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To explain the presence and spatial distribution of NO3− and N–NH3 in the Aquifer of the Metropolitan Area of Mexico City (AMAMC), a hydrogeochemical and isotopic analysis using 13CDIC (as well as the stable isotopes 18O and 2H) in groundwater was conducted. This aquifer is located in an old closed lacustrine volcano-sedimentary basin; some wells hosted in the semi-confined zone contain high N–NH3 concentrations, while others present NO3− contents in the recharge zones (hosted in an oxidizing environment). In this study, a change in the isotopic signature (primarily in 18O and 2H) was observed from the recharge zones to the basin center in some of the wells with high NO3− concentrations, this behavior can be attributed to evaporation during the incorporation of recently infiltrated water. In addition, the results for 13C (along with 2H) in wells with the highest N–NH3 concentrations exhibited an atypically broad range of values. Results indicated the occurrence of hydrogeochemical and/or biochemical processes in the aquifer (in an oxidizing or reducing environment), such as organic degradation, bacterial decomposition (primarily in the ancient Lake Texcoco and which acts as a natural sink for carbon, nitrogen, sulfur, and phosphorus), besides rock weathering and dissolution, which may be responsible for a very marked isotopic modification of the 13C (and, to a lesser extent, 2H). Methanotrophic bacterial activity and methanogenic activity may be related to N–NH3 removal processes by oxidation and residual water incorporation respectively, whereas the increase in the NO3− content in some wells is due to the recent contribution of poor-quality water due to contamination. [ABSTRACT FROM AUTHOR]

A hydrogeochemical study of groundwater in Chhotanagpur Plateau, India, was accomplished to evaluate general hydrochemistry, hydrogeochemical processes and quality for irrigation purposes. Samples were collected and analysed for physico-chemical parameters including pH, conductivity and major ions. The analytical results indicate that groundwater is acidic to slightly alkaline. The overall ionic concentration in the area follows the order: Ca2+ > Mg2+> Na+ > K+ > NH4+ > Li+ and HCO3− > Cl− > SO42− > NO3- > F− > PO4−. Rock weathering, in particular carbonate and silicate weathering, determines groundwater hydrochemistry. The bivariate plot of (Ca + Mg) versus (HCO3 + SO4) reveals that the reverse ion exchange process has contributed to the hydrochemistry of the region. Piper diagram reveals that most of the groundwater samples are Ca–HCO3 and mixed Ca–Mg–SO4 type while some samples are Ca–Cl type. The results of the principal component analysis highlight that geological factors determine the characteristics of groundwater. However, anthropogenic activities like urban sewage discharge, chemical and pesticide discharge, and mining activities have a detrimental impact on groundwater quality. Spatial variation in the composite groundwater quality index for irrigation calculated by inverse distance weighted method reveals that the groundwater quality ranges from good to excellent in 16.5% and 83.5% of the samples, respectively. In a few samples, higher concentrations of magnesium, sodium and sulphate make the groundwater unsuitable for irrigation. The study recommends that anthropogenic activities should be carried out properly to ensure the long-term sustainability of groundwater in the area. The findings will be helpful to government officials and policy planners for proper groundwater management. [ABSTRACT FROM AUTHOR]

Groundwater is widely regarded as being among the freshwater natural resources with the lowest levels of contamination. Nevertheless, the saltwater intrusion has resulted in the contamination of groundwater in coastal regions with lower elevation. The rationale of the present work is to investigate the chemistry of groundwater, to identify the various facies of groundwater, to identify the processes that influence groundwater chemistry and saltwater intrusion, and to evaluate the groundwater's aptness for use in drinking and farming. In order to gain an understanding of the groundwater quality as well as the salinization process that occurs in coastal aquifers as a result of hydrogeochemical processes, a total of 108 groundwater samples (54 each in pre- and post-monsoon) were taken and analyzed for several physiochemical parameters in the southern part of the Puri district in the Indian state of Odisha. The data has undergone analysis and examination to identify the factors (such as hydrological facies, potential solute source in water, and salinization process) that contribute to groundwater salinity. The result showed the chemistry controlling processes of rock-water interaction as per Gibbs diagram. The majority of shallow aquifers exhibit the Na-Cl type of facies as per the Piper plot. A total of 37% pre-monsoon and 33% post-monsoon samples having Na+/Cl− ratio below the threshold of 0.86 indicating the influence of saltwater intrusion. In both seasons, it was observed that 74% of the samples exhibited a Na+ concentration that exceeded the permissible limit set by the World Health Organization (WHO) for drinking purposes. The findings indicate that most groundwater failed to pass safe drinking water and irrigation standards due to saltwater intrusion. Consequently, the monitoring of coastal aquifer quality has become imperative in order to ensure the sustainability of aquifers and the development of groundwater resources. This is because coastal aquifers are highly vulnerable to saltwater intrusion, primarily as a result of the extensive extraction of groundwater for diverse purposes. [ABSTRACT FROM AUTHOR]

This study examines the hydrogeochemical and heavy metal parameters of groundwater in Ojo District to determine its suitability for use, potential sources, and human health implications. Ten groundwater samples were assessed, and hydrogeochemical modelling was performed via the Aquachem software. The chemical ions were in the following order: EC > (107.78–448.65 μS/cm) > TDS (182.02–320.77 mg/l) > TH (46.22–182.45 mg/l) > pH (5.55–6.35); HCO3− (64.13–125.82 mg/l) > Na+ (36.87–96.49 mg/l) > Ca2+ (47.65–58.88 mg/l) > SO42− (19.94–53.67) > NO3− (15.55–44.25 mg/l) > Cl− (20.43–27.16 mg/l) > Mg2+ (11.09–16.87 mg/l) and K+ (2.55–7.86 mg/l). The concentrations of heavy metals in groundwater were in the range of: Fe (0.11–0.27 mg/l) > Mn (0.003–0.16 mg/l) > Ni (0.05–0.12 mg/l) > Zn (0.003–0.05 mg/l) > Pb (0.001–0.03 mg/l) > As (0.001–0.005 mg/l) > Cr (0.002–0.005 mg/l) > Cd (0.001–0.003 mg/l) and Cu (0.001–0.0002 mg/l), with Pb, Mn, and Ni exceeding their allowable limits. The Schoeller and Gibbs plots revealed that the major mechanisms controlling the aquifer groundwater in Ojo region are geological rock weathering and mineralization, with a minimal influence of saltwater intrusion. The piper trilinear diagram also revealed that none of the cation was dominant while the anions were strongly dominated by HCO3− (weak acids). The hydrogeochemical facies which describes the geochemical characteristics of the groundwater were classified into 3 types; “Ca2+–Mg+–HCO3– (65 %)”, “mixing zones (30 %)”, and “Na+–K+–Cl––HCO3– (5 %)”. The hydrogeochemical modelling revealed that the groundwater is characterized by forward cation exchange, while rock–water interactions (silicate dissolution) were heavily involved in the geochemical processes. The single pollution index showed that Pb, Ni, and Mn contributed significantly to contamination, and the multi–pollution indices showed that the groundwater was slightly-moderately polluted. The integrated groundwater quality index revealed that only 10 % were clean, 50 % were poor or moderately unclean, 30 % were highly unclean, and only 10 % were extremely unclean (unfit for utilization). The water pollution index showed that 70 % of the groundwater was good. The irrigation indices suggest that the groundwater would enhance soil quality and support plant growth. Multivariate analysis revealed that the groundwater is being influenced by geogenic factors and anthropogenic activities. The health risk assessment (Hazard Quotient and Hazard Index) showed that exposure of adults to the investigated groundwaters could result in noncarcinogenic adverse effects. The cancer risk values also exceeded the minimum limit (1.0 x 10−6) and thresholds (1.0 x 10−4) for adults, indicating the carcinogenic potential of the groundwater.

Frequent surface water–groundwater interactions and prevalent anthropogenic inputs make karst water systems vulnerable to human disturbance. As a typical karst region in North China, the Jinan Spring Catchment has become increasingly threatened due to rapid population growth and urban expansion. In this study, the local river–spring interaction and its interference with the hydrogeochemical evolution of groundwater are evaluated based on water stable isotopes and hydrochemistry. Twenty-two karst groundwater, eleven Quaternary pore water, sixteen spring water, and thirty-two surface water samples were collected during low- and high-flow conditions over the course of a year. The isotopic signatures of four different water types display significant differences, reflecting the recharge–discharge relationship of the karst water system. Mountainous springs feature lighter isotopes, whereas urban springs have significantly heavier isotopes. The result of end-member mixing analysis shows that the surface–groundwater interaction varies spatially and temporally within the spring catchment. Urban springs receive considerable replenishment from the surface water, especially after rainy episodes (up to 50%), while mountainous springs show little hydraulic dependence on surface water leakage (4~6%). Local mineral dissolution (including calcite, dolomite, gypsum, and halite), CO2 dissolution/exsolution, and cation exchange are the main hydrogeochemical processes constraining water chemistry in the spring catchment. The deterioration of water quality can be attributed to anthropogenic influences involving the discharge of domestic effluents, agricultural activities, and irrigation return flow. The findings of this work can improve our understanding of the complex karst water system and serve as a reference for sustainable groundwater management in other karst areas of northern China. [ABSTRACT FROM AUTHOR]

Chamwino district, central Tanzania is a semi-arid granitic complex province, where groundwater is the major source of water for domestic and other uses. However, groundwater in the area is affected by salinity, thus, lowering the availability of potable water for various uses, decrease in crop production, taste less, wastage of soap, and abnormal pain. Due to this, this study sought to characterize groundwater using hydrogeochemical facies and signatures in order to identify the factors influencing the distribution of salt water in the Chamwino Granitic Complex. A total of 141 groundwater samples were collected from wells spatially distributed within the study area from January 2023 to April 2023, (a season of relatively low rainfall). All samples were subjected to in situ analyses of physicochemical parameters pH, temperature (T), total dissolved solids (TDS), electrical conductivity (EC), and salinity using a multi-parameter water analyzer and analyses of major ions (Ca2+, Mg2+, K+, Na+, Cl−, SO42−, HCO3−, and NO3−). The study revealed that the dominant cations in the groundwater are Na+ > Ca2+ > Mg2+, and the anions are Cl− > HCO3− > SO42. Five geological formations (granodiorite, tonalitic orthogenesis, migmatite, tonalite, and alluvium) were identified, and each is characterized by its unique groundwater facie. In the areas that are dominated with granodiorite, the major hydrogeochemical facies were Ca–HCO3, Na–Cl, Ca–Na–HCO3, Ca–Mg–Cl, and Ca–Cl water types; tonalitic orthogenesis was dominated by Ca–HCO3, Na–Cl, Ca–Mg–Cl, and Ca–Cl water types; migmatite was dominated by Ca–HCO3, Na–Cl, Ca–Mg–Cl, and Ca–Cl water types; tonalite was dominated by Na–Cl, Ca–Mg–Cl, and Ca–Cl water types; and alluvium was dominated by Na–Cl and Ca–Mg–Cl and Ca–Cl water types. The common hydrogeochemical facies in all five geological units are Na–Cl, Ca–Mg–Cl, and Ca–Cl water types. It is revealed that the groundwater in the study area is alkaline in nature and slightly saline with salinity level between 0.2 mg/L (fresh water) and 2.8 mg/L (brackish water) with mean 1.07 mg/L (of 141 samples). The factors controlling groundwater salinity distribution are mainly rock-water interaction and ion exchange reactions. Groundwater salinity in the study area is largely attributed to the abundance of Na+, Ca2+, Cl− and SO42−. Abundance of Na+ and Ca2+ is the results of both, weathering of feldspar minerals particularly plagioclase (Na–Ca feldspars) which are the major mineral in granites, and evaporation crystallization cycles of evaporates in semi-arid areas such as Chamwino. Also, such evaporation crystallization cycles account for the abundance of Cl− and SO42− especially in areas dominated by alluvium. However, anthropogenic activities as evidenced by elevated nitrate up to 212.6 mg/L in congested areas are also likely to contribute in area) to the elevated Cl− and SO42−. In other geological units such as tonalitic orthogneiss, migmatite and granodiorite, there was an ostensible mixing of saline water with fresh water from local recharge as indicated by the abundance of HCO3− ions. Nonetheless, the hydrogeochemical characterization of groundwater in the Chamwino granitic complex suggests that there is little possibility for groundwater to evolve to a carbonate water type (fresh water) because the groundwater salinity is mainly geogenic, unless artificial recharge through rainwater harvesting is applied.

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. [ABSTRACT FROM AUTHOR]

This study investigates the hydrogeochemical processes of groundwater in the Naama watershed in southwestern Algeria, aiming to determine the relationship between geochemical processes and groundwater quality. Multivariate statistical and thermodynamic techniques were applied to 22 groundwater samples to understand the hydrochemical evolution of the watershed. The results indicate that the water is predominantly characterized by a calcium-bicarbonate water type in the center of the study area (23% of samples) and a sodium chloride sulfate water type mainly located in the north due to Triassic dissolution and proximity to Sabkha (50% of samples), and the remaining 27% of samples are represented by the sulfate-sodium facies. Cluster analysis and principal component analysis revealed three major hydrochemical types reflecting different hydrochemical processes occurring along groundwater flow as electrical conductivity increased. The findings of this study could inform strategies for the sustainable management of groundwater resources in the Naama region and similar regions. [ABSTRACT FROM AUTHOR]

Frequent surface water–groundwater interactions and prevalent anthropogenic inputs make karst water systems vulnerable to human disturbance. As a typical karst region in North China, the Jinan Spring Catchment has become increasingly threatened due to rapid population growth and urban expansion. In this study, the local river–spring interaction and its interference with the hydrogeochemical evolution of groundwater are evaluated based on water stable isotopes and hydrochemistry. Twenty-two karst groundwater, eleven Quaternary pore water, sixteen spring water, and thirty-two surface water samples were collected during low- and high-flow conditions over the course of a year. The isotopic signatures of four different water types display significant differences, reflecting the recharge–discharge relationship of the karst water system. Mountainous springs feature lighter isotopes, whereas urban springs have significantly heavier isotopes. The result of end-member mixing analysis shows that the surface–groundwater interaction varies spatially and temporally within the spring catchment. Urban springs receive considerable replenishment from the surface water, especially after rainy episodes (up to 50%), while mountainous springs show little hydraulic dependence on surface water leakage (4~6%). Local mineral dissolution (including calcite, dolomite, gypsum, and halite), CO2 dissolution/exsolution, and cation exchange are the main hydrogeochemical processes constraining water chemistry in the spring catchment. The deterioration of water quality can be attributed to anthropogenic influences involving the discharge of domestic effluents, agricultural activities, and irrigation return flow. The findings of this work can improve our understanding of the complex karst water system and serve as a reference for sustainable groundwater management in other karst areas of northern China.

Groundwater quality monitoring and geochemical characterization in the phreatic aquifer are critical for ensuring universal and equitable access to clean, reliable, and inexpensive drinking water for all. This research was intended to investigate the hydrogeochemical attributes and mechanisms regulating the chemistry of groundwater as well as to assess spatial variation in groundwater quality in Satna district, India. To accomplish this, the groundwater data comprising 13 physio-chemical parameters from thirty-eight phreatic aquifer locations were analysed for May 2020 by combining entropy-weighted water quality index (EWQI), multivariate statistics, geochemical modelling, and geographical information system. The findings revealed that the groundwater is fresh and slightly alkaline. Hardness was a significant concern as 57.89% of samples were beyond the permissible limit of the World Health Organisation. The dominance of ions were in the order of Ca2+ > Na+ > Mg2+ > K+ and HCO3− > SO42− > Cl− > NO3− > F−. Higher concentration of these ions is mainly concentrated in the northeast and eastern regions. Pearson correlation analysis and principal component analysis (PCA) demonstrated that both natural and human factors regulate groundwater chemistry in the region. The analysis of Q-mode agglomerative hierarchical clustering highlighted three significant water clusters. Ca–HCO3 was the most prevalent hydro-chemical facies in all three clusters. Geochemical modelling through various conventional plots indicated that groundwater chemistry in the research region is influenced by the dissolution of calcite/dolomite, reverse ion exchange, and by silicate and halite weathering. EWQI data of the study area disclosed that 73.69% of the samples were appropriate for drinking. Due to high salinity, Magnesium (Mg2+), Nitrate (NO3−), and Bicarbonate (HCO3−) concentrations, the north-central and north-eastern regions are particularly susceptible. The findings of the study may be accomplished by policymakers and groundwater managers to achieve sustainable groundwater development at the regional scale. [ABSTRACT FROM AUTHOR]

This study focuses on determining significant controlling factors of chemical consequences, inverse geochemical modeling, water quality, and human health risk in the Varuna River basin of India. The study interprets that according to pH, total dissolved solids, and total hardness, the maximum number of groundwater samples are alkaline, fresh, and have substantial hardness. The abundance of major ions follows a pattern: Na > Ca > Mg > K, and HCO3 > Cl > SO4 > NO3 > F. Piper diagram shows that Ca–Mg–HCO3 facies are predominant during both seasons. Na-normalized molar ratios of HCO3/Na, Mg/Na, and Ca/Na are 0.62, 0.95, and 1.82 (pre-monsoon) and 0.69, 0.91, and 1.71 (post-monsoon), respectively, elucidating the coupled silicate and carbonate weathering (dolomite dissolution) sources. The Na/Cl molar ratio is 5.3 (pre-monsoon) and 3.2 (post-monsoon), indicating silicate alteration as the primary process rather than halite dissolution. The chloro-alkaline indices confirm the presence of reverse ion- exchange. Geochemical modeling using PHREEQC identifies the formation of secondary kaolinite minerals. The inverse geochemical modeling categorizes the groundwaters along the flow path from recharge area waters (Group I: Na–HCO3–Cl), transitional area waters (Group II: Na–Ca–HCO3), and discharge area waters (Group III: Na–Mg–HCO3). The model demonstrates the prepotency of water–rock interactions in pre-monsoon justified by the precipitation of Chalcedony and Ca-montmorillonite. The mixing analysis shows that in the alluvial plains, groundwater mixing is a significant hydrogeochemical process that affects groundwater quality. The Entropy Water Quality Index ranks 45% (pre-monsoon) and 50% (post-monsoon) of samples as an excellent category. However, the non-carcinogenic health risk assessment shows that children are more susceptible to fluoride and nitrate contamination. [ABSTRACT FROM AUTHOR]

An understanding of the vertical variations in hydrogeochemical processes in various aquifers and quality suitability assessment is crucial for the utilization of groundwater in the Ningtiaota coalfield of Ordos Basin, Northwestern China. Based on 39 water samples collected from surface water (SW), Quaternary pore water (QW), weathered fissure water (WW), and mine water (MW), we conducted self-organizing maps (SOM) algorithm, multivariate statistical analysis (MSA), and classical graphical methods to elucidate the mechanisms controlling the vertical spatial variations in SW and groundwater chemistry and conducted a health risk assessment. The findings indicated that the hydrogeochemical type showed a transition from the HCO3−-Na+ type in SW to the HCO3−-Ca2+ type in QW, then to the SO42−-Mg2+ type in WW, and back to HCO3−-Na+ type in MW. Water–rock interaction, silicate dissolution, and cation exchange were the main hydrogeochemical processes in the study area. Additionally, groundwater residence time and mining operations were critical external factors that affect water chemistry. Contrary to phreatic aquifers, confined aquifers featured greater circulation depth, water–rock interactions, and external interventions leading to worse quality and higher health risks. Water quality surrounding the coalfield was poor, causing it to be undrinkable, with excessive SO42−, arsenic (As), and F−, etc. Approximately 61.54% of SW, all of QW, 75% of WW, and 35.71% of MW can be used for irrigation. [ABSTRACT FROM AUTHOR]

Freshwater lenses are groundwater sources of limited dimensions that can be usually found in a variety of climates worldwide. These aquifers' quality is important for socioeconomic development, being cation exchange one of the most important geochemical processes that can change the water geochemistry. This study aims to assess the cation exchange processes that determine the chemistry of freshwater lenses in a multilayer aquifer type, considering the center-east of the Pampean Region (Argentina) as a case study. Water samples were taken from the freshwater lenses at different depths to analyze major ions in the laboratory. In addition, geological profiles were made along with the extraction of sediment samples for X-ray diffractometry (XRD) and laboratory tests to analyze the cation exchange capacity. The results show that water stored in the lenses has a vertical facies variation from Ca-HCO3 to Na-HCO3. According to the laboratory results, the change of water facies mainly occurs in the clayey sediments that divide the carbonate bioclastic material above and the loessic sediment below, being cation exchange the most important process. Practitioner Points • Cation exchange is the main geochemical process regulating groundwater chemistry. • Hydrochemical changes determine the quality of freshwater lenses. • Na/Ca exchange is mainly regulated by the groundwater flow into the bioturbated clay. • Batch exchange tests were also carried out to quantify the Na/Ca exchange processes. [ABSTRACT FROM AUTHOR]

The High Oum-Er-Rbia basin, located in the Moroccan Middle Atlas, is a karstic region with significant water sources that have essential functions regarding agriculture, hydropower production, industrial and drinking water. The region contains abundant wetlands, especially springs, rivers and natural lakes. These systems are highly sensitive to the effects of climate change, experiencing considerable lake level, water chemistry, and biological fluctuations in response to regional hydrological balances. This study focuses on the hydrogeochemical processes and mechanisms that control the chemical composition and variability of Azigza Lake, a typical tectono-karstic lake system of the region. Water monitoring was implemented from July 2013 to October 2014 with a monthly water sampling for physicochemical measurements and major ion concentration analyses of lake water and the surrounding groundwater. Both waters show a relatively low salinity due to the fresh input from the Lower Jurassic karst formation. Lake waters are slightly alkaline and of the calcium-magnesium-bicarbonate type. The geochemistry of the lake waters is mainly controlled by carbonate weathering through water–rock interaction and, to a lesser extent, by cation exchange and precipitation of carbonate minerals. The hydrochemistry of the lake showed clear responses to seasonal changes in precipitation and evaporation, with higher conductivity during the wet period. During the beginning of the wet season, groundwater evolution could be explained by a simple first flush stormwater. The rapid response of lake water to subsurface and underground waters confirms the dominance of an underground conduct flow regime. These changes and behaviors highlight the sensitivity of Azigza system to regional hydrological and climatic changes. [ABSTRACT FROM AUTHOR]

Due to the special hydrogeological conditions in karst areas, groundwater responds quickly to rainfall. The covariation of ion concentrations and spring discharge can help better understand the hydrogeochemical process of groundwater occurring in the heterogeneous karst aquifers. In this study, high-resolution monitoring of groundwater discharge, hydrochemistry, and stable isotopes was conducted at the Qingjiangyuan (QJY), a spring of the Qingjiang watershed in Hubei, China. The purpose is to investigate the changes in hydrogeochemical processes and chemical weathering under the influence of rainfall. The dynamics of spring discharge indicate the presence of pipelines and fissures of different sizes. According to the spring discharge attenuation curves, there are at least three medium types in the aquifer, which account for 45.7%, 34.2%, and 20.1% of the total groundwater. Pearson correlation analysis shows that the main sources of the solute in the QJY are carbonate minerals (mainly calcite and dolomite), evaporites (mainly gypsum and sylvite), celestite, and strontianite. Anthropogenic activities have less impact on groundwater solutes. Although carbonate minerals dominate the hydrochemistry, the changes in hydrogeochemical behavior caused by rainfall may come from gypsum, which is supported by the ion concentrations. At the early rainfall stage, Ca2+ concentration increased from 42.9 to 45.6 mg/L, followed by the SO42− from 15.2 to 16.6 mg/L. When the discharge increased to the maximum (2320 L/s), Ca2+ and SO42− showed opposite trends, decreased to 39.7 mg/L and 10.4 mg/L, respectively. The results also suggest that carbonate rocks and evaporites have important roles in hydrochemistry. The contributions of these three end-members were quantified based on the law of mass conservation. The proportions of carbonate weathering and evaporite weathering were 83.4% (85.2–80.3%) and 11.6% (6.9–18.0%), respectively, and rain was 5.0% (0.1–10.4%). These results were integrated into a hydrogeological conceptual model that explains the hydrogeochemical processes, including rock weathering, piston, and dilution effects caused by rainfall. The proposed conceptual model helps to improve the understanding of hydrogeochemical processes and chemical weathering in karst areas. [ABSTRACT FROM AUTHOR]

Carbonate weathering by rain is considered to play an important role in the karst landform evolution. Rock outcrops (or stone teeth) are frequently visible on the earth’s surface, especially in karst landscapes, but there is no consensus on how they appeared or increased in number. This study estimated the extent of rain-induced weathering dissolution of limestone using hydro-chemical data from a karst area enjoying a subtropical monsoon climate, and proposed a mechanism of soil sinking and rock outcrops emerging, based on the assumption that the dissolved subsoil limestone is the main cause of geomorphic reworking of the karst surface topography. By calculation, the weathering dissolution rate of subsoil limestone is greater than the residue formation rate by dissolution of exposed and subsoil limestone in both forested and cleared karst surfaces, and soil sink at a rate of 0.126 mm a−1 in forested and 0.111 mm a−1 in the cleared karst, implying relative growth of exposed limestone and the spontaneity of the karst process. Besides, smaller values of subsoil dissolution rate and soil sinking rate in the cleared than in the forested demonstrate that soil sinking and rock outcrops emergence are both slower without the cover of forests, while the opposite was true for dissolution of exposed limestone, implying that deforestation may not an absolute promoting factor to karst landscape. This soil sinking model provides a new explanation for the changes in the soil–rock position relationship, which is contrasting with the traditional karst soil loss model that generally attributes rock emergence to soil slope erosion or/and underground soil leaks. [ABSTRACT FROM AUTHOR]

With the gradual increase of global temperature, thermokarst lakes are widely developed and become major environmental disasters in the Tundra Plateau which have impacted the stability of the project such as the Qinghai–Tibetan highway. In this study, some typical thermokarst lakes in the Qinghai–Tibet Plateau (QTP) were selected as the research object. And four samples were taken from different freezing–thawing processes of the lakes in 2019 to analyze the hydrogeochemical process of the thermokarst lake in the context of climate change. Results show that the main hydrogeochemical types of the lake water in the northern part of the study area were HCO3·Cl − Na·Ca·Mg or Cl·HCO3 − Na·Mg, whereas in the central and southern parts were mainly Cl − Na·Mg. The variations of hydrogeochemical concentration in thermokarst lake water are mainly affected by evaporation concentration, rock differentiation, freezing desalination in the active layer, and plant photosynthesis, which are mainly due to temperature changes. Furthermore, the results of the saturation index (SI) show that dolomite and calcite leaching control the hydrogeochemical composition in thermokarst lakes. In addition, the evaporation-to-inflow (E/I) ratios of the lake reach the maximum in the middle and later periods of the active layer thawing. On the contrary, the E/I values of the lakes decrease during the initial thawing or freezing periods of the active layer. HIGHLIGHTS First, the formation process of hot melt lakes in high-altitude areas is analyzed.; Second, the chemical properties of the thermal melting lake in different regions are analyzed, and the reasons that affect the chemical properties are analyzed.; Third, through the calculation of the lake (E/I) ratio, the supply relationship between groundwater and lake water and the development of the lake are analyzed.;

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.

This study focused on water quality and hydro-geochemical processes (evolution, origin) in the Maadher region, central Hodna in Algeria. In recent decades, the excessive exploitation of this resource due to urbanization, irrigation, and the effect of climate change reaching the countries of northern Africa have caused a decline in water levels and hydrochemical changes in the aquifer. The sampling campaign in 2019 based on 13 physicochemical parameters was carried out on the water from 32 boreholes in the study area, compared to data archives of both sampling campaigns in 1967 and 1996. The result revealed that the groundwater as a whole has moderate freshwater quality, due to its total dissolved solids (TDS) content and other dissolved ions of concern (nitrate NO3−), which exceed WHO standards. In addition, Piper diagram indicates that the hydrochemical facies of sulfate–chloride–nitrate–calcium (SO42−–Cl−–NO3−–Ca2+ type), which globally characterizes the study area and these elements are the dominant dissolved ions. Principal component analysis and hierarchical cluster analysis (HCA) methodologies are applied in order to define the major control factors that affect the hydrochemistry of Maadher plain. Three distinct water groups were found, illustrating a different evolution of salinity (EC and TDS). The HCA indicated an interesting cluster with a distinct contamination signature and most likely with significantly higher sulfate, chloride, and nitrate concentrations. Anthropogenic processes also play an important role in the study area. The water resource comes from Bousaada Wadi, the exchange at the aquifer depth and the agricultural practices contribute to the deterioration of the quality. [ABSTRACT FROM AUTHOR]

Hydrochemical analysis, geological study and evaluation of hydrogeochemical processes play a crucial role to understand the variability of fluoride ion concentration in groundwater. The present study is focused on a watershed boundary comprising of parts of two river basins namely Ruparail and Banganga within Bharatpur district of Rajasthan in India. Administratively, the study area is covered in five blocks of Bharatpur district viz. Deeg, Kaman, Nagar, Pahari and Kumher. The study area and sampling locations were identified based on the spectral signatures of satellite data, literature study and field-based experience. Seventy-five groundwater samples were collected for pre and post-monsoon seasons, separately. The hydrochemical results have shown that Banganga basin has experienced greater fluoride enrichment in groundwater as compared to Ruparail basin. Both the basins have experienced more groundwater samples in the class of high-risk water (more than 1.5 mg/l F−) during the post-monsoon season due to mineral dissolution with the surface run-off water in the aquifer material. The shallow aquifers (< 40 m bgl) have experienced high fluoride distribution in groundwater as compared to deeper aquifers (> 40 m bgl). The spatiotemporal interpolation maps for fluoride ion concentration generated by following inverse distance weighted (IDW) method have shown the varied fluoride concentration with geologic, geomorphic and seismo-tectonic features. Chadha's plot for hydrochemical facies has revealed that the groundwater of the study area is mainly of Na–Cl and Ca–Mg–Cl type. The evaluation of hydrochemical facies has suggested that Na–Cl water type is having elevated fluoride ion concentration as compared to Ca–Mg–Cl and Ca–Mg–HCO3 water types. The interpretation of hydrogeochemical processes based on scatter plots of hydrochemical parameters has revealed that processes such as silicate weathering, direct-ion exchange, mineral dissolution and rock–water interaction are responsible for fluoride augmentation in groundwater. The enrichment is also governed by evaporation, semiarid environment, salinity hazard and overdraft of groundwater. The water types having inhibited fluoride ion concentration are found dominated with carbonate weathering and recharge water (Ca–Mg–HCO3 type) and reverse-ion exchange process (Ca–Mg–Cl type). Moreover, the geochemical modeling is indicative of under-saturation of fluorite with over-saturation of calcite and dolomite, augmenting fluoride ion concentration in groundwater. The comprehensive understanding of hydrogeochemical processes controlling fluoride enrichment is found useful for planning strategies adopted for providing safe drinking water in a sustainable way. [ABSTRACT FROM AUTHOR]

Seawater and groundwater interactions shape the hydrogeochemical profile of mangrove aquifers, revealing how biogeochemical processes adapt to saline-freshwater mixing via the fluctuating patterns of key hydrochemical indicators and primary biogenic elements. This study, utilizing a multi-level monitoring profile spanning the entire submerged aquifer within a mangrove wetland, analyzed the spatiotemporal dynamics of DO, ORP, pH, alkalinity and biogenic elements (C, N, S). The results revealed that among the basic hydrochemical parameters, total alkalinity showed the most stable spatiotemporal distribution and was positively correlated with salinity. pH demonstrated a significant negative correlation with salinity, whereas the correlations of ORP and DO with salinity were not substantial. The discharge of terrestrial freshwater into the mangrove wetland is marked by hydrogeochemical reactions favoring the input of Mg 2+ and DIC, with potential iron mineral precipitation within the aquifer. Spatial distribution of biogenic elements in the groundwater showed no apparent pattern across sampling periods. DOC concentrations ranged from 0.3 to 1.3 mmol/L. Three components of dissolved organic matter were identified using three-dimensional fluorescence spectroscopy, with high molecular weight components (C1 + C2) accounting for an average of 47 to 73 %. Both elevated DOC concentrations and high molecular weight component ratios were primarily found in shallow layers of dense mangrove areas, decreasing with depth. Concentrations of ammonia, nitrite, and nitrate varied dynamically, reflecting active biochemical processes in the shallow to mid-layers of the aquifer. Furthermore, sulfate and sulfide concentrations, ranging from 0 to 26 mmol/L and 0.4 to 576.8 μmol/L, respectively, underscore the interplay of biogeochemical reactions, especially sulfate reduction. These findings highlight valuable insights into the complex biogeochemical processes within mangrove aquifers and provide theoretical guidance for protecting the ecological health of mangrove wetlands., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

This study examines the hydrogeochemical and heavy metal parameters of groundwater in Ojo District to determine its suitability for use, potential sources, and human health implications. Ten groundwater samples were assessed, and hydrogeochemical modelling was performed via the Aquachem software. The chemical ions were in the following order: EC > (107.78-448.65 μS/cm) > TDS (182.02-320.77 mg/l) > TH (46.22-182.45 mg/l) > pH (5.55-6.35); HCO 3 - (64.13-125.82 mg/l) > Na + (36.87-96.49 mg/l) > Ca 2+ (47.65-58.88 mg/l) > SO 4 2- (19.94-53.67) > NO 3 - (15.55-44.25 mg/l) > Cl - (20.43-27.16 mg/l) > Mg 2+ (11.09-16.87 mg/l) and K + (2.55-7.86 mg/l). The concentrations of heavy metals in groundwater were in the range of: Fe (0.11-0.27 mg/l) > Mn (0.003-0.16 mg/l) > Ni (0.05-0.12 mg/l) > Zn (0.003-0.05 mg/l) > Pb (0.001-0.03 mg/l) > As (0.001-0.005 mg/l) > Cr (0.002-0.005 mg/l) > Cd (0.001-0.003 mg/l) and Cu (0.001-0.0002 mg/l), with Pb, Mn, and Ni exceeding their allowable limits. The Schoeller and Gibbs plots revealed that the major mechanisms controlling the aquifer groundwater in Ojo region are geological rock weathering and mineralization, with a minimal influence of saltwater intrusion. The piper trilinear diagram also revealed that none of the cation was dominant while the anions were strongly dominated by HCO 3 - (weak acids). The hydrogeochemical facies which describes the geochemical characteristics of the groundwater were classified into 3 types; "Ca 2+ -Mg + -HCO 3 - (65 %)", "mixing zones (30 %)", and "Na + -K + -Cl - -HCO 3 - (5 %)". The hydrogeochemical modelling revealed that the groundwater is characterized by forward cation exchange, while rock-water interactions (silicate dissolution) were heavily involved in the geochemical processes. The single pollution index showed that Pb, Ni, and Mn contributed significantly to contamination, and the multi-pollution indices showed that the groundwater was slightly-moderately polluted. The integrated groundwater quality index revealed that only 10 % were clean, 50 % were poor or moderately unclean, 30 % were highly unclean, and only 10 % were extremely unclean (unfit for utilization). The water pollution index showed that 70 % of the groundwater was good. The irrigation indices suggest that the groundwater would enhance soil quality and support plant growth. Multivariate analysis revealed that the groundwater is being influenced by geogenic factors and anthropogenic activities. The health risk assessment (Hazard Quotient and Hazard Index) showed that exposure of adults to the investigated groundwaters could result in noncarcinogenic adverse effects. The cancer risk values also exceeded the minimum limit (1.0 x 10 -6 ) and thresholds (1.0 x 10 -4 ) for adults, indicating the carcinogenic potential of the groundwater., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Author(s).)

Contaminants can be found in the groundwater through natural processes, such as seawater intrusion, or due to human activities that can adversely affect the quantity, quality, and distribution of the groundwater. In order to assess the influence of human activities and seawater intrusion on the groundwater chemistry in the Central Nile Delta region, groundwater was collected from 167 production wells, with depths of 15–120 m. In addition, eight soil-water samples were collected from depths of about 1 m. The groundwater samples were divided based on well depths into three zones: shallow zone (60 m depth). The TDS, EC, pH, K+, Na+, Mg2+, Ca2+, Cl−, HCO3−, and SO42- were determined for all water samples. The groundwater samples with Cl of 100–200 mg/L and EC of 600–2,000 μs/cm represent mixing between freshwater and saltwater. The increase in TDS and concentrations of all major ions toward the northern parts reflected the impact of the seawater intrusion. The groundwater had an Na/Cl ratio of 0.46–2.75, indicating the influence of both seawater intrusion and anthropogenic activities on groundwater chemistry. In addition, the high Ca/Mg, Ca/SO4, and Ca/HCO3 ratios (>1) indicated that the groundwater was intruded by seawater. The obtained water types, the ionic ratios, and the saturation index results suggested that anthropogenic activities, water-rock interaction, infiltration, mineral weathering, and seawater intrusion are the main processes controlling the variation and evolution of groundwater chemistry.

Understanding the hydrochemical evolutionary mechanisms of surface water and groundwater in saline-alkali wetlands in arid and semi-arid regions is necessary for assessing how wetland water resource utilization and restoration processes may affect the natural interface between wetland salinity and water. The Momoge National Nature Reserve (MNNR) is an inland wetland in northeastern China that is mainly fed by irrigation water and floods from the Nenjiang River. The purpose of the present study is to describe the spatial distribution characteristics of surface water and groundwater hydrochemistry and salinity in the MNNR and analyze the main processes controlling these parameters. The composition of stable isotopes (δ2H and δ18O) and water chemistry, including the levels of Na, K, Ca, Mg, HCO3, SO4, and Cl, of 156 water samples were analyzed. The results show that the lake water in the MNNR is at a risk of salinization owing to a high degree of evaporation. The analysis of the ion ratio and mineral saturation index showed that the ions in water are primarily derived from aquifer leaching, and the precipitation of Ca2+ and Mg2+ resulted in lower Ca2+ and Mg2+ levels in lake water than in groundwater. Hydrogen and oxygen stable isotope and deuterium excess analyses show that evaporation is the dominant factor controlling the hydrochemistry and salinity of lake water in the MNNR. Long-term effective monitoring of lake water and groundwater must be developed to provide an early warning for the salinization of lake water and a scientific basis for the protection and restoration of wetland ecosystem functions within the MNNR.

Groundwater is essential for both water supply and environmental conservation, especially in semi-arid and desert areas. Managing groundwater resources requires a thorough understanding of groundwater characteristics and dynamics. The hydrogeochemical properties and evolution of groundwater in the Essaouira synclinal basin in northwest Morocco were studied in this research, with 105 water samples collected in 2009, 2017, 2018, and 2019. The Water Quality Index (WQI) and Irrigation Water Quality Index (IWQI) were developed to determine groundwater quality for consumption and irrigation purposes. The chemical evolution of groundwater is mainly dominated by evaporite, mineral carbonate dissolutions, and cation exchange. Contamination by nitrates is particularly severe in agricultural and tourist areas. The WQI of the 2019 campaign showed that 6.7% of groundwater samples are unsuitable for drinking; 76.7% are poor quality water; and 13.3% are very poor-quality water; while only 3.3% are drinkable. According to IWQI, the total study area has been split into 50% (good), 43.3% (bad), and 6.6% (unfit), respectively, and no excellent groundwater areas have been identified. Therefore, the water is suitable for agriculture but must be treated for drinking. The presence of evaporation and maritime intrusion and the contribution of recent precipitations to aquifer recharging were demonstrated by stable isotope content. [ABSTRACT FROM AUTHOR]

This work aims to investigate the hydrochemical characteristics and formation mechanisms of shallow groundwater in a part of the Nanchang section of Ganfu plain. The hydrochemical data from 90 groundwater samples were interpreted by the methods of mathematical statistics, Piper diagrams, Gibbs plots, ratio graphs of ions, and geochemical modeling. The results show that shallow groundwater is weakly acidic, the average concentration of cation in groundwater decrease in Ca2+ > Na+ > Mg2+ > K+, and the abundance is in the order HCO3− > NO3− > SO42− > Cl− for anions. The hydrochemical type of groundwater was dominated by HCO3-Na·Ca·Mg, HCO3·Cl-Na·Ca·Mg, and HCO3-Na·Ca. Moreover, the main controlling factor of groundwater hydrochemistry is water-rock interactions. Na+ and K+ mainly originate from the dissolution of halite. Ca2+ and Mg2+ are mainly controlled by carbonate dissolution, while the main anions come from the dissolution of evaporite and carbonate. The groundwater chemical evolution is affected by the dissolution and precipitation of the mineral phase and cation exchange. [ABSTRACT FROM AUTHOR]

In the present study, the geochemical origin of groundwater of Viswamitri River Basin (VRB), Gujarat, is established by integrating the different types of hydrogeochemical investigations and multivariate statistical techniques. Here, both natural and anthropogenic activities induce the hydrogeo-chemical origin of groundwater. Geochemistry of groundwater is primarily regulated by the evaporation process as confirmed by Gibbs diagram. X–Y scatter plots indicate that the source of major cations in groundwater is the weathering of rock and/or soil. The SI values of hematite, dolomite, and goethite depict an oversaturated state, and therefore, the groundwater of VRB is incapable of dissolving any additional amount of that mineral. The plots of Piper trilinear diagram, expanded Durov diagram, Langelier and Ludwig diagram, box-whisker plots, and R-mode HCA reveal that the dominant facies, covering 648 sq. km of the study area, is saline water facies. The high concentration of these major ions is primarily associated with the processes like cation exchange, mineral dissolution in the aquifer system as proved by the saturation indices and Giggenbach triangle. The stable isotopic signature of the groundwater of VRB point towards evaporation as the primary process accompanied simultaneously by precipitation during the formation of groundwater. Climate change, alteration in land use, anthropogenic activities, surface water infiltration, and social evolution all have an impact on groundwater resources. [ABSTRACT FROM AUTHOR]

In the Braga aquifer, groundwater quality and mineralization processes have been assessed using a qualitative hydrogeochemical data analysis. The interpretation of physico-chemical parameters indicates that all groundwater samples have TDS and EC values superior to the permissible limits of WHO standards and are classified as very hard (TH > 300). According to Gibbs diagrams, these high values are in part related to the predominance of evaporation process, which indicates the importance of the return flow phenomenon. While, the WQI classification shows that roughly 2.3% of groundwater is unsuitable for human consumption, 27.9 is very poor, 62.8 is poor, and 7% is good. For irrigation purposes, more than 93% of samples are unsuitable and 7% are suitable based on the SAR. However, the Permeability index (PI) and the Kelly Ratio (KR) demonstrate that almost all samples are suitable for irrigation. The interpretation major ion analyses demonstrate that groundwater mineralization is mainly controlled by the dissolution of evaporate minerals, the direct/reverse ion exchange process, and the leaching of nitrogen and fertilizers. A higher concentration of nitrate in the groundwater of the Braga aquifer was mainly located in the north-east and the central parts and may cause a serious impact on human health. The non-carcinogenic health risk assessment of nitrate (NO3) indicated that the children are more vulnerable to direct ingestion of drinking water than adults. [ABSTRACT FROM AUTHOR]

Abstract Hydrogeochemical processes responsible for groundwater composition within the Asutifi-North district were assessed. The aim was to delineate the factors influencing groundwater within the district. Results show that the pH values of groundwater within the district are moderately acidic to neutral and ranged from 4.4 to 7.5 with a mean value and standard deviation of 6.1 ± 0.7 pH units. 67.4% of groundwater is acidic (pH 4–6.5) due principally to the influence of aquifer materials on the chemistry of groundwater. Acid mine drainage investigations in groundwater within the district shows that, when exposed, sulphides such as pyrites (FeS2) and arsenopyrite (FeAsS) react with water and oxygen to principally produce Fe(OH)3. The major ion concentrations are within the WHO (2004) Guideline values for drinking water. The relative abundance of cations and anions in groundwater within the district is in the order of: Ca2+ > Na+ > Mg2+ > K+ and HCO3 − > Cl− > SO4 2−, respectively. The study further shows that, albite/anorthite-(plagioclase) and calcite/dolomite(carbonates) dissolution as well as ion-exchange reactions may have contributed significantly to major ion concentrations in groundwater within the district. Hydrochemical facies using Piper trillinear diagrams delineated two major water types, the Ca–Mg–HCO3 and Na–Cl water types, with Ca–Mg–Cl, Ca–Mg–SO4–Cl and Na–K–HCO3 as minor water types. Using principal component analysis (PCA), three (3) main principal components accounting for 73.1% of the total variance with eigenvalues > 1 were extracted. PCA delineated the main natural processes through which groundwater within the district acquires its chemical characteristics, the incongruent dissolution of silicate/aluminosilicates and the prevalence of pollution principally from the application of inorganic fertilizers such as nitrates and ammonia via agricultural activities within the district.

Abstract In this study, hydrogeochemical processes controlling groundwater chemistry and groundwater quality were investigated. Drinking water is supplied from groundwater (mostly spring and well water) in the study area. The various parameters such as physicochemical parameters, major ions, trace elements and nitrogen derivatives of groundwater samples of were analyzed. These analysis results are compared with drinking water standards for suitability and it does not exceed the permissible limit values, except for the As and F contents of some samples. The results of major ion chemistry of groundwater in the Yalvaç–Gelendost basin suggest that the silicate weathering and ion exchange are the main controlling hydrogeochemical processes in the variation of groundwater quality. The water types are Ca–Mg–HCO3, Mg–Ca–HCO3 and Ca–HCO3 in the basin. Non-carcinogenic health risk assessment associated with arsenic, nitrate and fluoride was assessed by oral (ingestion) and dermal pathways for adult and child. For child, hazard coefficient and hazard index values are less than 1, and a negative effect on usage as drinking water and dermal (skin contact) absorption not expected. But, potential non-carcinogenic effect with oral intake is likely to occur for some water samples for adults. In addition, carcinogenic risk of As element was evaluated for adults and child related to oral and dermal effect. The carcinogenic risk of As through oral intake may pose health risks for children. For adults, it has been determined that water ingestion with dermal exposure may cause cancer. Arsenic is the main toxic element for human health in the study area. The content of As decreases in seasonal water samples. In this case, the negative effect of arsenic intake with ingestion and dermal pathways on health decreases.

• Revealed the distribution characteristics of hydrochemical processes in the central depression of the Songliao Basin. • Elucidated the enrichment patterns of Type B typical moderate-to-low temperature sedimentary basins in Northeast China. • Unveiled the inhibitory effects of feldspar dissolution and desulfurization on B concentration. • Summarized the origins and influencing factors of boron (B) concentration in different geothermal systems. • Provided new insights into the factors affecting B concentration. The presence of boron (B) in geothermal water is prevalent and detrimental to the growth and utilization of geothermal resources. The Songliao Basin is a typical sedimentary basin-type geothermal system characterized by elevated B concentrations and an abundance of geothermal resources. However, the precise origins, pathways, and mechanisms of B enrichment in the basin are still unknown, which limits the development and utilization of geothermal energy effectively. This study collected 468 geothermal water samples from the Quantou Formation in the central depression of the southern Songliao Basin. The origins and drivers of B in the catchment were examined by integrating the results of the hydrochemical analysis and neural network classification with those of prior research. This study examined the variables that impact the concentration of boron (B) in groundwater through the implementation of an innovative approach. Firstly, the distribution characteristics of hydrochemical processes were analyzed in the study area. After that, through the manipulation of variables, the effects of various hydrochemical processes on the concentration of B were investigated, resulting in the identification of the underlying mechanism accountable for the enrichment of B. The results showed that B primarily originates from geothermal water, and its passage into aquifers is facilitated by prolific fractures. B experiences mixing and dilution events as it ascends from the groundwater. High concentrations of B are primarily found in areas with elevated total dissolved solids levels. Furthermore, the presence of kaolinite resulting from feldspar dissolution in geothermal water diminishes B concentration, while the desulfurization process indirectly inhibits the enrichment of B in the study area. This work can contribute to a better comprehension of the sources of B in sedimentary basin-type geothermal systems and its patterns of enrichment. Additionally, it can guide the development and application of geothermal resources in these environments. [ABSTRACT FROM AUTHOR]

Groundwater is the main water source for different uses in Sana'a Basin, Yemen, in which low and erratic rainfall pattern and abundance of agricultural land are observed, and groundwater is usually prone to abstraction, leading to exhaustion and quality deterioration. This study aims to assess the quality, origin, evolution, and processes controlling groundwater chemistry in the Sana'a aquifer system. A total of 119 samples representing all aquifers were collected in 2020 and were analyzed. Various hydrogeochemical analyses and factorial statistical modeling such as PCA and HCA were performed on the hydrochemical data set. Results revealed that groundwater from volcanic and sandstone aquifers has good quality compared to groundwater from alluvial and limestone aquifers due to natural lithology and topography content and anthropogenic activities. The average TDS (in mg/l) values for volcanic, sandstone, alluvial, and limestone aquifers were 419.26 < 533.7 < 778.25 < 859.8, respectively. Piper and Chadha diagrams show six water types, Ca-HCO3, Ca-SO4, Na-SO4, Mixed Ca–Mg–Cl-SO4, Mixed Na-Ca-HCO3, and Na-HCO3, where some types had more than origin linked to different lithologic of aquifers. Results highlighted that silicate and carbonate weathering was identified as the dominant geochemical processes, plus other processes such as gypsum and halite dissolution, evaporation, and normal ion exchange. PCA and HCA in R and Q modes demonstrate that high groundwater mineralization is principally related to gypsum and carbonate dissolution and anthropogenic activities. These findings are interesting and allow decision support for good groundwater resources sustainable management of Sana'a basin and similar aquifer in the world. [ABSTRACT FROM AUTHOR]

Mahoba district comes under the state of Uttar Pradesh (U.P.), India which is a part of mighty Bundelkhand Granitic Terrain known for its water debt condition. The region is hard rock terrain having recent alluvium cover of variable thickness relating to slope and level of erosion. Secondary porosity i.e. in the fractures and cracks present hosts the groundwater in the study area. The high-water scarcity and poor drinking quality led us to carry out our research work in the study area. The water facies analysed shows Ca–Mg–HCO3 and Na–HCO3 water types which indicated their compositional source from rock and anthropogenic inputs. Majority of the samples showed the dominance of alkaline earths over alkalies and weak acids over stronger counterparts. The correlation coefficients calculated between hydrochemical parameters projects a strong positive correlation of EC and TDS with most of the major ions, including SO42−, NO3−. The hierarchical cluster analysis of all samples was classified into five clusters (C1A, C1B, C2A, C2B1 and C2B2). The sites of cluster C1 water samples were found located closer to drainage streams than C2 cluster water samples. The excessive fertilizers, unplanned municipal wastes and agricultural wastes resulted in high SO42− and NO3−. High F− showed concentration in various samples may have geogenic sources due to flour-apatite in granitic terrain and Fe found in excess gives an unpleasant taste on drinking. The analysed irrigation parameters (%Na, MR, TDS, RSC, SAR, TH, and KI) revealed perfect under permissible quality. Various negative human health issues like indigestion, bone problems, alimentary canal problems have been seen due to excess of SO42−, NO3− and F−). The study reflects the need for immediate preventive measures to improve drinking quality from health alarming ion concentrations and also would help for further management programs. [ABSTRACT FROM AUTHOR]

The aim of this work is to determine the hydrochemical characteristics of groundwater in littoral ridges, sand sheets, and lunettes environments to evaluate the control that hydro-geomorphological features exert over salinity and water chemistry. To achieve this, geomorphological units were mapped and a groundwater monitoring network was established comprising shallow exploration wells and pre-existing deeper wells. Hydrolithological characteristics of sediments were described during field surveys, and also analyzed by XRD technique and binocular magnifying glass observation. Physicochemical parameters of water were measured in situ and samples were taken for major and trace elements (As, Sr, Fe, and Mn) analysis. Both littoral ridges and sand sheets are constituted by shell fragments and sands which are highly permeable sediments where thicker and freshwater lenses are stored. Conversely, lunettes develop smaller lenses due to the presence of silty sediments, which are shallow salinized. Additionally, water—sediment interaction determines geochemical processes like precipitation—dissolution of minerals (mainly carbonates), cation exchange, amorphous and biogenic silica dissolution, and silicate weathering which also regulate the presence of elements, such as As, Fe, and Mn. Given the relevance of littoral ridges, sand sheets, and lunettes in the development of freshwater lenses for water supply for the population and ecological sustenance, it is important to understand the factors and processes which regulate groundwater quality, primarily in sectors where freshwater sources are scarce. [ABSTRACT FROM AUTHOR]

In this study, an attempt was made to understand the hydrogeochemical processes controlling water resources (surface and groundwater) evolution in El Fayoum depression, Egypt. Hydrochemical, inverse geochemical modeling integrated with environmental isotopes was applied. Forty-three surface and groundwater samples were collected and analyzed for major chemistry (cations, anions) and environmental stable isotopes (δ18O, δD). The ionic sequence based on relative molar proportions for cations was Na+ > Ca2+ > Mg2+ > K+ and Na+ > Mg2+ > Ca2+ > K+ for surface and groundwater, respectively and for anions was HCO3− > Cl− > SO42− for all water samples. δ18O and δD relationship plot on a typical evaporation line, enhance potential evaporation of recharging water prior to infiltration. Saturation index estimation revealed that water resources were affected by carbonate and evaporites minerals dissolution and supersaturated with Goethite, Gibbsite and Barite minerals. Inverse geochemical modeling using PHREEQC was used to identify water resources evolution in the study area through two flow paths A, B. The inverse model was constrained so the primary mineral phase including calcite, Aragonite, Anhydrite and Gypsum with Carbon dioxide (gas) are constrained to dissolve until they reach saturation, Whereas H2(g), hydrogen sulphide (gas) and O2(g) are constrained to out gas in all models for flow path (A). For flow path (B), Dolomite, Anhydrite and Gypsum are tend to dissolve with carbon dioxide (gas), H2(g) and O2(g) gases tend to outgassed. Finally, two processes controlling water resource evolution; carbonate and evaporites dissolution and development of cation exchange process through the aquifer system. [ABSTRACT FROM AUTHOR]

It is of significance to elucidate the groundwater quality and hydrogeochemical processes for sustainable utilization of groundwater resources in water shortage regions. A total of 256 groundwater samples were collected in typical watersheds in Zhangjiakou, northern China. The hydrochemical parameters, conventional ions, and trace elements were measured, and δD and δ18O data were collected to delineate the groundwater quality and hydrogeochemical processes. The results showed that 32.91% of the groundwater could be directly used for drinking water sources in the Bashang Plateau, north of the study area. The F− and NO3−-N were the main parameters above the standard threshold for drinking water. In contrast, the groundwater quality in the Baxia River Basins, south of the study area, was of a better scenario. Nonetheless, high concentrations of F−, total hardness, and SO42− were still observed. Most samples in the Bashang Plateau had relatively higher salinity than the Baxia River Basins. Both surface water and groundwater in the study area originated from local meteoric water with considerable hydraulic connections. The high-fluoride groundwater was primarily formed by dissolution of fluoride-rich minerals under conditions of high pH and Na+, low Ca2+, and rich in HCO3−. The dissolution of carbonate and silicate minerals accompanied by strong cation exchange and weak evaporation was the dominant water-rock interaction affecting the hydrochemical composition of groundwater, and anthropogenic NO3− input had an extra influence on hydrochemical process. This study provides a scientific guideline for the protection and allocation of local groundwater resources. [ABSTRACT FROM AUTHOR]

Volcanic aquifers are regarded as important aquifer systems. They have quite variable chemical, structural, and hydrologic properties. In this study, hydrochemical analysis, multivariate statistical and clustering techniques were used to investigate water quality in Mt. Erciyes stratovolcano aquifer system, in central Turkey. Equilibrium analysis and saturation indices were also calculated to understand the evolution of groundwater chemistry. Twenty-eight physicochemical variables were evaluated for 13 sampling stations for 12 months. The results indicate that the groundwater is generally fresh and has moderately hard to hard character. The major ions with respect to their abundance are in the order HCO3> SO4> Cl and Ca> Na> Mg> K. The water type of groundwater is Ca–HCO3 and Ca–Mg–HCO3 type based on hydrogeochemical facies. Gibbs diagram revealed that chemical quality of groundwater is governed by water–rock interactions. The results of saturation index of waters indicated that water samples are almost saturated with carbonate minerals (aragonite and calcite) but undersaturation with SO4 minerals. Heavy metals, F and NO3 concentrations in water samples were within the permissible limits according to the Regulation on Waters Intended for Human Consumption. Hierarchical clustering grouped 13 sampling sites into three clusters based on the similarity of groundwater characteristics. Principal component analysis revealed that groundwater quality is controlled by natural processes. As a result, we showed that water – rock interactions, the dissolution of basaltic minerals and residence time are important in the formation of chemical composition of waters in the volcanic aquifer. [ABSTRACT FROM AUTHOR]

The safety of groundwater quantity and quality is essential for economic development and the ecological environment in the Baotu Spring Basin (BTSB). Thus, it is important to correctly recognize groundwater recharge, the source of major ions, seasonal differences, and the mechanisms of groundwater hydrogeochemical processes. To investigate these issues, surface and groundwater samples were collected and analyzed for hydrochemical components in both the dry and wet seasons in the BTSB. Stable isotope samples of the surface water and groundwater were collected and analyzed in the dry season. The hydrochemical results show that Ca and HCO3 are the dominant cations and anions, and HCO3·SO4-Ca is the dominant groundwater type in the dry and wet seasons. The stable isotope results indicate that precipitation is the primary recharge source of groundwater and surface water in the study area, and precipitation may undergo secondary evaporation under clouds that are in the process of dropping. Moreover, surface water recharges groundwater in infiltration areas near rivers or lakes, where mixing action occurs. The dissolution of calcite, dolomite, and gypsum is the primary water-rock interaction in hydrochemical evolutionary processes. Furthermore, anthropogenic inputs, such as NO3 and Cl, become more important factors affecting the chemical compositions of the surface water and groundwater. Moreover, three ion types (K, Na, and Cl/Ca; Mg and HCO3/NO3; and SO4) were classified in the study area according to the distribution of the ion ratios in the dry and wet seasons. This work provides hydrochemical evidence for water resource management and ecological restoration in the BTSB. [ABSTRACT FROM AUTHOR]

Study region: Olézoa watershed, Yaoundé-Cameroon, Central Africa Study Focus: This study aimed to determine the hydrogeological characteristics of shallow hard rock aquifer and the environmental levels of heavy metals in an urbanized equatorial region. Physico-chemical parameters and heavy metals were determined on 25 groundwater samples and analyzed using conventional hydrochemical methods, multivariate analysis, heavy metal pollution index (HPI) and natural background levels (NBL). New Hydrological Insights for the Region: Hydrogeological functioning is not marked by a mass of basal groundwater with a low hydraulic gradient Hydrochemical facies were predominantly Ca-Mg-Cl, HCO3-Ca-Mg and Ca-Cl type, which were controlled water-rock interaction, cation exchange, dissolution of silicates and anthropogenic activities. Multivariate analysis did not show very significant hydrochemical spatial zonation but the first major component can be used as an indication of the groundwater flow direction. Vertically, a three-part structure around depths of 1 m and 3−7 m were identified and associated with local and intermediate flow systems at the Olézoa watershed-scale.HPI showed short range variations similar to that of EC, suggesting compartmentalization of the shallow aquifer on a small scale. Thus, a preliminary conceptual model describing groundwater dynamics has been proposed. NBL and median HPI values indicate a serious concern in terms of groundwater qualitative potential and the urgency of regular monitoring of heavy metals in groundwater in this urbanized part of sub-Saharan Africa.

In this study, hydrogeochemical processes controlling groundwater chemistry and groundwater quality were investigated. Drinking water is supplied from groundwater (mostly spring and well water) in the study area. The various parameters such as physicochemical parameters, major ions, trace elements and nitrogen derivatives of groundwater samples of were analyzed. These analysis results are compared with drinking water standards for suitability and it does not exceed the permissible limit values, except for the As and F contents of some samples. The results of major ion chemistry of groundwater in the Yalvaç–Gelendost basin suggest that the silicate weathering and ion exchange are the main controlling hydrogeochemical processes in the variation of groundwater quality. The water types are Ca–Mg–HCO3, Mg–Ca–HCO3 and Ca–HCO3 in the basin. Non-carcinogenic health risk assessment associated with arsenic, nitrate and fluoride was assessed by oral (ingestion) and dermal pathways for adult and child. For child, hazard coefficient and hazard index values are less than 1, and a negative effect on usage as drinking water and dermal (skin contact) absorption not expected. But, potential non-carcinogenic effect with oral intake is likely to occur for some water samples for adults. In addition, carcinogenic risk of As element was evaluated for adults and child related to oral and dermal effect. The carcinogenic risk of As through oral intake may pose health risks for children. For adults, it has been determined that water ingestion with dermal exposure may cause cancer. Arsenic is the main toxic element for human health in the study area. The content of As decreases in seasonal water samples. In this case, the negative effect of arsenic intake with ingestion and dermal pathways on health decreases. [ABSTRACT FROM AUTHOR]

Hydrogeochemical processes responsible for groundwater composition within the Asutifi-North district were assessed. The aim was to delineate the factors influencing groundwater within the district. Results show that the pH values of groundwater within the district are moderately acidic to neutral and ranged from 4.4 to 7.5 with a mean value and standard deviation of 6.1 ± 0.7 pH units. 67.4% of groundwater is acidic (pH 4–6.5) due principally to the influence of aquifer materials on the chemistry of groundwater. Acid mine drainage investigations in groundwater within the district shows that, when exposed, sulphides such as pyrites (FeS2) and arsenopyrite (FeAsS) react with water and oxygen to principally produce Fe(OH)3. The major ion concentrations are within the WHO (2004) Guideline values for drinking water. The relative abundance of cations and anions in groundwater within the district is in the order of: Ca2+ > Na+ > Mg2+ > K+ and HCO3− > Cl− > SO42−, respectively. The study further shows that, albite/anorthite-(plagioclase) and calcite/dolomite(carbonates) dissolution as well as ion-exchange reactions may have contributed significantly to major ion concentrations in groundwater within the district. Hydrochemical facies using Piper trillinear diagrams delineated two major water types, the Ca–Mg–HCO3 and Na–Cl water types, with Ca–Mg–Cl, Ca–Mg–SO4–Cl and Na–K–HCO3 as minor water types. Using principal component analysis (PCA), three (3) main principal components accounting for 73.1% of the total variance with eigenvalues > 1 were extracted. PCA delineated the main natural processes through which groundwater within the district acquires its chemical characteristics, the incongruent dissolution of silicate/aluminosilicates and the prevalence of pollution principally from the application of inorganic fertilizers such as nitrates and ammonia via agricultural activities within the district. [ABSTRACT FROM AUTHOR]

Ooty Lake, one of the famous tourist destinations in south India, deteriorates due to tourism activities and urbanisation. The present study aims in characterising the quality of lake water (both surface and depth) and groundwater besides addressing its suitability for various purposes by collecting samples during premonsoon, monsoon and post monsoon seasons of the years 2015 to 2017. Collected samples are analysed for physicochemical parameters using potentiometric technique. Major ions, trace metals and stable isotopes are determined by titrimetric, spectroscopy techniques. Statistical analysis involves principal component and cluster analysis with correlation coefficient. Major chemistry of lake water and groundwater exhibits Ca2+Na+HCO3− type and mainly dominated by silicate weathering. Water chemistry and statistical study indicate that chromium, zinc and cobalt in groundwater and lake water are attributed to the dominance of rock weathering. Copper, chromium along with zinc and lead in stream and inlet locations can be attributed to the influence of domestic waste water entering the lake. Phosphorous in the lake is also derived mainly through the domestic waste entering the lake. Water quality and heavy metal pollution indices show unsuitability of lake water for drinking, whereas, ecological risk assessment indicates that water is safe for aquatic life. Sodium absorption ratio, permeability index, residual sodium carbonate and sodium percentage of water samples indicate suitability for agricultural activities. Stable isotopic composition of lake water and groundwater samples shows possible southwest monsoon precipitation as the major source. Ineffective water treatment at inlet and stream water chemistry affects the lake water quality, which could be focussed for enriching quality. [ABSTRACT FROM AUTHOR]

Water resource is a valuable resource for human beings to survive and maintain social stability and development. However, in recent years, the process of urbanization has been accelerated, and many cities and towns have presented groundwater pollution. To investigate the spatial distribution of hydrochemical components in urban areas after groundwater pollution and the hydrogeochemical effects on surrounding areas, using multifarious methods such as classical statistics, geostatistics, saturation index, and stable isotopes, the hydrogeochemical effects along groundwater flow were analyzed and deduced. The results show that the main ions of the groundwater in the Yiyuan are Ca2+ and HCO3−, it is mainly low-salinity fresh water, and the hydrochemistry type is mainly HCO3–Ca·Mg type. Groundwater pollution in urban areas increases the content of inorganic and organic matter in groundwater, the main ions affected are NO3−, Cl−, Ca2+, and SO42−, and their concentrations increased by 12.3, 22.3, 7.6, and 12.3 mg/L, respectively. In the city, negative cation exchange occurs mainly, after leaving the city, cation exchange occurs mainly. The results of the saturation index calculation indicate that groundwater pollution has little effect on the dissolution and precipitation of minerals. After leaving the town, denitrification, desulphurization, and cation exchange occurs in the underground aquifer, which reduces the concentration of pollutants in the groundwater. The study suggests that a variety of hydrogeochemical processes play an important role in the spontaneous reduction of some pollutant concentrations in groundwater away from the pollution source, while the concentration of other substances may rise. [ABSTRACT FROM AUTHOR]