Hydrogen and oxygen stable isotopes and hydrochemical characteristics of the Kaidu River

Hydrogen and oxygen stable isotopes and hydrochemical characteristics of the Kaidu River | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Hydrogen and oxygen stable isotopes and hydrochemical characteristics of the Kaidu River Shuai Yuan, Xueqiong Zhang, Song Feng, Hongbin Hou, Liming Gao, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8790990/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract To investigate the recharge sources and major ion origins of the Kaidu River, twelve river water samples were collected. By analyzing ion ratios and isotopic characteristics of the water, combined with Piper trilinear diagrams and Gibbs diagrams, we examined the hydrochemical and hydrogen-oxygen isotopic features to explore water recharge relationships. The results indicate that: 1) The river water is weakly alkaline, with the main cation concentration order being Ca 2+ > Mg 2+ > Na + > K + , and the primary anion content sequence as HCO 3 - > SO 4 2- > Cl - > NO 3 - . In the upper reaches of the Kaidu River, ion concentrations show significant variations, while changes are smaller in the lower reaches. All water samples exhibit a HCO 3 -Ca hydrochemical type. 2) Rock weathering is the primary factor influencing ion concentrations in river water. Based on Gaillardet diagrams and ion ratios, the main sources of riverine ions are the dissolution of carbonate and silicate minerals. 3) The hydrogen and oxygen isotopic characteristics indicate that atmospheric precipitation is the major source of the river, with some degree of evaporation occurring along its course. The δD and δ 18 O values of the Kaidu River water exhibit a strong negative correlation with elevation, decreasing as elevation increases. For every 100 m rise in elevation, δD decreases by 1.29‰ and δ 18 O by 0.21‰. The δD and δ 18 O values of the Kaidu River water show a notable continental effect, decreasing with increasing latitude. Earth and environmental sciences/Biogeochemistry Earth and environmental sciences/Environmental sciences Earth and environmental sciences/Hydrology Kaidu River hydrochemistry hydrogen and oxygen isotopes isotope effects Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1 Introduction Water, as a unique natural resource, serves as the foundation supporting the entire life system on Earth[ 1 ]. River water, characterized by rapid renewal and convenient exploitation, is widely utilized by humans for various purposes, including production, domestic use, and industrial and agricultural water supply. However, under the influence of global warming, lakes in the arid regions of Northwest China are shrinking, and river runoff is decreasing, which greatly restricts the rational development, utilization, and protection of regional water resources. Natural aqueous solute assemblages, as the core carriers of hydrogeochemical cycles, represent the dynamic equilibrium products of multi-interface reactions involving water, rock, gas, and biota. By studying the hydrochemical characteristics of water bodies, researchers can infer their evolutionary processes. Numerous methods exist for studying hydrochemistry, typically including statistical analysis, Piper trilinear diagrams, Gibbs diagrams, ion ratios, and hydrogeochemical modeling. These approaches have been widely applied in hydrochemical research for both surface water and groundwater[ 2 – 8 ]. Xinjiang is located in the northwest region of China, where its unique natural geographical conditions determine the central role of river water in regional development. The area experiences scarce precipitation and intense evaporation, making rivers formed by glacial and snow meltwater the lifeline for oasis survival and development. Studying the hydrochemical and isotopic characteristics of river water can elucidate the controlling factors of hydrochemical evolution within the watershed [9–21], providing a scientific basis for the protection and management of river water resources. Wang Xiaoyan et al. conducted a study on the hydrochemical characteristics of river water during the summer flood season in the Yushugou watershed of Hami, Tianshan Mountains. They found that the concentrations of hydrochemical ions in the river during summer were primarily influenced by the weathering and dissolution of carbonate rocks such as limestone within the watershed, as well as being modulated by flood discharge [ 22 ]. Marhubai Yasheng et al. analyzed river water samples from the Ili River and Bortala River in the western Tianshan Mountains of Xinjiang. Their results indicated that the chemical composition of the river water samples was mainly controlled by carbonate rock weathering. In the Ili River samples, the concentrations of HCO 3 − , Ca 2+ , Mg 2+ , and K + gradually increased with rising elevation, while the spatial distributions of other ion concentrations remained relatively consistent. For the Bortala River samples, all ion concentrations exhibited a gradual increasing trend from the upper reaches to the lower reaches [ 23 ]. Liu Jiaju et al discovered through hydrogen-oxygen isotope studies of the Yarlung Zangbo River that the river water exhibits certain seasonal characteristics in hydrogen-oxygen isotopes, significantly influenced by precipitation [24]. Through hydrogen and oxygen isotope analysis of the Bohe and Jinghe rivers, Zhu Shidan et al. found that the δ 18 O values of surface water in both rivers generally exhibit a gradually increasing trend along the flow path. The upstream river water is primarily recharged by glacial snowmelt, while the middle and downstream sections are mainly fed by precipitation. Additionally, the δ 18 O values in Bohe River water show a negative correlation with altitude [25]. We conduct a case study in Kaidu River, which is situated in the eastern section of the southern foothills of the Tianshan Mountains and among the most water-abundant rivers on the southern slope of the Tianshan range. It plays a crucial role in the economic development and ecological construction of the Bayingolin Mongol Autonomous Prefecture in Xinjiang. This paper analyzes the hydrochemical and isotopic characteristics of the Kaidu River water as of July 2024, exploring the relationship between hydrogen and oxygen isotopes, hydrochemical features, and geographical factors. This research holds significant practical implications for a deeper understanding of the hydrological cycle processes within the Kaidu River Basin, the rational development and utilization of water resources, and the assurance of ecological security. 2. Materials and Methods 2.1 Study Area The Kaidu River originates in the high mountain region of the southern Central Tianshan Mountains, flowing through the Greater and Lesser Yulduz Basins before turning eastward and entering the Yanqi Basin via the Xiaoshan Pass. It passes by Yanqi County and subsequently turns southward, bifurcating into eastern and western branches at Baolangsom. The eastern branch discharges into Bosten Lake, while the western branch flows into the marsh reed lake located at the southwestern end of Bosten Lake. The upper reaches of the Kaidu River experience a typical alpine climate, with an average annual temperature ranging from -5.2°C to 3.8°C. Annual precipitation is approximately 276 mm at an elevation of 2,500 m, increasing to over 450 mm in the high-altitude zone at 3,200 m. The downstream Yanqi Basin, in contrast, has low annual precipitation but high evaporation, characterized by arid conditions, sparse rainfall, dry weather, and frequent winds, which exemplify typical continental and basin climate features [26-28]. According to long-term observational data, the water discharge of the Kaidu River exhibits distinct seasonal variation patterns. From April to May, snowmelt in mountainous areas initiates increased river flow. During June to August, rising temperatures lead to substantial melting of alpine ice and snow, combined with abundant rainfall, marking the flood season. By September, as temperatures drop, water volume begins to decrease. The period from November to March of the following year constitutes the dry season [29,30]. In terms of runoff volume, the combined discharge from April to June accounts for approximately 44% of the annual total flow [29]. 2.2 Sample Collection and Analysis Methods. A total of 12 samples were collected from the upper to lower reaches of the Kaidu River between July 9 and July 11, 2024. During the field sampling, portable GPS instruments were utilized to accurately determine the latitude and longitude of each sampling point (refer to Figure 1 for sampling locations). For the water quality analysis, the sampling bottles were rinsed 3 to 5 times prior to collecting the river water samples. The collected samples were then transferred into 1500 mL polyethylene bottles, sealed with parafilm, and stored at 4.0°C for refrigeration. For isotope analysis, the water was initially filtered through a 0.45 μm membrane, after which it was collected into 150 mL polyethylene bottles, sealed with parafilm, and also stored at 4.0°C for refrigeration. Both water quality and isotope samples were subsequently sent to the Institute of Hydrogeology and Environmental Geology at the Chinese Academy of Geological Sciences for testing. The testing methods for the samples are as follows in the table. The testing methods for the samples are as follows in the table. Table 1. Test items and Detection Limits for Sample. Testing items Instrument Detection limit.mg/L） K Inductively Coupled Plasma Spectrometer (ICP Spectrometer). Avio550Max 0.18 Na 0.47 Ca 0.08 Mg 0.01 HCO 3 Acid burette 25mL 5 CO 3 5 Cl 3.0 Total hardness 3.0 SO 4 Ion chromatograph. Metrohm 930 0.072 NO 3 0.064 TDS electronic balance. MS105DU/A / pH pH meter PB-10 / δD、δ 18 O Water isotope analyzer L2130i / 3. Results and Analysis 3.1 Descriptive Statistics of Kaidu River Water Quality The total dissolved solids (TDS) of the Kaidu River water range from 185 to 237 mg/L, indicating relatively low values throughout the entire river. The mean TDS value is 185.08 mg/L. The pH of the river water varies between 7.99 and 8.82, demonstrating an overall weak alkalinity. The ion content in the upper reaches is lower than that in the lower reaches. The mean concentrations of K + , Na + , Ca 2+ , and Mg 2+ in the Kaidu River water are (1.40, 8.35, 46.38, 11.65 mg/L), with the cation content ranked as Ca 2+ > Mg 2+ > Na + > K + , indicating that Ca 2+ is the dominant cation. The mean concentrations of SO 4 2- , Cl - , HCO 3 - , and NO 3 - are (26.49, 11.75, 149.25, 2.08 mg/L), with the anion content ranked as HCO 3 - > SO 4 2- > Cl - > NO 3 - , where HCO 3 - is the dominant anion. Table 2 Statistics of hydrochemical characteristics of Kaidu River K + mg/L Na + mg/L Ca 2+ mg/L Mg 2+ mg/L SO 4 2- mg/L Cl - mg/L HCO 3 - mg/L NO 3 - mg/L TDS mg/L pH Whole process (n=12) Average 1.40 8.35 46.38 11.65 26.49 11.75 149.25 2.08 185.08 8.25 Max 1.85 15.10 72.40 14.10 32.20 29.90 204.00 3.41 237.00 8.82 Min 0.76 5.21 24.20 6.60 11.70 8.80 105.00 0.28 154.00 7.99 SD 0.33 2.54 10.70 2.47 6.31 6.25 22.83 0.79 20.59 0.23 CV 0.24 0.30 0.23 0.21 0.24 0.53 0.15 0.38 0.11 0.03 Upstream (n=6) Average 1.12 9.09 46.17 10.70 22.05 14.60 147.50 1.85 182.17 8.35 Max 1.41 15.10 72.40 14.10 29.00 29.90 204.00 3.41 237.00 8.82 Min 0.76 5.21 24.20 6.60 11.70 9.00 105.00 0.28 154.00 8.12 SD 0.23 3.56 15.86 3.35 6.30 8.15 33.07 1.09 30.16 0.27 CV 0.21 0.39 0.34 0.31 0.29 0.56 0.22 0.59 0.17 0.03 Downstream (n=6) Average 1.67 7.62 46.58 12.60 30.93 8.90 151.00 2.32 188.00 8.15 Max 1.85 8.54 47.60 12.90 32.20 9.10 157.00 2.53 190.00 8.34 Min 1.59 7.19 45.70 12.00 30.30 8.80 141.00 2.06 185.00 7.99 SD 0.10 0.49 0.63 0.35 0.69 0.15 6.78 0.20 1.79 0.13 CV 0.06 0.06 0.01 0.03 0.02 0.02 0.04 0.09 0.01 0.02 The concentrations of total dissolved solids (TDS) and major ions along the Kaidu River exhibit distinct patterns: at elevations between 3,184 and 2,500 meters, both TDS and major ion contents decrease with descending altitude; conversely, from elevations of 2,500 to 1,049 meters, they increase with decreasing elevation, although the magnitude of this increase remains modest. When comparing variations between upstream and downstream sections, ion concentrations fluctuate more significantly in upstream areas, while remaining relatively stable downstream. This phenomenon primarily arises because the upstream reaches have smaller discharge volumes and a greater number of tributaries. When low-concentration glacial meltwater enters the Kaidu River system, it dilutes the ion concentrations. In contrast, the downstream region does not receive inputs from tributaries, and with channel widening and increased discharge, evaporation intensifies, leading to higher ion concentrations in the river water. The cations in the river water are predominantly concentrated within the small triangle at the lower left of the ternary diagram. The hydrochemical type of the Kaidu River water is consistently classified as HCO 3 -Ca type [31], with Ca 2+ being the dominant ion. The anions are mainly distributed in the small triangle at the lower left corner of the anion ternary diagram, where HCO 3 - serves as the primary ion. When data points are located near the HCO 3 - side or the Ca-Mg end of the ternary diagram, they indicate carbonate rock weathering zones. This observation demonstrates that the Kaidu River water is primarily influenced by carbonate rock weathering. 3.2Analysis of hydrogen and oxygen stable isotope characteristics. The ranges of δD, δ 18 O, and d-excess in the Kaidu River were -87.25‰ to -60.19‰, -14.44‰ to -9.33‰, and 13.23‰ to 28.24‰, respectively, with average values of -71.90‰, -11.71‰, and 21.76‰. Table 2 Isotopic data of Kaidu River δD (‰) δ 18 O (‰) d (‰) Average -71.90 -11.71 21.76 Min -87.25 -14.44 13.23 Max -60.19 -9.33 28.24 As shown in Figure 4, the fitted equation for δD and δ 18 O of the Kaidu River water is δD=5.95δ 18 O-2.18, with R 2 =0.95. The slope of the river water's fitted equation is slightly lower than that of the local meteoric water line, and all sample points fall near the local meteoric water line, indicating that atmospheric precipitation is the primary source of the river water, which has undergone some degree of evaporation along its course [32,33]. The isotopic composition of hydrogen and oxygen in river water, from upstream to downstream, is influenced by factors such as topography, human activities, and climate [34]. In the Kaidu River, the δD and δ 18 O isotopes typically show a trend of lower values in the upstream regions and higher values downstream, from the upper to the middle and lower reaches. This trend is primarily attributed to river water evaporation, as well as recharge from groundwater and precipitation. In the upper reaches of the Kaidu River, the δD and δ 18 O isotopes exhibit a fluctuating upward trend, primarily due to significant elevation variations and numerous tributaries with lower isotopic values that reduce the isotopic composition upon merging into the main river. In contrast, the lower reaches of the Kaidu River experience fewer tributaries joining the main channel, and the effects of evaporative fractionation result in a gradual increase in δD and δ 18 O values. The average δD value in the upper reaches is -87.10, and the average δ 18 O value is -13.15; in the lower reaches, the average δD value is -60.87, and the average δ 18 O value is -9.98. There is a significant difference in isotopic values between the upper and lower reaches, primarily because the upper Kaidu River is mainly recharged by snow and glacial meltwater, while the middle and lower reaches consist of flat basins where the river channel widens and the flow velocity decreases. The increased evaporation effect on the river leads to isotopic changes due to surface evaporation, during which the lighter isotopes in water vapor evaporate first, resulting in the remaining water being enriched with heavier isotopes. In 1964, Dansgaard proposed the deuterium excess parameter ( d ), based on global atmospheric precipitation isotope studies, defined as d = δD-8δ 18 O [35]. This parameter essentially represents the intercept when the precipitation line has a slope of 8. Factors influencing this parameter include climatic characteristics of the vapor source region (such as temperature, humidity, and wind speed), migration pathways of water masses, and isotopic fractionation during precipitation phase changes [36]. In recent years, the d-value has not only been used to trace different moisture sources but has also been extended to groundwater cycle research. Variations in d-values within groundwater runoff can indicate the degree of water-rock interactions in aquifers and are closely related to groundwater age, infiltration rates, and the solubility of surrounding rocks. In surface water systems, a decrease in d-values typically suggests an increased proportion of groundwater mixing. The d values of the Kaidu River water range from 13.23‰ to 29.42‰, all of which are positive. Notably, the d values in the upper reaches, characterized by significant altitude variations, are markedly higher than those in the downstream areas. This indicates that after the river flows out of the mountain pass, groundwater and river water begin to exchange recharge, with the recharge volume being greater than that in the upper reaches. 4. Discussion 4.1 Analysis of Major Ion Sources in Kaidu River Water The Gibbs diagram, a classical tool for hydrochemical genesis analysis, systematically reveals the formation mechanisms of groundwater and the coupling relationships among its dominant controlling factors. This model quantitatively characterizes the genetic types of natural water bodies (such as atmospheric precipitation, rock weathering, and evaporation concentration) and their contribution weights through the spatial projection of hydrochemical parameters, while also analyzing the control pathways of water-rock interactions on ion sources. As shown in the figure, most water samples from the Kaidu River exhibit Cl - /(Cl - +HCO 3 - ) ratios between 0.08 and 0.30, and Na + /(Na + +Ca 2+ ) ratios ranging from 0.16 to 0.31. Therefore, nearly all sampling data from the Kaidu River fall within the rock weathering-dominated zone delineated by the dashed lines. The major chemical composition of the river water essentially belongs to the 'rock weathering type,' primarily reflecting the influence of rock dissolution processes on river hydrochemistry. The Gaillardet [37] diagram is constructed using Na-normalized ionic molar ratios to quantitatively characterize the dominant reaction pathways of heterogeneous water-rock interactions. The three endmember domains, distributed along the main diagonal of the coordinate system, correspond to the carbonate dissolution zone, the silicate dissolution zone, and the evaporite dissolution zone. By projecting hydrochemical data onto this diagram, one can determine the dominant hydrochemical processes based on the regions where the projection points fall. If sample points cluster within a particular endmember, this indicates that the ionic composition of the water body is controlled by that endmember's hydrochemical process. Conversely, if sample points are located in transitional zones between endmembers, it reflects a multiphase synergistic mechanism. The diagram demonstrates that the ionic composition of river water in the study area lies between the carbonate rock basin and the silicate rock basin, with a tendency toward the carbonate rock basin. This indicates that the water bodies in the area are primarily influenced by the weathering of carbonate rocks. Ionic ratios can further elucidate the influence of various rock weathering processes on hydrochemical components [38]. Since the ratios between major ions produced by the weathering and dissolution of common minerals and rocks remain fixed, groundwater circulation processes modify ionic compositions and ratios as hydrogeological conditions evolve. Through a quantitative analysis of characteristic ionic equivalent ratios (e.g., Na/Cl, Ca/HCO₃) and composite parameters (e.g., alkalinity index, chloro-alkaline coefficient), the dominant driving factors of hydrochemical components can be systematically interpreted. To satisfy charge balance constraints, this study adopted milliequivalent concentration (meq/L) standardization for data processing. 1) γ(Na + )/γ(Cl - ) The natural sources of chloride ions in water bodies primarily include the dissolution of rock salt or other chlorides contained in sedimentary rocks. When rock salt (NaCl) dissolves, the dissociated Na + and Cl - jointly enter the groundwater system. Apart from the dissolution of halite minerals, geochemical processes such as the weathering of feldspar minerals can significantly alter the ionic composition characteristics of groundwater. The γ(Na + )/γ(Cl - ) ratio in river water ranges from 0.52 to 1.86. Most samples exhibit a Na + /Cl - ratio greater than 1, with only a small portion of water samples showing higher Cl - concentrations than Na + . This indicates that in these regions, the sources of Na + and Cl - are not solely from rock salt dissolution, but also include Na + contributions from silicate weathering [39]. 2) γ(Ca 2+ +Mg 2+ )/γ(SO 4 2- +HCO 3 - ) The sources of Ca 2+ and Mg 2+ in water bodies can be inferred based on the γ(Ca 2+ +Mg 2+ )/γ(SO 4 2- +HCO 3 - ) ratio. When sampling points are distributed along the 1:1 equivalent line, it indicates that the water body is primarily governed by dissolution processes dominated by carbonate rock-evaporite composite systems. A ratio >1 reflects predominant cooperative dissolution of aluminosilicate minerals (e.g., feldspar, mica) and sulfate rocks (gypsum, anhydrite), while a ratio <1 suggests the controlling influence of pure carbonate rock dissolution. Most sampling points of river water in the study area are located near the 1:1 line, indicating that the dissolution of carbonate minerals serves as the primary source of Ca 2+ and Mg 2+ ions in the river water of the study area [40]. 3) γ(Ca 2+ )/γ(Mg 2+ ) The γ(Ca 2+ )/γ(Mg 2+ ) ratio serves as a crucial method for deciphering the sources of cations in groundwater. Variations in this ratio are primarily governed by the phase equilibrium states of carbonate minerals (calcite and dolomite): when a ratio is 2 reveals intense calcite dissolution and its controlling effect on cation composition. In river water, most Ca 2+ /Mg 2+ ratios exceed 2, demonstrating that the dissolution of calcite minerals is the predominant factor governing cation composition in river water [40]. 4) γ( HCO 3 - ) /γ( Cl - + SO 4 2- ) The dissolution proportions of carbonate rocks, silicate rocks, and evaporite rocks were analyzed by calculating the γ(HCO 3 - )/γ(Cl - + SO 4 2- ) ratio. When the ratio exceeds 1, it indicates that the ion content is primarily controlled by the dissolution of carbonate and silicate rocks. When the ratio is below 1, it suggests that the ion content is mainly governed by evaporite dissolution. The river water in the study area consistently exhibited ratios greater than 1, demonstrating that the ion sources were predominantly derived from carbonate and silicate rocks, which aligns with the conclusions drawn from the ion end-member diagram [41]. 4.2 Altitude and Latitude Effects of River Water Isotopes When an air mass ascends along terrain, the decrease in temperature causes water vapor condensation, with light isotopes ( 16 O and 1 H) preferentially entering the gas phase while heavy isotopes ( 18 O and D) become enriched in the liquid phase[42]. As elevation increases, the δD and δ 18 O values in precipitation gradually decrease. This indicates that both δD and δ 18 O in the Kaidu River exhibit a clear negative correlation with altitude, decreasing at rates of 1.29 × 10 -3 /(100 m) and 0.21 × 10 -3 /(100 m), respectively. The latitude effect refers to the phenomenon where the isotopic composition of atmospheric precipitation decreases with increasing latitude. When water vapor moves from low to high latitudes, the heavier isotopes ( 18 O, D) preferentially condense due to decreasing temperatures, leaving the remaining vapor progressively depleted. This results in lower isotopic values in high-latitude precipitation. Analysis of the correlation between Kaidu River water and latitude/altitude (Figure 9) shows that hydrogen and oxygen isotopes exhibit strong correlations with both latitude and altitude, with a better correlation observed for latitude. This reflects the latitude effect and altitude effect in the distribution of hydrogen and oxygen isotopes in Kaidu River water. 5 Conclusion This study employs hydrochemical and stable isotope analysis techniques, combined with Piper trilinear diagrams, Gibbs diagrams, Gaillardet diagrams, ion ratios, and hydrogen-oxygen isotope relationships to analyze the hydrochemical types, controlling factors, ion sources, and recharge sources of the Kaidu River water. 1) The Kaidu River water is overall weakly alkaline. In the upper reaches, ion concentrations exhibit significant variations, while in the lower reaches, the changes in ion content are minimal. From an elevation of 3184 m to 2500 m, TDS and major ion concentrations decrease with decreasing elevation. From 2500 m to 1049 m, TDS and major ion concentrations increase with decreasing elevation. 2) The concentration order of major cations in the river water was Ca 2+ > Mg 2+ > Na + > K + , while the anion content followed the sequence: HCO 3 − > SO 4 2− > Cl − > NO 3 − . The hydrochemical type was consistently HCO 3 -Ca. Rock weathering was the primary factor influencing ionic concentrations in the river water. Based on Gaillardet diagrams and ion ratios, the main sources of river ions were derived from the dissolution of carbonate and silicate minerals. 3) In the Kaidu River water body, the ranges of δD, δ 18 O, and d-excess were − 87.25‰ to -60.19‰, -14.44‰ to -9.33‰, and 13.23‰ to 28.24‰, respectively. Both δD and δ 18 O values gradually increasing trends along the flow path. The fitted equation for δD and δ 18 O in the Kaidu River water is δD = 5.95δ 18 O-2.18, with R 2 = 0.95. The slope of the river water's fitting equation is slightly lower than that of the local meteoric water line, and all sample points fall near the global meteoric water line, indicating that atmospheric precipitation is the primary source of the river water, which has undergone some degree of evaporation along its course. 4) The δD and δ 18 O values of Kaidu River water exhibit a good negative correlation with elevation, decreasing as elevation increases. For every 100 m increase in elevation, δD decreases by 1.29‰ and δ 18 O decreases by 0.21‰. The δD andδ 18 O values of Kaidu River water show a notable continental effect, decreasing with increasing latitude. Declarations Funding This research was funded by the Survey of Lakes in the Mengxin Plateau Lake Region (DD20230510) and Natural Science Foundation of Inner Mongolia Autonomous Region of China (2024QN04003). Author Contribution Conceptualization, S.Y. and X.Z.; methodology, S.Y. and X.Z..; software,S.F.; validation, S.F. and H.H.; formal analysis, S.Y. and X.Z..; investigation, S.Y. ,L.M. and Z.T.; resources, Z.T.; data cura-tion, S.Y. and X.Z.; writing—original draft preparation, S.Y. and X.Z..; writing—review and editing, S.Y. and X.Z..; supervision, R.L.; project administration, Y.H. All authors have read and agreed to the published version of the manuscript. Data Availability The datasets used and/or analysed during the current study available from the first/corresponding author on reasonable request. References Zhang J G, Lai P, Wang J T. Research on the spatio-temporal evolution of water resources ecological footprint and sustainable utilization in Guizhou Province[J]. Environmental pollution and Control, 2024, 46(10): 1521-1528+1537. Wu JL, Liu W, Zeng HA, et al.Water quantity and quality of six lakes in the arid Xinjiang Region,NW China[J]. Environmental Processes, 2014, 1(2): 115-125. Gaillardet J, Dupré B, Louvat P, et al. Global silicate weathering and CO 2 consumption rates deduced from the chemistry of large rivers[J]. Chemical Geology, 1999, 159(1- 4) : 3-30. Gou L F, Jin Z D, Pogge von Strandmann P A E, et al. Li isotopes in the middle Yellow River: seasonal variability,sources and fractionation[J]. Geochimica et Cosmochimica Acta, 2019, 248: 88-108. Ding T P, Gao J F, Tian S H, et al. Chemical and isotopic characters of the water and suspended particulate materials in the Yellow River and their geological and nvironmental implications[J] Acta Geologica Sinica (English Edition), 2016, 90(1):285-351． Zhang Q Q, Jin Z D, Zhang F, et al. Seasonal variation in river water chemistry of the middle reaches of the Yellow River and its controlling factors[J]. Journal of Geochemical Exploration, 2015, 156:101-113. Li X Q, Gan Y Q, Zhou A G, et al. Relationship between water discharge and sulfate sources of the Yangtze River inferred from seasonal variations of sulfur and oxygen isotopic compositions[J] Journal of Geochemical Exploration, 2015, 153: 30-39. Li S L, Chetelat B, Yue F J, et al. Chemical weathering processes in the Yalong River draining the eastern Tibetan Plateau, China[J]. Journal of Asian Earth Sciences, 2014, 88:74-84. Li X Q, Gan Y Q, Zhou A G, et al. Hydrological controls on the sources of dissolved sulfate in the Heihe River,a large inland river in the arid northwestern China, inferred from S and O isotopes[J]. Applied Geochemistry, 2013, 35: 99-109. An R, Liu J, Gao Z, el at. Hydrochemical Characterization, Controlling Factors and Water Quality of Surface Water in Shandong Province, North China [J]. Journal of Earth Science, 2024, 35(01): 155-66. Xie F, Chai S, Wang Z L, et al. Evolution of hydrochemical characteristics and the influence of environmental background in the Hailar River basin, China[J]. Environmental monitoring and assessment, 2024, 196(10): 968. Liu H Y, Liu W, Yang G L, el at. Distribution Characteristics and Formation Mechanism of Main Hydrochemical Ions in Qingshui River[J]. Environmental Science,2024, (2024), 12-7134-12. Ren W, Yao T D, Xie S Y. Stable isotopic composition reveals the spatial and temporal dynamics of discharge in the large river of Yarlungzangbo in the Tibetan Plateau[J]. Science of the Total Environment,2018,625: 373-381. Qiu X, Zhang M, Wang S. Preliminary research on hydrogen and oxygen stable isotope characteristics of different water bodies in the Qilian Mountains, northwestern Tibetan Plateau[J]. Environmental Earth Sciences, 2016, 75(23): 1491. Fan Y, Wu Y, Wang Y, el at. An Analysis of Surface Water–Groundwater Interactions Based on Isotopic Data from the Kaidu River Basin, South Tianshan Mountain[J]. Water 2022, 14, 2259. Yang Z, Zhou Y X, Wenninger J, el at. A multi-method approach to quantify groundwater/surface water-interactions in the semi-arid Hailiutu River basin, northwest China[J]. Appl. Hydrogeol. 2014, 22, 527–541. Meredith K, Hollins S, Hughes C, el at. The influence of groundwater/surface water exchange on stable water isotopic signatures along the darling river, NSW, Australia. In Groundwater and Ecosystems; CRC Press: Boca Raton, FL, USA, 2013. Meng Y, Liu, G.; Li, M. Tracing the Sources and Processes of Groundwater in an Alpine Glacierized Region in Southwest China: Evidence from Environmental Isotopes[J]. Water, 2015, 7, 2673–2690. Vystavna Y, Harjung A, Monteiro L R, et al. Stable isotopes in global lakes integrate catchment and climatic controls on evaporation[J]. Nat Commun, 2021, 12(1): 7224. Omonona O V, Ajibero K, Okogbue C O. Investigation of the Geochemical Evolution of Groundwater Using Major Ions and Stable Isotopes Signatures: A Case Study in Transboundary Aquifers [J]. Arabian Journal for Science and Engineering, 2025, 50(1): 419-31. Kong Y L, Pang Z H. Evaluating the sensitivity of glacier rivers to climate change based on hydrograph separation of discharge. Journal of Hydrology, 2012, 434/435: 121-129. Sun C, Chen Y, Li X, et al. Analysis on the streamflow components of the typical inland river, Northwest China[J]. Hydrological Sciences Journal, 2016, 61(5): 970-981. Wang Xiaoyan, Li Zhongqin, Jiang Chanwen, et al. Hydrochemical characteristics and causes of the summer river water in Yushugou basin, Eastern Tianshan Mountains[J]. Journal of Glaciology and Geocryology, 2016, 38(5): 1385－1393． Maerhubai Yasheng， MA Long, Jilili Abuduwaili, ZHANG Weiyan, Hydrochemical characteristics and their influence on rivers in the Western part of the Tianshan Mountains, Xinjiang, China[J]. ARID ZONE RESEARCH, 2021, 38(03): 600-609. Liu J J,Guo H C. Temporal and spatial variation characteristics of hydrogen and oxygen isotopes in Yarlung Zangbo River[J]. China Environmental Science. 2021, 41(11): 5194-200. Zhu S D, Zhang F, Zhang H W, et al. Seasonal variation of the isotope and hydrochemical characteristics of the main lake rivers in Lake Ebinur, Xinjiang[J]. J Lake Sci,2018, 30(6): 1707⁃ 1721 TOHTI G，SAI B，ZHANG J P，et al. Study on water environmental characteristics of River Kaidu Catchment in Xinjiang[J]. Journal of Environmental Engineering Technology. 2021, 11(6): 1102-1109. SUN Gui-yan, LIU Xiang, LIU Xiang. Spatial Distributions of Water Physicochemical Properties in the Kaidu River[J]. ARID ZONE RESEARCH, 2017, 34(02): 259-65. ZHENG Peng, CHEN Yaning, WANG Huaijun, et al. The impact of climate change on extreme runoffs in the Tianshan region: Taking Kaidu River as an example[J]. Journal of Irrigation and Drainage. 2024, 43(04): 0105-08. TAO Hui, WANG Guoya, SHAO Chun, et al. Climate change and its effects on runoff at the headwater of Kaidu River[J]. Journal of Glaciology and Geocryology, 2007, 29(3): 413-417. XIANG Yanyun, CHEN Yaning, ZHANG Qifei, et al. Trends of snow cover and streamflow variation in Kaidu River and their influential factors[J]. Resources Science, 2018, 40(9): 1855-1 865. Feng S, Guo H M, Sun X, et al. Limited roles of anthropogenic activities on arsenic mobilization in groundwater from the Yinchuan Basin, China [J]. Journal of Hydrology, 2022, 610: 127910. Wu H, Wu J, Song F, et al. Spatial distribution and controlling factors of surface water stable isotope values (δ 18 O andδ 2 H) across Kazakhstan, Central Asia [J]. Science of the Total Environment, 2019, 678(No.0): 53-61. Wu H, Li X, He B, et al.Characterizing the Qinghai Lake watershed using oxygen-18 and deuterium stable isotopes [J]. Journal of Great Lakes Research, 2017, 43(3): 33-42. SIEGENTHALE R U, OESCHGE R H. Correlation of 18O in precipitation with temperature and altitude[J]. Nature. 1980, 285(5763): 314-317． Dansgaard W. Stable isotopes in precipitation. Tellus. 1964, 16(4): 436-468. Merlivat L, Jouzel J. Global climatic interpretation of the deuterium-oxygen-18 relationship for precipitation[J]. Journal of Geophysical Research-Oceans, 1979, 84(C8): 5029-5033. GAILLARDET J, DUPRE B, ALLEGRE C J, el at. Chemical and physical denudation in the Amazon River Basin [J]. Chemical Geology, 1997, 142(3-4): 141-73. Zhang B, Zhao D, Zhou P, et al. Hydrochemical characteristics of groundwater and dominant water-rock interactions in the Delingha Area, Qaidam Basin, Northwest China[J]. Water. 2020, 12, 836. Yuan R, Wang M, Wang S, et al. Water transfer imposes hydrochemical impacts on groundwater by altering the interaction of groundwater and surface water[J]. Journal of Hydrology, 2020, 583 , 124617. Pu J B, Yuan D X, Xiao Q, et al. Hydrogeochemical characteristics in karst subterranean streams: a case history from Chongqing, China[J]. Carbonates and Evaporites, 2015, 30(3): 307-319. Hong T, Xie Y Q, Yu Q W, et al. Hydrochemical characteristics study and genetic analysis of groundwater in a key region of the Wumeng Mountain, Southwestern China[J]. Earth and Environment, 2016, 44(1): 11-18. Wu H W, Wu J L, Song F, et al. Spatial distribution and controlling factors of surfacewater stable isotope values (δ 18 Oand δ 2 H) across Kazakhstan, Central Asia[J]. Science of the Total Environment, 2019, 678: 53-61. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8790990","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":593384830,"identity":"ecc565f8-853e-455e-9e97-3dc4ada91477","order_by":0,"name":"Shuai Yuan","email":"","orcid":"","institution":"Hohhot General Survey of Natural Resources Center of China Geological Survey","correspondingAuthor":false,"prefix":"","firstName":"Shuai","middleName":"","lastName":"Yuan","suffix":""},{"id":593384831,"identity":"0ce3da49-9366-4adb-a967-0262e23e202d","order_by":1,"name":"Xueqiong 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1","display":"","copyAsset":false,"role":"figure","size":177298,"visible":true,"origin":"","legend":"\u003cp\u003eThe study area of Kaidu river basin location and distribution of sampling sites\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8790990/v1/72d16f6741fd208218d84594.jpeg"},{"id":103049988,"identity":"18b578ff-9b5d-4097-ab79-bba866dff6cb","added_by":"auto","created_at":"2026-02-20 07:47:34","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":168558,"visible":true,"origin":"","legend":"\u003cp\u003eVariation of ion concentration and TDS in river water with the flow path in Kaidu River\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8790990/v1/3ac667a722d773e502fd908f.jpeg"},{"id":103005477,"identity":"0f6c1eba-7afa-454e-a9fe-efbf0e11d7b5","added_by":"auto","created_at":"2026-02-19 14:59:03","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":162587,"visible":true,"origin":"","legend":"\u003cp\u003ePiper diagram of Kaidu River\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8790990/v1/aab6ccb6922b426ff48af36b.jpeg"},{"id":103005480,"identity":"e83629ed-eb8e-4816-97f2-4d2f9fd252bb","added_by":"auto","created_at":"2026-02-19 14:59:03","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":106123,"visible":true,"origin":"","legend":"\u003cp\u003eWater components’ relationship displayed by the bivariate plot of δD versus δ\u003csup\u003e18\u003c/sup\u003eO of Kaidu River\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8790990/v1/7646270747992f7798cf1cc5.jpeg"},{"id":103056427,"identity":"87963d5c-7445-4740-b5fb-bf9a49055563","added_by":"auto","created_at":"2026-02-20 09:10:11","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":54190,"visible":true,"origin":"","legend":"\u003cp\u003eDownstream variations of δD and δ\u003csup\u003e18\u003c/sup\u003eO in the Kaidu River.\u003c/p\u003e","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8790990/v1/863fee76adade50a2dbcf4e7.jpeg"},{"id":103050145,"identity":"1d4d9390-05de-4f91-8747-552b660162e0","added_by":"auto","created_at":"2026-02-20 07:48:27","extension":"jpeg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":52560,"visible":true,"origin":"","legend":"\u003cp\u003eGibbs of Kaidu River\u003c/p\u003e","description":"","filename":"floatimage6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8790990/v1/465b9a1fa94eee47d45e7a2e.jpeg"},{"id":103005481,"identity":"49d28f12-7164-4245-8faa-e58af3d4f970","added_by":"auto","created_at":"2026-02-19 14:59:03","extension":"jpeg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":64629,"visible":true,"origin":"","legend":"\u003cp\u003eGaillardet of Kaidu River\u003c/p\u003e","description":"","filename":"floatimage7.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8790990/v1/13aff7aee1d1afb3f5060f5e.jpeg"},{"id":103049940,"identity":"85aca1b0-ec83-445f-9206-9653c7b3828a","added_by":"auto","created_at":"2026-02-20 07:47:21","extension":"jpeg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":116663,"visible":true,"origin":"","legend":"\u003cp\u003eRelationship of ion concentration\u003c/p\u003e","description":"","filename":"floatimage8.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8790990/v1/f2480349b2571b93cb65f47b.jpeg"},{"id":103005482,"identity":"ae352561-8860-41b3-b669-77b53c9ecebc","added_by":"auto","created_at":"2026-02-19 14:59:03","extension":"jpeg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":150878,"visible":true,"origin":"","legend":"\u003cp\u003eThe δ\u003csup\u003e18\u003c/sup\u003eO and δD of Kaidu River change with elevation and latitude\u003c/p\u003e","description":"","filename":"floatimage9.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8790990/v1/a4e735f01829f82f8bb8c949.jpeg"},{"id":104405189,"identity":"022e8c96-ec13-4616-af6f-e947f36f8641","added_by":"auto","created_at":"2026-03-11 12:22:03","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1812280,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8790990/v1/f36c2264-1b15-40ee-b05a-f3e07c8f895d.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Hydrogen and oxygen stable isotopes and hydrochemical characteristics of the Kaidu River","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eWater, as a unique natural resource, serves as the foundation supporting the entire life system on Earth[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. River water, characterized by rapid renewal and convenient exploitation, is widely utilized by humans for various purposes, including production, domestic use, and industrial and agricultural water supply. However, under the influence of global warming, lakes in the arid regions of Northwest China are shrinking, and river runoff is decreasing, which greatly restricts the rational development, utilization, and protection of regional water resources. Natural aqueous solute assemblages, as the core carriers of hydrogeochemical cycles, represent the dynamic equilibrium products of multi-interface reactions involving water, rock, gas, and biota. By studying the hydrochemical characteristics of water bodies, researchers can infer their evolutionary processes. Numerous methods exist for studying hydrochemistry, typically including statistical analysis, Piper trilinear diagrams, Gibbs diagrams, ion ratios, and hydrogeochemical modeling. These approaches have been widely applied in hydrochemical research for both surface water and groundwater[\u003cspan additionalcitationids=\"CR3 CR4 CR5 CR6 CR7\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eXinjiang is located in the northwest region of China, where its unique natural geographical conditions determine the central role of river water in regional development. The area experiences scarce precipitation and intense evaporation, making rivers formed by glacial and snow meltwater the lifeline for oasis survival and development. Studying the hydrochemical and isotopic characteristics of river water can elucidate the controlling factors of hydrochemical evolution within the watershed [9\u0026ndash;21], providing a scientific basis for the protection and management of river water resources.\u003c/p\u003e \u003cp\u003eWang Xiaoyan et al. conducted a study on the hydrochemical characteristics of river water during the summer flood season in the Yushugou watershed of Hami, Tianshan Mountains. They found that the concentrations of hydrochemical ions in the river during summer were primarily influenced by the weathering and dissolution of carbonate rocks such as limestone within the watershed, as well as being modulated by flood discharge [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Marhubai Yasheng et al. analyzed river water samples from the Ili River and Bortala River in the western Tianshan Mountains of Xinjiang. Their results indicated that the chemical composition of the river water samples was mainly controlled by carbonate rock weathering. In the Ili River samples, the concentrations of HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e, Ca\u003csup\u003e2+\u003c/sup\u003e, Mg\u003csup\u003e2+\u003c/sup\u003e, and K\u003csup\u003e+\u003c/sup\u003e gradually increased with rising elevation, while the spatial distributions of other ion concentrations remained relatively consistent. For the Bortala River samples, all ion concentrations exhibited a gradual increasing trend from the upper reaches to the lower reaches [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eLiu Jiaju et al discovered through hydrogen-oxygen isotope studies of the Yarlung Zangbo River that the river water exhibits certain seasonal characteristics in hydrogen-oxygen isotopes, significantly influenced by precipitation [24]. Through hydrogen and oxygen isotope analysis of the Bohe and Jinghe rivers, Zhu Shidan et al. found that the δ\u003csup\u003e18\u003c/sup\u003eO values of surface water in both rivers generally exhibit a gradually increasing trend along the flow path. The upstream river water is primarily recharged by glacial snowmelt, while the middle and downstream sections are mainly fed by precipitation. Additionally, the δ\u003csup\u003e18\u003c/sup\u003eO values in Bohe River water show a negative correlation with altitude [25].\u003c/p\u003e \u003cp\u003eWe conduct a case study in Kaidu River, which is situated in the eastern section of the southern foothills of the Tianshan Mountains and among the most water-abundant rivers on the southern slope of the Tianshan range. It plays a crucial role in the economic development and ecological construction of the Bayingolin Mongol Autonomous Prefecture in Xinjiang. This paper analyzes the hydrochemical and isotopic characteristics of the Kaidu River water as of July 2024, exploring the relationship between hydrogen and oxygen isotopes, hydrochemical features, and geographical factors. This research holds significant practical implications for a deeper understanding of the hydrological cycle processes within the Kaidu River Basin, the rational development and utilization of water resources, and the assurance of ecological security.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cp\u003e\u003cstrong\u003e2.1 Study Area\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe Kaidu River originates in the high mountain region of the southern Central Tianshan Mountains, flowing through the Greater and Lesser Yulduz Basins before turning eastward and entering the Yanqi Basin via the Xiaoshan Pass. It passes by Yanqi County and subsequently turns southward, bifurcating into eastern and western branches at Baolangsom. The eastern branch discharges into Bosten Lake, while the western branch flows into the marsh reed lake located at the southwestern end of Bosten Lake. The upper reaches of the Kaidu River experience a typical alpine climate, with an average annual temperature ranging from -5.2\u0026deg;C to 3.8\u0026deg;C. Annual precipitation is approximately 276 mm at an elevation of 2,500 m, increasing to over 450 mm in the high-altitude zone at 3,200 m. The downstream Yanqi Basin, in contrast, has low annual precipitation but high evaporation, characterized by arid conditions, sparse rainfall, dry weather, and frequent winds, which exemplify typical continental and basin climate features [26-28].\u003c/p\u003e\n\u003cp\u003eAccording to long-term observational data, the water discharge of the Kaidu River exhibits distinct seasonal variation patterns. From April to May, snowmelt in mountainous areas initiates increased river flow. During June to August, rising temperatures lead to substantial melting of alpine ice and snow, combined with abundant rainfall, marking the flood season. By September, as temperatures drop, water volume begins to decrease. The period from November to March of the following year constitutes the dry season [29,30]. In terms of runoff volume, the combined discharge from April to June accounts for approximately 44% of the annual total flow [29].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.2\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eSample Collection and Analysis Methods.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA total of 12 samples were collected from the upper to lower reaches of the Kaidu River between July 9 and July 11, 2024. During the field sampling, portable GPS instruments were utilized to accurately determine the latitude and longitude of each sampling point (refer to Figure 1 for sampling locations). For the water quality analysis, the sampling bottles were rinsed 3 to 5 times prior to collecting the river water samples. The collected samples were then transferred into 1500 mL polyethylene bottles, sealed with parafilm, and stored at 4.0\u0026deg;C for refrigeration. For isotope analysis, the water was initially filtered through a 0.45 \u0026mu;m membrane, after which it was collected into 150 mL polyethylene bottles, sealed with parafilm, and also stored at 4.0\u0026deg;C for refrigeration. Both water quality and isotope samples were subsequently sent to the Institute of Hydrogeology and Environmental Geology at the Chinese Academy of Geological Sciences for testing.\u003c/p\u003e\n\u003cp\u003eThe testing methods for the samples are as follows in the table. The testing methods for the samples are as follows in the table.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1.\u0026nbsp;\u003c/strong\u003eTest items and Detection Limits for Sample.\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"522\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eTesting items\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 274px;\"\u003e\n \u003cp\u003eInstrument\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003eDetection limit.mg/L）\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"4\" style=\"width: 274px;\"\u003e\n \u003cp\u003eInductively Coupled Plasma Spectrometer (ICP Spectrometer).\u003c/p\u003e\n \u003cp\u003eAvio550Max\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e0.18\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eNa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e0.47\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eCa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e0.08\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eMg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eHCO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"4\" style=\"width: 274px;\"\u003e\n \u003cp\u003eAcid burette\u003c/p\u003e\n \u003cp\u003e25mL\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eCO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eCl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e3.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eTotal hardness\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e3.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eSO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 274px;\"\u003e\n \u003cp\u003eIon chromatograph.\u003c/p\u003e\n \u003cp\u003eMetrohm 930\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e0.072\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eNO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e0.064\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eTDS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 274px;\"\u003e\n \u003cp\u003eelectronic balance.\u003c/p\u003e\n \u003cp\u003eMS105DU/A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003epH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 274px;\"\u003e\n \u003cp\u003epH meter PB-10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003e\u0026delta;D、\u0026delta;\u003csup\u003e18\u003c/sup\u003eO\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 274px;\"\u003e\n \u003cp\u003eWater isotope analyzer\u003c/p\u003e\n \u003cp\u003eL2130i\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e"},{"header":"3. Results and Analysis","content":"\u003cp\u003e\u003cstrong\u003e3.1 Descriptive Statistics of Kaidu River Water Quality\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe total dissolved solids (TDS) of the Kaidu River water range from 185 to 237 mg/L, indicating relatively low values throughout the entire river. The mean TDS value is 185.08 mg/L. The pH of the river water varies between 7.99 and 8.82, demonstrating an overall weak alkalinity. The ion content in the upper reaches is lower than that in the lower reaches. The mean concentrations of K\u003csup\u003e+\u003c/sup\u003e, Na\u003csup\u003e+\u003c/sup\u003e, Ca\u003csup\u003e2+\u003c/sup\u003e, and Mg\u003csup\u003e2+\u003c/sup\u003e in the Kaidu River water are (1.40, 8.35, 46.38, 11.65 mg/L), with the cation content ranked as Ca\u003csup\u003e2+\u003c/sup\u003e \u0026gt; Mg\u003csup\u003e2+\u003c/sup\u003e \u0026gt; Na\u003csup\u003e+\u003c/sup\u003e \u0026gt; K\u003csup\u003e+\u003c/sup\u003e, indicating that Ca\u003csup\u003e2+\u003c/sup\u003e is the dominant cation. The mean concentrations of SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e, Cl\u003csup\u003e-\u003c/sup\u003e, HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e, and NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e are (26.49, 11.75, 149.25, 2.08 mg/L), with the anion content ranked as HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e \u0026gt; SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e\u0026gt; Cl\u003csup\u003e-\u0026nbsp;\u003c/sup\u003e\u0026gt; NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e, where HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e is the dominant anion.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2\u003c/strong\u003e Statistics of hydrochemical characteristics of Kaidu River\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"564\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 66px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003eK\u003csup\u003e+\u003c/sup\u003e\u003c/p\u003e\n \u003cp\u003emg/L\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003eNa\u003csup\u003e+\u003c/sup\u003e\u003c/p\u003e\n \u003cp\u003emg/L\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003eCa\u003csup\u003e2+\u003c/sup\u003e\u003c/p\u003e\n \u003cp\u003emg/L\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003eMg\u003csup\u003e2+\u003c/sup\u003e\u003c/p\u003e\n \u003cp\u003emg/L\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003eSO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e\u003c/p\u003e\n \u003cp\u003emg/L\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003eCl\u003csup\u003e-\u003c/sup\u003e\u003c/p\u003e\n \u003cp\u003emg/L\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003eHCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003emg/L\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003eNO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e\u003c/p\u003e\n \u003cp\u003emg/L\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003eTDS\u003c/p\u003e\n \u003cp\u003emg/L\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 34px;\"\u003e\n \u003cp\u003epH\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"5\" style=\"width: 66px;\"\u003e\n \u003cp\u003eWhole process\u003c/p\u003e\n \u003cp\u003e(n=12)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003eAverage\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003e1.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e8.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003e46.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e11.65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e26.49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e11.75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e149.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e2.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e185.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 34px;\"\u003e\n \u003cp\u003e8.25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003eMax\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003e1.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e15.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003e72.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e14.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e32.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e29.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e204.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e3.41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e237.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 34px;\"\u003e\n \u003cp\u003e8.82\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003eMin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003e0.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e5.21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003e24.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e6.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e11.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e8.80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e105.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e0.28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e154.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 34px;\"\u003e\n \u003cp\u003e7.99\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003eSD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003e0.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e2.54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003e10.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e2.47\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e6.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e6.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e22.83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e0.79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e20.59\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 34px;\"\u003e\n \u003cp\u003e0.23\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003eCV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003e0.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e0.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003e0.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e0.21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e0.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e0.53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e0.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e0.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 34px;\"\u003e\n \u003cp\u003e0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"5\" style=\"width: 66px;\"\u003e\n \u003cp\u003eUpstream\u003c/p\u003e\n \u003cp\u003e(n=6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003eAverage\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003e1.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e9.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003e46.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e10.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e22.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e14.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e147.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e1.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e182.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 34px;\"\u003e\n \u003cp\u003e8.35\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003eMax\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003e1.41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e15.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003e72.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e14.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e29.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e29.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e204.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e3.41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e237.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 34px;\"\u003e\n \u003cp\u003e8.82\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003eMin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003e0.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e5.21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003e24.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e6.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e11.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e9.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e105.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e0.28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e154.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 34px;\"\u003e\n \u003cp\u003e8.12\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003eSD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003e0.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e3.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003e15.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e3.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e6.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e8.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e33.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e1.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e30.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 34px;\"\u003e\n \u003cp\u003e0.27\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003eCV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003e0.21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e0.39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003e0.34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e0.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e0.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e0.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e0.22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e0.59\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e0.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 34px;\"\u003e\n \u003cp\u003e0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"5\" style=\"width: 66px;\"\u003e\n \u003cp\u003eDownstream (n=6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003eAverage\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003e1.67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e7.62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003e46.58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e12.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e30.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e8.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e151.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e2.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e188.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 34px;\"\u003e\n \u003cp\u003e8.15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003eMax\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003e1.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e8.54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003e47.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e12.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e32.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e9.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e157.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e2.53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e190.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 34px;\"\u003e\n \u003cp\u003e8.34\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003eMin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003e1.59\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e7.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003e45.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e12.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e30.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e8.80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e141.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e2.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e185.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 34px;\"\u003e\n \u003cp\u003e7.99\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003eSD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003e0.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e0.49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003e0.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e0.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e0.69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e0.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e6.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e0.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e1.79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 34px;\"\u003e\n \u003cp\u003e0.13\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003eCV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003e0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003e0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49px;\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 44px;\"\u003e\n \u003cp\u003e0.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 34px;\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eThe concentrations of total dissolved solids (TDS) and major ions along the Kaidu River exhibit distinct patterns: at elevations between 3,184 and 2,500 meters, both TDS and major ion contents decrease with descending altitude; conversely, from elevations of 2,500 to 1,049 meters, they increase with decreasing elevation, although the magnitude of this increase remains modest. When comparing variations between upstream and downstream sections, ion concentrations fluctuate more significantly in upstream areas, while remaining relatively stable downstream. This phenomenon primarily arises because the upstream reaches have smaller discharge volumes and a greater number of tributaries. When low-concentration glacial meltwater enters the Kaidu River system, it dilutes the ion concentrations. In contrast, the downstream region does not receive inputs from tributaries, and with channel widening and increased discharge, evaporation intensifies, leading to higher ion concentrations in the river water.\u003c/p\u003e\n\u003cp\u003eThe cations in the river water are predominantly concentrated within the small triangle at the lower left of the ternary diagram. The hydrochemical type of the Kaidu River water is consistently classified as HCO\u003csub\u003e3\u003c/sub\u003e-Ca type [31], with Ca\u003csup\u003e2+\u003c/sup\u003e being the dominant ion. The anions are mainly distributed in the small triangle at the lower left corner of the anion ternary diagram, where HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e serves as the primary ion. When data points are located near the HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e side or the Ca-Mg end of the ternary diagram, they indicate carbonate rock weathering zones. This observation demonstrates that the Kaidu River water is primarily influenced by carbonate rock weathering.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.2Analysis of hydrogen and oxygen stable isotope characteristics.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe ranges of \u0026delta;D, \u0026delta;\u003csup\u003e18\u003c/sup\u003eO, and d-excess in the Kaidu River were -87.25\u0026permil; to -60.19\u0026permil;, -14.44\u0026permil; to -9.33\u0026permil;, and 13.23\u0026permil; to 28.24\u0026permil;, respectively, with average values of -71.90\u0026permil;, -11.71\u0026permil;, and 21.76\u0026permil;.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2\u003c/strong\u003e Isotopic data of Kaidu River\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"353\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 62px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 88px;\"\u003e\n \u003cp\u003e\u0026delta;D (\u0026permil;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 96px;\"\u003e\n \u003cp\u003e\u0026delta;\u003csup\u003e18\u003c/sup\u003eO (\u0026permil;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 108px;\"\u003e\n \u003cp\u003e\u003cem\u003ed\u003c/em\u003e (\u0026permil;)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 62px;\"\u003e\n \u003cp\u003eAverage\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 88px;\"\u003e\n \u003cp\u003e-71.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 96px;\"\u003e\n \u003cp\u003e-11.71\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 108px;\"\u003e\n \u003cp\u003e21.76\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 62px;\"\u003e\n \u003cp\u003eMin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 88px;\"\u003e\n \u003cp\u003e-87.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 96px;\"\u003e\n \u003cp\u003e-14.44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 108px;\"\u003e\n \u003cp\u003e13.23\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 62px;\"\u003e\n \u003cp\u003eMax\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 88px;\"\u003e\n \u003cp\u003e-60.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 96px;\"\u003e\n \u003cp\u003e-9.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 108px;\"\u003e\n \u003cp\u003e28.24\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eAs shown in Figure 4, the fitted equation for \u0026delta;D and \u0026delta;\u003csup\u003e18\u003c/sup\u003eO of the Kaidu River water is \u0026delta;D=5.95\u0026delta;\u003csup\u003e18\u003c/sup\u003eO-2.18, with R\u003csup\u003e2\u003c/sup\u003e=0.95. The slope of the river water\u0026apos;s fitted equation is slightly lower than that of the local meteoric water line, and all sample points fall near the local meteoric water line, indicating that atmospheric precipitation is the primary source of the river water, which has undergone some degree of evaporation along its course [32,33].\u003c/p\u003e\n\u003cp\u003eThe isotopic composition of hydrogen and oxygen in river water, from upstream to downstream, is influenced by factors such as topography, human activities, and climate [34]. In the Kaidu River, the \u0026delta;D and \u0026delta;\u003csup\u003e18\u003c/sup\u003eO isotopes typically show a trend of lower values in the upstream regions and higher values downstream, from the upper to the middle and lower reaches. This trend is primarily attributed to river water evaporation, as well as recharge from groundwater and precipitation.\u003c/p\u003e\n\u003cp\u003eIn the upper reaches of the Kaidu River, the \u0026delta;D and \u0026delta;\u003csup\u003e18\u003c/sup\u003eO isotopes exhibit a fluctuating upward trend, primarily due to significant elevation variations and numerous tributaries with lower isotopic values that reduce the isotopic composition upon merging into the main river. In contrast, the lower reaches of the Kaidu River experience fewer tributaries joining the main channel, and the effects of evaporative fractionation result in a gradual increase in \u0026delta;D and \u0026delta;\u003csup\u003e18\u003c/sup\u003eO values. The average \u0026delta;D value in the upper reaches is -87.10, and the average \u0026delta;\u003csup\u003e18\u003c/sup\u003eO value is -13.15; in the lower reaches, the average \u0026delta;D value is -60.87, and the average \u0026delta;\u003csup\u003e18\u003c/sup\u003eO value is -9.98. There is a significant difference in isotopic values between the upper and lower reaches, primarily because the upper Kaidu River is mainly recharged by snow and glacial meltwater, while the middle and lower reaches consist of flat basins where the river channel widens and the flow velocity decreases. The increased evaporation effect on the river leads to isotopic changes due to surface evaporation, during which the lighter isotopes in water vapor evaporate first, resulting in the remaining water being enriched with heavier isotopes.\u003c/p\u003e\n\u003cp\u003eIn 1964, Dansgaard proposed the deuterium excess parameter (\u003cem\u003ed\u003c/em\u003e), based on global atmospheric precipitation isotope studies, defined as \u003cem\u003ed\u003c/em\u003e = \u0026delta;D-8\u0026delta;\u003csup\u003e18\u003c/sup\u003eO [35]. This parameter essentially represents the intercept when the precipitation line has a slope of 8. Factors influencing this parameter include climatic characteristics of the vapor source region (such as temperature, humidity, and wind speed), migration pathways of water masses, and isotopic fractionation during precipitation phase changes [36]. In recent years, the d-value has not only been used to trace different moisture sources but has also been extended to groundwater cycle research. Variations in d-values within groundwater runoff can indicate the degree of water-rock interactions in aquifers and are closely related to groundwater age, infiltration rates, and the solubility of surrounding rocks. In surface water systems, a decrease in d-values typically suggests an increased proportion of groundwater mixing. The \u003cem\u003ed\u003c/em\u003e values of the Kaidu River water range from 13.23\u0026permil; to 29.42\u0026permil;, all of which are positive. Notably, the \u003cem\u003ed\u003c/em\u003e values in the upper reaches, characterized by significant altitude variations, are markedly higher than those in the downstream areas. This indicates that after the river flows out of the mountain pass, groundwater and river water begin to exchange recharge, with the recharge volume being greater than that in the upper reaches.\u003c/p\u003e"},{"header":"4. Discussion","content":"\u003cp\u003e\u003cstrong\u003e4.1 Analysis of Major Ion Sources in Kaidu River Water\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe Gibbs diagram, a classical tool for hydrochemical genesis analysis, systematically reveals the formation mechanisms of groundwater and the coupling relationships among its dominant controlling factors. This model quantitatively characterizes the genetic types of natural water bodies (such as atmospheric precipitation, rock weathering, and evaporation concentration) and their contribution weights through the spatial projection of hydrochemical parameters, while also analyzing the control pathways of water-rock interactions on ion sources. As shown in the figure, most water samples from the Kaidu River exhibit Cl\u003csup\u003e-\u003c/sup\u003e/(Cl\u003csup\u003e-\u003c/sup\u003e+HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e) ratios between 0.08 and 0.30, and Na\u003csup\u003e+\u003c/sup\u003e/(Na\u003csup\u003e+\u003c/sup\u003e+Ca\u003csup\u003e2+\u003c/sup\u003e) ratios ranging from 0.16 to 0.31. Therefore, nearly all sampling data from the Kaidu River fall within the rock weathering-dominated zone delineated by the dashed lines. The major chemical composition of the river water essentially belongs to the \u0026apos;rock weathering type,\u0026apos; primarily reflecting the influence of rock dissolution processes on river hydrochemistry.\u003c/p\u003e\n\u003cp\u003eThe Gaillardet [37] diagram is constructed using Na-normalized ionic molar ratios to quantitatively characterize the dominant reaction pathways of heterogeneous water-rock interactions. The three endmember domains, distributed along the main diagonal of the coordinate system, correspond to the carbonate dissolution zone, the silicate dissolution zone, and the evaporite dissolution zone. By projecting hydrochemical data onto this diagram, one can determine the dominant hydrochemical processes based on the regions where the projection points fall. If sample points cluster within a particular endmember, this indicates that the ionic composition of the water body is controlled by that endmember\u0026apos;s hydrochemical process. Conversely, if sample points are located in transitional zones between endmembers, it reflects a multiphase synergistic mechanism. The diagram demonstrates that the ionic composition of river water in the study area lies between the carbonate rock basin and the silicate rock basin, with a tendency toward the carbonate rock basin. This indicates that the water bodies in the area are primarily influenced by the weathering of carbonate rocks.\u003c/p\u003e\n\u003cp\u003eIonic ratios can further elucidate the influence of various rock weathering processes on hydrochemical components [38]. Since the ratios between major ions produced by the weathering and dissolution of common minerals and rocks remain fixed, groundwater circulation processes modify ionic compositions and ratios as hydrogeological conditions evolve. Through a quantitative analysis of characteristic ionic equivalent ratios (e.g., Na/Cl, Ca/HCO₃) and composite parameters (e.g., alkalinity index, chloro-alkaline coefficient), the dominant driving factors of hydrochemical components can be systematically interpreted. To satisfy charge balance constraints, this study adopted milliequivalent concentration (meq/L) standardization for data processing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e1) \u0026gamma;(Na\u003csup\u003e+\u003c/sup\u003e)/\u0026gamma;(Cl\u003csup\u003e-\u003c/sup\u003e)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe natural sources of chloride ions in water bodies primarily include the dissolution of rock salt or other chlorides contained in sedimentary rocks. When rock salt (NaCl) dissolves, the dissociated Na\u003csup\u003e+\u003c/sup\u003e and Cl\u003csup\u003e-\u003c/sup\u003e jointly enter the groundwater system. Apart from the dissolution of halite minerals, geochemical processes such as the weathering of feldspar minerals can significantly alter the ionic composition characteristics of groundwater. The \u0026gamma;(Na\u003csup\u003e+\u003c/sup\u003e)/\u0026gamma;(Cl\u003csup\u003e-\u003c/sup\u003e) ratio in river water ranges from 0.52 to 1.86. Most samples exhibit a Na\u003csup\u003e+\u003c/sup\u003e/Cl\u003csup\u003e-\u003c/sup\u003e ratio greater than 1, with only a small portion of water samples showing higher Cl\u003csup\u003e-\u003c/sup\u003e concentrations than Na\u003csup\u003e+\u003c/sup\u003e. This indicates that in these regions, the sources of Na\u003csup\u003e+\u003c/sup\u003e and Cl\u003csup\u003e-\u003c/sup\u003e are not solely from rock salt dissolution, but also include Na\u003csup\u003e+\u003c/sup\u003e contributions from silicate weathering [39].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2) \u0026gamma;(Ca\u003csup\u003e2+\u003c/sup\u003e+Mg\u003csup\u003e2+\u003c/sup\u003e)/\u0026gamma;(SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e+HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe sources of Ca\u003csup\u003e2+\u003c/sup\u003e and Mg\u003csup\u003e2+\u003c/sup\u003e in water bodies can be inferred based on the \u0026gamma;(Ca\u003csup\u003e2+\u003c/sup\u003e+Mg\u003csup\u003e2+\u003c/sup\u003e)/\u0026gamma;(SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e+HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e) ratio. When sampling points are distributed along the 1:1 equivalent line, it indicates that the water body is primarily governed by dissolution processes dominated by carbonate rock-evaporite composite systems. A ratio \u0026gt;1 reflects predominant cooperative dissolution of aluminosilicate minerals (e.g., feldspar, mica) and sulfate rocks (gypsum, anhydrite), while a ratio \u0026lt;1 suggests the controlling influence of pure carbonate rock dissolution. Most sampling points of river water in the study area are located near the 1:1 line, indicating that the dissolution of carbonate minerals serves as the primary source of Ca\u003csup\u003e2+\u003c/sup\u003e and Mg\u003csup\u003e2+\u003c/sup\u003e ions in the river water of the study area [40].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3) \u0026gamma;(Ca\u003csup\u003e2+\u003c/sup\u003e)/\u0026gamma;(Mg\u003csup\u003e2+\u003c/sup\u003e)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe \u0026gamma;(Ca\u003csup\u003e2+\u003c/sup\u003e)/\u0026gamma;(Mg\u003csup\u003e2+\u003c/sup\u003e) ratio serves as a crucial method for deciphering the sources of cations in groundwater. Variations in this ratio are primarily governed by the phase equilibrium states of carbonate minerals (calcite and dolomite): when a ratio is 2 reveals intense calcite dissolution and its controlling effect on cation composition. In river water, most Ca\u003csup\u003e2+\u003c/sup\u003e/Mg\u003csup\u003e2+\u003c/sup\u003e ratios exceed 2, demonstrating that the dissolution of calcite minerals is the predominant factor governing cation composition in river water [40].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4) \u0026gamma;(\u003c/strong\u003e\u003cstrong\u003eHCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e\u003c/strong\u003e\u003cstrong\u003e)\u003c/strong\u003e\u003cstrong\u003e/\u0026gamma;(\u003c/strong\u003e\u003cstrong\u003eCl\u003csup\u003e-\u003c/sup\u003e+ SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e\u003c/strong\u003e\u003cstrong\u003e)\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe dissolution proportions of carbonate rocks, silicate rocks, and evaporite rocks were analyzed by calculating the \u0026gamma;(HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e)/\u0026gamma;(Cl\u003csup\u003e-\u003c/sup\u003e+ SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e) ratio. When the ratio exceeds 1, it indicates that the ion content is primarily controlled by the dissolution of carbonate and silicate rocks. When the ratio is below 1, it suggests that the ion content is mainly governed by evaporite dissolution. The river water in the study area consistently exhibited ratios greater than 1, demonstrating that the ion sources were predominantly derived from carbonate and silicate rocks, which aligns with the conclusions drawn from the ion end-member diagram [41].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4.2 Altitude and Latitude Effects of River Water Isotopes\u003c/strong\u003eWhen an air mass ascends along terrain, the decrease in temperature causes water vapor condensation, with light isotopes (\u003csup\u003e16\u003c/sup\u003eO and \u003csup\u003e1\u003c/sup\u003eH) preferentially entering the gas phase while heavy isotopes (\u003csup\u003e18\u003c/sup\u003eO and D) become enriched in the liquid phase[42]. As elevation increases, the \u0026delta;D and \u0026delta;\u003csup\u003e18\u003c/sup\u003eO values in precipitation gradually decrease. This indicates that both \u0026delta;D and \u0026delta;\u003csup\u003e18\u003c/sup\u003eO in the Kaidu River exhibit a clear negative correlation with altitude, decreasing at rates of 1.29 \u0026times; 10\u003csup\u003e-3\u003c/sup\u003e/(100 m) and 0.21 \u0026times; 10\u003csup\u003e-3\u003c/sup\u003e/(100 m), respectively. The latitude effect refers to the phenomenon where the isotopic composition of atmospheric precipitation decreases with increasing latitude. When water vapor moves from low to high latitudes, the heavier isotopes (\u003csup\u003e18\u003c/sup\u003eO, D) preferentially condense due to decreasing temperatures, leaving the remaining vapor progressively depleted. This results in lower isotopic values in high-latitude precipitation. Analysis of the correlation between Kaidu River water and latitude/altitude (Figure 9) shows that hydrogen and oxygen isotopes exhibit strong correlations with both latitude and altitude, with a better correlation observed for latitude. This reflects the latitude effect and altitude effect in the distribution of hydrogen and oxygen isotopes in Kaidu River water.\u0026nbsp;\u003c/p\u003e"},{"header":"5 Conclusion","content":"\u003cp\u003eThis study employs hydrochemical and stable isotope analysis techniques, combined with Piper trilinear diagrams, Gibbs diagrams, Gaillardet diagrams, ion ratios, and hydrogen-oxygen isotope relationships to analyze the hydrochemical types, controlling factors, ion sources, and recharge sources of the Kaidu River water.\u003c/p\u003e \u003cp\u003e1) The Kaidu River water is overall weakly alkaline. In the upper reaches, ion concentrations exhibit significant variations, while in the lower reaches, the changes in ion content are minimal. From an elevation of 3184 m to 2500 m, TDS and major ion concentrations decrease with decreasing elevation. From 2500 m to 1049 m, TDS and major ion concentrations increase with decreasing elevation.\u003c/p\u003e \u003cp\u003e2) The concentration order of major cations in the river water was Ca\u003csup\u003e2+\u003c/sup\u003e \u0026gt; Mg\u003csup\u003e2+\u003c/sup\u003e \u0026gt; Na\u003csup\u003e+\u003c/sup\u003e \u0026gt; K\u003csup\u003e+\u003c/sup\u003e, while the anion content followed the sequence: HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e \u0026gt; SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e \u0026gt; Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e \u0026gt; NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e. The hydrochemical type was consistently HCO\u003csub\u003e3\u003c/sub\u003e-Ca. Rock weathering was the primary factor influencing ionic concentrations in the river water. Based on Gaillardet diagrams and ion ratios, the main sources of river ions were derived from the dissolution of carbonate and silicate minerals.\u003c/p\u003e \u003cp\u003e3) In the Kaidu River water body, the ranges of δD, δ\u003csup\u003e18\u003c/sup\u003eO, and d-excess were \u0026minus;\u0026thinsp;87.25\u0026permil; to -60.19\u0026permil;, -14.44\u0026permil; to -9.33\u0026permil;, and 13.23\u0026permil; to 28.24\u0026permil;, respectively. Both δD and δ\u003csup\u003e18\u003c/sup\u003eO values gradually increasing trends along the flow path. The fitted equation for δD and δ\u003csup\u003e18\u003c/sup\u003eO in the Kaidu River water is δD\u0026thinsp;=\u0026thinsp;5.95δ\u003csup\u003e18\u003c/sup\u003eO-2.18, with R\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.95. The slope of the river water's fitting equation is slightly lower than that of the local meteoric water line, and all sample points fall near the global meteoric water line, indicating that atmospheric precipitation is the primary source of the river water, which has undergone some degree of evaporation along its course.\u003c/p\u003e \u003cp\u003e4) The δD and δ\u003csup\u003e18\u003c/sup\u003eO values of Kaidu River water exhibit a good negative correlation with elevation, decreasing as elevation increases. For every 100 m increase in elevation, δD decreases by 1.29\u0026permil; and δ\u003csup\u003e18\u003c/sup\u003eO decreases by 0.21\u0026permil;. The δD andδ\u003csup\u003e18\u003c/sup\u003eO values of Kaidu River water show a notable continental effect, decreasing with increasing latitude.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThis research was funded by the Survey of Lakes in the Mengxin Plateau Lake Region (DD20230510) and Natural Science Foundation of Inner Mongolia Autonomous Region of China (2024QN04003).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eConceptualization, S.Y. and X.Z.; methodology, S.Y. and X.Z..; software,S.F.; validation, S.F. and H.H.; formal analysis, S.Y. and X.Z..; investigation, S.Y. ,L.M. and Z.T.; resources, Z.T.; data cura-tion, S.Y. and X.Z.; writing\u0026mdash;original draft preparation, S.Y. and X.Z..; writing\u0026mdash;review and editing, S.Y. and X.Z..; supervision, R.L.; project administration, Y.H. All authors have read and agreed to the published version of the manuscript.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets used and/or analysed during the current study available from the first/corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eZhang J G, Lai P, Wang J T. Research on the spatio-temporal evolution of water resources ecological footprint and sustainable utilization in Guizhou Province[J]. Environmental pollution and Control, 2024, 46(10): 1521-1528+1537.\u003c/li\u003e\n\u003cli\u003eWu JL, Liu W, Zeng HA, et al.Water quantity and quality of six lakes in the arid Xinjiang Region,NW China[J]. Environmental Processes, 2014, 1(2): 115-125.\u003c/li\u003e\n\u003cli\u003eGaillardet J, Dupr\u0026eacute; B, Louvat P, et al. Global silicate weathering and CO\u003csub\u003e2\u003c/sub\u003e consumption rates deduced from the chemistry of large rivers[J]. Chemical Geology, 1999, 159(1- 4) : 3-30. \u003c/li\u003e\n\u003cli\u003eGou L F, Jin Z D, Pogge von Strandmann P A E, et al. Li isotopes in the middle Yellow River: seasonal variability,sources and fractionation[J]. Geochimica et Cosmochimica Acta, 2019, 248: 88-108.\u003c/li\u003e\n\u003cli\u003eDing T P, Gao J F, Tian S H, et al. Chemical and isotopic characters of the water and suspended particulate materials in the Yellow River and their geological and nvironmental implications[J] Acta Geologica Sinica (English Edition), 2016, 90(1):285-351． \u003c/li\u003e\n\u003cli\u003eZhang Q Q, Jin Z D, Zhang F, et al. Seasonal variation in river water chemistry of the middle reaches of the Yellow River and its controlling factors[J]. Journal of Geochemical Exploration, 2015, 156:101-113.\u003c/li\u003e\n\u003cli\u003eLi X Q, Gan Y Q, Zhou A G, et al. Relationship between water discharge and sulfate sources of the Yangtze River inferred from seasonal variations of sulfur and oxygen isotopic compositions[J] Journal of Geochemical Exploration, 2015, 153: 30-39.\u003c/li\u003e\n\u003cli\u003eLi S L, Chetelat B, Yue F J, et al. Chemical weathering processes in the Yalong River draining the eastern Tibetan Plateau, China[J]. Journal of Asian Earth Sciences, 2014, 88:74-84. \u003c/li\u003e\n\u003cli\u003eLi X Q, Gan Y Q, Zhou A G, et al. Hydrological controls on the sources of dissolved sulfate in the Heihe River,a large inland river in the arid northwestern China, inferred from S and O isotopes[J]. Applied Geochemistry, 2013, 35: 99-109.\u003c/li\u003e\n\u003cli\u003eAn R, Liu J, Gao Z, el at. Hydrochemical Characterization, Controlling Factors and Water Quality of Surface Water in Shandong Province, North China [J]. Journal of Earth Science, 2024, 35(01): 155-66.\u003c/li\u003e\n\u003cli\u003eXie F, Chai S, Wang Z L, et al. Evolution of hydrochemical characteristics and the influence of environmental background in the Hailar River basin, China[J]. Environmental monitoring and assessment, 2024, 196(10): 968.\u003c/li\u003e\n\u003cli\u003eLiu H Y, Liu W, Yang G L, el at. Distribution Characteristics and Formation Mechanism of Main Hydrochemical Ions in Qingshui River[J]. Environmental Science,2024, (2024), 12-7134-12.\u003c/li\u003e\n\u003cli\u003eRen W, Yao T D, Xie S Y. Stable isotopic composition reveals the spatial and temporal dynamics of discharge in the large river of Yarlungzangbo in the Tibetan Plateau[J]. Science of the Total Environment,2018,625: 373-381.\u003c/li\u003e\n\u003cli\u003eQiu X, Zhang M, Wang S. Preliminary research on hydrogen and oxygen stable isotope characteristics of different water bodies in the Qilian Mountains, northwestern Tibetan Plateau[J]. Environmental Earth Sciences, 2016, 75(23): 1491. \u003c/li\u003e\n\u003cli\u003eFan Y, Wu Y, Wang Y, el at. An Analysis of Surface Water\u0026ndash;Groundwater Interactions Based on Isotopic Data from the Kaidu River Basin, South Tianshan Mountain[J]. Water 2022, 14, 2259.\u003c/li\u003e\n\u003cli\u003eYang Z, Zhou Y X, Wenninger J, el at. A multi-method approach to quantify groundwater/surface water-interactions in the semi-arid Hailiutu River basin, northwest China[J]. Appl. Hydrogeol. 2014, 22, 527\u0026ndash;541.\u003c/li\u003e\n\u003cli\u003eMeredith K, Hollins S, Hughes C, el at. The influence of groundwater/surface water exchange on stable water isotopic signatures along the darling river, NSW, Australia. In Groundwater and Ecosystems; CRC Press: Boca Raton, FL, USA, 2013.\u003c/li\u003e\n\u003cli\u003eMeng Y, Liu, G.; Li, M. Tracing the Sources and Processes of Groundwater in an Alpine Glacierized Region in Southwest China: Evidence from Environmental Isotopes[J]. Water, 2015, 7, 2673\u0026ndash;2690. \u003c/li\u003e\n\u003cli\u003eVystavna Y, Harjung A, Monteiro L R, et al. Stable isotopes in global lakes integrate catchment and climatic controls on evaporation[J]. Nat Commun, 2021, 12(1): 7224.\u003c/li\u003e\n\u003cli\u003eOmonona O V, Ajibero K, Okogbue C O. Investigation of the Geochemical Evolution of Groundwater Using Major Ions and Stable Isotopes Signatures: A Case Study in Transboundary Aquifers [J]. Arabian Journal for Science and Engineering, 2025, 50(1): 419-31.\u003c/li\u003e\n\u003cli\u003eKong Y L, Pang Z H. Evaluating the sensitivity of glacier rivers to climate change based on hydrograph separation of discharge. Journal of Hydrology, 2012, 434/435: 121-129.\u003c/li\u003e\n\u003cli\u003eSun C, Chen Y, Li X, et al. Analysis on the streamflow components of the typical inland river, Northwest China[J]. Hydrological Sciences Journal, 2016, 61(5): 970-981.\u003c/li\u003e\n\u003cli\u003eWang Xiaoyan, Li Zhongqin, Jiang Chanwen, et al. Hydrochemical characteristics and causes of the summer river water in Yushugou basin, Eastern Tianshan Mountains[J]. Journal of Glaciology and Geocryology, 2016, 38(5): 1385－1393． \u003c/li\u003e\n\u003cli\u003eMaerhubai Yasheng， MA Long, Jilili Abuduwaili, ZHANG Weiyan, Hydrochemical characteristics and their influence on rivers in the Western part of the Tianshan Mountains, Xinjiang, China[J]. ARID ZONE RESEARCH, 2021, 38(03): 600-609.\u003c/li\u003e\n\u003cli\u003eLiu J J,Guo H C. Temporal and spatial variation characteristics of hydrogen and oxygen isotopes in Yarlung Zangbo River[J]. China Environmental Science. 2021, 41(11): 5194-200.\u003c/li\u003e\n\u003cli\u003eZhu S D, Zhang F, Zhang H W, et al. Seasonal variation of the isotope and hydrochemical characteristics of the main lake rivers in Lake Ebinur, Xinjiang[J]. J Lake Sci,2018, 30(6): 1707⁃ 1721\u003c/li\u003e\n\u003cli\u003eTOHTI G，SAI B，ZHANG J P，et al. Study on water environmental characteristics of River Kaidu Catchment in Xinjiang[J]. Journal of Environmental Engineering Technology. 2021, 11(6): 1102-1109.\u003c/li\u003e\n\u003cli\u003eSUN Gui-yan, LIU Xiang, LIU Xiang. Spatial Distributions of Water Physicochemical Properties in the Kaidu River[J]. ARID ZONE RESEARCH, 2017, 34(02): 259-65.\u003c/li\u003e\n\u003cli\u003eZHENG Peng, CHEN Yaning, WANG Huaijun, et al. The impact of climate change on extreme runoffs in the Tianshan region: Taking Kaidu River as an example[J]. Journal of Irrigation and Drainage. 2024, 43(04): 0105-08.\u003c/li\u003e\n\u003cli\u003eTAO Hui, WANG Guoya, SHAO Chun, et al. Climate change and its effects on runoff at the headwater of Kaidu River[J]. Journal of Glaciology and Geocryology, 2007, 29(3): 413-417.\u003c/li\u003e\n\u003cli\u003eXIANG Yanyun, CHEN Yaning, ZHANG Qifei, et al. Trends of snow cover and streamflow variation in Kaidu River and their influential factors[J]. Resources Science, 2018, 40(9): 1855-1 865.\u003c/li\u003e\n\u003cli\u003eFeng S, Guo H M, Sun X, et al. Limited roles of anthropogenic activities on arsenic mobilization in groundwater from the Yinchuan Basin, China [J]. Journal of Hydrology, 2022, 610: 127910.\u003c/li\u003e\n\u003cli\u003eWu H, Wu J, Song F, et al. Spatial distribution and controlling factors of surface water stable isotope values (\u0026delta;\u003csup\u003e18\u003c/sup\u003eO and\u0026delta;\u003csup\u003e2\u003c/sup\u003eH) across Kazakhstan, Central Asia [J]. Science of the Total Environment, 2019, 678(No.0): 53-61.\u003c/li\u003e\n\u003cli\u003eWu H, Li X, He B, et al.Characterizing the Qinghai Lake watershed using oxygen-18 and deuterium stable isotopes [J]. Journal of Great Lakes Research, 2017, 43(3): 33-42.\u003c/li\u003e\n\u003cli\u003eSIEGENTHALE R U, OESCHGE R H. Correlation of 18O in precipitation with temperature and altitude[J]. Nature. 1980, 285(5763): 314-317．\u003c/li\u003e\n\u003cli\u003eDansgaard W. Stable isotopes in precipitation. Tellus. 1964, 16(4): 436-468.\u003c/li\u003e\n\u003cli\u003eMerlivat L, Jouzel J. Global climatic interpretation of the deuterium-oxygen-18 relationship for precipitation[J]. Journal of Geophysical Research-Oceans, 1979, 84(C8): 5029-5033. \u003c/li\u003e\n\u003cli\u003eGAILLARDET J, DUPRE B, ALLEGRE C J, el at. Chemical and physical denudation in the Amazon River Basin [J]. Chemical Geology, 1997, 142(3-4): 141-73.\u003c/li\u003e\n\u003cli\u003eZhang B, Zhao D, Zhou P, et al. Hydrochemical characteristics of groundwater and dominant water-rock interactions in the Delingha Area, Qaidam Basin, Northwest China[J]. Water. 2020, 12, 836.\u003c/li\u003e\n\u003cli\u003eYuan R, Wang M, Wang S, et al. Water transfer imposes hydrochemical impacts on groundwater by altering the interaction of groundwater and surface water[J]. Journal of Hydrology,\u003cem\u003e \u003c/em\u003e2020, \u003cem\u003e583\u003c/em\u003e, 124617.\u003c/li\u003e\n\u003cli\u003ePu J B, Yuan D X, Xiao Q, et al. Hydrogeochemical characteristics in karst subterranean streams: a case history from Chongqing, China[J]. Carbonates and Evaporites, 2015, 30(3): 307-319.\u003c/li\u003e\n\u003cli\u003eHong T, Xie Y Q, Yu Q W, et al. Hydrochemical characteristics study and genetic analysis of groundwater in a key region of the Wumeng Mountain, Southwestern China[J]. Earth and Environment, 2016, 44(1): 11-18.\u003c/li\u003e\n\u003cli\u003eWu H W, Wu J L, Song F, et al. Spatial distribution and controlling factors of surfacewater stable isotope values (\u0026delta;\u003csup\u003e18\u003c/sup\u003eOand \u0026delta;\u003csup\u003e2\u003c/sup\u003eH) across Kazakhstan, Central Asia[J]. Science of the Total Environment, 2019, 678: 53-61. \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Kaidu River, hydrochemistry, hydrogen and oxygen isotopes, isotope effects","lastPublishedDoi":"10.21203/rs.3.rs-8790990/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8790990/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eTo investigate the recharge sources and major ion origins of the Kaidu River, twelve river water samples were collected. By analyzing ion ratios and isotopic characteristics of the water, combined with Piper trilinear diagrams and Gibbs diagrams, we examined the hydrochemical and hydrogen-oxygen isotopic features to explore water recharge relationships. The results indicate that: 1) The river water is weakly alkaline, with the main cation concentration order being Ca\u003csup\u003e2+\u003c/sup\u003e \u0026gt; Mg\u003csup\u003e2+\u003c/sup\u003e \u0026gt; Na\u003csup\u003e+ \u003c/sup\u003e\u0026gt; K\u003csup\u003e+\u003c/sup\u003e, and the primary anion content sequence as HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e- \u003c/sup\u003e\u0026gt; SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e \u0026gt; Cl\u003csup\u003e- \u003c/sup\u003e\u0026gt; NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e. In the upper reaches of the Kaidu River, ion concentrations show significant variations, while changes are smaller in the lower reaches. All water samples exhibit a HCO\u003csub\u003e3\u003c/sub\u003e-Ca hydrochemical type. 2) Rock weathering is the primary factor influencing ion concentrations in river water. Based on Gaillardet diagrams and ion ratios, the main sources of riverine ions are the dissolution of carbonate and silicate minerals. 3) The hydrogen and oxygen isotopic characteristics indicate that atmospheric precipitation is the major source of the river, with some degree of evaporation occurring along its course. The δD and δ\u003csup\u003e18\u003c/sup\u003eO values of the Kaidu River water exhibit a strong negative correlation with elevation, decreasing as elevation increases. For every 100 m rise in elevation, δD decreases by 1.29‰ and δ\u003csup\u003e18\u003c/sup\u003eO by 0.21‰. The δD and δ\u003csup\u003e18\u003c/sup\u003eO values of the Kaidu River water show a notable continental effect, decreasing with increasing latitude.\u003c/p\u003e","manuscriptTitle":"Hydrogen and oxygen stable isotopes and hydrochemical characteristics of the Kaidu River","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-19 14:58:57","doi":"10.21203/rs.3.rs-8790990/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"78cf29ed-5c37-48e5-aa48-8400a75ced7d","owner":[],"postedDate":"February 19th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":63143180,"name":"Earth and environmental sciences/Biogeochemistry"},{"id":63143181,"name":"Earth and environmental sciences/Environmental sciences"},{"id":63143182,"name":"Earth and environmental sciences/Hydrology"}],"tags":[],"updatedAt":"2026-03-09T17:10:20+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-19 14:58:57","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8790990","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8790990","identity":"rs-8790990","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}