Identification of major sources controlling groundwater chemistry from a hard rock terrain — A case study from Mettur taluk,Salem district,Tamil Nadu,India

The study area Mettur forms an important industrial town situated NW of Salem district. The geology of the area is mainly composed of Archean crystalline metamorphic complexes. To identify the major process activated for controlling the groundwater chemistry an attempt has been made by collecting a total of 46 groundwater samples for two different seasons, viz., pre-monsoon and post-monsoon. The groundwater chemistry is dominated by silicate weathering and (Na + Mg) and (Cl + SO₄) accounts of about 90% of cations and anions. The contribution of (Ca + Mg) and (Na + K) to total cations and HCO₃ indicates the domination of silicate weathering as major sources for cations. The plot for Na to Cl indicates higher Cl in both seasons, derived from Anthropogenic (human) sources from fertilizer, road salt, human and animal waste, and industrial applications, minor representations of Na also indicates source from weathering of silicate-bearing minerals. The plot for Na/Cl to EC indicates Na released from silicate weathering process which is also supported by higher HCO₃ values in both the seasons. Ion exchange process is also activated in the study area which is indicated by shifting to right in plot for Ca + Mg to SO₄ + HCO₃. The plot of Na-Cl to Ca + Mg-HCO₃-SO₄ confirms that Ca, Mg and Na concentrations in groundwater are derived from aquifer materials. Thermodynamic plot indicates that groundwater is in equilibrium with kaolinite, muscovite and chlorite minerals. Saturation index of silicate and carbonate minerals indicate oversaturation during pre-monsoon and undersaturation during post-monsoon, conforming dissolution and dilution process. In general, water chemistry is guided by complex weathering process, ion exchange along with influence of Cl ions from anthropogenic impact.     

The evolution of groundwater in the Tyrrell catchment, south-central Murray Basin, Victoria, Australia

The Tyrell catchment lies on the western margin of the Riverine Province in the south-central Murray Basin, one of Australia’s most important groundwater resources. Groundwater from the shallow, unconfined Pliocene Sands aquifer and the underlying Renmark Group aquifer is saline (total dissolved solids up to 150,000 mg/L) and is Na-Cl-Mg type. There is no systematic change in salinity along hydraulic gradients implying that the aquifers are hydraulically connected and mixing during vertical flow is important. Stable isotopes (¹⁸O+²H) and Cl/Br ratios indicate that groundwater is entirely of meteoric origin and salts in this system have largely been derived by evapotranspiration of rainfall with only minor halite dissolution, rock weathering (mainly feldspar dissolution), and ion exchange between Na and Mg on clays. Similarity in chemistry of all groundwater in the catchment implies relative consistency in processes over time, independent of any climatic variation. Groundwater in both the Pliocene Sands and Renmark Group aquifers yield ages of up to 25 ka. The Tyrrell Catchment is arid to semi-arid and has low topography. This has resulted in relatively low recharge rates and hydraulic gradients that have resulted in long groundwater residence times.     

Effect of agricultural land use on the chemistry of groundwater from basaltic aquifers, Jeju Island, South Korea

Geochemical processes were identified as controlling factors of groundwater chemistry, including chemical weathering, salinization from seawater and dry sea-salt deposition, nitrate contamination, and rainfall recharge. These geochemical processes were identified using principal component analysis of major element chemistry of groundwater from basaltic aquifers in Jeju Island, South Korea, a volcanic island with intense agricultural activities. The contribution of the geochemical processes to groundwater chemistry was quantified by a simple mass-balance approach. The geochemical effects due to seawater were considered based on Cl contributions, whereas the effects due to natural chemical weathering were based on alkalinity. Nitrogenous fertilizers, and especially the associated nitrification processes, appear to significantly affect groundwater chemistry. A strong correlation was observed between Na, Mg, Ca, SO₄ and Cl, and nitrate concentrations in groundwater. Correspondingly, the total major cations, Cl, and SO₄ in groundwater were assessed to estimate relative effect of N-fertilizer use on groundwater chemistry. Cl originates more from nitrate sources than from seawater, whereas SO₄ originates mostly from rainwater. N-fertilizer use has shown the greatest effect on groundwater chemistry, particularly when nitrate concentrations exceed 6–7 mg/L NO₃–N. Nitrate contamination significantly affects groundwater quality and 18% of groundwater samples have contamination-dominated chemistry.     

Assessment of hydrogeochemistry and contamination of Varamin deep aquifer,Tehran Province,Iran

The present study investigates the hydrogeochemistry and contamination of Varamin deep aquifer located in the southeast of Tehran province, Iran. The study also evaluates groundwater suitability for irrigation uses. The hydrogeochemical study was conducted by collecting and analyzing 154 groundwater samples seasonally during 2014. Based on evolutionary sequence of Chebotarev, the aquifer is in the stage of SO₄ + HCO₃ in the north half of the plain and it has evolved into SO₄ + Cl in the south half. The unusual increase in TDS and Cl^? toward the western boundaries of the aquifer indicates some anomalies. These anomalies have originated from discharge of untreated wastewater of Tehran city in these areas. The studied aquifer contains four dominant groundwater types including Na–Ca–SO₄ (55%), Na–Ca–HCO₃ (22%), Na–Cl (13%) and Ca–Cl (10%). The spatial distributions of Na–Cl and Ca–Cl water types coincide with observed anomalies. Ionic relationships of SO₄ ^2? versus Cl^? and Na⁺ versus Cl^? confirm that water–rock interaction and anthropogenic contribution are main sources of these ions in the groundwater. The main processes governing the chemistry of the groundwater are the dissolution of calcite, dolomite and gypsum along the flow path, and direct ion exchange. Reverse ion exchange controls the groundwater chemistry in the areas contaminated with untreated wastewater. Based on Na% and SAR, 10.3 and 27% of water samples are unsuitable for irrigation purposes, respectively. Regarding residual sodium carbonate, there is no treat for crop yields. Only 6% of water samples represent magnesium adsorption ratios more than 50% which are harmful and unsuitable for irrigation.     

Statistical and geochemical assessment of groundwater quality in Teboursouk area (Northwestern Tunisian Atlas)

Teboursouk region, Northwestern Tunisia, is characterized by the diversity of its natural resources (petroleum, groundwater and minerals). It constitutes a particular site widely studied, especially from a tectonic stand point as it exhibits a complex architecture dominated by multi-scale synclinals and Triassic extrusions. It has typical karst landform that constitutes important water resources devoted for human consumption and agriculture activities, besides to the exploitation of the Mio-Plio-Quaternary aquifer (MPQ). Thus, hydrogeological investigations play a significant role in the assessment of groundwater mineralization and the evaluation of the used water quality for different purposes. Hence, the current study based on a combined geochemical–statistical investigation of 50 groundwater samples from the multilayered aquifer system in the study area give crucial information about the principal factors and processes influencing groundwater chemistry. The chemical analysis of the water samples showed that Teboursouk groundwater is dominantly of Ca–Mg–Cl–SO₄ water type with little contribution of Ca–Mg–HCO₃, Na–K–Cl–SO₄ and Na–K–HCO₃. The total dissolved solids (TDS) values range from 0.37 to 3.58 g/l. The highest values are located near the Triassic outcrops. Furthermore, the hydrogeochemistry of the studied system was linked with various processes such as carbonates weathering, evaporites dissolution of Triassic outcrops and anthropogenic activities (nitrate contamination). Additionally, the main processes controlling Teboursouk water system were examined by means of multivariate statistical analysis (PCA and HCA) applied in this study based on 10 physicochemical parameters (TDS, pH, SO₄, HCO₃, pCO₂, Ca, Mg, Na, K, Cl and NO₃). Two principal components were extracted from PCA accounting 61% of total variance and revealing that the chemical characteristics of groundwater in the region were acquired through carbonates and evaporite dissolution besides to nitrate contamination. Similarly, according to Cluster analysis using Ward’s method and squared Euclidean distance, groundwater from the studied basin belongs to five different groups suggesting that the geochemical evolution of Teboursouk groundwater is controlled by dissolution of carbonates minerals, chemical weathering of Triassic evaporite outcrops, cation exchange and anthropogenic activities (nitrate contamination).     

Use of hydrogeochemistry and environmental isotopes for evaluation of groundwater in Qingshuihe Basin,northwestern China

Hydrogeochemistry and environmental isotope data were utilized to understand origin, geochemical evolution, hydraulic interconnection, and renewability of groundwater in Qingshuihe Basin, northwestern China. There are four types of groundwater: (1) shallow groundwater in the mountain front pluvial fans, originating from recent recharge by precipitation, (2) deep paleo-groundwater of the lower alluvial plains, which was formed long ago, (3) shallow groundwater in the lower alluvial plains, which has undergone evaporation during the recharge process, and (4) mixed groundwater (shallow and deep groundwater in the plain). The main water types are Na–HCO₃, which dominates type (1), and Na–SO₄, which dominates types (2) and (3). Geochemical evolution in the upper pluvial fans is mainly the result of CO₂ gas dissolution, silicates weathering and cation exchange; in the lower alluvial plains, it is related to mineral dissolution. The evaporative enrichment only produces significant salinity increases in the shallow groundwater of the lower alluvial plains. Shallow groundwater age in the upper plain is 10 years or so, showing a strong renewability. Deep groundwater ages in the lower plain are more than 200 years, showing poor renewability. In the exploitation areas, the renewability of groundwater evidently increases and the circulation period is 70–100 years.     

Multivariate statistical analysis of chemical and stable isotopic data as indicative of groundwater evolution with reduced exploitation

Groundwater resources in the North China Plain (NCP) are undergoing tremendous changes in response to the operation of groundwater exploitation reduction (GWER) project. To identify groundwater evolution in this complex context, hierarchical cluster analysis (HCA) and principal component analysis (PCA) were combined to interpret an integrated dataset of stable isotopes and chemical data from four sampling campaigns in a pilot area of groundwater control. We proposed a novel HCA approach integrating stable isotopes and chemical signals, which successfully partitioned the groundwater samples into the unconfined and the confined water samples. Stable isotopic evidence showed that the lateral inflow and the surface water may contribute more to groundwater recharge in this region than local modern precipitation. The unconfined water’s main hydrochemical types were Na type with mixed anions, and Na–Cl–SO₄ type, while the confined water was mainly Na–Cl and Na–SO₄ types. Geochemical processes mainly involved the dissolution/precipitation of halite, gypsum, Glauber's salt, feldspar, calcite and dolomite, as well as the cation exchange. PCA results showed that water–rock interaction (i.e., salinity-based and alkalinity-based processes) predominated the hydrochemical evolution, along with local nitrate contamination resulting from fertilizers and domestic sewage. The GWER project regulated the natural evolution of unconfined water chemistry, and significantly reduced the unconfined water’s salinity (mainly Na⁺, Mg²⁺, SO₄^2?). This may be attributed to upward leakage from low-salinity confined water at some parts of the aquifer. Additionally, insignificant changes in the confined water’s salinity reflected that the impact of GWER on the confined aquifer was negligible. This study facilitates the groundwater classification effectively in the areas lack of geological data, and enhances the knowledge of groundwater chemical evolution in such a region where groundwater restoration is in progress, with important implications for groundwater sustainable management in similar basins worldwide.     

Principal component and multivariate statistical approach for evaluation of hydrochemical characterization of fluoride-rich groundwater of Shaslar Vagu watershed,Nalgonda District,India

In order to assess the impact of fluoride-rich groundwater of Shasilair Vagu watershed on groundwater regime, more than hundred groundwater samples for pre- and post-monsoon seasons were collected from bore wells/dug wells and analyzed for major ions. Water quality analysis of major ion chemistry shows elevated concentration of fluoride in groundwater samples. The fluoride concentration ranges from 1.4 to 5.9 mg/l and 1.5 to 5.8 mg/l in pre- and post-monsoons, respectively. The result clearly shows that the seasonal variation of fluoride in groundwater is due to recharge of rain water during monsoon. The water quality data was analyzed by hydrochemical facies (Piper diagram), Gibbs plot, and various plots. Plots of Na versus Cl, Ca versus SO₄, and (Na+Cl)-(SO₄+HCO₃) versus (Na+K-Cl) shows positive and negative values, indicating that their source of high concentration are aquifer, evapotranpiration, and other anthropogenic sources. Saturation index of halite and gypsum shows that all groundwater samples were undersaturated and suggests that carbonate minerals influence the concentration. Using multivariate statistical techniques, viz., principal component (factor analysis and cluster analysis), the analysis brought out impact of intensity of excess use of fertilizers and excess withdrawal of groundwater regime. Multivariate statistical techniques are potential tools and provide greater precision for identifying contaminant parameter linkages.     

Spatiotemporal variation of groundwater quality in an arid area experiencing long-term paper wastewater irrigation,northwest China

Groundwater is crucial for multiple uses over the world, especially in arid and semiarid regions. However, human activities significantly decreased groundwater quality. In this study, the spatiotemporal variation of groundwater quality was evaluated in an arid area where long-term paper wastewater irrigation has been implemented. For this study, seven wells were regularly monitored for physicochemical parameters over a period of 1 year. Statistical and graphical approaches were applied to interpret the spatiotemporal variation of groundwater quality parameters in the wastewater irrigation zone. Correlation analysis was also carried out to reveal the sources of some major ions. The results indicate that the groundwater type in the study area is dominated by the Cl–Na, followed by the HCO₃–Na, the HCO₃–Ca·Mg, and the SO₄·Cl–Ca·Mg types. Groundwater in the area is significantly contaminated locally with fluoride, nitrite and ammonia, and the chemical oxygen demand levels were increased in some groundwater monitoring wells. Most contaminants showed an increasing trend from the Yellow River water irrigation zone toward the wastewater irrigation zone. Rock weathering, mineral dissolution, and cation exchange are important processes controlling groundwater quality, but human activities, such as wastewater irrigation, play an undeniable role in affecting groundwater quality in this area. The results of this study contribute to the understanding of the formation and circulation of groundwater under human activities and provide a scientific basis for regional water quality evaluation, water quality improvement, and protection.     

Assessment of natural and anthropogenic influences on regional groundwater chemistry in a highly industrialized and urbanized region: a case study of the Vaal River Basin,South Africa

The Vaal River Basin is an economically significant area situated in the interior of South Africa (SA), where mining, industrial, domestic and agricultural activities are very intense. The purpose of the study was to assess the influence of geology and anthropogenic activities on groundwater chemistry, and identify the predominant hydrochemical processes in the basin. Data from seventy groundwater sites were retrieved from the national database, and attention was paid to fifteen water quality parameters. Groundwater samples were clustered into seven hydrochemically distinct groups using Hierarchical Cluster Analysis (HCA), and three samples treated independently. A Piper plot revealed two major water types, Ca–Mg–HCO₃ and Ca–Mg–SO₄-Cl, which were linked to dissolution of the underlying geology and mine pollution. The Ca?+?Mg vs HCO₃?+?SO₄ plot indicated that reverse ion exchange is an active process than cation exchange in the area. Principal component analysis (PCA) was used to identify the main natural and anthropogenic processes causing variation in groundwater chemistry. Four principal components were extracted using PCA that explains 82% of the total variance in the chemical parameters. The PCA results can be categorized by four components: (1) evaporites and silicates weathering enrichment of Na, K, Cl, SO₄ and F, and anthropogenic Cl; (2) dissolution of dolomite, limestone and gypsum; (3) agricultural fertilizers (4) wastewater treatment. This study reveals that both natural and anthropogenic activities are the cause of groundwater variation in the basin.     

Hydrogeochemical processes affecting groundwater in an irrigated land in Central Tunisia

Detailed hydrogeochemical investigation has provided new information concerning the major factors and mechanisms controlling the groundwater chemistry of Chougafiya basin. The hydrogeochemical characteristics of groundwaters comprise three main types: Cl–SO₄–Ca, Cl–SO₄–Na and Cl–Na. Hydrochemical characteristics based on the bivariate diagrams of major (Cl^?, SO₄ ^2?, NO₃ ^?, HCO₃ ^?, Na⁺, Mg²⁺, K⁺ and Ca²⁺) and some trace (Br^? and Sr²⁺) ions, mineral saturation indices and hierarchical cluster analysis indicate different origins of groundwater mineralization. The water–rock interaction (dissolution of evaporitic minerals), followed by cation exchange reactions with clay minerals, constitute the main processes that control groundwater salinization. However, the chemical composition of brackish groundwater in the central and southern parts of the study area is influenced by a mixing process with Sabkhas salt groundwater. The mixing proportions inferred from chloride mass balance prove that the contribution of Sabkhas groundwater to Quaternary aquifer ranges between 2.7 and 9.1 %. These intrusion rates reflect the progress of the saltwater–freshwater interface, which is mainly controlled by the piezometric level variation and the distance to the Sabkhas.     

Hydrogeochemical evolution of the shallow and deep basaltic aquifers in Tamborine Mountain,Queensland (Australia)

Tamborine Mountain, Queensland (Australia), is a prime example of a basalt fractured-rock aquifer. Yet very little is known about the hydrochemistry of this groundwater system. Both analytical (major ions and stable isotopes) and multivariate (hierarchical cluster analysis, principal component analysis and factor analysis) analyses were used in this study to investigate the factors that interact within this aquifer system, in order to determine groundwater hydrogeochemistry. A new approach was applied to the data by classifying hydrographs by water type to clearly identify differing aquifer zones. Three distinct groundwater chemistry types were identified, and they were differentiated by variations in depth. Shallow bores were dominated by Na–Cl waters, deep bores were dominated by Na–HCO₃ and Ca–HCO₃ waters, and the two deepest bores were dominated by mixed water types. The evaluation of hydrogeochemical data has determined that both mineral weathering processes and groundwater/surface-water interaction had a strong influence on the hydrogeochemistry. Seasonal effects were minimal in the study area based on physicochemical parameters and ion chemistry. However, stable isotopic data show temporal trends. Increased rainfall events during the wet season produced a depletion in δ¹⁸O and increased d-excess values. The opposite is found during the dry season as a result of higher evaporation rates that are not hindered by intense rainfall events.

     

Tracing ionic sources and geochemical evolution of groundwater in the Intermountain Una basin in outer NW Himalaya,Himachal Pradesh,India

The present research aims to identify sources of ions and factors controlling the geochemical evolution of groundwater in an intermountain basin, comprising hill and valley fill region, of Outer Himalaya in Himachal Pradesh, India. The groundwater samples collected from 81 tubewells and handpumps are analyzed for major ions, trace metals and stable isotopes (δ¹⁸O and δD). Geochemically the dominant hydrochemical facies in the Una basin are Ca–HCO₃, Ca–Mg–HCO₃ and Na–Cl types at few locations. A relatively lower ionic concentration in the valley fills indicates dilution and low residence time of water to interact with the aquifer mass due to high porosity and permeability. The ionic ratios of 0.9, 0.8 and 3.8 to 5.7, respectively, for (Ca?+?Mg): HCO₃, (Ca?+?Mg): (HCO₃?+?SO₄) and Na: Cl, suggests that ionic composition of groundwater is mainly controlled by rock weathering of, particularly by dissolution/precipitation of calcrete and calcite hosted in rock veins and Ca–Na feldspar hosted in conglomerate deposits derived from the Higher and Lesser Himalaya during the formation of Siwalik rocks. Although Na, K, NO₃ and SO₄ are introduced in the groundwater through agricultural practices, Na has also been introduced through ion exchange processes that have occurred during water–rock interaction, as indicated by negative CAI values. Factor analysis further suggests three major factors affecting the water chemistry of the area. The first two factors are associated with rock weathering while the third is anthropogenic processes associated with high nitrate and iron concentration. High concentrations of Fe and Mn ions that are exceeded that of WHO and BIS standards are also present at few locations. The recharge of groundwater in the Outer Himalaya is entirely through Indian Southwest Monsoon (ISM) and depleted ratios of δ¹⁸O/δD in valley region indicate infiltration from irrigation in recharging the groundwater and fractionation of isotopes of precipitation due to evaporation before infiltration. High d-excess values and inverse relation with δ¹⁸O are indicative of secondary evaporation of precipitation during recharge of groundwater.     

Geochemical patterns and origin of alkaline thermal waters in Central Greece (Platystomo and Smokovo areas)

This study investigates the origin and chemical composition of the thermal waters of Platystomo and Smokovo areas in Central Greece as well as any possible relationships of them to the neighboring geothermal fields located in the south-eastern part of Sperchios basin. The correlations between different dissolved salts and the temperature indicate that the chemical composition of thermal waters are controlled by, the mineral dissolution and the temperature, the reactions due to CO₂ that originates possibly by diffusion from the geothermal fields of Sperchios basin and the mixing of thermal waters with fresh groundwater from karst or shallow aquifers. Two major groups of waters are recognized on the basis of their chemistry: thermal waters of Na–HCO₃–Cl type and thermal waters mixed with fresh groundwater of Ca–Mg–Na–HCO₃ type. All thermal waters of the study area are considered as modified by water–rock interaction rainwater, heated in depth and mixed in some cases with fresh groundwater when arriving to the surface. Trace elements present low concentrations. Lithium content suggests discrimination between the above two groups of waters. Boron geochemistry confirms all the above remarks. Boron concentration ranges from 60 μg L^?1 to 10 mg L^?1, while all samples’ constant isotopic composition (δ¹¹B ≈ 10 ‰) indicates leaching from rocks. The positive correlation between the chemical elements and the temperature clearly indicates that much of the dissolved salts are derived from water–rock interactions. The application of geothermometers suggests that the reservoir temperature is around 100–110 °C. Chalcedony temperatures are similar to the emergent temperatures and this is typical of convective waters in fault systems in normal thermal gradient areas.     

Hydrochemical appraisal of groundwater and its suitability in the intensive agricultural area of Muzaffarnagar district,Uttar Pradesh,India

Muzaffarnagar is an economically rich district situated in the most fertile plains of two great rivers Ganga and Yamuna in the Indo-gangetic plains, with agricultural land irrigated by both surface water as well as groundwater. An investigation has been carried out to understand the hydrochemistry of the groundwater and its suitability for irrigation uses. Groundwater in the study area is neutral to moderately alkaline in nature. Chemistry of groundwater suggests that alkaline earths (Ca + Mg) significantly exceed the alkalis (Na + K) and weak acids exceed the strong acids (Cl + SO₄), suggesting the dominance of carbonate weathering followed by silicate weathering. Majority of the groundwater samples (62%) posses Ca–Mg–HCO₃ type of hydrochemical species, followed by Ca–Na–Mg–HCO₃, Na–Ca–Mg–HCO₃, Ca–Mg–Na–HCO₃–Cl and Na–Ca–HCO₃–SO₄ types. A positive high correlation (r ² = 0.928) between Na and Cl suggests that the salinity of groundwater is due to intermixing of two or more groundwater bodies with different hydrochemical compositions. Barring a few locations, most of the groundwater samples are suitable for irrigation uses. Chemical fertilizers, sugar factories and anthropogenic activities are contributing to the sulphate and chloride concentrations in the groundwater of the study area. Overexploitation of aquifers induced multi componential mixing of groundwater with agricultural return flow waters is responsible for generating groundwater of various compositions in its lateral extent.     

Hydrogeochemical and Isotopic Study of Groundwater in a Semi-arid Region: Yeniceoba Plain (Cihanbeyli-KONYA), Central Anatolia,Turkey

Groundwater is the most important source of water supply in the Yeniceoba Plain in Central Anatolia,Turkey.An understanding of the geochemical evolution of groundwater is important for the sustainable development of water resources in this region.A hydrogeochemical investigation was conducted in the Plio-Quaternary aquifer system using stable isotopes(δ~(18)O andδD),tritium(~3H),major and minor elements(Ca,Na,K,Mg,Cl,SO_4,NO_3,HCO_3 and Br)in order to identify groundwater chemistry patterns and the processes affecting groundwater mineralization in this system.The chemical data reveal that the chemical composition of groundwater in this aquifer system is mainly controlled by rock/water interactions including dissolution of evaporitic minerals,weathering of silicates,precipitation/dissolution of carbonates,ion exchange,and evaporation.Based on the values of Cl/Br ratio(300 mg/l)in the Plio-Quaternary groundwater,dissolution of evaporitic minerals in aquifer contributes significantly to the high mineralization.The stable isotope analyses indicate that the groundwater in the system was influenced by evaporation of rainfall during infiltration.Low tritium values(generally1 tritium units)of groundwater reflect a minor contribution of recent recharge and groundwater residence times of more than three or four decades.     

Hydrochemistry of groundwater in a coastal region of Cuddalore district, Tamilnadu, India: implication for quality assessment

A hydrogeochemical investigation was conducted in a coastal region of Cuddalore district to identify the influence of saltwater intrusion and suitability of groundwater for domestic and agricultural purposes. The geology of the study area comprises of sandstone, clay, alluvium, and laterite soils of Tertiary and Quaternary age. A total of 18 groundwater samples were analyzed for 14 different water quality parameters and the result indicates higher concentrations of ions like Cl (3,509 mg/l), Na (3,123 mg/l), and HCO₃ (998 mg/l) when compared with WHO, BIS, and ISI standards. A positive correlation (r ²?=?0.82) was observed between Na and Cl, indicating its sources from salt water intrusion. Three factors were extracted with a total variance of 64% which indicates the sources of salinization, cation exchange, and anthropogenic impact to the groundwater. The Piper trilinear diagram indicates both Na–Cl and mixed Na–HCO₃–Cl-type, indicating that groundwater was strongly affected by anthropogenic activities. The plot of (Ca?+?Mg)/(K?+?Na) indicates evidences of cation exchange and salt water intrusion. The (Ca–0.33*HCO₃)/ SO₄ plot indicates salt water intrusion for elevated SO₄ levels rather than gypsum dissolution. The spatial distribution of total dissolved solid indicates the saline water encroachment along the SW part of the study area. As per sodium adsorption ratio (SAR), 50% of the samples with <10 SAR are suitable for irrigation and >10 SAR indicates that water is unsuitable for irrigation purposes. The residual sodium carbonate classification indicates that 50% of the samples fall in safe and 50% of the samples fall in bad zones and prolonged usage of this water will affect the crop yield. The Chloro Alkaline Index of water indicates disequilibrium due to a higher ratio of Cl?>?Na–K, indicating the influence of salt water intrusion. The Permeability Index of the groundwater indicates that the groundwater from the study area is moderate to good for irrigation purposes.     

Hydrogeochemistry of a deep gas-storage cavern,Czech Republic

Groundwater was occasionally found during the construction of a deep gas-storage cavern at approximately 1 km below land surface near Pribram, Czech Republic. The individual groundwater seeps, with a discharge not exceeding 0.01 l/s and T?=?23°C, were usually a strongly alkali natural solution with maximum pH values of 9.9 and TDS concentrations from 0.2 to 0.86 g/l; Na⁺, \({\text{HCO}}^{ - }_{3}\), and Cl^? ions were the major dissolved chemical constituents. Two main groundwater quality groups were defined: Na–Cl and Na–HCO₃. Based on the stable isotope (¹⁸O/¹⁶O, D/H), tritium and radiocarbon analyses, some groundwater originated from rainwater infiltrating during the Upper Pleistocene Epoch. Strontium in the groundwater of the crystalline aquifer was isotopically homogenous and equilibrates with strontium in the granite and granodiorite of the gas-storage cavern. Based on the information, the deep groundwater seeps were associated with slow or ‘stagnant’ groundwater circulation, without direct relation to the recent groundwater of faster circulation near the surface, which is periodically recharged by precipitation. The results of the water-quality monitoring of the deep groundwater seeps have been used in estimating the insulating properties of the neighboring rocks near the gas-storage cavern. This information will be important in the safe operation of the gas-storage cavern.     

Geochemical assessment of groundwater contamination with special emphasis on fluoride concentration, North Jordan

The concentrations of fluorine in groundwater of North Jordan range from 0.009 to 0.055 mg/l. Other chemical parameters, e.g. pH, EC, TDS, Cl, TH, HCO₃, PO₄, SO₄, NO₃, NH₄, K, Ca, Mg, and NO₃ have been studied and showed higher concentrations in HCO₃⁻ and NO₃⁻ of 307 and 51 mg/l, respectively. Thermodynamic considerations show that almost all the analyzed samples are undersaturated with respect to calcite and fluorite. This undersaturation is probably due to their low availability in the locations. Fluoride concentration shows a positive relation to pH and HCO₃, whereas Cl, Mg, Ca, and Na initially increase and then decrease with increasing fluoride in the water. Saturation indexes of fluorite and calcite are estimated. The chemistry of the groundwater is controlled by the fluorite and calcite solubility. The topography of the area has exerted control on the aerial extent of fluoride concentration.     

Groundwater quality assessment using WQI and GIS techniques, Dindigul district, Tamil Nadu, India

The quality of groundwater was assessed by determining the physicochemical parameters (pH, EC, TDS and TH) and major ions concentration (HCO₃, Cl, FSO₄, Ca, Mg, Na and K) around Dindigul district, Tamil Nadu, India. The groundwater samples were collected from 59 bore wells covering the entire study area and analyzed using standard methods. The GIS mapping technique were adopted to highlight the spatial distribution pattern of physicochemical parameters and major ion concentration in the groundwater. Gibbs diagram reveals that the source of major ions is predominantly derived from rock–water interaction and evaporation dominance process. The salt combinations of the aquifers are dominated by CaHCO₃, mixed CaMgCl, mixed CaMgHCO₃ and CaCl facies type due to leaching and dissolution process of weathered rocks. The Canadian Council of Ministers of Environment Water Quality Index (CCMEWQI) suggests that most of the groundwater quality falls under good to marginal category. The statistical analysis indicates that the presence of major ions and physicochemical parameters are chiefly controlled by rock–water interaction and residence time of the groundwater. However, the major nutrient like nitrite in the groundwater probably comes from anthropogenic process. Based on the groundwater quality standards, majority of the samples are suitable for drinking purposes except few in the study area.