Hydrogeochemical and isotopic study of groundwater in the Habor Lake Basin of the Ordos Plateau,NW China

Hydrogeochemistry and isotopes were used to understand the origin and geochemical evolution in the Habor Lake Basin, northwestern China. Groundwater samples were taken, and the isotopic compositions δD, δ¹⁸O and major ions were analyzed. The groundwater can be divided into three types: the Quaternary groundwater, the shallow Cretaceous groundwater and the deep Cretaceous groundwater. The groundwater chemistry is mainly controlled by the feldspar weathering and dolomite weathering, the dissolution of Glauber’s salt, and cation exchange. Chemistry of lake water is mainly controlled by evaporation and precipitation. The stable isotopes of oxygen and hydrogen in groundwater cluster along the local meteoric water line, indicating that groundwater is of meteoric origin. Comparing with shallow groundwater, deep groundwater is depleted in heavy isotopes indicating that deep groundwater was recharged during late Pleistocene and Holocene, during which the climate was more wetter and colder than today.     

Hydrogeochemical processes in the groundwater environment of Heihe River Basin,northwest China

The Heihe River Basin is a typical arid inland river basin for examining stress on groundwater resources in northwest China. The basin is composed of large volumes of unconsolidated Quaternary sediments of widely differing grain size, and during the past half century, rapid socio-economic development has created an increased demand for groundwater resources. Understanding the hydrogeochemical processes of groundwater and water quality is important for sustainable development and effective management of groundwater resources in the Heihe River basin. To this end, a total of 30 representative groundwater samples were collected from different wells to monitor the water chemistry of various ions and its quality for irrigation. Chemical analysis shows that water presents a large spatial variability of chemical facies (SO₄ ²⁻–HCO₃⁻, SO₄ ²⁻–Cl⁻, and Cl⁻–SO₄ ²⁻) as groundwater flow from recharge area to discharge area. The ionic ratio indicates positive correlation between the flowing pairs of parameters: Cl⁻ and Na⁺(r = 0.95), SO₄ ²⁻ and Na⁺ (r = 0.84), HCO₃ ⁻ and Mg²⁺(r = 0.86), and SO₄ ²⁻ and Ca²⁺ (r = 0.91). Dissolution of minerals, such as halite, gypsum, dolomite, silicate, and Mirabilite (Na₂SO₄·10H₂O) in the sediments results in the Cl⁻, SO₄ ²⁻, HCO₃ ⁻, Na⁺, Ca²⁺ and Mg²⁺ content in the groundwater. Other reactions, such as evaporation, ion exchange, and deposition also influence the water composition. The suitability of the groundwater for irrigation was assessed based on the US Salinity Laboratory salinity classification and the Wilcox diagram. The results show that most of the groundwater samples are suitable for irrigation uses barring a few locations in the dessert region in the northern sub-basin.     

Hydrogeochemical and isotopic evidence of groundwater evolution and recharge in aquifers in Beijing Plain, China

An investigation was conducted in Beijing to identify the groundwater evolution and recharge in the quaternary aquifers. Water samples were collected from precipitation, rivers, wells, and springs for hydrochemical and isotopic measurements. The recharge and the origin of groundwater and its residence time were further studied. The groundwater in the upper aquifer is characterized by Ca-Mg-HCO₃ type in the upstream area and Na-HCO₃ type in the downstream area of the groundwater flow field. The groundwater in the lower aquifer is mainly characterized by Ca-Mg-HCO₃ type in the upstream area and Ca-Na-Mg-HCO₃ and Na-Ca-Mg-HCO₃ type in the downstream area. The δD and δ¹⁸O in precipitation are linearly correlated, which is similar to WMWL. The δD and δ¹⁸O values of river, well and spring water are within the same ranges as those found in the alluvial fan zone, and lay slightly above or below LMWL. The δD and δ¹⁸O values have a decreasing trend generally following the precipitation → surface water → shallow groundwater → spring water → deep groundwater direction. There is evidence of enrichment of heavy isotopes in groundwater due to evaporation. Tritium values of unconfined groundwater give evidence for ongoing recharge in modern times with mean residence times <50 a. It shows a clear renewal evolution along the groundwater flow paths and represents modern recharge locally from precipitation and surface water to the shallow aquifers (<150 m). In contrast, according to ¹⁴C ages in the confined aquifers and residence time of groundwater flow lines, the deep groundwater is approximately or older than 10 ka, and was recharged during a period when the climate was wetter and colder mainly from the piedmont surrounding the plain. The groundwater exploitation is considered to be “mined unsustainably” because more water is withdrawn than it is replenished.     

Hydrogeochemical characteristics and evolution of the aquifer systems of Gonghe Basin,Northern China

We present the first systematic hydrogeological analysis to grain insights on the evolution of the Gonghe Basin in North China. Two hundred and forty seven water samples were collected from the Gonghe East Basin, Gonghe West Basin and Chaka Basin. The three groundwater systems of Gonghe Basin from west to east display different geochemical signatures. Based on Na/Cl ratios and Langelier-Ludwig diagram, it is inferred that the groundwater recharge potential of the Gonghe East Basin is much prosperous than the other areas. The renewability of the aquifers in alluvial-proluvial fan of Wahonghe and Gonghe East Basin margin is much faster than in the other basins. The groundwater quality in Chaka Salt Lake,Shazhuyu and Qiabuqia River Valley plains is low due to strong evaporation and cation exchange. The groundwater quality of the phreatic aquifers in the Qiabuqia River Valley plain is further deteriorated by mixing of high-arsenic and high-mineralization water from the deep fault structures.     

Soil geochemistry and groundwater contamination in an arsenic-affected area of the Datong Basin,China

This study describes the geochemistry of the topsoils from an arsenic (As)-affected area of the Datong Basin and identifies the possible sources and the enrichment mechanisms of As in groundwater. A total of 122 soil samples were collected from the study area. Analytical results indicate that soil As is higher than the average value of the Shanxi province topsoils. Fertilizer application and weathering of the bedrock both contributed to the presence of elements, including As, in the soil of the area. Furthermore, these elements may be strongly bound to Fe and Mn oxides/hydroxides. In addition, the depletion of K indicates that this element is readily leached into the groundwater rather than being retained in the soils. A groundwater area with high As levels corresponding spatially to soil samples with no As accumulation clearly shows the effects of irrigation or salt flushing on the soil compositions. Arsenic can be mobilized under reducing condition due to organic matter input or changes in redox conditions induced by irrigation or salt flushing and can be transported with vertically recharged water into shallow, unconfined aquifers, thus elevating the As concentration in groundwater.     

Hydrogeochemical and isotopic characterization of the groundwater in the Chari-Baguirmi depression, Republic of Chad

The Chari Baguirmi groundwater in the Republic of Chad is undergoing a steady deterioration both qualitative and quantitative due to climatic (severe droughts) and anthropogenic (overexploitation) constraints. However, this major water resource has not been to date the object of any comprehensive scientific investigation. To fill this gap and consider a sustainable exploitation, a hydrodynamic and hydrochemical study was undertaken. This aquifer is located south of Lake Chad and displays a significant natural piezometric depression. Piezometric campaign on an area of 70,000 km², bounded by Lake Chad, the Chari River, the mountains of Guera and the dunes of Harr, was conducted to understand the hydrodynamics of the groundwater. Water samples were collected on 124 points scattered over the study area. Hydrochemical and isotopic analyses (¹⁸O and ²H) were achieved on all samples. The interpretation of hydrochemical data was done using the Piper diagram, the multivariate analysis (hierarchical ascending classification), the index of base exchanges and ratios of Na/Cl, Na/SO₄, Cl/SO₄, Br/Cl, Sr/Ca. The hydrochemical results coupled with groundwater isotopes data allowed to understand the processes that govern the mineralization and the origin of groundwater salinity. These investigations allowed on the one hand to differentiate between two poles of water mixing and second, to demonstrate that the mineralization process and origin of salinity in the center of depression are both related to the lithology of the geological formations crossed by groundwater flow and climatic events causing evaporation of water from the aquifer.     

Environmental isotopic and hydrochemical study of groundwater in the Ejina Basin,northwest China

The study investigates the groundwater evolution and its residence time in the Ejina Basin, northwest China according to isotope and hydrochemical analyses results. The groundwater chemistry is mainly controlled by the dissolution of halite, Glauber’s salt, gypsum, dolomite and calcite, also influenced by other processes such as evaporation, ion exchange, and deposition. Based on tritium content in atmospheric precipitation and by adopting a model with exponential time distribution function, the mean residence time of the unconfined aquifer groundwater with fairly high tritium activities (21–49 TU) is evaluated. The results show that these groundwaters have low residence time (5–120 years) and are renewable. In contrast, the deep confined groundwaters are tritium-free and radiocarbon values range from 18.3 to 26.7 pmc. According to the most commonly used ¹⁴C correction models, the radiocarbon groundwater ages were calculated which yield ages of approximately 4,087–9,364 years BP. Isotopic signatures indicate formation of deep confined groundwaters in a colder and wetter climate during the late Pleistocene and Holocene. It is suggested that long-term, rational water usage guide should be set up for the Heihe River Basin as a whole to permit a considerable discharge to the Ejina Basin.     

The origin of groundwater in Zhangye Basin,northwestern China,using isotopic signature

Zhangye Basin, in arid northwestern China, has recently been repeatedly flooded by rising groundwater. Isotope signatures of sampled waters gained insight into the recharge source of the groundwater. The summer Heihe River water and most of the spring water in Zhangye and Yongchang basins plotted above the global meteoric water line (GMWL) on the δ¹⁸O-δD plot. The spring water had R/Ra ratio >1, low TDS and high tritium, which indicates origin from Qilian Mountain glacier meltwater. The groundwater of Qilian Mountains was transported to the Hexi Corridor (in which Zhangye Basin is located) through underground fault zones. Additionally, some of the groundwater in the alluvial plain, and all spring water surrounding Zhangye Basin, plotted below the GMWL on the δ¹⁸O-δD plot along an evaporation line, and had R/Ra ratio?<?1 and high TDS. It is proposed that the Tibetan rivers or lakes source the Hexi Corridor groundwater through either the NE-trending or NW-trending buried fault zones. The isotopic signatures presented as part of this study rule out the conventional viewpoint that groundwater of the Zhangye Basin was recharged by local precipitation and infiltration of Heihe River water on the alluvial plain.     

Hydrochemical and isotopic characteristics of groundwater in the Yanqi Basin of Xinjiang province, northwest China

In this study, hydrochemical and isotope investigations were conducted in the Yanqi Basin to determine the chemical composition, and to gain insight into the groundwater recharge process in the Yanqi Basin. It mainly used hydrochemistry, environmental isotopes, and a series of comprehensive data interpretation, e.g., statistics, ionic ratios, and Piper diagram to obtain a better understanding of the functioning of the system. The following hydrochemical processes were identified as the main factors controlling the water quality of the groundwater system: weathering of silicate minerals, dissolution, ion exchange, and to a lesser extent, evaporation, which seemed to be more pronounced down gradient of the flow system. As groundwater flows from the recharge to discharge areas, chemical patterns evolve in the order of Ca²⁺–HCO₃ ^?, Ca²⁺/Mg²⁺–HCO₃ ^? to Ca²⁺–Mg²⁺–Cl^?–SO₄ ^2?, Na⁺–K⁺–Cl^?–SO₄ ^2? and Na⁺–Cl^? according to lithology. The environmental isotope (δ ¹⁸O, δ ²H, ³H) measurements further revealed that precipitation was the main recharge source for the groundwater system; some local values indicated high levels of evaporation. Tritium and CFC analysis were used to estimate the ages of the different groundwater; the tritium values of the groundwater samples varied from 2.82 to 29.7 TU. The age of the groundwater at depths of <120 m is about 30–50 years. CFC values obtained for six samples to determine groundwater age; the age of the groundwater is about 20–50 years.     

Model for the formation of arsenic contamination in groundwater. 1. Datong Basin,China

Mineral equilibria were analyzed in the system As-bearing rock-meteoric water. It was shown that carbonate rocks are the most probable source of As and Sr in the waters of the Datong Basin (People's Republic of China). The reason for groundwater enrichment in As is the shift of the equilibrium FeCO₃ (siderite) + H₂O = FeOOH(goethite) + CO₂(g) + H₂(g) to the left (toward siderite formation) owing to organic matter oxidation by atmospheric oxygen and an increase in the equilibrium partial pressure of CO₂, while the Eh of the system remains below ?0.30 ± 0.06 V.     

Hydrogeochemical assessment of groundwater in Neyveli Basin, Cuddalore District, South India

In the light of progressive depletion of groundwater reservoir and water quality deterioration of the Neyveli basin, an investigation on dissolved major constituents in 25 groundwater samples was performed. The main objective was detection of processes for the geochemical assessment throughout the area. Neyveli aquifer is intensively inhabited during the last decenniums, leading to expansion of the residential and agricultural area. Besides semi-aridity, rapid social and economic development stimulates greater demand for water, which is gradually fulfilled by groundwater extraction. Groundwaters of the study area are characterized by the dominance of Na?+?K over Ca?+?Mg. HCO₃ was found to be the dominant anion followed by Cl and SO₄. High positive correlation was obtained among the following ions: Ca–Mg, Cl–Ca,Mg, Na–K, HCO₃–H₄SiO₄, and F–K. The hydrochemical types in the area can be divided into two major groups: the first group includes mixed Ca–Mg–Cl and Ca–Cl types. The second group comprises mixed Ca–Na–HCO₃ and Ca–HCO₃ types. Most of the groundwater samples are within the permissible limit of WHO standard. Interpretation of data suggests that weathering, ion exchange reactions, and evaporation to some extent are the dominant factors that determine the major ionic composition in the study area.     

山东高密地区高F区水文地球化学特征

F中毒是在特定的地理环境中发生的一种生物地球化学性疾病。高密地区F中毒是由饮用水引起的。根据国家饮用水的标准,F〉1mg／L称为高F地下水。高密地区北部六镇地下水的F含量一般为5mg／L,极值达到18．00mg／L,当地居民长期饮用高F水,对身心健康造成了极大的危害。高F地下水的形成受多种因素的影响和制约,高密地区的地势南高北低,最高海拔92m,最低海拔7．5m。地下水主要以大气降水为补给源,水位标高由南向北逐渐降低。通过对高密市的地理、地貌、岩石、水化学类型等特征的分析,阐明了高密市高F地下水的成因,并且提出了合理可行的治理措施。     

Hydrogeochemical characterization and quality assessment of groundwater using self-organizing maps in the Hangjinqi gasfield area,Ordos Basin,NW China

Water resources are scarce in arid or semiarid areas,which not only limits economic development,but also threatens the survival of mankind.The local communities around the Hangjinqi gasfield depend on groundwater sources for water supply.A clear understanding of the groundwater hydrogeochemical characteristics and the groundwater quality and its seasonal cycle is invaluable and indispensable for groundwater protection and management.In this study,self-organizing maps were used in combination with the quantization and topographic errors and K-means clustering method to investigate groundwater chemistry datasets.The Piper and Gibbs diagrams and saturation index were systematically applied to investigate the hydrogeochemical characteristics of groundwater from both rainy and dry seasons.Further,the entropy-weighted theory was used to characterize groundwater quality and assess its seasonal variability and suitability for drinking purposes.Our hydrochemical groundwater dataset,consisting of 10 parameters measured during both dry and rainy seasons,was classified into 6 clusters,and the Piper diagram revealed three hydrochemical facies:Cl-Na type(clusters 1,2 and 3),mixed type(clusters 4 and 5),and HCO3-Ca type(cluster 6).The Gibbs diagram and saturation index suggested thatweathering of rock-forming mineralswere the primary process controlling groundwater chemical composition and validated the credibility and practicality of the clustering results.Two-thirds of 45 groundwater samples were categorized as excellent-or good-quality and were suitable as drinking water.Cluster changes within the same and different clusters from the dry season to the rainy season were detected in approximately 78%of the collected samples.The main factors affecting the groundwater quality were hydrogeochemical characteristics,and dry season groundwater quality was better than rainy season groundwater quality.Based on this work,such results can be used to investigate the seasonal variation of hydrogeochemical characteristics and assess water quality accurately in the others similar area.     

Hydrogeochemical and isotopic constraints on the origins of dryland salinity,Murray Basin,Victoria, Australia

Combined hydrogeological and hydrogeochemical data allow flow systems and the origins of solutes in the Honeysuckle Creek area of the southeastern Murray Basin, which is an area affected by dryland salinity, to be constrained. Recharge occurs both on the uplands that are composed of fractured Violet Town Volcanic rocks and the Riverine Plain that comprises sediments of the Shepparton and Coonambidgal Formations. Groundwater from the Violet Town Volcanics has low salinity (<20 mmol/L Cl) and major ion geochemistry that is controlled largely by dissolution of silicate minerals. Low Cl/Br ratios (as low as 281 molar) suggest that this groundwater has not dissolved halite. Groundwater that recharged through the Riverine Plain sediments has higher Cl/Br ratios (up to 1146) and Cl concentrations of <20 mmol/L, consistent with it dissolving minor halite. Higher salinity (>20 mmol/L) groundwater has intermediate Cl/Br ratios (600–1000), which indicate that the high salinities do not simply result from halite dissolution. Rather, mixing of groundwater homogenises Cl/Br ratios, and evaporation as a consequence of a shallow water table is the dominant process that increases salinity. Oxygen and H isotopes also indicate that mixing and evaporation have occurred. These results indicate that land use over the whole region, not just the uplands, needs to be considered in any salinity management plans. Additionally future development of salinity is controlled by depth to the water table on the plains and the efficiency of recharge rather than by salt stores (halite or brines) in the unsaturated zone.     

Arsenic mobilization in shallow aquifers of Datong Basin: Hydrochemical and mineralogical evidences

To better understand the sources and mobilization processes responsible for arsenic enrichment in groundwater in the central part of Datong Basin where serious arsenic poisoning cases have been reported, hydrochemical characteristics of the groundwater and the geochemical and mineralogical features of the aquifer sediments were studied. The aqueous arsenic levels are strongly depth-dependent in the study area and the high arsenic concentrations are found at depths between 15 m and 60 m, with a maximum up to 1820 μg/L. The hydrochemical characteristics of high arsenic groundwater from the Datong Basin indicate that the mobilization of arsenic is related to reductive dissolution of Fe oxides/oxyhydroxides and/or desorption from the Fe oxides/oxyhydroxides at high pH (above 8.0). The bulk chemical results of sediments show the arsenic and iron are moderately correlated, suggesting that arsenic is associated with iron-bearing minerals. Results of sequential-extraction experiment show that solid-phase arsenic is similarly distributed among the different pools of reservoir in the aquifer sediments. Strongly adsorbed arsenic and co-precipitated arsenic are its dominant species in the solid-phase. Geochemical studies using chemical analysis, X-ray diffraction and scanning electron microscopy on magnetically separated fractions demonstrate that iron oxides/oxyhydroxides with residual magnetite and chlorite, illite, iron oxides/oxyhydroxides-coated quartz and feldspar, and ankerite are the dominant carriers of arsenic in the sediments. The major processes of arsenic mobilization are probably linked to desorption of As from Fe oxides/oxyhydroxides and reductive dissolution of Fe-rich phases in the aquifer sediments under reducing and alkaline conditions.     

Environmental isotopic study on the recharge and residence time of groundwater in the Heihe River Basin, northwestern China

The recharge and origin of groundwater and its residence time were studied using environmental isotopic measurements in samples from the Heihe River Basin, China. δ¹⁸O and δD values of both river water and groundwater were within the same ranges as those found in the alluvial fan zone, and lay slightly above the local meteoric water line (δD=6.87δ¹⁸O+3.54). This finding indicated that mountain rivers substantially and rapidly contribute to the water resources in the southern and northern sub-basins. δ¹⁸O and δD values of groundwater in the unconfined aquifers of these sub-basins were close to each other. There was evidence of enrichment of heavy isotopes in groundwater due to evaporation. The most pronounced increase in the δ¹⁸O value occurred in agricultural areas, reflecting the admixture of irrigation return flow. Tritium results in groundwater samples from the unconfined aquifers gave evidence for ongoing recharge, with mean residence times of: less than 36 years in the alluvial fan zone; about 12–16 years in agricultural areas; and about 26 years in the Ejina oasis. In contrast, groundwater in the confined aquifers had ¹⁴C ages between 0 and 10 ka BP.     

Hydrochemical and isotopic study of groundwater in the Yinchuan plain, China

The Yinchuan plain is located in the arid climate zone of NW China. The western margin of the plain is the Helan mountain connecting a series of normal slip faults. The eastern margin of the plain connects with the Yellow River and adjacents with the Ordos platform. The south of the plain is bordered by the EN fault of the Niushou mountain. The bottom of the plain is the Carboniferous, Permian, or Ordovician rocks. Based on the analysis of groundwater hydrochemical and isotopic indicators, this study aims to identify the groundwater recharge and discharge in the Yinchuan plain, China. The hydrochemical types of the groundwater are HCO₃–SO₄ in the west, HCO₃–Cl in the middle, and Cl–SO₄ in the east. The hydrochemical types are HCO₃–SO₄ in the south, HCO₃–Cl and SO₄–HCO₃ in the middle. The hydrochemical types are complex in the north, mainly SO₄–HCO₃ and Cl–SO₄. Deuterium, ¹⁸O, and tritium values of groundwater indicate that groundwater recharge sources include precipitation, bedrock fissure water, and irrigation return water. Groundwater discharges include evaporation, abstraction, and discharge to surface water. According to the EW isotopic profile, the groundwater flow system (GFS) in the Yinchuan plain can be divided into local flow systems (LFS) and regional flow systems (RFS). Groundwater has lower TDS and higher tritium in the southern Yellow River alluvial plain and groundwater age ranges from 6 to 25 years. The range of groundwater renewal rates is from 11 to 15 % a^?1. The depth of the water cycle is small, and groundwater circulates fast and has high renewal rates. Groundwater has higher TDS and lower tritium in the northern Yellow River alluvial plain. The range of groundwater age is from 45 to 57 years, and renewal rate is from 6 to 0.1 % a^?1. The depth of the water cycle is larger. Groundwater circulates slowly and has low renewal rates.     

Hydrogeochemical characteristics of groundwater depression cones in Yinchuan City, Northwest China

Groundwater in Yinchuan City has been heavily over-exploited, thus leading to the formation of depression cones in confined and phreatic groundwater environments. The depression cones have an important influence on the hydrodynamic and hydrochemical fields of groundwaters. The evolution of depression cones was analyzed on the basis of the monitoring data on groundwater level accumulated in the past 14 years. The ratio of rCl-/rCa2 showed that phreatic water circulation was intensified, and confined groundwater was affected by external factors. Mass balance of Cl- showed confined water mixed with about 11% phreatic water. It is shown that the alternative function of confined water was affected by external factors. At last, the evolution of groundwater hydrochemical field on the basis of groundwater chemical composition showed that phreatic water quality has been improved whereas confined water quality has been deteriorated. Saturation indices of minerals with respect to phreatic and confined waters were calculated by using PHREEQC.