SO4 Ca Research Articles

Hydrochemical Evolution Process and Mechanism of Groundwater in the Hutuo River Alluvial Fan, North China

Due to extensive groundwater exploitation, a groundwater funnel has persisted in the Hutuo River alluvial fan in Shijiazhuang since the 1980s, lasting nearly 40 years and significantly impacting the groundwater chemical characteristics. In this study, based on the groundwater level and chemistry data, the hydrochemical evolution processes and mechanisms of the groundwater during the 1980 groundwater funnel period and the post-2015 artificial governance period were investigated using traditional hydrogeochemical methods and inverse hydrogeochemical simulations. The results show the following: (1) The ion concentrations gradually increased along the groundwater flow path, where they displayed a pattern of lower levels in the northwest and higher levels in the southeast. From 1980 to 2021, the concentrations of major ions were increased. (2) In 1980s, the groundwater hydrochemical type predominantly exhibited HCO3—Ca. From 1980 to 2015, the hydrochemical types diversified into HCO3·Cl—Ca, HCO3—Ca·Mg, and HCO3·SO4—Ca types. Following the artificial governance, the groundwater level rise led to an increase in the concentrations of SO42− and Mg2+. Post-2015, the prevailing hydrochemical type changed to HCO3·SO4—Ca·Mg. (3) The changes in the groundwater level and ion concentrations were quantitatively strongly correlated and exhibited spatial similarity. (4) In the 1980s, the groundwater hydrochemical composition was primarily controlled by the dissolution of albite, dolomite, halite, and quartz; reverse cation exchange; and groundwater exploitation. Since 2015, the hydrochemical composition has mainly been influenced by the dissolution of albite, calcite, and quartz; positive cation exchange; river–groundwater mixing; and industrial activities, with increasing intensities of both water–rock interactions and human activities.

Under the Strong Influence of Human Activities: The Patterns and Controlling Factors of River Water Chemistry Changes—A Case Study of the Lower Yellow River

This study provides an in-depth analysis of the hydrochemical characteristics and their controlling factors in the lower reaches of the Yellow River. Through water quality sampling and analysis over two hydrological periods within a year, combined with hydrochemical methods and machine learning techniques, the study reveals the joint impact of natural factors and human activities on the spatiotemporal variations in hydrochemical constituents. The findings indicate that the water in the lower reaches of the Yellow River exhibits weak alkalinity (the pH is between 7 and 8), with the primary hydrochemical type being HCO3·SO4—Ca·Na·Mg. The temporal variation in the hydrochemical constituents is mainly influenced by rainfall, where nitrate levels are higher during the flood season due to the flushing effect of rainfall, whereas other hydrochemical constituents show an opposite temporal pattern due to the dilution effect of rainfall. The spatial variation in the Yellow River’s hydrochemistry is primarily controlled by a combination of human activities and rainfall. Using Gibbs diagram analysis, it is identified that rock weathering is the main source of ionic constituents, while agricultural fertilization, industrial emissions, and domestic wastewater discharge have significant impacts on the hydrochemical constituents. Compared to other rivers worldwide, the concentration of hydrochemical constituents in the lower reaches of the Yellow River is relatively high, especially nitrate and sulfate, which is closely related to the geological characteristics of the Yellow River basin and intense human activities in the middle and lower reaches. Principal component analysis reveals that the main controlling factors for hydrochemical constituents during the dry season in the lower reaches of the Yellow River are rock weathering dissolution and industrial activities, followed by domestic wastewater; during the flood season, the main controlling factors are rock weathering dissolution and industrial activities, followed by agricultural activities and domestic wastewater. The research findings provide theoretical support for water resource management and water quality protection in the lower reaches of the Yellow River.

The Quality and Classification of some Slack Water at Digha Shore, Midnapur District, West Bengal

Slack waters at Digha, Midnapur district, West Bengal are used for irrigation in Betel Cultivation. For quality of slack waters, estimations for pH, T. S. S., CO2, HCO3, Cl, SO4 Ca, Mg and Na were done. These slack Waters are compared - with the local sea water and world average Fresh water It is inferred that these slack waters-are not under the Influence of sea water and can well be compared with world average fresh water. Salinity and sodium hazards are low in slack waters, as such they can be used for irrigation with advantage.

Evolution origin analysis and health risk assessment of groundwater environment in a typical mining area: Insights from water-rock interaction and anthropogenic activities

Coal mining changes groundwater environment, results in deterioration of water quality and endangering human health in the mining area. However, the comprehensive study of groundwater evolution and its potential impact in mining area is still insufficient. In this study, 95 groundwater samples were collected from 2019 to 2020 in a typical mining area of China. Ion ratio coefficients, isotopic tracing technology, Entropy-weighted water quality index (EWQI) and human health risk assessment model (HHRA) were applicated to investigate the hydrochemical variation reasons, groundwater quality and its potential health risk in the study area. Results showed that the groundwater hydrochemical types changed from HCO3∙SO4–Ca∙Mg type to SO4–Ca∙Mg and SO4∙Cl–Ca∙Mg type. Water-rock interaction, agricultural activities, manure and sewage input, precipitation and evaporation controlled the groundwater hydrochemical composition. Groundwater quality showed a trend of fluctuation with an average EWQI of 59.23, 68.92, 63.75, 58.02 and 64.92, respectively. 91.6% of the water samples was fair and acceptable for drinking. The groundwater health risk of nitrate in the study area ranged from 0.03 to 17.80. Infants had the highest health risk and nitrate concentration was the most sensitive parameter. The results will present a comprehensive research of groundwater evolution and potential impacts through a typical mining area example. Thereby offering valuable insights into the influencing factors identification, hydrochemical processes evolution, protection and utilization of groundwater in global mining areas.

Groundwater Hydrogeochemical Processes and Potential Threats to Human Health in Fengfeng Coal Mining Area, China

The Fengfeng mining area is in the transition zone between the North China Plain and the Taihang Mountains, and groundwater is the main source of water supply in the district. Under the combined influence of human activities and natural geological conditions, the quality of different types of groundwater varies greatly, posing a potential threat to the safety of drinking water. In this study, hydrogeochemical processes in different types of groundwater were analyzed using multivariate statistical analysis methods with ion–ratio relationships, and a groundwater quality and health risk assessment model was developed. The research findings show that the main chemical components and TDS in the groundwater have obvious spatial distribution characteristics, i.e., the content of deep karst water (DKW) in the west is significantly lower than that of shallow pore water (SPW) in the east, and the hydrochemical type has changed from HCO3–Ca to SO4–Ca. The chemical components of SPW and DKW are mainly derived from silicates and carbonates, accompanied by weathering dissolution of sulphidic minerals, especially SPW. The chemical components of the groundwater was also influenced by the cation exchange reaction and human activities. The quality of the SPW was significantly worse than that of the DKW, and the nitrates in SPW carry a high non-carcinogenic risk, especially to children. The shallow pore water is not suitable for drinking water. This study can provide guidance on the safety of drinking water in the Fengfeng coal mining area and other areas with intensive industrial, mining, and agricultural activities.

Water–Rock Interactions, Genesis Mechanism, and Mineral Scaling of Geothermal Waters in Northwestern Sichuan, SW China

Geothermal resources are the vital renewable energy for resolving energy crisis and environmental deterioration. Understanding hydrogeochemical processes, genesis mechanisms and scaling trends is crucial for securing the sustainable utilization of geothermal resources. In this study, fourteen geothermal waters were collected for hydrochemical and δ2H–δ18O isotopic analyses in northwestern Sichuan, SW China to clarify hydrogeochemical processes, genesis mechanisms, and scaling trends. Geothermal waters were recharged via atmospheric precipitation. Three different types of geothermal waters were identified using a piper diagram. Class 1 geothermal water with HCO3–Na and HCO3–SO4–Na types formed in the contact zone with Yanshanian intrusions and heated by residual radioactive heat. The hydrochemical processes were sodium/potassium silicate dissolution and positive cation–exchange. Class 2 geothermal water with HCO3–Ca and HCO3–Ca–Mg type was carbonate–type and heated by geothermal gradient. The dissolution of carbonate minerals dominated the hydrochemical process. Class 3 geothermal water with the SO4–Ca–Mg type was determined within deep faults. The dissolution of carbonatite and gypsum minerals and the oxidation of sulfides played a vital role in the hydrochemical process. The reservoir temperatures of geothermal waters followed the orders of Class 1 (74.9–137.6 °C) > Class 3 (85.9–100 °C) > Class 2 (38.7–93.5 °C). Calcium carbonate scaling should be paid attention to in Class1 and Class 3 geothermal water, and calcium sulfate scaling merely occurs in Class 3 geothermal water. This study provides vital information for geothermal exploitation in western Sichuan and other similar areas.

Synthesis, structure, and hydration of stoichiometric ye’elimite and iron-bearing ye’elimite

Ye’elimite is the primary mineral component in calcium sulfoaluminate cements and is responsible for their early hydraulic reactivity. Herein, ye’elimite was synthesized using a novel method with CaSO4 as the sole CaO source to achieve high purity. Stoichiometric ye’elimite and iron-bearing ye’elimite were synthesized, with the highest purity obtained through sintering at 1250°C for 4 h. The crystal structure of iron-bearing ye’elimite was represented through dynamical disordering of the SO4 tetrahedron and Ca atom with the space group I 4 ¯ 3m. Moreover, the early hydration behaviors of stoichiometric ye’elimite and iron-bearing ye’elimite reacting with and without gypsum were studied. In the absence of gypsum, stoichiometric ye’elimite reacts faster than iron-bearing ye’elimite. However, in the presence of gypsum, the hydration of the former is faster than that of the latter and the hydration rates of both these minerals are higher than those observed in the absence of gypsum.

Assessment of Hydrogeochemical Characteristics and Seawater Intrusion in Coastal Aquifers by Integrating Statistical and Graphical Techniques: Quaternary Aquifer, West Nile Delta, Egypt

The Quaternary aquifer in the western Nile Delta is threatened by seawater intrusion. Few studies have integrated diverse techniques for the assessment of seawater intrusion in this aquifer. The present study aims to determine the geochemical processes and impact of seawater intrusion on this aquifer. To accomplish this investigation, the integration of hydrogeochemical, statistical, multivariate statistical, and graphical tools were implemented on 75 groundwater samples and 5 soil samples. The physicochemical variables were analyzed using hierarchical cluster analysis (HCA), saturation index (SI), ionic ratios, ionic relationships, the seawater intrusion index (SWI) and the correlations among 16 hydrochemical parameters, to identify the influencing processes of groundwater quality in the study area. According to the statistical study, the groundwater is divided into four groups. Those are distributed, from north to south: Group1 (G1), Group2 (G2), Group4 (G4), and Group3 (G3). The samples of G1 and G2 are distinguished by Na–Cl chemical type. While G4 has two main ion associations, HCO3–Ca–Mg and Cl–SO4–Na, G3 is characterized by HCO3–Cl–SO4–Ca–Na type. The processes that affect the chemistry of the groundwater are the seawater intrusion, ion exchange, silicate and Ca-rich mineral weathering, and mineral deposition. G1 and G2 groups are primarily influenced by seawater incursion, evaporation, and the ion exchange mechanism. In addition, the weathering of silicate minerals has a substantial effect on G3 and G4 groups, resulting in the creation of carbonate minerals.

Identification of the hydrochemical features, genesis, water quality and potential health hazards of groundwater in Dawen River Basin, North China

Groundwater resources fulfill a key role in socioeconomic development and residential water use in the Dawen River Basin (DRB). This study sampled and tested three types of groundwater in the DRB, including pore groundwater (PGW), fissure groundwater (FGW), and karst groundwater (KGW). Groundwater in the DRB was assessed for hydrochemical characteristics, quality, and hazards to human health by nitrate contents. Results identified the dominant groundwater anion and cation to be HCO3− and Ca2+, respectively, whereas groundwater was generally weakly alkaline hard-fresh water. The groundwater contents of main chemical components during wet season exceeded those in the dry season, with the rank of groundwater types by chemical component contents being: PGW > KGW > FGW. A Durov diagram indicated groundwater in the DRB to be mixed HCO3-Ca and HCO3·SO4–Ca·Mg types. Rock weathering (silicate and carbonate rocks) was found to be the predominant process regulating groundwater chemistry of the DRB, whereas human activities also had a significant impact, particularly for high NO3− related to agricultural activities. Groundwater quality of the DRB was relatively good overall, falling into the good and moderate classification grades, with that of the PGW the worst. Long-term human direct consumption or exposure to groundwater of DRB poses certain health risks due to groundwater nitrate, with the risk for children highest. The spatial variations in quality of groundwater and nitrate health hazard in the DRB were relatively consistent, with better quality and lower health risk of PGW and FGW in the east than in the west, and that of KGW better in the center than in the east and west. The present study can provide some reference for groundwater safety and protection management in DRB and other similar areas in the world.

Hydrogeochemical characterization of groundwater resources in Wadi Araba Basin, Southern Jordan

Groundwater quality is an important factor that determines its usage for drinking and irrigational use. This study was carried out along the quaternary alluvial aquifer which extends along Wadi Araba groundwater basins, in southern Jordan. Chemical and physical parameters were measured and analyzed for thirty-seven groundwater samples collected from twenty-one wells in the study area during two periods in the year 2019; the spring season (April–May) was represented by fourteen samples and the autumn season (August–September) represented by twenty-three samples were collected to determine its suitability for drinking and irrigational purposes. The groundwater in the study area is generally of low alkalinity with an average pH value of less than 8 for both spring and autumn seasons. The water of the area is excessively mineralized due to salinity, and the increase in water salinity of the southern Wadi Araba basin is less expressed than in the northern part. The hydrochemical characterization shows that most wells of the study area are characterized by HCO3–Ca–Mg and HCO3–SO4–Ca–Mg types in the eastern escarpments of Wadi Araba (i.e., recharge area) and Cl–SO4–Na and Cl–Na types in the discharge area. There is no substantial change in the hydrochemical composition during the two seasons. Based on the Piper diagram, most of the groundwater samples (91.8%) belong to class “E” as “earth alkaline water with increased portions of alkalis with prevailing sulfate and chloride.” The Durov diagram reveals that most groundwater samples (62.2%) lay in the water genesis “field 6” which indicates that the water may be related to the reverse ion exchange of Na–Cl. The chemical composition of the water samples was compared with the drinking water standards of the World Health Organization and the Jordanian Standard. Groundwater from this area was not suitable to be a source for direct drinking based on total hardness and total dissolved solids. The dominant cation is sodium, while the dominant anion is chloride. The calculations of saturation indices for the two sampling campaigns for different minerals showed negative values of (SI) for carbonates minerals (anhydrite, gypsum, sylvite, and halite). This suggests that the groundwater in the alluvial aquifer is undersaturated with respect to these minerals in most of the study area. This is indicative of the fact that these minerals are undergoing the process of dissolution. The mineral saturation indices suggest that the dominating hydrochemical processes were dissolutions of evaporite minerals (halite and gypsum), carbonate minerals (such as calcite, dolomite, and rhodochrosite), the manganese oxide minerals (such as jarosite-K, hausmannite, pyrochroite, and pyrolusite) and reverse ion exchange.

Application of geothermometric and hydrochemical methods to the investigation of thermal water of sources in the Northeastern of Algeria case of Setif city

Thermal water in northeastern Algeria (Setif) is a promising, sustainable resource of energy. To date, thermal water has not been used as a source of renewable energy in Algeria as no clear strategy has yet been developed for its use. In this study, eight samples of thermal water springs distributed within the area of Setif city were assessed, and their physical and chemical parameters (such as temperature, potential of hydrogen, electrical conductivity, and major ionic composition, including the K+, Na+, Ca2+, Mg2+, Cl−, SO42− and HCO3−) were measured. The results show that the temperature, potential of hydrogen and the electrical conductivity range between 30 and 52 °C (as measured in field), 6.92 and 7.35, and 1170 and 3160 µS/cm, respectively. Furthermore, the results indicate the existence of four hydrogeochemical facies dominating the hydrogeological system, which are SO4–Ca, Na–SO4, HCO3–Na and Cl–Na. The interaction with Jurassic limestone and the existence of evaporates along the upwelling system, respectively, control this. Due to the high variation of temperature, different geothermometers were used to estimate the geothermal reservoir temperature, the application of silica geothermometer (Quartz), because it is the most suitable in our case, gives temperatures estimated at the origin of the order of 80° C. It is higher than that measured at emergence, it reflects an average dissipation of 48° C. According to an analysis of these findings and the geothermal gradient in the area, two aquifer systems of the thermal complex are supplied by a reservoir that is stored in fissured Jurassic limestone that is more than 2600 m deep.

Evaluation of groundwater quality and hydrochemical characteristics in the shallow aquifer of El-Oued region (Algerian Sahara)

The water quality of the aquifer of the El-Oued region (Algerian Sahara) is deteriorating in water quality due to anthropogenic effects and over exploitation of the groundwater resources. This study assesses the quality of groundwater in the El-Oued shallow aquifer for domestic and irrigation purposes and highlights the various geochemical processes that contribute to the mineralization of this water. Twenty-five water samples were collected. The measured and analyzed parameters are: pH, EC, TDS, Na+, K+, Ca2+, Mg2+, Cl−, SO42−, NO3− and HCO3−. The assessment of water potability using the Water Quality Index (WQI) method shows two classes of water quality, namely, the very poor class (8%) and the unsuitable for drinking class (92%). Agricultural water quality was assessed using the parameters; electrical conductivity (EC), sodium adsorption ratio (SAR), sodium percentage (Na %), Kelly ratio (KR), permeability index (PI), magnesium hazard (MH), residual sodium carbonate (RSC) and chloride content. The results showed that the water of this shallow aquifer is unsuitable for irrigation based on EC, Cl− and USSL diagram. This aquifer discloses three facies of water: Cl–Na–Ca (12%), SO4–Na (36%) and SO4–Ca–Mg (52%). In addition, an analysis of physicochemical data obtained from water samples was conducted using correlation matrices, PCA, bivariate plots, and Gibbs diagrams; the saturation indices of the main minerals was also calculated. These analyses have shown that the main reactions responsible for the evolution of water types in the El-Oued shallow aquifer fall into four categories: (1) a mixing process in the waters of deep aquifers (the Complexe Terminal aquifer and the Continental Intercalaire aquifer); (2) the dissolution of salts (in particular, gypsum and halite); (3) cation exchange processes affecting the concentration of Na+, K+, Mg2+, and Ca2+; and (4) anthropogenic influences from domestic sewerage and agricultural activities.

Recharge sources and hydrogeochemical evolution of groundwater in a heterogeneous karst water system in Hubei Province, Central China

Although numerous studies on hydrogeochemistry in karst catchments have been performed, some challenges in understanding their hydrogeochemical behavior remain due to the unique architecture of karst groundwater systems and the high heterogeneity of the karst medium. Here we used a multicriteria approach combining hydrodynamic, hydrochemical, and stable isotopic tools to investigate the impact of heterogeneity on karst hydrogeochemistry in a mountainous area of Hubei Province, Central China. Our results showed that groundwater was dominated by Ca2+, Mg2+, HCO3−, and SO42−, and typically characterized by HCO3–Ca·Mg type in the shallow aquifer and by SO4–Ca·Mg type in the deep aquifer. With increasing circulation depth, water-rock interactions and the heterogeneity of the karst medium produced water with increased Ca2+, Mg2+, Sr2+, and SO42− concentrations, and also increased the dissolved total solids. Calcite, dolomite, and gypsum dissolution in local and intermediate flows were important geochemical processes in groundwater evolution, and calcite precipitation occurred in the regional flow due to dedolomitization, supported by PHREEQC modeling of minerals. The decreased major ions and increased nitrate with increasing δ18O due to the dilution of shallow groundwater by high δ18O recharge and nitrogen fertilizer required during the summer rainy season were found relying on Plots of δ18O vs major ions, which offer an alternative approach to learn seasonal effects of hydrogeochemistry. All advances presented were integrated into a hydrogeochemical conceptual model, including local, intermediate, and regional flows, hydrogeochemical evolution, horizontal and vertical karst zones, hydrochemistry, and stable isotopes of groundwater, providing a typical model for multiple karst groundwater systems in Central China.

Origin of the low-medium temperature hot springs around Nanjing, China

Abstract The exploration of the origin of hot spring is the basis of its development and utilization. There are many low-medium temperature hot springs in Nanjing and its surrounding karst landform areas, such as the Tangshan, Tangquan, Lunshan, and Xiangquan hot springs. This article discusses the origin characters of the Lunshan hot spring with geological condition analysis, hydrogeochemical data, and isotope data. The results show that the hot water is SO4–Ca type in Lunshan area, and the cation content of SO4 is high, which are related to the deep hydrogeological conditions of the circulation in the limestone. Carbonate and anhydrite dissolutions occur in the groundwater circulation process, and they also dominate the water–rock interaction processes in the geothermal reservoir of Lunshan. The hot water rising channels are deeply affected by the NW and SN faults. Schematic diagrams of the conceptual model of the geothermal water circulation in Lunshan are plotted. The origin of Tangshan, Tangquan, and Xiangquan hot springs are similar to the Lunshan hot spring. In general, the geothermal water in karst landforms around Nanjing mainly runs through the carbonate rock area and is exposed near the core of the anticlinal structure of karst strata, forming SO4–Ca/SO4–Ca–Mg type hot spring with the water temperature less than 60°C. The characters of the hot springs around Nanjing are similar, which are helpful for the further research, development, and management of the geothermal water resources in this region.

Hydrochemical characteristics and pollution source apportionment of the groundwater in the east foothill of the Taihang Mountains, Hebei Province

The east foothill of the Taihang Mountains, Hebei Province, is an important groundwater recharge and transport area in the North China Plain. It is of practical significance to study the groundwater hydrochemical characteristics of this area for rational groundwater regulation. In this study, the Chadha rectangular diagram and Piper trilinear diagram were adopted to identify the relevant hydrochemical processes, and the main groundwater hydrochemical type was the HCO3·SO4–Ca. Descriptive statistical methods, correlation analysis, major ion ratio determination and principal component analysis (PCA) were employed to analyze the formation mechanism of groundwater hydrogeochemical characteristics and to identify the sources of the main groundwater ions in the study area. The results showed that Ca2+ and HCO3− were the dominant groundwater cation and anion, respectively, and the Gibbs diagram demonstrated that the majority of groundwater samples occurred in the rock weathering-dominated area. Bivariate diagrams revealed that mineral dissolution and ion exchange controlled the groundwater geochemistry. The study area was seriously polluted by NO3–, which might be due to the application of farmland fertilizers and leakage of rural domestic sewage and garbage. PCA yielded three principal components (PCs), which represented processes influenced by salinity, human activity and fluoride impacts on the groundwater chemistry. The distribution of high-positive PC scores verified the influences of the various processes on the groundwater study area, which is an effective tool to formulate and implement management strategies for the sustainable development of groundwater areas.

Groundwater Chemical Characteristics and Controlling Factors in a Region of Northern China with Intensive Human Activity.

The identification of groundwater chemical characteristics and the controlling factors is of major concern in water environment studies. In this study, we identified the groundwater chemical characteristics, evolution laws and main control factors in a region severely affected by human activities using hydrochemical and multivariate statistical techniques. The results showed that the concentrations of NO3− and TH were the primary pollution factors in the region with intensive human activity because of high concentration and over the standard rates. The major types of groundwater chemistry were HCO3·SO4–Ca and HCO3·SO4–Ca·Mg. The sulfate-type water was as high as 75.0%, 69.2% and 41.2% in the three hydrogeological units. In addition, there were Cl-type and Na-type waters, indicating that the groundwater in this area has been significantly affected by human activities. A principal component analysis (PCA) indicated that the three factors affecting groundwater hydrochemistry in the study area are domestic sewage and fertilizer, water–rock interactions and industrial wastewater. Therefore, we suggest that the government and water environment management departments should prevent the discharge of domestic and industrial wastewater without standardized treatment first in order to effectively prevent the further deterioration of groundwater quality in this area.

Multidimensional Analysis of the Contamination Status, Corrosivity and Hydrogeochemistry of Groundwater from Parts of the Anambra Basin, Nigeria

Groundwater samples from five rural agricultural villages within the Anambra basin of southeastern Nigeria were selected for the determination of their drinking quality, hydrogeochemical characteristics, corrosivity and scaling potentials. The groundwater temperature ranged from 10 to 31 °C. The pH measurements revealed that the samples are acidic. Parameters such as total dissolved solids, electrical conductivity, magnesium, calcium, sodium, chloride, bicarbonate, sulfate and nitrate recorded scores within their respective standard limits. However, potassium and phosphate pollution was observed in some samples. Synthetic pollution index was used to summarize the drinking water quality of the samples. The results showed that 88% of the samples were moderately polluted while 12% were highly polluted. Thus, the results show that they have questionable drinking water quality. Several indices used for corrosivity and scaling analyses indicated that, although the samples pose low risk of scaling (encrustation), they are severely aggressive. Hence, they are likely to deteriorate metallic water storage and distribution facilities in the study area. The predominant water facies are Cl·SO4–Ca·Mg and Cl·SO4–Na·K. Multiple hydrogeochemical and chemometric analytical models were integrated to better unravel and understand the geochemical history, processes and evolution of the groundwater. All of the models used jointly indicated that mixed, multiple processes, namely mineral-rock weathering, ionic exchange processes and anthropogenic inputs, are responsible for the predominant hydrogeochemistry observed in the study area. However, in this regard, natural, geogenic processes were identified as more important factors than those from anthropogenic activities.

Hydrogeochemical characteristics of a closed karst groundwater basin in North China

Understanding the hydrogeochemical processes of carbonate aquifers is essential for utilizing local karst groundwater resources sustainability. Integrating hydrochemistry, environmental isotopes and hydrogeological conditions was used to study hydrogeochemical characteristics of a closed karst groundwater basin located in Shandong Province, North China. The dominant hydrochemistry type was HCO3–SO4–Ca in the karst groundwater system. Carbonates dissolution (especially calcite dissolution) as the main rock chemical weathering dominated the chemical compositions of the carbonate aquifers. Hydrogeochemical evolution processes of the closed karst groundwater basin were mainly carbonates dissolution accompanied with weak influences of human activities and weak evaporation during the recharging of atmospheric precipitation.

The use of GIS and water quality index to assess groundwater quality of krimat aquifer (Essaouira; Morocco)

The aim of this present study was to evaluate groundwater quality in the upstream part of the Essaouira basin. A detailed geochemical study of groundwater region is described, and the origin of the chemical composition of groundwater has been qualitatively evaluated, using multivariate statistical methods (PCA, HCA), and Water Quality Index (WQI) was used to determine the suitability of water for drinking. To attempt this investigation, 38 samples were analysed for various physicochemical parameters such as temperature, pH, TDS, Na, NO3, K, Ca, HCO3, Cl, Mg, and SO4. The results obtained showed that the facies characterizing the study area was a combination of Ca–SO4 and mixed Ca–Mg–Cl. Hydrochemical approach based on the bivariate diagrams of major ions indicates that the origins of groundwater mineralization are the result of (I) evaporite dissolution; (II) cation-exchange reactions; and (III) evaporation processes. The WQI values range from 82.3 to 390.9, and therefore the water samples can be categorized into five groups: excellent water to water unsuitable for drinking. In global, 61% of the groundwater sampled had poor water quality, 18% were very poor water quality, 16% are unsuitable for drinking, and just 6% represent a good quality. However, the results of this paper indicate that most water is not safe for drinking and needs further treatment.

Hydrogeochemistry characteristic contrasts between low- and high-antimony in shallow drinkable groundwater at the largest antimony mine in hunan province, China

The antimony (Sb) content of shallow drinkable groundwater at Xikuangshang mine area (in Hunan province, China) has exceeded China's national drinking water quality guidelines, posing a serious threat to the health of residents in the mine area. The difference in hydrogeochemistry characteristics and water-rock interactions between low Sb groundwater (<0.015 mg/L) and high Sb groundwater (>0.015 mg/L), however, remains unclear. In this study, 24 samples were collected from shallow drinkable groundwater at the mine area. The hydrogeochemistry data and water-rock interactions were analyzed to reveal the condition leading to the formation of high Sb groundwater. Compared with low Sb groundwater, high Sb groundwater has a higher level of Na+, TDS, and SO42-, which increase by 6.38, 1.84, and 4.04 times, respectively. The low Sb groundwater is mainly controlled by Ca–HCO3–SO4 type, whereas the high Sb groundwater is controlled by Ca–HCO3–SO4 type as the main facies, and Ca–Na–SO4 type and Ca–SO4–HCO3 type as the secondary facies. The chemical composition of low Sb groundwater is mainly influenced by the dissolution of carbonate minerals and the chemical composition of high Sb groundwater is controlled by ion-exchange interaction and dissolution of carbonate minerals and silicate minerals, among which ion-exchange interaction is the most important factor. The outcomes of this research provide a better understanding of the mechanisms of Sb pollution in groundwater and it will help in securing safe drinking water sources for local communities.