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Relict caves in fenglin karst may typically have numerous entrances and openings. Hence, they host a variety of environments in which parameters such as light, airflow, humidity, and temperature may vary significantly over short distances. Similarly, drip water hydrochemistry, including isotopic values, may vary due to different contributions of various sources and residence time in the karst. This study investigated environmental parameters, including radiation, using hand-held instruments, along a transect within several major caves in the Niah karst of Sarawak (Malaysia). This has led to a baseline data set which showed an inverse relationship between humidity and temperature, gamma radiation levels that are about 25% of that in surrounding non-karst region, and high percentages of twilight zones in the studied caves. Airflow was found to be variable, with high values of 530 m3/s in Painted Cave and 122 m2/s in parts of Gan Kira passage, with flow towards the southeast at the time of the study. The hydrochemistry of the drip water and surface water was also analyzed and found to be dominantly Ca–Mg–Cl water type which indicates dissolution of minerals through water–rock interaction. In addition, the cave environment, particularly air temperature, humidity, and ventilation, also influences the drip water composition and isotopic values. Three different origins (precipitation, evaporation, and paleo-recharge) of drip water have been identified through the δ18O-δ2H diagram. Enriched isotopic values were observed in the cave entrance due to increased evaporation caused by lower humidity and higher air temperature. Factor analysis identifies the key geochemical processes responsible for the drip water chemistry. The outcome of this study provides the first baseline environmental data for the Niah caves, which could support future initiatives for sustainable management of this famous archeological site in southeast Asia. [ABSTRACT FROM AUTHOR]

The increasing global nitrogen input poses a significant threat to aquatic environments, particularly in agricultural watersheds, where intensive human activities and insufficient water protection infrastructure exacerbate the risk of nitrogen pollution. Accurate identification of nitrogen pollution sources and the associated transformation processes is essential for protecting watershed ecosystems. In this study, a combination of hydrochemical analysis, correlation and principal component analysis, and stable nitrate isotopes (δ15N-NO3− and δ18O-NO3−) were employed to trace nitrogen transport pathways and source contributions in both surface water and groundwater within a typical agricultural watershed. The results revealed the presence of nitrogen pollution, including total nitrogen (TN), ammonia nitrogen (NH3-N), and nitrate nitrogen (NO3−-N), with significant spatial and seasonal variations in both surface water and groundwater. The spatiotemporal evolution of hydrochemical indicators and nitrate isotope compositions highlighted multiple potential sources of nitrogen, including soil input, agricultural input, and manure and sewage input. The results from stable isotope analysis in an R (SIAR) model indicated that ammonium fertilizers (7.1~78.4%) and manure and sewage (2.6~69.7%) were the primary sources of nitrates in surface water, while manure and sewage were the main sources in groundwater (67.9~73.7%). This research demonstrated that nitrification, seasonal variations, and human activities significantly impact nitrogen migration and transformation in agricultural watersheds. However, the issue of groundwater severely polluted by manure and sewage has received insufficient attention. To effectively control nitrogen pollution in agricultural watersheds, it is necessary to improve septic tanks and sewage networks, as well as implement scientific fertilization practices. [ABSTRACT FROM AUTHOR]

Groundwater quality is a serious concern in alluvial aquifers undergoing vast agricultural transformation around the globe. Mehsana district of Gujarat is an example of agricultural landscape having most of the seasonal crops and vegetables. Groundwater samples were collected in monsoon 2017 and pre-monsoon 2018 to analyze major ions and isotopes to derive the hydrochemistry. The hydrochemical facies reveal Na+–Cl−, Na+–HCO3− and Ca2+–HCO3− type water suggesting complex hydrochemical reaction taking place in the region. The scatter plot of Ca2+ + Mg2+ versus HCO3− + SO42− and Na+ versus Cl− shows the ion exchange and silicate weathering along with intermixing of saline water. The presence of high sodium, alkaline pH and bicarbonate promotes the release of fluoride from minerals in groundwater which is high during monsoon. The fluoride concentration increases progressively along the Sabarmati River. The spatial variation map of nitrate in the district shows both point and non-point sources of NO3− contamination. This evidence will support the strong contribution of agricultural activities, as shown by land use that long-term flood irrigation practices have enhanced this impact. The deep aquifers are suitable for drinking purposes as compared to shallow aquifers which are affected with NO3− pollution due to the leaching process during the pre-monsoon season. The agriculture indices show contaminated groundwater for irrigation in more than 50% of wells. The composition of isotopes varied between (δ18O − 2.08 to − 4.41‰ and δD − 19.19 to − 32.28‰). The groundwater trendline was found below the local meteoric water line which indicates evaporation due to semiarid climate before infiltration. [ABSTRACT FROM AUTHOR]

The Ngari region has many important rivers and is critical to water resource security and water resource continuity in China and even in adjoining Asian countries. However, the spatial distribution and monthly variation in local water quality have been poorly understood until recently. In this study, the spatial–temporal variations of 12 water quality parameters, including pH, dissolved oxygen (DO), permanganate index (IMn), chemical oxygen demand (COD), five-day biochemical oxygen demand (BOD5), ammonia nitrogen (NNH3), total nitrogen (Ntotal), total phosphorus (Ptotal), copper (Cu), fluoride (F), arsenic (As) and cadmium (Cd), were determined from samples collected monthly at 22 water cross-sectional sites in the Ngari region in 2020. The surface water pollution in the southern Ngari region was the most serious, and the water pollution level in winter was higher than that in the other seasons. As (0.0781 ~ 0.6154 mg/L) and F (1.05 ~ 4.64 mg/L) were the main exceedance factors derived from the recharge of high arsenic and fluoride geothermal water and weathering of As and F-bearing minerals. The hazard quotient and carcinogenic risk for As and F at the five contaminated sampling sites indicated potential health risks and even carcinogenicity to local populations. The hydrochemistry types of the lakes and rivers in the Ngari region were mainly chloride water and carbonate water. The results from this study can provide a scientific basis for the prevention and control of surface water pollution in the Ngari region and contribute to subsequent research on the ecology of water bodies. [ABSTRACT FROM AUTHOR]

An investigation of the distribution and control factors of groundwater is significant for the rational exploitation and utilization of groundwater resources. This study analyzes the hydrogeochemical processes and control factors of shallow groundwater in the Guohe River Basin. A hydrogeological survey was conducted, and hydrochemical and hydrogen–oxygen isotopic data of 125 samples of surface water and groundwater were analyzed. The results showed that the total dissolved solid (TDS) content in shallow groundwater was 138–2967 mg/L, with an average of 831 mg/L. A decline in the TDS was observed from the upper to the lower reaches. The contents of the anions and cations in the shallow groundwater were in the order HCO3− > Cl− > SO42− and Na+ and K+ > Mg2+ > Ca2+, respectively. The cation exchange increased the aqueous concentrations of Na+ and K+, and the TDS content was highly correlated with the contents of Na+, Cl−, and SO42− ions. The δD and δ18O values in shallow groundwater increased from the upper to the lower reaches, with the mean δD values being −59.72‰, −53.58‰, and −47.17‰ and the mean δ18O values being −8.33‰, −7.37‰, and −6.43‰. The contribution rates of the recharge source, evaporation, and water–rock interaction to the groundwater TDS concentration were 20.4%, 29.5%, and 50.1%, respectively. The water–rock interaction dominated the formation of shallow groundwater in the Guohe River Basin. The dissolution of salt rock and gypsum contributed to ion formation in shallow groundwater. The research findings can be used to improve the groundwater quality in the Guohe River Basin. [ABSTRACT FROM AUTHOR]

A complete understanding of groundwater dynamics and its interaction with surface water under the impact of agricultural activities is vital for local agriculture, ecology, and residents of dry regions, which is not commonly recognized in arid areas. This research outlines the geochemical characteristics, recharge sources, and potential factors impacting groundwater quality in a new land reclamation located in the small basin of Abu Mina, which is part of the Western Nile Delta region.1 Thirty-one groundwater samples and two surface water samples were collected in 2021 to represent the Pleistocene aquifer and were subjected to multivariate statistical, hydrochemical, and stable isotope analyses. Data analysis demonstrates that Na+ > Ca2+ > Mg2+ > K+ and SO42– > Cl– > HCO3– > NO3– are the predominant cations and anions, respectively. Groundwater salinity ranged from 465.60 to 6455.18 mg/l, with slightly alkaline. Most of the water samples fall into one of three types of facies: Ca–Cl, Na–Cl, and Mixed Ca–Mg–Cl, in decreasing order. The meteoric genesis index (r2) indicates that deep meteoric water percolation dominates the Pleistocene aquifer. The aquiline diagrams, correlation matrix, and different ionic ratios indicate that evaporation, reverse ion exchange reactions, and the dissolution of carbonate and silicate minerals are the main processes governing groundwater chemistry. Factor analysis (FA) indicated that three factors explain groundwater hydrochemistry, accounting for 71.98% of the total variance. According to the rotating components matrix (F1–F3), the chemistry of the Quaternary aquifer is principally affected by evaporation, ion exchange reactions, and anthropogenic influences. Additionally, salinity increases due to the return flow of irrigation activities and mixing between old and recent water. The stable isotopes (δ18O and δ2H) indicate that the Quaternary aquifer receives groundwater recharge through the return flow of excess irrigation and canal seepage. Under desert reclamation conditions, groundwater salinization processes should be given special consideration. All groundwater samples are appropriate for agricultural irrigation based on the Sodium Adsorption Ratio (SAR), Permeability Index (PI), Percent Sodium (%Na), and Residual Sodium Carbonate (RSC). [ABSTRACT FROM AUTHOR]

Numerous geothermal systems are hosted by extensional rifts that transect the Himalayas and Lhasa block in the Himalayan–Tibetan orogen. However, the relationships between hydrogeological processes and geothermal fluid circulation in different tectonic units remain unclear. Here, we report an integrated dataset of chemical and isotopic compositions (including major and trace elements, δD, δ18O, and 87Sr/86Sr) of thermal spring water from the Tingri-Tangra Yumco rift to assess their origins and circulation processes. δ18O (− 21.3 to − 17.0‰) and δD (− 166 to − 135‰) values of thermal springs indicate dominant recharge of meteoric waters from areas with elevation of > 6000 m and minor addition of magmatic fluids. Meteoric water could infiltrate to depths of about 1700–2900 m along the faults, whereby it is influenced by geothermal gradient and/or conductive heat transfer of magmatic fluids. The thermal spring waters are mainly Na-HCO3 type and are controlled by dissolution of silicate and carbonate minerals and mixing with deep fluids. The results of chemical and multicomponent geothermometers indicate reservoir temperatures of 115 − 195 ℃, corresponding to a convection heat flux of 3.96 × 105 J/s to 1.78 × 107 J/s from geothermal systems, which are comparable to that of the low-enthalpy geothermal systems in southern Italy. Geochemical modeling is conducted to assess the water–mineral equilibria in the reservoir. Trace elements and 87Sr/86Sr data suggest spatially variable controlling factors for the rift-related geothermal systems: (1) interaction with granitoid and carbonate in the Himalayas; (2) cold groundwater mixing with that leaching from granite and volcanic rocks in the Lhasa block; (3) the input of vapors from magmatic degassing. The geochemistry of thermal springs associated with extensional rift is largely induced by the interaction between fluid and different reservoir rocks in the Himalayas and Lhasa block. Based on these findings, a genetic model is proposed for exploration and development of geothermal resources in the Tingri-Tangra Yumco rift. [ABSTRACT FROM AUTHOR]

This study investigates the chemical characteristics, formation, and sources of inorganic nitrogen (IN) of shallow groundwater across the Sanjiang Plain, aiming to enhance drinking water safety management and pollution control. A total of 167 groundwater and 27 surface water samples were collected for constituents and isotopes (H2 and O18). The hydrogeochemical characteristics showed that the major type is HCO3‐ Ca·Mg, with low total dissolved solids and a neutral to weak alkaline nature. Rock weathering processes govern the hydrochemical composition of groundwater. Hydrogen and oxygen stable isotopes analyses revealed that precipitation serves as the main water source. In alluvial areas, oxidative conditions lead to the enrichment of NO3‐N concentrations, with sewage, manure, and fertilizers being the primary IN sources. In lacustrine areas, intensive rice cultivation results in reductive conditions and strong denitrification processes, causing the loss of NO3‐N and leaving NH4‐N as the dominant IN form. Organic matter mineralization is likely a more significant contributor to NH4‐N concentrations than ammonium fertilizers. These findings provide valuable information for further research on natural sources and groundwater pollution in areas with similar hydrogeological conditions. Practitioner Points: Rock weathering processes govern the hydrochemical composition of groundwater, and precipitation serves as the main water source.In alluvial areas, oxidative conditions lead to the enrichment of NO3‐N. In lacustrine areas, intensive rice cultivation results in reductive conditions and strong denitrification processes.Organic matter mineralization is likely a more significant contributor to NH4‐N concentrations than ammonium fertilizers.These findings provide references for water management and information for further research on natural sources and groundwater pollution in areas with similar hydrogeological conditions. [ABSTRACT FROM AUTHOR]

The Arabian Desert is characterised by very low rainfall and high evaporation, yet over 210 springs are on its northeastern edge in central Iraq along the Abu Jir lineament, which represents the western depositional margin of a foreland basin infilled by the floodplain sediments of the Tigris and Euphrates Rivers; there is little evidence of faulting. The springs discharge from gently east-dipping Paleocene–Eocene limestones, either where groundwater flowpaths intersect the ground surface or where groundwater flow is forced to the surface by confining aquitards. Calculated annual recharge to the aquifer system across the Arabian Desert plateau (130–500 million m3) is significant, largely due to rapid infiltration through karst dolines, such that karst porosity is the primary enabler of groundwater recharge. The recharge is enough to maintain flow at the Abu Jir springs, but active management of groundwater extraction for agriculture is required for their long-term sustainability. The hydrochemistry of the springs is determined by evaporation, rainfall composition (high SO4 concentrations are due to the dissolution of wind-blown gypsum in rainfall), and plant uptake of Ca and K (despite the sparse vegetation). Limestone dissolution has relatively little impact; many of the springs are undersaturated with respect to calcite and lack tufa/travertine deposits. The springs at Hit-Kubaysa contain tar and high levels of H2S that probably seeped upwards along subvertical faults from underlying oil reservoirs; this is the only location along the Abu Jir lineament where deep-seated faults penetrate to the surface. The presence of hydrocarbons reduces the Hit-Kubaysa spring water and converts the dissolved SO4 to H2S. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The water quality of the Tigris Channel at Al-Taji area were studied in both periods (August, and March, 2022). Eight samples were collected from Tigris channels to investigate water quality and parameters such as electrical conductivity (EC), total dissolved solids (TDS), Temperature (T), hydrogen number (pH), Total Hardness (T.H), as well as significant cations (Ca2+, Mg 2+, Na+, and K+ ), significant anions (CO3 2-, HCO3-, Cland SO4 2- ) and Heavy metals (Cd, Pb, Fe, Zn, Ni and Cr). The results show that the maximum value of EC is 1182 (µS/cm) in Ch3 in the dry period, while the lowest value of EC is1105 (µS/cm) in Ch1 in the wet period. The hydrochemical formula of water samples in both periods is CaCl. In this study, the dominating cation is Ca2+, followed by Na+, Mg2+, and K+, whereas the dominant anion is Cl-, followed by SO4 2-, HCO3-, and CO3- . According to Piper's illustration, all water samples that fall in class (e) are arranged together for both periods (wet and dry) "Earth alkaline water with a higher percentage of alkali and a sulfate and chloride predominance." Finally, the WQI is rated excellent for the wet Tigris channel and good water for the dry Tigris channel. [ABSTRACT FROM AUTHOR]

The study area covers the Banaz (Usak) basin located in the Aegean Region in the western part of Turkey. Metamorphic, sedimentary, ultramafic, and volcanic rocks are dominant in the basin. The groundwaters in the study area are used for domestic, irrigational, and industrial purposes. Hence, the groundwater chemistry and major geochemical processes in the region were determined. The dominance of major elements was of the order of Ca2+. Mg2+ Na+. K+ and HCO3-. CO3-. Cl-. SO42-. Piper, Durov, Chadha, and Radial plots identified generally Ca2+Mg2+-HCO-3 type waters as the dominant types of water in this area. In terms of physical parameters in the basin, the waters are suitable for drinking. However, arsenic content in Yesilyurt and Corum settlements exceeds the limit values of drinking water standards. In addition, the ammonium value is high in the water sample in the Corum region. Isotope contents in water samples from 2008 to 2023 were evaluated in the study area. The waters in the basin are of meteoric origin according to their stable isotope content. Tritium content in the plain waters indicates recent recharge. Additionally, for children, As and U elements were identified as risky with oral intake and As with dermal contact. [ABSTRACT FROM AUTHOR]

The confined groundwater of arid sedimentary plains has been disturbed by long‐term anthropogenic extraction, and its hydrochemical quality is required for sustainable development. The present research investigates the hydrochemical characteristics, formation, potential health threats, and quality suitability of the confined groundwater in the central North China Plain. Results show that the confined groundwater has a slightly alkaline nature in the study area, predominantly dominated by fresh‐soft Cl‐Na and HCO3‐Na types. Water chemistry is governed by water–rock interactions, including dissolution of evaporites and cation exchange. Approximately 97% of the sampled confined groundwaters exceed the prescribed standard for F−. It is mainly due to geological factors such as mineral dissolution, cation exchange, and competitive adsorption of HCO3− and may also be released from compacted soils because of groundwater extraction. Enriched F− in the confined groundwater can pose an intermediate and higher non‐carcinogenic risk to more than 90% of the population. It poses the greatest health threat to the population in the north‐eastern part of the study area, especially to infants and children. For sustainable development, the long‐term use of confined groundwater for irrigation in the area should be avoided, and attention should also be paid to the potential soil salinization and infiltration risks. In the study area, 97% of the confined groundwaters are found to be excellent or good quality for domestic purposes based on Entropy‐weighted Water Quality Index. However, the non‐carcinogenic health risk caused by high contents of F− cannot be ignored. Therefore, it is recommended that differential water supplies should be implemented according to the spatial heterogeneity of confined groundwater quality to ensure the scientific and rational use of groundwater resources. Practitioner Points: The hydrochemistry quality of confined groundwater in an arid sedimentary plain disturbed by long‐term anthropogenic extraction was investigated.The suitability of confined groundwater for multiple purposes such as irrigation and drinking were evaluated.The hydrochemical characteristics and formation mechanism of confined groundwater under the influence of multiple factors were revealed. [ABSTRACT FROM AUTHOR]

Studying lakes in background areas of high-latitude regions is an important component of hydrological and ecological research. The article presents new data on the chemical composition of water and recent sediments of six small lakes located in the Natural Park “Rybachy and Sredny Peninsulas” (the Russian Arctic). The main hydrochemistry parameters, including pH, conductivity, alkalinity, the content of main ions (Ca+, Mg+, Na+, K+, HCO3−, SO4−, Cl−), and other elements were measured in the water of selected lakes. Furthermore, concentrations of heavy metals (Pb, Sb, Cd, Ni, Cu, and others) were estimated in the upper layers of recent sediments of the lakes. The integral pollution loan index (PLI), designed for geochemical studies of sediments, was calculated to determine the level of chemical pollution of the lakes. The results showed that, in general, the studied parameters did not exceed the background level. There was no serious impact of the Kola Mining and Metallurgical Company, which is situated ~ 80 km to the west from the lakes. It was revealed that the studied lakes were less contaminated with heavy metals in comparison with the previously researched lakes of urban territories of the Russian Arctic zone. However, the analysis of distribution of concentrations of Ni (up to 127 mg/kg), Cu (up to 370 mg/kg), Pb (up to 90 mg/kg) revealed the influence of long-range atmospheric pollution on lakes of the Natural Park “Rybachy and Sredny Peninsulas”. The fractional analysis of the metals in the sediments showed that the elements were mainly associated with stable compounds of the sediments and, thus, there was an only potential environmental risk for the biota of the studied lakes. Elevated levels of Pb, Cd, and Zn have been found in the water and sediments of Lake Pitevoe, which is likely caused by natural processes. Samples of the sediments also revealed particles of the mineral sphalerite containing traces of Pb and Cd. The calculation of the integral pollution load index (PLI) showed that, from the point of view of sediment geochemistry, the values of the lakes of the Natural Park “Rybachy and Sredny Peninsulas” corresponded to the moderate level of pollution or the absence of any pollution. The exception is lakes where natural geochemical anomalies have been identified. Sediments of lakes Pitevoe and №4 are characterized as polluted (PLI value is more 3). It is should develop recommendations for monitoring the water bodies in the Natural Park «Rybachy and Sredny Peninsulas» and establish measures to ensure safety and counter potential threats to the well-being of people visiting the park.Highlights: The background water level of the lakes of the Natural Park “Rybachy and Sredny Peninsulas” has been confirmed. Sediments of lakes reflect the influence of a metallurgical plant 80 km from the study area. Natural contamination of sediments with U, Zn, Pb, and Cd was established due to the specific geological conditions. [ABSTRACT FROM AUTHOR]

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This study investigated the mineralogical and chemical characteristics of ochreous precipitates and mine water samples from abandoned Upper Carboniferous hard coal mines in an extensive former mining area in western Germany. Mine water characteristics have been monitored and assessed using a multi-methodological approach. Thirteen mine water discharge locations were sampled for hydrochemical analysis, with a total of 46 water samples seasonally collected in the whole study area for stable isotopic analyses. Mineralogical composition of 13 ochreous precipitates was identified by a combination of powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FE-SEM/EDS). Results showed that abandoned mine drainage was characterized by circumneutral pH, Eh values ranging from 163 to 269 mV, relatively low concentrations of Fe and Mn, and was dominated by HCO3− > SO42− > Cl− > NO3− and Na+ > Ca2+ > Mg2+ > K+. Goethite and ferrihydrite were the dominant precipitated Fe minerals, with traces of quartz, dolomite, and clay minerals. Some metal and metalloid elements (Mn, Al, Si, and Ti) were found in the ochreous sediments. The role of bacteria in the formation of secondary minerals was assessed with the detection of Leptothrix ochracea. The δ18O and δ2H values of mine water plotted on and close to the GMWL and LMWLs indicated local derivation from meteoric water and represented the annual mean precipitation isotopic composition. Results might help to develop strategies for the management of water resources, contaminated mine water, and public health. [ABSTRACT FROM AUTHOR]

In arid and semiarid zones, groundwater is a vital and indispensable natural resource. Indeed, these water resources have become extremely limited due to several factors, including climate change, salinization, and overexploitation. This study covers the hydrochemical characterization of groundwater in the Nekor-Ghiss plain which is located in northern Morocco. To achieve this objective, a set of 79 water samples was analyzed, for various physical and chemical parameters of the samples, including E.C, pH, TDS, HCO3−, SO42−, Ca2+, Mg2+, Na+, K+, PO43−, NO3−, NO2− and NH4+. Several methods were used to interpret the hydrochemical data, namely graphical methods, principal component analysis (PCA), hierarchical ascending classification, and ion exchange indices. A detailed geochemical study of groundwater is described to identify the origin of the chemical composition of groundwater. The results show that the samples studied are characterized by very high mineralization (> 1500 mg/l), with the predominance of Na+, Cl− and SO42− ions. The interpretation of geochemical signatures of groundwater in the Nekor-Ghiss plain shows sulfate-sodium (Na–SO4) and chloride-sodium (Na–Cl) facies. Natural geochemical processes are responsible for water regulation, while human activities exert a limited influence on this control. Marine intrusion, evaporation, and the ion exchange process largely control the chemistry of the aquifer. Using PCA to confirm controlled water chemistry processes revealed three homogeneous groups. The study contributes to a better understanding of the quality and mineralization of groundwater in the Nekor-Ghiss plain, and it will serve as a reference for other plains with similar characteristics. [ABSTRACT FROM AUTHOR]

The Shendong mining area,located in Northwestern China,is characterized by a dry climate and scarce water resources. A large amount of mine water is used for ecological irrigation in this mining area. This study investigated the suitability of mine water for irrigation through on-site sampling and hydrochemical testing of mine water in the mining area. We analyzed the spatial distribution patterns of water quality parameters and hydrochemical types. This study also evaluated and predicted the suitability of long-term irrigation using sodium ion adsorption ratio(SAR), soluble sodium percentage (KNa), Kelly ratio (KR),permeability index (PI),residual sodium carbonate (RSC), magnesium adsorption ratio (KMg) single indicator methods,as well as USSL and Wilcox graphical methods. Taking into account the groundwater level,we discussed soil texture types,climatic conditions of the mining area and the applicability of the evaluative indicators. The results show that the main ions in the mine water of Shendong mining area are sorted by mass concentration. The cations are Na+,Ca2+,Mg2+ and K+,and the anions are HCO-3,SO2- 4,Cl-and NO-3 . The mine water is weakly alkaline as a whole,and the concentrations of Cl-and NO-3 vary significantly with space. There was a significant positive correlation among Na+,Cl-,SO2- 4,total dissolved solid (TDS),electric conductivity (γ),Ca2+ and Mg2+,and a negative correlation between F-and Ca2+,Mg2+. The hydrochemical type of mine water in the mining area is primarily the NaHCO3 type. The chemical composition of mine water is mainly affected by ion exchange and evaporation. Na+,Cl-,SO2- 4,Ca2+,Mg2+ and F-in the mine water were abnormally enriched and the TDS and γ values exceeded the standard. The salt accumulation effect is not obvious under the combined influence of groundwater and surface water waterlogging in the mining area,and the soil compaction is not prominent. The PI method and the USSL graphic method are not suitable for evaluating irrigation water quality in this area. The evaluation results based on Wilcox graphical method show that the mine water of Halagou,Shigetai and Daliuta mines are suitable as irrigation water. The mine water from Bulianta,Shangwan,Buerta,Wulanmulun,and Huojitu mines should not be used for long-term direct irrigation. This study has theoretical and practical significance for the rational development and utilization of mine water resources in mining areas. [ABSTRACT FROM AUTHOR]

Jinan, renowned as the "Spring City" in China, relies significantly on karst groundwater as an indispensable resource for socio-economic development, playing a crucial role in ecological regulation, tourism, and historical and cultural aspects. The Yufu River basin, situated within Jinan's karst region, represents a vital riverine leakage zone. Therefore, investigating the evolutionary characteristics and causative mechanisms of surface water and groundwater at different aquifer levels in the Yufu River basin can provide a scientific foundation for the protection of Jinan's springs. This study, based on hydrogeochemical and isotopic data from the river water, shallow groundwater, deep groundwater, and springs in the Yufu River basin, explored the hydrogeochemical evolution in this region. The findings revealed significant spatial variations in the hydrochemical parameters of the Yufu River basin. Groundwater received contributions from surface water, while springs represented a mixture from both surface water and various recharge aquifers. Dominant ions include Ca2+ and HCO3−, with prevailing hydrochemical types being HCO3·SO4-Ca and HCO3-Ca. Atmospheric precipitation served as the primary source of recharge for surface water and groundwater in the Yufu River basin, albeit influenced by pronounced evaporation processes. The hydrochemical composition in the Yufu River basin was primarily attributed to water–rock interactions, mainly driven by the combined effects of carbonate rock, silicate rock, and gypsum weathering and dissolution. Among these, the weathering and dissolution of carbonate rocks played a dominant role, with human activities exerting a relatively minor influence on the hydrochemistry of the Yufu River basin. [ABSTRACT FROM AUTHOR]

Groundwater, as an essential resource, holds significant importance for human production and livelihoods. With the deterioration of the water environment, the issue of groundwater quality has become an urgent international concern. This study focused on the Fenghuang Mountain Area (FMA) and collected a total of 41 sets of samples including pore groundwater (PGW), fissure groundwater (FGW), karst groundwater (KGW), and river water (RW). Hydrochemical analysis methods were employed to identify the hydrochemical characteristics and controlling factors. The entropy-weighted water quality index (EWQI) and health risk assessment model were utilized to assess the groundwater quality and nitrate health risk, respectively. The results indicated that the dominant anion and cation in both groundwater and surface water in the FMA were HCO3− and Ca2+, respectively, with the main hydrochemical type being HCO3-Ca. Groundwater and surface water in the FMA were primarily controlled by rock weathering process, with ion concentrations influenced mainly by the dissolution of halite, sylvite, carbonates (calcite and dolomite), silicates, and gypsum, as well as by reverse anion exchange process. PGW was significantly affected by agricultural activities, with NO3− concentration closely related to human activities. The water quality of FGW was relatively good, with Class I and Class II water accounting for the highest proportion, reaching 84.62%. The high-value area of EWQI in PGW was influenced by human activities. The impact of nitrate health risk on children was significantly greater than on adults, with FGW having the lowest health risk and PGW having the highest health risk. The research results can provide important guarantees for the rational development and utilization of water resources in the FMA and the sustainable development of the economy in Northeast China. [ABSTRACT FROM AUTHOR]

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Copyright of Acta Sedimentologica Sinica is the property of Acta Sedimentologica Sinica Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract A complete understanding of groundwater dynamics and its interaction with surface water under the impact of agricultural activities is vital for local agriculture, ecology, and residents of dry regions, which is not commonly recognized in arid areas. This research outlines the geochemical characteristics, recharge sources, and potential factors impacting groundwater quality in a new land reclamation located in the small basin of Abu Mina, which is part of the Western Nile Delta region.1 Thirty-one groundwater samples and two surface water samples were collected in 2021 to represent the Pleistocene aquifer and were subjected to multivariate statistical, hydrochemical, and stable isotope analyses. Data analysis demonstrates that Na+ > Ca2+ > Mg2+ > K+ and SO4 2– > Cl– > HCO3 – > NO3 – are the predominant cations and anions, respectively. Groundwater salinity ranged from 465.60 to 6455.18 mg/l, with slightly alkaline. Most of the water samples fall into one of three types of facies: Ca–Cl, Na–Cl, and Mixed Ca–Mg–Cl, in decreasing order. The meteoric genesis index (r2) indicates that deep meteoric water percolation dominates the Pleistocene aquifer. The aquiline diagrams, correlation matrix, and different ionic ratios indicate that evaporation, reverse ion exchange reactions, and the dissolution of carbonate and silicate minerals are the main processes governing groundwater chemistry. Factor analysis (FA) indicated that three factors explain groundwater hydrochemistry, accounting for 71.98% of the total variance. According to the rotating components matrix (F1–F3), the chemistry of the Quaternary aquifer is principally affected by evaporation, ion exchange reactions, and anthropogenic influences. Additionally, salinity increases due to the return flow of irrigation activities and mixing between old and recent water. The stable isotopes (δ18O and δ2H) indicate that the Quaternary aquifer receives groundwater recharge through the return flow of excess irrigation and canal seepage. Under desert reclamation conditions, groundwater salinization processes should be given special consideration. All groundwater samples are appropriate for agricultural irrigation based on the Sodium Adsorption Ratio (SAR), Permeability Index (PI), Percent Sodium (%Na), and Residual Sodium Carbonate (RSC).

Abstract Numerous geothermal systems are hosted by extensional rifts that transect the Himalayas and Lhasa block in the Himalayan–Tibetan orogen. However, the relationships between hydrogeological processes and geothermal fluid circulation in different tectonic units remain unclear. Here, we report an integrated dataset of chemical and isotopic compositions (including major and trace elements, δD, δ18O, and 87Sr/86Sr) of thermal spring water from the Tingri-Tangra Yumco rift to assess their origins and circulation processes. δ18O (− 21.3 to − 17.0‰) and δD (− 166 to − 135‰) values of thermal springs indicate dominant recharge of meteoric waters from areas with elevation of > 6000 m and minor addition of magmatic fluids. Meteoric water could infiltrate to depths of about 1700–2900 m along the faults, whereby it is influenced by geothermal gradient and/or conductive heat transfer of magmatic fluids. The thermal spring waters are mainly Na-HCO3 type and are controlled by dissolution of silicate and carbonate minerals and mixing with deep fluids. The results of chemical and multicomponent geothermometers indicate reservoir temperatures of 115 − 195 ℃, corresponding to a convection heat flux of 3.96 × 105 J/s to 1.78 × 107 J/s from geothermal systems, which are comparable to that of the low-enthalpy geothermal systems in southern Italy. Geochemical modeling is conducted to assess the water–mineral equilibria in the reservoir. Trace elements and 87Sr/86Sr data suggest spatially variable controlling factors for the rift-related geothermal systems: (1) interaction with granitoid and carbonate in the Himalayas; (2) cold groundwater mixing with that leaching from granite and volcanic rocks in the Lhasa block; (3) the input of vapors from magmatic degassing. The geochemistry of thermal springs associated with extensional rift is largely induced by the interaction between fluid and different reservoir rocks in the Himalayas and Lhasa block. Based on these findings, a genetic model is proposed for exploration and development of geothermal resources in the Tingri-Tangra Yumco rift.

[Objective] Current research mainly focuses on long-term frequency studies in non-karst areas, but there is insufficient research on hydrochemical sampling frequency under different rainfall levels in karst areas Inorder on determining the optimal sampling frequency of hydrochemistry at different rainfall levels in Karst small watersheds. [Methods] Based on high-frequency electrical conductivity (EC) data of different rainfall levels (heavy rainstorm, heavy rain and moderate rain) with a 1 hour interval from June 2022 to July 2023 in the typical Karst small watershed of the central Guizhou Plateau, low-frequency data of 2~15 hours were resampled. Combined with various evaluation indicators and catastrophe point theory, the optimal sampling frequency of hydrochemistry under different rainfall levels in the Karst small watershed was determined. [Results] (1) Due to the influence of geological background, the hydrochemistry response to rainfall in the small watershed of the Karst area is characterized by rapid rise and fall, and the loss of sampling error is large. (2) Factors such as I60 (maximum 60 min rainfall intensity), the number of rain-free days, and the amount of rainfall all impacted the hydrological process, which in turn altered the characteristics of hydrochemical changes and ultimately affected the sampling frequency; (3) It was recommended to use a sampling frequency of 4 hours during heavy rain events, a frequency of 5 hours during moderate rain events when I60>10 mm/h, and 6 hours frequency when I60 was small (I60

ABSTRACTThis study focuses on the Manimala River Basin (MMRB) situated in the Western Ghats region of Kerala, which has been significantly affected by landslides. The water quality in the MMRB is likely to be impacted by heavy rainfall and the resulting debris flows. A comprehensive analysis was conducted for 157 water samples collected from the MMRB, with an objective to evaluate the hydrogeological conditions and estimation of 23 physico-chemical parameters to determine the water quality. Pearson’s correlation matrix for geochemical data was performed to investigate the relationships among physical and chemical parameters, and various ions in the MMRB. The present study also aimed to identify the dominant geochemical facies present in the water samples and determine the geochemical processes responsible for modifying the hydrochemistry. The results revealed that elevated concentrations of Ca2+ and SO42- ions, which exert influence on the hydrochemistry of the region. Moreover, we utilized a fuzzy logic tool to categorize the water samples based on a water quality index, which indicated that approximately 92% of the MMRB samples are suitable for human consumption. This study offers valuable insights into the interplay of geochemical factors and water quality assessment, contributing to effective strategies for water resource management and conservation.

Abstract The traceability of groundwater nitrate pollution is crucial for controlling and managing polluted groundwater. This study integrates hydrochemistry, nitrate isotope (δ15N-NO3 − and δ18O-NO3 −), and self-organizing map (SOM) and end-member mixing (EMMTE) models to identify the sources and quantify the contributions of nitrate pollution to groundwater in an intensive agricultural region in the Sha River Basin in southwestern Henan Province. The results indicate that the NO3 −-N concentration in 74% (n = 39) of the groundwater samples exceeded the WHO standard of 10 mg/L. According to the results of EMMTE modeling, soil nitrogen (68.4%) was the main source of nitrate in Cluster-1, followed by manure and sewage (16.5%), chemical fertilizer (11.9%) and atmospheric deposition (3.3%). In Cluster-2, soil nitrogen (60.1%) was the main source of nitrate, with a significant increase in the contribution of manure and sewage (35.5%). The considerable contributions of soil nitrogen may be attributed to the high nitrogen fertilizer usage that accumulated in the soil in this traditional agricultural area. Moreover, it is apparent that most Cluster-2 sampling sites with high contributions of manure and sewage are located around residential land. Therefore, the arbitrary discharge and leaching of domestic sewage may be responsible for these results. Therefore, this study provides useful assistance for the continuous management and pollution control of groundwater in the Sha River Basin.

Abstract In arid and semiarid zones, groundwater is a vital and indispensable natural resource. Indeed, these water resources have become extremely limited due to several factors, including climate change, salinization, and overexploitation. This study covers the hydrochemical characterization of groundwater in the Nekor-Ghiss plain which is located in northern Morocco. To achieve this objective, a set of 79 water samples was analyzed, for various physical and chemical parameters of the samples, including E.C, pH, TDS, HCO3 −, SO4 2−, Ca2+, Mg2+, Na+, K+, PO4 3−, NO3 −, NO2 − and NH4 +. Several methods were used to interpret the hydrochemical data, namely graphical methods, principal component analysis (PCA), hierarchical ascending classification, and ion exchange indices. A detailed geochemical study of groundwater is described to identify the origin of the chemical composition of groundwater. The results show that the samples studied are characterized by very high mineralization (> 1500 mg/l), with the predominance of Na+, Cl− and SO4 2− ions. The interpretation of geochemical signatures of groundwater in the Nekor-Ghiss plain shows sulfate-sodium (Na–SO4) and chloride-sodium (Na–Cl) facies. Natural geochemical processes are responsible for water regulation, while human activities exert a limited influence on this control. Marine intrusion, evaporation, and the ion exchange process largely control the chemistry of the aquifer. Using PCA to confirm controlled water chemistry processes revealed three homogeneous groups. The study contributes to a better understanding of the quality and mineralization of groundwater in the Nekor-Ghiss plain, and it will serve as a reference for other plains with similar characteristics.

The present study offers a quality assessment of the mineral and spring waters marketed in Algeria within the national and international legislations, examine the potential contribution of bottled waters to essential elements intake and effects on public health based on empirical, graphical tools, multivariate statistical techniques and (DRI) system. The study covered a dataset of 30 mineral and 33 spring brands. The parameters included, from bottle labels, were of physicochemical nature. All brands comply with national and WHO norms for the bottled waters, except for (Brand#63) in which NO2− exceeded the maximum permissible limit for mineral water and (Brands#4 and #21) where TH and TDS exceeded the Algerian recommended guidelines for spring water. Nearly 5% of the total brands were of bicarbonate nature belonging to mineral water, while 25% of all brands were suitable for low-sodium-diet. PCA and HCA showed that bottled waters could be classified into two distinct groups, according to degree of mineralization. The DRI-system revealed that Algerian bottled waters contributed substantially to the daily intake for Mg2+ with up to (63%), Na+ (40.36%) and Ca2+ (36%) for spring water for different ages and genders, whereas mineral water exceeded the maximum recommended daily intake for Ca2+ (128%) and Na+ (148.36%) for adults. HIGHLIGHTS An updated survey of the bottled water production units and consumption in Algeria was carried out.; A spatial distribution of the bottled water production units nationwide was studied.; Particularly, a quality assessment of the bottled mineral and spring waters marketed in Algeria was analyzed.; For the first time, an estimate of the bottled waters minerals contribution to dietary intake based on the DRI system was done.; Their effects on public health were studied.;

Groundwater is a crucial water resource for various usages worldwide. The Quetta Valley of Pakistan was investigated regarding its groundwater quality sustainability based on integrated approaches of hydrochemistry, geographic information system, and multivariate statistics. A total of 29 groundwater samples were collected from monitoring wells to get insights into the hydrochemical suitability of groundwater for sustainable irrigation and drinking utilization. The results indicate groundwater is mainly featured by the hydrochemical facies of HCO3·Cl-Ca. Groundwater hydrochemical composition is dominantly governed by the dissolution of carbonates and silicate minerals in combination with positive cation exchange in the valley. Principal component analysis reveals a significant influence of geogenic factors on groundwater chemistry, further supported by PHREEQC simulation that detects a supersaturation of calcite, dolomite, and sulphate minerals in the aquifer. The irrigation water quality index divides groundwater in the study area into three zones, which signify low restriction and no restriction, except for a severe restriction in the southwestern part of the valley. Groundwater is generally suitable for irrigation across the valley. The entropy-weighted water quality index classifies groundwater as excellent and good quality for drinking. This study can provide crucial insights for authorities on groundwater suitability in Quetta Valley and similar regions worldwide. HIGHLIGHTS Traditional hydrochemical techniques integrated with multivariate statistical analysis and Geographic Information System (GIS)-based methods were employed to provide a nuanced understanding of hydrochemical parameters and their spatial distribution.; Hydrochemical fingerprints were recognized to assess groundwater quality for drinking and irrigation purposes.; The irrigation water quality index delineates zones for irrigation suitability, while the entropy-weighted water quality index ranks water quality for drinking purposes.;

This manuscript presents the first inventory of dissolved ions (cations and anions) and trace metals (Pb, Mn, Cr, Co, Ni, Cu and Zn) in the Punpun River water to assess its irrigational suitability, pollution sources and hydrogeochemical processes. For this, the physicochemical parameters and trace metals in river water were analysed in the pre- and post-monsoon seasons. The results showed that the concentrations of cations and anions were Ca2+ > Na+ > Mg2+ > K+ and HCO3− > SO42- > Cl− > NO3− > PO43-, respectively, in both the pre- and post-monsoon seasons. However, trace metal concentration in pre- and post-monsoon followed the trend of Pb > Mn > Cr > Ni > Cu > Zn > Co and Pb > Ni > Mn > Cr > Zn > Co > Cu, respectively. The results reveal that combined effects of rock weathering and evaporation-concentration influence hydrochemistry, along with anthropogenic factors like industrial effluents, urban domestic sewage and agricultural runoff. Piper and Durov plots suggest that the river water is dominated by Ca–Mg–HCO3− type, and the processes were governed by simple ion dissolution and mixing. However, the Gibbs plot shows that silicate and carbonate weathering govern the hydrochemical properties. Irrigational indices like sodium adsorption ratio, %Na, residual sodium carbonate, Kelly's ratio, magnesium hazard, and trace metals indicate that most of the water samples are suitable for irrigation. Comprehensive pollution index values suggest that the river water quality ranges from sub-clean to slightly to moderately polluted. HIGHLIGHTS The dominant cation and anion in the Punpun River water were Ca2+ and HCO3−, respectively.; The Punpun River water is influenced by silicate and carbonate weathering.; Different water processes indicate ion dissolution and mixing.; Sodium adsorption ratio, %Na, residual sodium carbonate, Kelly's ratio and MH irrigational indices show that most river water is suitable for irrigation.; Comprehensive pollution index value shows that river water falls into a slightly to moderately polluted category.;

The traceability of groundwater nitrate pollution is crucial for controlling and managing polluted groundwater. This study integrates hydrochemistry, nitrate isotope (δ15N-NO3− and δ18O-NO3−), and self-organizing map (SOM) and end-member mixing (EMMTE) models to identify the sources and quantify the contributions of nitrate pollution to groundwater in an intensive agricultural region in the Sha River Basin in southwestern Henan Province. The results indicate that the NO3−-N concentration in 74% (n = 39) of the groundwater samples exceeded the WHO standard of 10 mg/L. According to the results of EMMTE modeling, soil nitrogen (68.4%) was the main source of nitrate in Cluster-1, followed by manure and sewage (16.5%), chemical fertilizer (11.9%) and atmospheric deposition (3.3%). In Cluster-2, soil nitrogen (60.1%) was the main source of nitrate, with a significant increase in the contribution of manure and sewage (35.5%). The considerable contributions of soil nitrogen may be attributed to the high nitrogen fertilizer usage that accumulated in the soil in this traditional agricultural area. Moreover, it is apparent that most Cluster-2 sampling sites with high contributions of manure and sewage are located around residential land. Therefore, the arbitrary discharge and leaching of domestic sewage may be responsible for these results. Therefore, this study provides useful assistance for the continuous management and pollution control of groundwater in the Sha River Basin. [ABSTRACT FROM AUTHOR]

This study investigates the Batha endorheic basin in Chad, situated east of the Lake Chad basin in the arid to semi-arid Sahelian zone. This region has not yet undergone comprehensive geological and hydrogeological studies. More broadly, the transition zone between semi-arid and arid climates has been minimally explored. This research aims to evaluate the resources and dynamics of this multi-layered system using a combined geology-hydrogeology-hydrochemistry-isotopes approach. The multilayer system includes sedimentary layers (Quaternary, Pliocene, and Eocene) over a crystalline basement. A piezometric investigation of the system shows a general SE–NW groundwater, indicating an interconnection between all layers. Hydrochemical analyses identifies four main facies (calcium-bicarbonate, sodium-bicarbonate, sulphate-sodium, and mixed), primarily controlled by water–rock interaction with secondary influences from base-exchange and evaporation. Saturation indices indicate that these waters are close to equilibrium with the calcite-Mg phases, gaylussite and gypsum. Stable isotopes (oxygen-18 and deuterium) categorize groundwater into three groups: ancient water, recent and older meteoric water mixtures affected by evaporation, and mixtures more heavily impacted by evaporation. Tritium contents reveal three groups: current rainwater, modern water, and sub-modern water. These results indicate that ionic and isotopic differentiations cannot be strictly linked to specific layers, confirming the interconnected nature of the Batha system. The observed heterogeneity is mainly influenced by lithological and climatic variations. This study, though still limited, enhances significantly the understanding of the basin's functioning and supports the rational exploitation of its vital resources for the Batha area's development. Future investigations to complete the present study are highlighted. [ABSTRACT FROM AUTHOR]

The Hongjiang—Qianshan fault has abundant medium-low temperature geothermal resources. However, the excessive fluorine concentration in geothermal groundwater restricts the development and utilization of geothermal resources. 20 samples were collected in this region for identifying the genetic mechanism of medium-low temperature of fluoride-enriched geothermal resources. The hydrochemical results indicate that the hydrochemical characteristic of high fluoride geothermal groundwater is HCO3-Na. The groundwater environment is alkaline and weakly alkaline. The fluoride concentration in geothermal groundwater is 2−12 times greater than the upper limited value, while those in the surface water and shallow groundwater are within the permittable threshold range. The isotopic results reveal that the recharge elevations and circulation depth are 797−2186m and 893−1893m, respectively. Quartz provides the most reliable estimations of reservoir temperatures, ranging from 79.4℃ to 113.1℃. The fluoride in geothermal groundwater originates from the rock weathering and mineral dissolution. Cation exchange and alkaline condition are the main influence factors for fluorine enrichment. [ABSTRACT FROM AUTHOR]

Karst groundwater, which is one of most important drinking water sources, is vulnerable to be polluted as its closed hydraulic relation with surface water. Thus, it is very important to identify the groundwater source to control groundwater pollution. The Pearson correlation coefficient among major ions (Na + K+, Ca2+, Mg2+, HCO3−, SO42−, and Cl−) was employed to deduce the groundwater types in Zhong Liang Mountain, Southwest China. Then, the combined method of principal component analysis and cluster analysis were employed to identify the groundwater sources in a typical karst region of southwest China. The results shown that (1) the high positive correlation between cations and anions indicated the water–rock reaction of Ca‐HCO3, Ca‐SO4, (Na + K)‐Cl, and Mg‐SO4. (2) The major two principal components that would represent water–rock reaction of CaSO4 and Ca‐HCO3 would, respectively, explain 60.41% and 31.80% of groundwater information. (3) Based on the two principal components, 33 groundwater samples were clustered into eight groups through hierarchical clustering, each group has similar water–rock reaction. The findings would be employed to forecast the surge water, that was an important work for tunnel construction and operation. Practitioner Points: The components of groundwater was highly correlated with water–rock reaction.The principal component analysis screens the types of groundwater.The cluster analysis identifies the groundwater sources. [ABSTRACT FROM AUTHOR]

The Groot Aub (GA) settlement depends entirely on groundwater for domestic purposes and other development activities. Development activities are mainly agriculture, such as animal husbandry, chicken farming and crop farming using irrigation. However, these activities have the potential to contaminate the groundwater system. A total of 87 groundwater samples were collected from the boreholes in the study area during the dry and wet season. Water quality parameters (pH, salinity, total dissolved solids (TDS), electrical conductivity (EC) and hydrochemistry (Na+ > Ca2+ > Mg2+ > K+, and HCO3 − > SO4 2− > Cl−) of 5 boreholes and 1 reservoir tank were analysed. The dominant cations were attributed to cation exchange processes as a coupled exchange of Na+ + K+ replacing Ca2+; and Na+ replacing Mg2+ ions in the rock–water interactions. The HCO3 − anion is attributed to underlying rich carbonate rocks in the study area and chemical reactions between groundwater and silicate minerals. TDS ranged from 639.01 to 1 998.96 mg/L. The microbial levels as indicated by heterotrophic plate count (HPC) values exceed the limits imposed by the local Namibian and WHO drinking water regulations. The Piper diagrams showed a mixed water type of mainly HCO3 − and SO4 2− anions and Na+ and Ca2+ > Mg2+ cations. The study shows that the elemental composition of the groundwater is impacted significantly by primarily anthropogenic activities and secondarily geogenic processes. Based on the results of this study it is recommended that a buffer zone be created between human activities and production boreholes to avoid further groundwater contamination. [ABSTRACT FROM AUTHOR]

In this study, we investigate chemical and isotopic characteristics of thermal waters of the Emir geothermal field in the Kula region, which hosts the youngest volcanism in Turkey. Studied thermal waters with temperature and electrical conductivity values of 21–63 °C and 3840 to 5210 μS/cm are of Na–HCO3 type and have neutral character. δ18O and δD of thermal waters are − 9.40 to − 8.41‰ and − 64.16 to − 56.38‰ (VSMOW) and indicate a meteoric source with local recharge. Tritium values of thermal waters in the Emir geothermal field are mostly < 1 TU signifying a deep circulation. Positive δ13C values (1.32–4.46‰ VPDB) imply that carbon is derived dominantly from marine limestone and dominantly from endogenic CO2. δ18O and δ34S of dissolved sulfate yield that marine limestone is the source of sulfur in thermal waters, which are partly affected by sulfide oxidation and bacterial reduction processes. At discharge temperatures, Emir thermal waters are oversaturated with respect to albite, aragonite, calcite, α-cristobalite, dolomite, gibbsite, illite, K-feldspar, kaolinite, muscovite and quartz but undersaturated for anhydrite and wairakite. The activity diagrams suggest that high Na+ and K+ concentrations in waters are attributed to dissolution of muscovite, K-feldspar and albite. Chemical and isotopic compositions of the Emir thermal waters are controlled by a combination of processes including water–rock interaction, dissolution/precipitation and ion exchange. Various chemical and isotopic geothermometers applied to the thermal waters yielded reservoir temperatures in the range of 80–125 °C. Paleo-temperatures estimated from δ18O values of travertines and thermal waters (isotope fractionation) are consistent with modern discharge temperatures. [ABSTRACT FROM AUTHOR]

Effectively managing water resources in karst systems requires a thorough understanding of their general conduit network along with their seasonal dynamics. Their investigation has involved well construction or several advanced natural tracer data, most of which are not always available. Hence, this work showcases a pragmatic approach that makes use of basic hydrochemical variables of springs with coarse temporal resolution in characterising a karst system. In this study's example, physicochemical variables like major ion concentrations/ratios, Electrical Conductivity (EC), pH and water temperature (Tw) were measured on 20-day basis for a hydrological year at the Louros Catchment, Greece. We further performed the frequency distribution and variation analysis of EC and Tw, principal component analysis (PCA), scatter plots of carbonate ions vs sulphate and hydrochemographs to determine relevant hydrochemical processes and hydrogeological features. PCA and the scatter plots showed that the simple-type upper karst level is entirely dominated by carbonate dissolution, whereas the complex-type middle and lower levels also involve gypsum and dolomite dissolution. Presence of mixing between karst units was also detected. EC and Tw analyses revealed the degree of karstification of different units and relative depths of flow systems. Hydrochemographs reflected the seasonality of limestone and gypsum dissolution's contributions linked to the dominant flow type (conduit vs diffuse). This study thus was able to demonstrate the usefulness of such holistic hydrochemical analyses to better understand karst systems. Given their cost-effectiveness, they can be easily applied to any understudied karst system worldwide. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In recent times, drilling groundwater wells for irrigation, domestic, and industrial uses is increasing at a high rate in Saudi Arabia, meaning that groundwater is becoming a primary water resource. In the study region, over-exploitation and unsustainable performance severely deteriorate groundwater. Therefore, it is important to monitor the groundwater levels and quality as well as to detect the hydraulic parameters in order to plan and maintain groundwater sustainability. Knowledge of aquifer hydraulic parameters and groundwater quality is essential for the productivity planning of an aquifer. Therefore, this study carried out a thorough analysis on measured depth to groundwater data (2017 and 2022), borehole pumping test records, and chemical analysis of the collected water samples, especially in the presence of overexploitation and scarcity of recharge scale. To accomplish this aim, measurements of 113 groundwater wells (including 103 water samples) and analysis of 29 pumping tests between step and long-duration tests were made of all aquifer characteristics. These parameters consist of well loss, formation loss, well efficiency, specific capacity, transmissivity, hydraulic conductivity, resulted drawdown, and physiochemical parameters. Thematic maps were generated for all parameters using the geographic information system (GIS) and diagrams to strategize the groundwater productivity in Al-Madinah Al-Munawarah Province. The estimated hydraulic parameters are highly variable. Four distinct portions were identified for aquifer potentiality based on these varying ranges. Both the north and east of the region are good for groundwater productivity due to good aquifer materials, whereas the southwestern and western portions have relatively poor values. The analyzed groundwater was categorized as fresh to slightly salty water, with two primary chemical types identified showing a prevalence of mixed NaCl and Ca-Mg-SO4/Cl water. Finally, groundwater productivity assessment predicts that the aquifers can support the Al-Madinah Al-Munawarah Province demand for several years if certain well distributions are adopted and for a few hours/day of pumping rate. The maps that have been created can be examined to aid in making decisions related to hydrology. [ABSTRACT FROM AUTHOR]

The Ras Elma region, situated to the south of the city of Taza in northern Morocco, boasts abundant travertine formations that continue to develop, albeit selectively in specific sheltered sites. This development is influenced by various parameters, including the role of water chemistry. This article presents a spatio-temporal analysis of various hydrochemical parameters, including conductivity, pH, temperature, magnesium, calcium, and others. It's worth noting that the water from the Ras Elma Vauclusian spring, a key driver of travertinization in the region, is sourced from water infiltrating through faults and flowing into Lake Tompraire, known as Dayat Chikker near the Bab Boudir area. The findings suggest that the water in Ras Elma has turned aggressive, as revealed by the examination of the calcaro-carbonic equilibrium. CaCO3 precipitation occurs predominantly in the summer, significantly impacting the formation of travertines, particularly those of the spring and dam types. However, valley-type travertines exhibit more extensive development compared to the other two types. [ABSTRACT FROM AUTHOR]

Renowned for its agriculture, livestock, and mining, Zhob district, Pakistan, faces the urgent problem of declining groundwater quality due to natural and human-induced factors. This deterioration poses significant challenges for residents who rely on groundwater for drinking, domestic, and irrigation purposes. Therefore, this novel study aimed to carry out a comprehensive assessment of groundwater quality in Zhob district, considering various aspects such as hydrochemical characteristics, human health risks, and suitability for drinking and irrigation purposes. While previous studies may have focused on one or a few of these aspects, this study integrates multiple analyses to provide a holistic understanding of the groundwater quality situation in the region. Additionally, the study applies a range of common hydrochemical analysis methods (acid–base titration, flame atomic absorption spectrometry, and ion chromatography), drinking water quality index (WQI), irrigation indices, and health risk assessment models, using 19 water quality parameters. This multi-method approach enhances the robustness and accuracy of the assessment, providing valuable insights for decision-makers and stakeholders. The results revealed that means of the majority of water quality parameters, such as pH (7.64), electrical conductivity (830.13 μScm–1), total dissolved solids (562.83 mgL–1), as well as various anions, and cations, were in line with drinking water norms. However, the water quality index (WQI) predominantly indicated poor drinking water quality (range = 51–75) at 50% sites, followed by good quality (range = 26–50) at 37% of the sites, with 10% of the sites exhibiting very poor quality (range = 76–100). For irrigation purposes, indices such as sodium percent (mean = 31.37%), sodium adsorption ratio (mean = 0.98 meqL–1), residual sodium carbonate (– 3.15 meqL–1), Kelley's index (mean = 0.49), and permeability (mean = 49.11%) indicated suitability without immediate treatment. However, the magnesium hazard (mean = 46.11%) and potential salinity (mean = 3.93) demonstrated that prolonged application of groundwater for irrigation needs soil management to avoid soil compaction and salinity. Water samples exhibit characteristics of medium salinity and low alkalinity (C2S1) as well as high salinity and low alkalinity (C3S1) categories. The Gibbs diagram results revealed that rock weathering, including silicate weathering and cation exchange, is the primary factor governing the hydrochemistry of groundwater. The hydrochemical composition is dominated by mixed Ca–Mg–Cl, followed by Na–Cl and Mg–Cl types. Furthermore, the human health risk assessment highlighted that fluoride (F–) posed a higher risk compared with nitrate (NO3–). Additionally, ingestion was found to pose a higher risk to health compared to dermal contact, with children being particularly vulnerable. The average hazard index (HI) for children was 1.24, surpassing the allowable limit of 1, indicating detrimental health effects on this subpopulation. Conversely, average HI values for adult females (0.59) and adult males (0.44) were within safe levels, suggesting minimal concerns for these demographic groups. Overall, the study's interdisciplinary approach and depth of analysis make a significant contribution to understanding groundwater quality dynamics and associated risks in Zhob district, potentially informing future management and mitigation strategies. [ABSTRACT FROM AUTHOR]

Owing to increasing anthropogenic impacts, wetlands have suffered a serious environmental decline in recent decades. The sustainable management of these natural resources is fundamental to maintain both the ecosystems and the economic activities. The Lake Massaciuccoli and nearby areas represent one of the largest residual coastal marshy areas in Tuscany (Italy). This wetland is characterized by large-scale and intensive agricultural use and affected by reclamation activities, with consequent problems of erosion, subsidence and lake eutrophication and siltation. In this context, an integrated study combining hydrochemical data (water levels, electrical conductivity, pH, turbidity, major ions, trace metals) and stable isotopes (H, O, S) has been performed in the southernmost part of the basin, to better disentangle processes and interactions between groundwater and surface water and to understand the origin of solutes and their evolution. Our results indicated that both groundwater and surface water have a meteoric origin and that geochemical composition of groundwater is mainly affected by local geological and biological processes. Moreover, surface water is affected by sea water mixing and evapotranspiration/precipitation processes. The impact of agricultural activity and the use of fertilizers on the water quality appears to be limited as regards nitrates, indicating that less intense agricultural practices implemented in recent years have been successful. As regards sulfates, Fe, and Mn, we cannot fully elucidate the mechanisms underlying human influence, but the oscillation of water level and degradation of peat enhanced by reclamation and agriculture activities likely played an important role in controlling the fate of these elements. Overall, these results underline the importance of integrated approaches to disentangle geochemical processes and will be useful in supporting policy implementation and environmental protection in this valuable area of Tuscany. Findings from this work suggest the need for policy-making authorities to take actions as soon as possible to mitigate risks. Closer co-operation is essential between authorities and farmers to reduce inputs of fertilizers and chemicals into the lake and the surrounding area. Also, additional policy measures should be enforced to reduce the mechanical soil tillage and limit erosion and runoff, such as the NBSs implemented within the Phusicos Project. [ABSTRACT FROM AUTHOR]

The water level of Lake Hulun has changed dramatically in recent years. The interannual interaction between groundwater and lake water is an important factor affecting Lake Hulun's water level. Vertical recharge between groundwater and the lake is particularly important. Based on an analysis of differences between the hydrogeochemical and water quality characteristics of the spring water, the lake water, and the surrounding groundwater, the source and recharge mechanism of the spring water in the vertical recharge lake are determined. The results show that spring water is exposed at the bottom of Lake Hulun, and there are obvious differences between spring water and lake water in lake ice thickness, ion characteristics, and water quality characteristics. For example, the ice thickness at the spring site is only 6.8% of the average ice thickness of the lake, and there is a triangular area directly above the spring water area that is not covered by ice; the ion contents of the spring water at the lake bottom were less than 50% of those in the lake water; and the NH4+-N content of the spring water at the lake bottom was only 3.0% of the mean content of the lake water. In addition, the total nitrogen (TN), dissolved oxygen (DO), and NH4+-N contents of the spring water at the lake bottom all fall outside the range of contents of the surrounding groundwater. In general, the source of the spring water at the lake bottom is not recharged by the infiltration recharge of the phreatic aquifer but by the vertical recharge of the confined aquifer. Additionally, the Lake Hulun basin may be supplied with confined water through basalt channels while it is frozen. The vertical groundwater recharge mechanism may be that spring water at the lake bottom is first supplied by the deep, confined aquifer flowing through the fault zone to the loose-sediment phreatic aquifer under the lake, and finally interacts with the lake water through the phreatic aquifer. [ABSTRACT FROM AUTHOR]

Hydrochemical analysis is crucial for understanding soil and water composition dynamics in coastal aquifers. This study presents a novel framework for the comprehensive assessment of groundwater quality, integrating multivariate analysis and hydrochemical techniques. It comprises seven stages aimed at characterizing physicochemical properties, identifying water constituents, elucidating dominant mechanisms in water composition, evaluating ion exchange processes, analyzing spatial distribution of components, identifying impacting processes, and assessing drinking water quality. The framework was applied to the coastal unconfined Arroyo Grande aquifer in Cartagena, Colombia. Fifteen points were sampled, assessing physicochemical parameters such as total hardness, alkalinity, pH, temperature, electrical conductivity, anions, cations, among others. Findings reveal the presence of dominant anions including bicarbonate, chloride, and sulfate, with relevant variations observed between the dry and wet season, with manganese and iron surpassing WHO drinking water standards. The prevalence of these constituents has been attributed to mineral dissolution, ion exchange, salinization due to seawater intrusion, and anthropogenic contamination. Over 50% of samples in both seasons fail to meet freshwater drinking standards due to elevated dissolved mineral concentrations in groundwater. These findings provide insights for sustainable management and mitigation strategies, and the systematic approach enables researchers to identify key factors influencing water composition. [ABSTRACT FROM AUTHOR]

Water quality deterioration in the Main Ethiopian Rift Lakes is a problem affecting the area’s public health and socioeconomic development. The present study aimed to assess the water level rise in Lake Beseka using Landsat images from 1975 to 2023 and dilution trends at the pumping site from 2004 to 2022. In addition, the spatial water quality parameters, including pH, EC, TDS, and water surface temperature, for the years 2007, 2018, 2021, and 2023 were determined. The water level increased dramatically from 3 km2 in the 1960s to 27.5 km2 in 1980 following the construction of the Koka dam and the beginning of irrigation activity (sugarcane plantation) for the Metehara sugar estate factory. The water level reached a maximum (50 km2 in the dry season) in the mid of 1910s and become decreased and fluctuated after 2015. The observed pH, EC, and TDS were higher in the central portion of the lake, grouped under brackish water, and lower in the southwest, south, and northeast shores. The EC and TDS were higher in 2007, decreased in 2018, and fluctuated. The geothermal anomaly of the area varies from 23.1 to 47.9°C with the highest anomaly occurring at the northern side of the lake at a recent volcanic area that interlinked with geological structures. However, the observed and estimated water temperatures of the lake decreased from west to east due to hot spring discharge from the southwest shore of the lake. The series of hot springs in the southwest and west shores of the lake with high discharge rates indicate the presence of structural connectivity that leads to the emission of heat from a deep-seated source and heated groundwater of the area recharged from irrigation activity. Overall, spatiotemporal lake water quality variations were due to anthropogenic and geogenic factors, including hot springs and groundwater discharge to the lake, water level rise and bathymetric depth variation, evaporation, and irrigation activity. This study is significant in continuously estimating water level fluctuations and providing early warnings and preparedness to maintain the region's socioeconomic development. [ABSTRACT FROM AUTHOR]

An in-depth understanding of nitrate-contaminated surface water and groundwater quality and associated risks is important for groundwater management. Hydrochemical characteristics and driving forces of groundwater quality and non-carcinogenic risks of nitrate were revealed by the integrated approaches of self-organizing map analysis, spatial visualization by geography information system, entropy and irrigation water quality indices, and human health risk model. Groundwater samples were categorized into two clusters by SOM analysis. Cluster I including three samples were Ca-SO4 type and cluster II of remaining 136 samples were Ca-HCO3 type. Hydrochemical compositions of two cluster samples were dominated by water–rock interaction: (1) calcite and gypsum dissolution for cluster I samples and (2) calcite dissolution, silicate weathering, and positive cation exchange for cluster II samples. Nitrate contamination occurred in both cluster I and II samples, primarily induced by agricultural nitrogen fertilizer. The EWQI results showed that 90.97% in total groundwater samples were suitable for drinking purpose, while the IWQI results demonstrated that 65.03% in total groundwater samples were appropriate for irrigation purpose. The HHR model and Monte Carlo simulation indicated that the non-carcinogenic nitrated risk was highest in children. Exposure frequency was the most sensitive factor (86.33% in total) influencing the total non-carcinogenic risk, indicated by sensitivity analysis. Compared with the two clusters of groundwater, surface water has a shorter circulation cycle and lower ion concentrations resulting in better water quality. This study can provide scientific basis for groundwater quality evaluation in other parts of the world. [ABSTRACT FROM AUTHOR]

The present study is conducted to assess the radiological and hydrogeochemical quality of earthly bore potable water in Haridwar, Uttarakhand, India. Radon activity concentrations in water samples ranged from 0.59 ± 0.04 to 57.32 ± 4.39 Bq/L. The average activity concentration of radon is estimated as 10.46 ± 1.05 Bq/L. Annual Effective Inhalation dose to humans ranged from 1.48 μSv/Y to 144.45 μSv/Y with an average value of 26.36 μSv/Y. Ca2+ > Na+ > Mg2+ > K+ and HCO3− > CaCO3− > SO42− > Cl− > NO3− > F− were the concentration orders of the primary cations and anions. The majority of tests contained acceptable levels of ions and TDS, indicating that the region's groundwater is safe for consumption. For irrigation purposes, the sodium absorption rate, sodium percentage, and magnesium risks were examined. The weathering of rocks was discovered to be the key factor influencing the chemistry of the groundwater in the region. The spatial patterns of observed fluctuations were investigated using the collected data set. [ABSTRACT FROM AUTHOR]

Geothermal resources are increasingly gaining attention as a competitive, clean energy source to address the energy crisis and mitigate climate change. The Wugongshan area, situated in the southeast coast geothermal belt of China, is a typical geothermal anomaly and contains abundant medium‐ and low‐temperature geothermal resources. This study employed hydrogeochemical and isotopic techniques to explore the cyclic evolution of geothermal water in the western Wugongshan region, encompassing the recharge origin, water–rock interaction mechanisms, and residence time. The results show that the geothermal water in the western region of Wugongshan is weakly alkaline, with low enthalpy and mineralization levels. The hydrochemistry of geothermal waters is dominated by Na‐HCO3 and Na‐SO4, while the hydrochemistry types of cold springs are all Na‐HCO3. The hydrochemistry types of surface waters and rain waters are Na‐HCO3 or Ca‐HCO3. The δD and δ18O values reveal that the geothermal waters are recharged by atmospheric precipitation at an altitude between 550.0 and 1218.6 m. Molar ratios of major solutes and isotopic compositions of 87Sr/86Sr underscore the significant role of silicate weathering, dissolution, and cation exchange in controlling geothermal water chemistry. Additionally, geothermal waters experienced varying degrees of mixing with cold water during their ascent. The δ13C values suggest that the primary sources of carbon in the geothermal waters were biogenic and organic. The δ34S value suggests that the sulfates in geothermal water originate from sulfide minerals in the surrounding rock. Age dating using 3H and 14C isotopes suggests that geothermal waters have a residence time exceeding 1 kaBP and undergo a long‐distance cycling process. [ABSTRACT FROM AUTHOR]

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