Search Results (292)

Isotopic and nuclear techniques, including fallout radionuclides (FRNs), fingerprinting (FP), and isotope hydrology (IH), are essential tools for assessing soil and water degradation. However, as in state-of-the-art reviews, isolated application of FRNs, FP and IH limits their potential to address complex, interconnected environmental processes across landscapes. This study proposes a novel methodology based on the concept of Synergistic Convergence to integrate FRNs, FP, and IH into a unified framework for assessing soil and water degradation. Validated through a case study in Cuba’s Hanabanilla sub-basin, the five-stage methodology improves the identification of erosion hotspots, sediment sources, and water resource vulnerabilities. Results demonstrate that combining FRNs (quantifying soil redistribution), FP (tracing sediment sources), and IH (evaluating water dynamics) provides a robust approach for sustainable landscape management, according to the United Nations Sustainable Development Goals (SDGs) and the One Health framework. The integrated methodology proves superior to the non-integrated approach, connecting causes (erosion), drivers (water), and consequences (sedimentation, pollution). The Synergistic Convergence methodology effectively integrates isotopic and nuclear techniques (INTs) (FRNs, FP, and IH), enabling a holistic assessment of soil and water degradation and their interactions within terrestrial and aquatic ecosystems. Full article

Modern scientific research approaches to studying the hydrological cycle of water in nature, in addition to the mathematical modeling of hydrological–hydraulic processes that have expanded in recent years, increasingly include isotope hydrology on a global scale. This paper presents the preliminary results of research in the Vardar River basin. The research is in the field of isotope hydrology with the analysis of stable isotopes of hydrogen (δ²H) and oxygen (δ¹⁸O) in precipitation (P), surface water (SW) and groundwater (GW). For this purpose, a network for taking water samples in the Vardar River basin has been established. The isotopic composition of precipitation shows a relatively wide variability, with δ²H values ranging from −83.7‰ to −12.4‰ and δ¹⁸O values from −11.65‰ to −2.99‰. In contrast, groundwater samples exhibit a considerably narrower isotopic range, with δ¹⁸O values between −10.98‰ and −10.1‰ and δ²H values between −73.3‰ and −68.1‰. Surface water samples show δ¹⁸O values ranging from −10.7‰ to −9.11‰ and δ²H values from −70.6‰ to −61.6‰. The results of the study show that the waters in the Vardar River basin are predominantly of meteoric origin, with their isotopic composition being strongly influenced by climatic factors and altitude, varying from approximately 1400 m and 2000 m a.s.l. The study confirms that precipitation is the primary source of both surface and groundwater. Evaporation is the dominant process that modifies isotopic signatures during rainfall, surface runoff and groundwater recharge. Due to good fit and nearly parallel meteoric lines observed in the three different locations, preliminary LMWLs and RMWL were estimated. A similar isotopic composition of surface water (SW) and groundwater (GW) in some locations indicates the presence of a direct and active hydrological connection between these water bodies, which need to be investigated in more detail in future research. However, one of the groundwater sampling locations suggest more depleted isotopic composition, which is probably related to different recharge altitudes, but also possibly very interesting relationship between Vardar River, alluvial aquifers and karst aquifer in the Žeden massif. Full article

Located in the northeastern Tibetan Plateau, the Qaidam Basin hosts abundant strategic lithium (Li) and boron (B) salt lake resources crucial for national resource security. Existing studies focus on individual lakes, lacking systematic Li-B geochemical and source–transport–sink research across the geothermal–river–lake system. Based on 40 water samples from 16 lakes and multi-isotope and hydrochemical data, this study explores Li-B spatial distribution, isotopic evolution and enrichment rules. The results reveal prominent spatial heterogeneity of Li and B distributions. The contents of riverine Li and B are higher than the global average level, and terminal salt lakes show the highest enrichment degree. Specifically, southern lakes are Li-dominant, while northern lakes are B-dominant, with both reaching industrial exploitation grades. Significant Li and B isotopic fractionation occurs throughout the hydrological system, with geothermal fluids presenting depleted isotopic compositions and lake waters showing enriched features. H-O isotopic evidence and Gibbs diagram analysis indicate that surface waters in the basin are primarily recharged by atmospheric precipitation, and their hydrochemical compositions are jointly controlled by rock weathering and strong evaporative concentration, accompanied by distinct north–south hydrogeological zonation differences. Source analysis demonstrates that Li is mainly derived from high-temperature water–rock interactions of Li-rich volcanic and granitic rocks in the southern East Kunlun Mountains, whereas B originates from ultrahigh-pressure B-rich metamorphic rocks along the northern North Qaidam margin. The migration and accumulation sequence of Li and B follows the pathway: geothermal fluid emission → fluvial transportation → terminal lake enrichment. Evaporation and mineral precipitation are the dominant factors controlling elemental enrichment and isotopic fractionation. This basin-wide study supplements salt lake critical mineral metallogenic theories and guides efficient Li-B exploration and sustainable development. Full article

Seasonal hydrology reshapes large-river food webs by altering habitat connectivity and basal resource availability. Trophic baselines from before the 2021 Yangtze ten-year fishing ban are now valuable because monitoring has shifted from fish abundance alone toward food-web function and ecological recovery. We analysed carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotopes of fish and the baseline bivalve Corbicula fluminea collected in March (dry season) and August (wet season) 2016 from the Jingjiang section of the lower Yangtze River. In the dry season, 100 individuals of 27 species were analysed; species mean δ¹³C ranged from −30.52‰ (Micropercops swinhonis) to −21.19‰ (Aristichthys nobilis) and δ¹⁵N from 6.30‰ (Hypophthalmichthys molitrix) to 14.90‰ (Lophiogobius ocellicauda). In the wet season, 187 individuals of 47 species were analysed; species mean δ¹³C ranged from −32.07‰ (Pseudobrama simoni) to −20.84‰ (Salanx ariakensis) and δ¹⁵N from 6.27‰ (Misgurnus anguillicaudatus) to 14.87‰ (Saurogobio gymnocheilus). Among 24 shared species, δ¹³C differed significantly between seasons (paired t = 4.30, p < 0.001), but δ¹⁵N did not (t = 1.52, p = 0.143). Mean trophic level fell from 3.07 to 2.74 (t = 3.85, p < 0.001). This decline remained significant in a trophic-enrichment-factor sensitivity analysis using 2.5–4.0‰. Community-wide carbon range (CR), nitrogen range (NR), total convex-hull area (TA), mean nearest-neighbour distance (NND), and the standard deviation of nearest-neighbour distance (SDNND) showed larger wet-season CR (9.08 vs. 7.51), slightly larger NR, TA and NND, and lower SDNND. Seasonal hydrology thus mainly altered basal carbon pathways and relative trophic positions rather than reorganising feeding guilds. The dataset provides a pre-ban isotopic baseline for assessing whether post-ban recovery in the lower Yangtze includes restoration of trophic structure and energy-flow pathways. Full article

Agricultural karst watersheds are highly vulnerable to nutrient loss because strong surface water–groundwater (SW–GW) connectivity can rapidly transfer nitrogen and sulfur species from soils, agricultural activities, and human settlements into aquatic systems. However, the coupled behavior and contrasting controls of nitrate (NO₃⁻) and sulfate (SO₄²⁻) in such agroecosystems remain insufficiently understood, limiting effective nutrient and groundwater-quality management. In this study, a typical karst agricultural watershed in Southwest China was selected to investigate the sources, transformation processes, and transport pathways of NO₃⁻ and SO₄²⁻ under strong SW–GW interactions. During the rainy season, 44 groundwater and 40 surface water samples were collected for major hydrochemical and nitrate–sulfate stable isotope analyses. An integrated framework combining hydrochemical analysis, self-organizing maps (SOM), positive matrix factorization (PMF), and MixSIAR were used to identify dominant sources, quantify source contributions, and clarify controlling processes. The results showed that groundwater was mainly characterized by carbonate-controlled Ca-HCO₃ facies, whereas surface water exhibited higher mineralization and a shift toward Ca-SO₄ facies, indicating stronger external inputs and rapid hydrological responses. Nitrate was primarily controlled by external nitrogen inputs, with manure and sewage and soil nitrogen contributing 39–62% and 16–33%, respectively. Nitrate was also regulated by nitrification under oxic conditions, while denitrification was negligible. In contrast, sulfate was predominantly governed by geogenic processes, with sulfide oxidation contributing 63–83%, while other sources were minor. These contrasting controls resulted in distinct spatial and process behaviors: nitrate showed source-driven variability associated with agricultural and domestic inputs, whereas sulfate displayed process-driven accumulation mainly controlled by water–rock interactions. Strong SW–GW connectivity enhanced the transfer of anthropogenic nutrient signals, while subsurface mixing and buffering regulated their expression in groundwater and surface water. These findings demonstrate a clear decoupling between nitrate and sulfate controls in agricultural karst systems and provide a scientific basis for nutrient pollution control, groundwater protection, and sustainable agricultural water management in vulnerable karst regions. Full article

Groundwater is an important resource for domestic, agricultural, and ecological use in the Surat Thani basin, southern Thailand, where increasing demand from agriculture, urbanization, and tourism is placing pressure on aquifer systems. This study investigates groundwater recharge and basin-scale flow dynamics using integrated numerical groundwater modeling, stable isotope analysis, and hydrochemical interpretation. A three-layer MODFLOW model representing floodplain (Qfd), terrace (Qt), and semi-consolidated aquifers was calibrated for 2018–2024 using PEST with pilot-point parameterization. Despite there being only four observation wells, the model achieved excellent agreement between simulated and observed heads (weighted RMSE = 0.0707 m). Simulated groundwater generally flows from western uplands toward the central floodplain and eastern coastal plain, with the Tapee River acting mainly as a gaining stream. Recharge rates range from 1.2 to 77.3 mm/yr (mean 23.7 mm/yr), representing only 1–4% of annual precipitation, while evapotranspiration is the dominant form of water loss. Stable isotope signatures (δ²H, δ¹⁸O) indicate recharge from direct monsoonal rainfall with minimal evaporation. Hydrochemical facies evolve from Ca–HCO₃ recharge waters to mixed facies along downgradient flow paths, reflecting increasing residence time and water–rock interaction. The results identify western and northern upland areas as key recharge zones requiring long-term protection and sustainable groundwater management. Full article

In mountainous river basins, groundwater systems are sustained by complex recharge processes and geological heterogeneity, making groundwater flow simulation challenging in data-scarce regions where hydrological inputs are often assumed to be spatially uniform. This study developed a heterogeneous geological model of the Kofu Basin, Japan, using multiple boreholes and simulated the groundwater flow by integrating MODFLOW with climate-driven recharge outputs from SWAT+. Simulated groundwater flow was evaluated against findings from previous stable isotope studies to assess the plausibility of the simulated recharge system. After calibration, the model performance improved substantially: RMSE decreased by 91.28%, MAE decreased by 84.38%, and NSE increased from 0.9530 to 0.9996. Independent validation showed good regional agreement between observed and simulated groundwater heads (R² = 0.9307; NSE = 0.9254), although RMSE and MAE remained relatively high at 32.70 m and 19.76 m, respectively, suggesting remaining uncertainty in local-scale groundwater head simulation. Simulated velocity vectors indicated localized shallow flow and more coherent regional basinward flow in the deeper aquifer. This pattern is consistent with the interpretation that mountain-derived recharge contributes to the deeper regional groundwater system. The results highlight the value of combining hydrogeological models and geochemical evidence to support recharge-process interpretation in complex mountainous basins. Full article

Marginal lacustrine systems are highly sensitive archives of hydrological fluctuations, climatic variability, and changes in sediment supply in continental basins. The Alagöz Formation (Late Miocene–Pliocene) exposed in the Haymana–Polatlı Basin, Central Anatolia, was investigated through integrated sedimentological, mineralogical, geochemical, and stable isotope analyses to constrain provenance, weathering history, and lacustrine hydrological variability. Facies analysis reveals a transition from alluvial–fluvial systems to a shallow marginal lacustrine environment subjected to short-term hydrological fluctuations. Mineralogical and geochemical data indicate that sedimentation occurred within a mixed carbonate–siliciclastic lacustrine system controlled by variable lake-water chemistry. Detrital mineral assemblages indicate contributions from metamorphic source rocks. Trace-element and REE signatures suggest derivation mainly from felsic-to-intermediate continental sources. Reworked carbonate fragments and fossil debris indicate recycling of older carbonate units. The occurrence of calcite, dolomite, and protodolomite reflects variable Mg/Ca ratios, whereas clay mineral assemblages record shifts between detrital input during relatively humid phases and chemically concentrated conditions. Palygorskite occurrence indicates localized and episodic alkaline conditions associated with short-lived evaporative concentration. Weathering indices (CIA, CIW, PIA, and ICV) suggest low-to-moderate chemical weathering and compositionally immature sediments, consistent with transitional humid to semi-arid climatic conditions. Trace-element systematics also indicate a minor mafic contribution to the detrital source. Stable isotope values (δ¹³C: −7.05‰ to +2.82‰; δ¹⁸O: −8.60‰ to −2.94‰ VPDB) and their weak correlation (r = 0.34) support a shallow, hydrologically dynamic lacustrine system dominated by freshwater input but episodically influenced by evaporative concentration. Taken together, the Alagöz Formation records a sensitive marginal lacustrine system shaped by short-term hydrological fluctuations. These findings provide a useful analog for understanding hydrologically sensitive marginal lacustrine systems developed in post-collisional continental basins under fluctuating semi-arid climatic conditions. Full article

To clarify the hydrocarbon-generation potential of deep source rocks in the Qingyang Gas Field, this study focuses on the Shanxi and Taiyuan Formation source rocks at burial depths of 4000–5000 m. Integrated organic geochemical analyses were conducted to investigate organic matter abundance, kerogen type, thermal maturity, hydrocarbon-generation conditions, and their significance for natural gas accumulation. The TOC values of the 12 valid mudstone samples range from 0.07% to 2.53%, with an average of 0.77%, indicating generally poor to fair organic matter abundance. Rock-Eval results show that S2 values range from 0.0681 to 6.2797 mg/g, with an average of 1.5946 mg/g, whereas S1 + S2 values range from 0.0948 to 6.9066 mg/g, with an average of 1.8582 mg/g, indicating generally limited Rock-Eval hydrocarbon-generating capacity, with local improvement. The kerogen assemblage is heterogeneous and is generally dominated by Type III humic kerogen, with subordinate Type II components and minor Type I components in some samples, indicating mixed organic-matter input but an overall gas-prone character. Tmax values range from 420 to 482 °C; however, because Tmax may be unreliable in samples with very low S2 values, thermal maturity was evaluated mainly using vitrinite reflectance and natural gas geochemical evidence. R_o values range from 2.03% to 2.22%, with an average of 2.11%, indicating that the source rocks have reached a high- to overmature stage. The natural gas is methane-rich, with an average methane content of 91.73% and an average heavy hydrocarbon content of only 0.16%, indicating a typical dry-gas composition. The carbon isotope values of methane and ethane are both negative, with δ¹³C₁ values ranging from −35.59‰ to −20.65‰ and δ¹³C₂ values ranging from −37.82‰ to −28.44‰, consistent with high-maturity coal-derived gas generated from humic organic matter. The formation water is mainly medium- to high-salinity CaCl₂ type, indicating a relatively closed hydrologic environment favorable for natural gas preservation. Clay mineral assemblages dominated by kaolinite and illite provide supplementary evidence for depositional conditions, burial diagenesis, and fluid–rock interaction. Overall, although the Rock-Eval hydrocarbon-generating capacity of the Shanxi and Taiyuan Formation source rocks is generally limited, the Type III-dominated mixed kerogen, high- to overmature R_o values, methane-rich dry-gas composition, and carbon isotope characteristics collectively indicate that these source rocks experienced effective natural gas generation during geological evolution and are genetically related to the present deep natural gas accumulation. This study provides fundamental geochemical constraints for further integrated exploration and evaluation of the deep coal-measure gas system in the Qingyang Gas Field. Full article

In complex hydrogeological systems, such as multilayered aquifers in densely urbanized coastal areas, multi-parametric, multi-depth networks are required for discriminating between anthropogenic and natural signals. This study presents an evaluation protocol of a pre-existing piezometric network, composed of 66 piezometers, aimed at implementing a near real-time (NRTM) hydrogeochemical monitoring system in the Strait of Messina (Sicily, Italy) area. A rigorous selection process was conducted to determine the suitability of these sites for hosting permanent, above-ground instrumentation. After excluding 55 sites for logistical and administrative reasons, the remaining piezometers were evaluated through a multi-step protocol. Video inspections and vertical logs of temperature and electric conductivity were carried out to identify pipe integrity and screened sections. Water samples were collected, for the execution of geochemical and isotopic analyses, to distinguish between groundwater bodies and stagnant water or local infiltration. Finally, preliminary near real-time monitoring of water level and temperature assessed the response of the sites to hydrological cycles and tidal effects. A scoring system was applied to rank the sites, resulting in a priority list for the installation of the permanent monitoring network. The evaluation protocol was tested in the Strait of Messina, but it is based on a generical approach, independent of the specific setting of a study area, making it suitable for general applications worldwide. Full article

This study investigated spring water in the core area and buffer zone of the Shibing Dolomite Karst World Heritage Site using one-year monthly monitoring, hydrochemistry, nitrate dual isotopes, and the MixSIAR model. The buffer zone spring exhibits shallow fissure-conduit flow with rapid hydrological response, anthropogenic nitrate dominance (>62%), nitrification as the main process, and limited denitrification. Its nitrate concentration shows seasonal peaks. In contrast, the core area spring is recharged by deep fissure water, with natural nitrate sources (>80%), stable nitrate levels (5–7.4 mg/L), and potential local denitrification. Nitrogen export in the buffer zone increases 4.5 times in the rainy season (NO₃⁻ accounting for 93% of TN). The core area shows higher TN export flux per unit area (3.34 vs. 0.4 g/m²/a) and greater DON proportion. Nitrogen export far exceeds that from rocky desertified areas, suggesting that dissolved nitrogen leaching drives karst rocky desertification evolution. Full article

Groundwater–surface water interactions in volcanic hydrogeological systems represent a key process in river dynamics and were preliminarily investigated along a river draining the southern sector of the Sabatini Mountains (central Italy) using an integrated hydrogeological and geochemical approach. Serial discharge measurements, combined with physico-chemical parameters, major ions, stable oxygen isotopes, and radon analyses, reveal marked spatial variability in river–aquifer exchanges along distinct river reaches. The Arrone River exhibits clear differences between upstream, intermediate, and downstream sections, reflecting the relative influence of localized anthropogenic inputs, diffuse groundwater discharge from the volcanic aquifer, and subsurface flow contributions. Upstream reaches are characterized by pronounced modifications in discharge and chemistry, whereas intermediate and downstream reaches show progressive groundwater influence, resulting in distinct geochemical signatures and changes in water quality. Correlation and cluster analyses identify reach-specific processes controlling water composition and support the recognition of gaining and mixed river conditions under varying hydrological regimes. These results constrain a conceptual model in which river behavior is governed by spatially heterogeneous groundwater inflows, modulated by seasonal discharge dynamics and local human pressures. This study highlights the importance of reach-scale investigations for understanding SW–GW interactions in volcanic settings and provides transferable insights relevant to groundwater-dependent river systems. Full article

Against the background of a warming and humidifying climate on the Qinghai–Tibet Plateau, increasing attention has been paid to the sustainability of water resources and ecosystems in the Qinghai Lake Basin. Investigating the characteristics of precipitation stable isotopes and moisture sources provides critical insights into the driving mechanisms of the regional hydrological cycle. In this study, precipitation samples collected at the Qinghai Lake Wetland Ecosystem National Observation and Research Station from June 2023 to October 2024 were analyzed for hydrogen (δ²H) and oxygen (δ¹⁸O) stable isotopes. The temporal variations of δ²H, δ¹⁸O, and deuterium excess (d-excess) were characterized, and their relationships with air temperature and precipitation amount were examined. In addition, a backward trajectory model was employed to identify the moisture sources of precipitation during the observation period. The results indicate that: (1) precipitation stable isotopes and d-excess exhibit pronounced seasonal variability, characterized by enrichment in summer and depletion in spring and autumn; (2) the Local Meteoric Water Line (LMWL) for the basin is defined as δ²H = 8.15δ¹⁸O + 38.71 (R² = 0.93), with both slope and intercept exceeding those of the Global Meteoric Water Line (GMWL); (3) precipitation isotopes show a discernible temperature effect but are jointly controlled by multiple moisture sources and meteorological factors; and (4) backward trajectory analysis combined with d-excess values reveals that precipitation moisture is primarily derived from westerly transport, while locally recycled moisture and continental air masses also exert significant influences. Overall, these findings reveal the multi-source driving mechanisms of the regional hydrological cycle and provide critical scientific support for understanding hydrological processes in alpine inland basins and their responses to future climate change, thereby contributing to the sustainable management of regional water resources. Full article

Water age reflects water sources, storage, and pathways, and regulates the solute retention and dissolution associated with biogeochemical processes, highlighting its hydrological and ecological importance. However, accurate water age estimation in tracer-aided models depends heavily on the quality and spatio-temporal resolution of precipitation isotopic signals. This study investigates how distributed rainfall δ²H signals affect the simulation of young water fraction (F_yw) via the Storage Age Selection (SAS) model in topographically complex subtropical mountain catchments. Eight precipitation δ²H scenarios were generated using two temporal approaches (stepwise and sinewave) and four spatial interpolation methods: (1) raw data, (2) reversed effective recharge elevation method (rERE), (3) linear regression with elevation (ER), and (4) regression-kriging (RK). Later on, the time-variant SAS model was calibrated against observed stream water δ²H collected from the year 2022 to the year 2024. Results show that the SAS model consistently produced similar F_yw estimates for catchments (8%~40%) across all eight scenarios, demonstrating strong robustness to input uncertainty and validating the dominant role of catchment characteristics in regulating water age. The combined stepwise temporal and rERE spatial approach provided better agreement with observed stream δ²H, particularly in the eastern, steeper catchments, yielding superior model efficiency along with better constrained uncertainty. This study highlights the sensitivity of age-tracking models to precipitation isotopic inputs and provides practical guidance for selecting an interpolation strategy in data-limited mountainous environments. Full article

Groundwater quantification is essential for sustainable water resources management, yet it is often hampered by limited data availability and difficulties in measuring spring discharges. This study investigates three carbonate aquifers in Central Italy’s Abruzzo region: the Genzana–Greco, Morrone, and Marsicano mountains. The aim is to resolve uncertainties in spring attribution, and groundwater flow patterns using isotopic analyses combined with field surveys. The Genzana–Greco aquifer was examined to clarify the sources of the Acquachiara spring and the previously unreported Germina spring, assessing whether recharge occurs locally or from the carbonate massif. In this case, the results indicate that the Germina, together with a similar known spring of Capolaia, share a common recharge sector, while the Acquachiara spring is mainly fed by higher-elevation carbonate areas, excluding significant contributions from local alluvial deposits. In the Morrone mountain aquifer, discharge gains along the Pescara River through the Gole di Popoli were quantified, and spring isotopic compositions were compared to the main basal spring Giardino to better define groundwater contributions. In this case study, the stable isotopes and tritium data confirm recharge from the central–southern massif and support the identification of basal springs and Pescara River gains as primary discharge points, with minimal influence from surface water. For the Marsicano mountain aquifer, the role of Lake Scanno in feeding the Villalago springs was investigated through isotopic analysis of inflows, downstream springs, and basal aquifer discharge points to constrain the hydrogeological water budget. The results highlight Lake Scanno’s role in the recharge of Villalago springs and delineate the Cavuto group as a major discharge system receiving inputs from central and northern sectors of the massif. Overall, the integration of isotopic tracers with hydrological measurements allowed a more precise characterization of aquifer recharge areas, Mean Residence Times, and groundwater flow paths, improving the understanding of regional water resources in a complex carbonate setting. Full article