Environmental Earth Sciences最新文献

Global freshwater discharge is essential for human development, influencing hydrological and water cycles and biogeochemical processes. The Red River system, a vital transboundary river, is driven by climate and regulated by dam construction and changes in land use and land cover (LULC). This study aims to quantitatively separate effects of human activities on discharge alterations from climate variability. We combined linear regression and double mass curve to estimate human contributions, in conjunction with Mann-Kendall, Pettitt, and Sen’s slope methods for trend analysis. The analyses were performed on daily discharge data from four stations (Hoa Binh, Vu Quang, Yen Bai, Ha Noi) from the 1950s to 2023, along with CHIRPS rainfall (1981–2023) and MODIS NDVI (2002–2023). Our findings reveal complex long-term trends: flood-season and maximum discharges generally decreased significantly across most months and locations (e.g., August at Hoa Binh: −61.4 m³/s/yr). Conversely, dry-season discharge at Hoa Binh and Vu Quang increased substantially, whereas at Yen Bai it decreased in all dry-season months. Flood season, maximum, and annual mean rainfalls remained statistically stable. This stability in rainfall, despite profound changes in discharge, indicates the increasingly dominant role of human activities in controlling the flow regime, surpassing climate variability. Hydropower dams are identified as the primary drivers of flood-season discharge decreases and dry-season discharge increases at Hoa Binh, Vu Quang, and Ha Noi. Quantitatively, human activities reduced the flood-season discharge by up to − 55.6% and increased the dry-season discharge by up to 67.7% at the Hoa Binh hydrological station, where the human effect was strongest.

Saline-sodic soils are a significant barrier to sustainable agriculture, requiring time-consuming and costly reclamation methods. This study evaluates ultrasound-assisted washing as a novel technique to address this challenge. Utilizing ultrasonic waves (20 kHz), the method induces cavitation, facilitating the detachment of exchangeable sodium ions from soil particles and enhancing their mobility. Experiments were conducted on highly saline-sodic soil (pH_s: 10.34, EC_e: 32.08 dS m⁻¹, and ESP: 68.16%) using varying ultrasound amplitudes (10–100%) and durations (1–60 min). Results demonstrated substantial reductions in pH_s, EC_e, and ESP, with up to 43.26% sodium removal confirmed by SEM and EDX analyses. The treatment also induced structural changes, including increased surface area and reduced particle aggregation. Although the ESP target (< 15%) was not fully achieved, the findings highlight the potential of ultrasound-assisted washing as an effective and sustainable alternative to conventional methods. This study contributes to global efforts to combat soil salinity and sodicity by introducing a novel, technology-driven solution that aligns with the Sustainable Development Goals for mitigating land degradation and enhancing agricultural resilience.

Drought, a multifaceted natural hazard, arises not only from extended periods of below-average precipitation, but also from anthropogenic exploitation of terrestrial water storage (TWS), and is affecting the agriculturally intensive Ganga-Brahmaputra Basin (GBB). Hence this study explores the drought scenario of GBB using a combined drought index which uses both precipitation and GRACE-derived total water storage anomaly (TWSA) as the indicators. Furthermore, the relative contribution of TWSA and precipitation anomaly is envisaged in this research to quantify the dominant contributor of drought in the basin. The results reveal a marked decline in TWSA across all sub-basins, with the Upper Ganga Basin (UGB) and Yamuna-Chambal Basin (YCB) exhibiting the sharpest declines of -2.622 cm/year and − 2.116 cm/year, respectively, largely driven by unsustainable groundwater extraction and climatic variability. In contrast, the Lower Ganga Basin (LGB) and Brahmaputra Basin (BB) experience slower declines in TWSA, at -0.840 cm/year and − 1.065 cm/year, owing to their distinct aquifer characteristics and higher precipitation levels. The Combined Climatologic Deviation Index (CCDI), used to identify the drought scenario of the basins, showed significant parts of YCB and UGB faced the most severe long-duration droughts. Relative importance analysis underscores the dominant role of TWSA in shaping drought severity, with greater influence than precipitation anomalies in UGB and YCB, while LGB and BB have much influence on precipitation. Drought propagation times representing catchment response vary significantly among basins, with UGB and YCB exhibiting rapid response to input precipitation (5–6 months), while LGB shows a slower response (6–7 months). BB, benefiting from higher rainfall, experiences a much shorter propagation time (2–3 months). This study concludes since TWSA is the dominant contributor in drought manifestations for UGB and YCB, their rapid decline has plunged the basin into long term droughts.

Climate change intensifies extreme hydrological events, river water stable isotopes serve as sensitive recorders of hydrometeorological changes, yet their controlling factors across scales remain unclear. This study characterized long-term isotope variability and assessed hydrometeorological influences at both site and basin scales in the Xiangjiang River Basin. Based on 13 hydrological years (2010–2022) at Changsha station, we integrated field observations (1668 precipitation events and 929 river water samples) with ERA5 reanalysis, isoGSM2 simulations, and GRACE water storage data. Standardized Runoff Index (SRI) classification and Partial Least Squares Path Modeling (PLS-PM) were applied to analyze 5-day interval variations in river water δ²H (Δδ²H_R). Major findings include: (1) Basin-scale data exhibited significantly stronger correlations with Δδ²H_R than site-scale data, demonstrating that river water integrated upstream basin information rather than merely reflecting local conditions; (2) Δδ²H_R showed distinct non-linear responses to precipitation, with a pronounced “threshold effect” whereby rapid isotopic depletion occurred once basin-scale 5-day precipitation exceeded 70 mm; (3) Basin water storage variation integrated the competing effects of precipitation input and evaporative enrichment, explaining both significant isotopic depletion during water surplus periods and enrichment during deficit periods; (4) PLS-PM revealed a clear seasonal shift in controlling factors: precipitation dominated river water isotopic composition during drought-free periods (SRI > − 0.5), whereas evaporation became the primary controlling factor during drought periods (SRI ≤ − 0.5). These results emphasize the necessity of adopting basin-scale perspectives and incorporating non-linear relationships when interpreting river water isotope dynamics. The findings provide critical scientific insights for paleoclimate reconstruction and offer practical recommendations for improving isotope-enabled hydrological models and regional water resource management in monsoon-influenced river basins.

True triaxial compression experiments were conducted on jointed rock with different Joint Roughness Coefficient (JRC, JRC = 4.78, 9.57, 14.74 and 19.47) or inclined angle (α = 30°, 45°, 60° and 90°) firstly. Then, the adaptive transform a Lagrangian solid element to Discrete Element Sphere particles (adaptive Solid to DES) method was employed to realize the true triaxial compression simulation on jointed rock with various JRC and α. The results show that: (1) The maximum equivalent stress and cracks are firstly concentrated at the joint asperities and develop into the rock matrix with increasing axial stress, resulting in joint-matrix coupled fracture mode. (2) The strength and peak strain of the jointed rock show a decreasing (30 ° ≤ α ≤ 60°) then increasing α = 90°) tendency as the α increased. Increasing JRC weaks the influence of α on strength but amplify on peak strain. (3) When the joint strike parallels to intermediate principal stress, the failure mode are matrix shear (α = 30°), matrix shear-joint sliding (α = 45°), joint sliding (α = 60°), to matrix shear failure (α = 90°), respectively. When the joint strike parallels to minor principal stress, the larger stress on the inclined side inhibits the influence of the joint, resulting in all jointed rock matrix shear fracture.

This study evaluates optimal water allocation within the Subak Bali irrigation system in the Petanu River Basin, focusing on return flow dynamics known locally as “natak tiyis.” The objective was to enhance water availability for downstream irrigation while ensuring system sustainability under increasing water scarcity. A synthetic rainfall-runoff model was employed to derive dependable discharge (Q80), and net field water requirements were calculated for irrigation area behind each weir, considering both the existing cropping pattern and a shift in planting start periods. Eight allocation scenarios were simulated using DSS-RIBASIM (Decision Support System - River Basin Simulation Model), varying return flow percentages incrementally. Optimal performance was assessed using a multi-criteria framework based on reliable water supply (Q80), water availability gain, irrigation equity, and system sustainability. Results indicate that the eighth scenario, with a 31.7% return flow, achieved the highest performance, increasing water availability by (:0.18{m}^{3}/s) and expanding irrigable areas downstream. This improvement supports agricultural resilience without requiring structural modifications, demonstrating that optimizing traditional water reuse mechanisms can serve as a sustainable, nature-based solution in UNESCO-recognized cultural landscapes. The findings underscore the value of integrating indigenous knowledge with hydrological modelling for climate-resilient water governance.

The water quality in lakes is an essential factor for ecosystem sustainability and quality of life in highly urbanized countries, where lakes play significant roles as potable water sources, flood control measures, and recreational spots. This research assesses the water quality of nine key lakes in Hyderabad, Telangana, India: Himayat Sagar, Hussain Sagar, Saroornagar, Alwal, Miralam, Safilguda, Kapra, Jeedimetla, and Nacharam, for a five-year period of 2018–2022. The Water Quality Index (WQI) was determined using six key parameters: temperature, pH, dissolved oxygen (DO), electrical conductivity (EC), biochemical oxygen demand (BOD), and nitrates. Data was collected from the Central Pollution Control Board (CPCB), and WQI calculations were made using index formulae recommended by the World Health Organization (WHO) and the Bureau of Indian Standards (BIS). Each lake is characterized by spatial and temporal discrepancies of water quality, and several of them have displayed significant deterioration, presumably due to anthropogenic activities such as effluent discharge and urban run-off. This study highlights the necessity of ongoing monitoring and adoption of effective water management practices to combat pollution and protect these essential water resources. Results showed that most lakes exhibited poor to very-poor water quality (WQI 158–270), driven by elevated conductivity and BOD. Himayat Sagar remained comparatively stable near the good-poor boundary, while Kapra showed slight post-lockdown improvement. Several lakes recorded critically low dissolved oxygen, indicating sustained anthropogenic pollution stress.

In semi-arid and arid parts of the globe, groundwater is the most vital natural resource meeting the needs of the agricultural, drinking, domestic and industrial sectors, owing to the inadequate availability of surface water and scant rainfall. The present study is focused on irrigation and drinking suitability, hydro-geochemistry, and source distribution of groundwater in the arid area of Rajasthan, India, where groundwater is utilized to meet the demands of the irrigation and drinking sectors. Fifty-six groundwater samples from tubewells installed at various rural locations of Ratangarh tehsil of Rajasthan were investigated for 15 parameters following standard procedures. Average dominance of ions followed the order : Cl⁻ > HCO₃⁻ > SO₄²⁻ > NO₃⁻ > CO₃²⁻ > F⁻ for anions, and Na⁺ > Mg²⁺ > Ca²⁺ > K⁺ for cations. The NO₃⁻ levels varied from 10.99 to 154.41 mg L^− 1. High nitrate levels might have originated from the application of nitrogenous fertilizers in this agriculture dominating area, and animal and human waste. Water Quality Index revealed that 98% groundwater samples are poor to unsuitable for human consumption. Multivariate statistical analysis suggests that the origin of F⁻ can be ascribed predominantly to lithogenic (geogenic) processes and that of nitrate to technogenic activities. Irrigation indices like %Na, Kelly’s Index, Residual Sodium Bicarbonate and Residual Sodium Carbonate indicate the unsuitability of groundwater for use in agriculture. Continual irrigation with such water may reduce the permeability of the soil, as the water has excessive sodium. Also, excessive bicarbonate may lead to alkalinity hazard and precipitation and deposition of sodium carbonate in soil. Na-HCO₃-Cl hydro-geochemical facies followed by Na-Cl-HCO₃ are the prevailing facies. Various bivariate ionic scatter plots, in addition to Chadha’s, and Gibbs plots, reveal that silicate or non-carbonate weathering, accompanied by ion-exchange and evaporite dissolution processes, are the major mechanisms governing the hydrogeochemistry of groundwater in Ratangarh area. Multivariate statistical analysis, along with diverse bivariate ionic crossplots, facilitated to unravel the hidden ionic relationships in the groundwater of Ratangarh area.

The hydrochemistry of river water is influenced by a variety of factors such as geological substrate, atmospheric inputs, anthropogenic pollution, and in-situ biological processes. Understanding the hydrochemistry is vital for managing and protecting river ecosystems as it provides the impact of natural processes and human activities on water quality, which is crucial for ensuring the sustainable use of water resources for drinking, recreation, and habitat preservation. This study evaluates the chemical and physical properties of water from 22 monitoring stations along Euphrates River in Iraq to assess the water quality and suitability for different uses as well as calculating the principal component analysis for the parameters. The results show that the water samples predominantly contain Sulphate and Chloride, which lead to a water quality index ranges between (42.07–97.14) from poor to very poor types. The concentration of Ca²⁺and Mg²⁺ ranges between (84.26–249.8) and (26.24-166.75) respectively, the Na⁺ and K⁺ ranges between (72.48-795.59) and (4.39–56.78) respectively, the Alkalinity and SO₄^2- ranges between (108.5-319.62) and (413.39–957.9) respectively, the PO₄^2- ranges between (0.04–0.42). Based on the PI, SAR, RSC, and magnesium hazard indices which ranged between (0.17–12.31), (0.07–0.67), (-23.19 - -4.97), (16.18–55.76) respectively, all samples are suitable for agriculture and irrigation.

Contamination of surface and underground waters is an important environmental implication of agrochemical use. Biochar is prominent in mitigating toxicants in soils. Still, there is a dearth of information on mitigating potentials of biochar from Tithonia diversifolia (TD) biomass on glyphosate residues and nutrient leaching in calcareous soils. The trial was a factorial combination of two glyphosate formulations with a.i. isopropylamine salts 340 and 480 g l^− 1 tagged Gly1 and Gly2, respectively, and three TD biochar types produced from sole TD, TD + poultry manure (PM), and TD + PM + bone meal (BM) tagged B1, B2 and B3 respectively. Each glyphosate was applied at the manufacturer’s recommended rate of 6 L ha^− 1 (equivalent to 0.90 µl glyphosate column^− 1) and each biochar at 5 t ha^− 1 (equivalent to 0.75 g column^− 1). Electrical conductivity, pH, NO₃-N, NH₄-N, PO₄, glyphosate, and metabolite residues were determined in leachates collected. Sole glyphosate treated soil leached the highest (23.32 mg kg^− 1) NH₄-N and glyphosate residue (0.90 µg l^− 1) and had the least (2.47%) soil organic matter (SOM). Soil pretreatment with B1, B2, and B3, respectively, reduced NH₄-N leached by 76.4, 68.5 and 67.9%, glyphosate residue by 88.9, 52.2 and 87.8% and enhanced SOM by 46.6, 39.3 and 26.7%. Correlation analysis indicated H/C and O/C as important tithonia biochar properties for reducing NO₃-N, PO_4, and glyphosate residues leaching. Biochar from Tithonia diversifolia biomass, therefore, provides a mitigating option for macronutrient and glyphosate residue leaching in agrochemical-treated calcareous soil.