Alkaline wastewater generated during bauxite processing represents an important environmental issue due to its high pH and the potential release of trace elements from red mud residues. At the former aluminium plant in Podgorica, Montenegro, red mud has been classified as non-hazardous waste; however, wastewater accumulated in the red mud disposal basins exhibits elevated alkalinity (pH > 10) and increased concentrations of Al, As, V, and F exceeding the regulatory limits. This study evaluated five laboratory treatment methods, including chemical neutralization, adsorption, and ion-exchange processes, to identify the most effective remediation strategy. The results showed that treatment efficiency varied considerably among the investigated methods. While chemical neutralization effectively reduced alkalinity, anionic ionexchange resin achieved the highest overall removal of the target contaminants and provided the highest overall compliance with environmental standards.
Indonesia is located in the Sunda Volcanic Arc and hosts abundant geologically controlled geothermal resources. Geothermal systems under different tectonic settings in this region exhibit significant differences in spatial distribution, reservoir characteristics, and fluid phases. Clarifying the geodynamic mechanisms underlying the genetic differences of these systems has fundamental guiding significance for regional geothermal resource assessment. Taking the fault-controlled geothermal systems in Sumatra and the volcano-hosted geothermal systems in West Java as comparative targets, this paper synthesizes existing geological literature and measured borehole temperature data to delineate the control laws of deep geodynamic processes on key elements of shallow hydrothermal systems. The comprehensive analysis indicates that: (1) The oblique subduction and thicker continental crust background in Sumatra are accompanied by assimilation and mixing processes, which tend to form large silicic magma chambers; under the orthogonal subduction and thinner crust background in geothermal systems are controlled by the strike-slip shear zone of the Great Sumatran Fault (GSF), with highpermeability zones concentrated within the principal faults and pull-apart basins; West Java geothermal systems are affected by the superimposition of local extension and magmatic thermal stress, developing diffuse secondary micro-fracture networks within the andesitic basement. (3) Sumatran pull-apart basins possess open fault recharge channels, maintaining a liquid-dominated hydrothermal convection circulation; the upper parts of some systems in West Java form low-permeability argillic caps due to hydrothermal rock alteration, and undergo boiling and phase separation driven by restricted recharge and basal heat flux, forming vapor-dominated geothermal systems. This review summarizes the controlling effects of different geodynamic backgrounds on the evolution of geothermal systems in Indonesia, providing a fundamental geological reference for the study of genetic mechanisms of geothermal fields in related active continental margins.
Pluvial flooding caused by intense rainfall events poses a significant and growing risk, particularly in urbanized areas with limited drainage capacity. This study presents a machine learning (ML)-based approach for rapid pluvial flood inundation mapping using hydraulically derived water depths and high-resolution spatial predictors. A two-dimensional hydraulic model (MIKE+) was used to simulate flow depths under four rainfall scenarios (20, 40, 60, and 80 mm/h), providing physically consistent training data for the ML models. A set of terrain, hydrological, and land surface predictors was prepared and evaluated through multicollinearity analysis, confirming their suitability for ML modeling. The eXtreme Gradient Boosting (XGB) algorithm was applied to predict both flood extent (classification) and water depth (regression) in the Teplica domain. Model performance was assessed using spatially structured cross-validation and standard evaluation metrics. The results demonstrate that the XGB model achieves acceptable performance, with F1-scores ranging from 0.69 to 0.88 for flood extent prediction. Water depth predictions resulted in the RMSE values between 2.5% and 13.7% and low bias. Model performance varied across rainfall scenarios and spatial folds, with better classification results under lower rainfall intensities and improved depth prediction for higher intensities. Predictor importance analysis identified Height Above the Nearest Drainage (HAND) as the dominant controlling factor, followed by slope and surface roughness. Despite the relatively large study area, the model training times ranged from 128 to 414 and from 105 to 483 seconds for the classification and regression, respectively. The inference time was within few seconds. The findings indicate that ML models trained on hydraulic simulations can effectively replicate flood inundation patterns to "unseen" spatial locations within the studied domain while significantly reducing computational demands.
The analyses of historical data from hydrometric stations and "in situ" measurements represent a solid foundation for the development of complex hydrological studies regarding the evolution of the hydro morphological regime of the Danube River. To better understand the outcomes of human activities and climatic changes upon the Sulina branch, this paper analyzes the variability of the water flow and suspended sediment transport in the Danube Delta, between the branches and on the Sulina branch. In this area of delta, the hydrotechnical works started at the beginning of 19th century, when besides the embankment of Sulina branch for navigation purpose, several important rectifications were done on the St. George and Sulina branches. The Sulina channel was prolonged also into the Black Sea by 8 km of dikes, that influenced irreversible the sediment transport regime at the mouth of the branch and along the coastal area. After completion of the hydrotechnical work, the flow repartition between the main branches (Sulina and St. George) of the Danube Delta has changed over time. We analyzed the evolution of liquid flow and suspended sediment load for the period 2000 divided by 2024. In terms of the mean annual values, we found a decreased tendency. Moreover, we detected the increase of accumulation processes, since 2020, on the first 40 km of the channel and on the last 20 km, before flowing into the Black Sea. Due to climate changes, the decrease in flow and, implicitly, in the transport of suspended sediments at the entrance to the Sulina branch, as well as the water exchange between the adjacent channels in the delta and this branch, has led to a significantly smaller contribution from the Danube River to the Black Sea. This study presents new aspects related to the sediment's issues, such as an analysis of suspended sediment budget along the Sulina branch over the past 25 years, as well as a quantitative assessment of the retention and export of suspended sediments to the Black Sea, that have not been conducted previously.
The soil erosion phenomenon is becoming a critical environmental challenge that is significantly impacting ecosystems, agriculture, and water resources. This study assesses and maps the soil erosion in the Upper and Middle Cheliff watershed in the northern part of Algeria by using the Universal Soil Loss Equation (USLE), which is integrated with Geographic Information Systems (GIS). Semi-arid climates, steep slopes, and sparse vegetation primarily cause significant soil erosion in the study area, which spans over 10,930 km2. The methodology applied in this paper incorporates thematic mapping of erosional management (C), and conservation practices (P). The results reveal several erosion levels across the watershed, ranging from negligible erosion in flat, vegetated areas to severe erosion in steep, barren regions. Annual soil loss rates were categorized into five classes, where the highest rates reached 20.33 t ha-1yr-1 in some areas. Such high rates of soil degradation indicate critical hotspots where land productivity and ecological stability are under serious threat. The study emphasizes the urgent need to carry out targeted interventions of conservation, such as reforestation to restore vegetation cover, contour farming to minimize runoff velocity on sloping lands, and the construction of gabions to stabilize stream banks and trap sediments. These practices, when integrated, can substantially mitigate the soil losses. The findings provide essential insights for sustainable land management and erosion control strategies adapted to the fragile conditions of Algeria's semi-arid regions, where soils and water resources are increasingly under pressure from both climate change and anthropogenic activities.
