquifer water suggests that a pulse of lake water diluted the calcium carbonate-rich aquifer water and transported ions from weathered minerals in a confining unit below the lakebed. These chemical impacts were not observed at Wakulla Spring, suggesting that the lake water was undetectable after flowing 32 km in the carbonate aquifer. This study showed for the first time in literature that, while lake dry-downs had notable short-term impacts on the water chemistry of karst aquifers, these impacts did not persist over long time periods or long distances.

Impacts on the ecological health of the numerous reservoirs located in the Lancang River Basin (LRB), China has drawn significant attention in recent years. Previous studies here mainly dealt with the conveyance and interception of nutrients by these reservoirs. This study focuses on the influences of hydrological processes in these reservoirs on water chemistry and the implications for host ecosystems. Longitudinal variations of water temperature, water chemistry, and H and O isotope values in the main stem of the Lancang River, and vertical variations in the reservoirs, were analyzed in relation to water sources and mixing. Results indicate that the main stem river waters enter the middle/bottom layers of the reservoirs through interflow/underflow in warm/cold seasons, and that waters from the tributaries enter the surface of the reservoirs through overflow. The large reservoirs are permanently stratified, which is verified by variations of δ¹⁸O values versus Cl⁻ concentrations. Consequently, surface waters cannot be fully renewed, and phosphorus derived mainly from tributary inflows tends to accumulate in surface layers. These conditions facilitate the development of algal blooms. The mechanism proposed here explains the progressive increases in algal densities observed in the large reservoirs. This study suggests that coupling of permanent stratification and distinctive circulation patterns substantially raises the risk of the development of algal blooms in these large reservoirs. Therefore, long-term and comprehensive observations focused on thermal stratification, water circulation, nutrient cycling, and phytoplankton growth are an urgent task in the future.

The present work elucidates late Permian vegetation dynamics and palaeoenvironment by analysing the adpressed plant fossils, palynological composition, organic geochemistry, petrography, and FTIR data procured from the sediments of the Bhanora coal mine, Raniganj Coalfield, Damodar Basin, India. The study enhances our understanding of the biostratigraphic age assessment and subtleties of the depositional environment of peat-forming vegetation during the late Permian (Lopingian). A macrofossil assemblage belonging to the typical ‘Glossopteris Flora’ is retrieved, comprising the major elements Glossopteridales-leaf form Glossopteris (23 species), seeds-Samaropsis, Dolianitia, and fructification-Ottokaria, followed by the minor elements Equisetales-Schizoneura, Phyllotheca, and stem axes, and Coenopteridales-Botrychiopsis. The palynological analysis asserts the presence of the Densipollenites magnicorpus assemblage, suggesting a late Permian (Lopingian) age for the studied rock deposits. The palynocomposition reveals the dominance of pollen showing affinities with Glosspotridales, followed by Coniferales, Peltaspermales, Cordaitales, and trilete spores of Filicales and Lycopsidales. The morphological structures, such as the organization of the central body, saccus infrastructures, patterns of striation, and taeniae, indicate the prevalence of a warm climate and high humidity during the deposition of these sediments. The geochemical study of coal reveals a bimodal distribution, suggesting multiple organic matter inputs, while the shale sample shows a unimodal distribution, suggesting increased input of microbially derived organic matter. The higher CH₂/CH₃ ratio and vitrinite reflectance further indicate the lower thermal maturity of the studied coal. The vitrinite reflectance analysis shows a ‘high volatile bituminous’ rank of the studied sample. This study indicates that the Raniganj Formation (Lopingian) marks the pinnacle of Permian Gondwana Flora, following its demise with the advent of Triassic environmental shifts.