Hydrogeochemistry for the assessment of groundwater quality in Varanasi: a fast-urbanizing center in Uttar Pradesh, India

The hydrogeochemical parameters for groundwater samples of the Varanasi area, a fast-urbanizing region in India, were studied to evaluate the major ion chemistry, weathering and solute acquisition processes controlling water composition, and suitability of water quality for domestic and irrigation uses. Sixty-eight groundwater samples were collected randomly from dug wells and hand pumps in the urban Varanasi area and analyzed for various chemical parameters. Geologically, the study area comprises Quaternary alluvium made up of an alternating succession of clay, silty clay, and sand deposits. The Total dissolved solids classification reveals that except two locations, the groundwater samples are desirable for drinking, and all are useful for irrigation purposes. The cationic and anionic concentrations indicated that the majority of the groundwater samples belong to the order of Na > Ca > Mg > K and HCO₃ > Cl > SO₄ types, respectively. Geochemical classification of groundwater based on the Chadha rectangular diagram shows that the majority (81%) of groundwater samples belong to the calcium?Cbicarbonate type. The HCO₃/ (HCO₃ + SO₄) ratio (0.87) indicates mostly carbonic acid weathering process due to presence of kankar carbonate mixed with clay/fine sand. The high nitrate concentration (>45?mg/l) of about 18% of the groundwater samples may be due to the local domestic sewage, leakage of septic tanks, and improper management of sanitary landfills. In general, the calculated values of sodium adsorption ratio, percent sodium, residual sodium carbonate, and permeability index indicate good to permissible use of water for irrigation, and only a few locations demand remedial measures for better crop yields.     

Major ion chemistry and weathering processes in the Midyan Basin, northwestern Saudi Arabia

Chemical characteristics of 72 groundwater samples collected from Midyan Basin have been studied to evaluate major ion chemistry together with the geochemical and weathering processes controlling the water composition. Water chemistry of the study area is mainly dominated by Na, Ca, SO₄, and Cl. The molar ratios of (Ca?+?Mg)/total cations, (Na?+?K)/total cations, (Ca?+?Mg)/(Na?+?K), (Ca?+?Mg)/(HCO₃?+?SO₄), (Ca?+?Mg)/HCO₃, and Na/Cl reveal that water chemistry of the Midyan Basin is controlled by evaporite dissolution (gypsum and/or anhydrite, and halite), silicate weathering, and minor contribution of carbonate weathering. The studied groundwater samples are largely undersaturated with respect to dolomite, gypsum, and anhydrite. These waters are capable of dissolving more of these minerals under suitable physicochemical conditions.     

Groundwater quality and its suitability for drinking and agricultural use in the Yanqi Basin of Xinjiang Province, Northwest China

The Yanqi Basin in Xinjiang Province is an important agricultural area with a high population density. The extensive agricultural activities in the Yanqi Basin started in the 1950s with flood irrigation techniques. Since then, the groundwater table was raised because of the absence of an efficient drainage system. This obstacle is a crucial factor that restricts sustainable socioeconomic development. Hydrochemical investigations were conducted in the Yanqi Basin, Northwestern China, to determine the chemical composition of groundwater. Sixty groundwater samples were collected from different wells to monitor the water chemistry of various ions. The results of the chemical analysis indicate that the groundwater in the area is generally neutral to slightly alkaline and predominantly contains Na⁺ and Ca²⁺ cations as well as HCO₃ ^? and SO₄ ²⁺ anions. High positive correlations between HCO₃ ^?–Mg²⁺ + Ca²⁺, SO ₄ ^2?–Mg²⁺, SO₄ ^2?–Na⁺ + K⁺, and Cl^?–Na⁺ + K⁺ were obtained. The total dissolved solids (TDS) mainly depend on the concentration of major ions such as HCO₃ ^?, SO₄ ^2?, Cl^?, Ca²⁺, Mg²⁺, and Na⁺ + K⁺. The dominant hydrochemical facies for groundwater are Ca²⁺–Mg²⁺–HCO₃ ^?, Mg²⁺–Ca²⁺–SO₄ ^2?–Cl^?, Na⁺–K⁺–Cl^?–SO₄ ^2?, and Na⁺–K⁺–Mg²⁺–Cl^?–HCO₃ ^? types. The hydrochemical processes are the main factors that determine the water quality of the groundwater system. These processes include silicate mineral weathering, dissolution, ion exchange, and, to a lesser extent, evaporation, which seem to be more pronounced downgradient of the flow system. The saturation index (SI), which is calculated according to the ionic ratio plot, indicates that the gypsum–halite dissolution reactions occur during a certain degree of rock weathering. SI also indicates that evaporation is the dominant factor that determines the major ionic composition in the study area. The assessment results of the water samples using various methods indicate that the groundwater in the study area is generally hard, fresh to brackish, high to very high saline, and low alkaline in nature. The high total hardness and TDS of the groundwater in several places indicate the unsuitability of the groundwater for drinking and irrigation. These areas require particular attention, particularly in the construction of adequate drainage as well as in the introduction of an alternative salt tolerance cropping.     

Physicochemical quality evaluation of groundwater and development of drinking water quality index for Araniar River Basin, Tamil Nadu, India

Groundwater is the most important natural resource which cannot be optimally used and sustained unless its quality is properly assessed. In the present study, the spatial and temporal variations in physicochemical quality parameters of groundwater of Araniar River Basin, India were analyzed to determine its suitability for drinking purpose through development of drinking water quality index (DWQI) maps of the post- and pre-monsoon periods. The suitability for drinking purpose was evaluated by comparing the physicochemical parameters of groundwater in the study area with drinking water standards prescribed by the World Health Organization (WHO) and Bureau of Indian Standards (BIS). Interpretation of physicochemical data revealed that groundwater in the basin was slightly alkaline. The cations such as sodium (Na⁺) and potassium (K⁺) and anions such as bicarbonate (HCO₃ ^?) and chloride (Cl^?) exceeded the permissible limits of drinking water standards (WHO and BIS) in certain pockets in the northeastern part of the basin during the pre-monsoon period. The higher total dissolved solids (TDS) concentration was observed in the northeastern part of the basin, and the parameters such as calcium (Ca²⁺), magnesium (Mg²⁺), sulfate (SO₄ ^2?), nitrate (NO₃ ^?), and fluoride (F^?) were within the limits in both the seasons. The hydrogeochemical evaluation of groundwater of the basin demonstrated with the Piper trilinear diagram indicated that the groundwater samples of the area were of Ca²⁺-Mg²⁺-Cl^?-SO₄ ^2?, Ca²⁺-Mg²⁺-HCO₃ ^? and Na⁺-K⁺-Cl^?-SO₄ ^2? types during the post-monsoon period and Ca²⁺-Mg²⁺-Cl^?-SO₄ ^2?, Na⁺-K⁺-Cl^?-SO₄ ^2? and Ca²⁺-Mg²⁺-HCO₃ ^? types during the pre-monsoon period. The DWQI maps for the basin revealed that 90.24 and 73.46 % of the basin area possess good quality drinking water during the post- and pre-monsoon seasons, respectively.     

Hydrochemistry and evaluation of groundwater suitability for irrigation and drinking purposes in the Markandeya River basin, Belgaum District, Karnataka State, India

Markandeya River basin stretches geographically from 15°56?? to 16°08?? N latitude and 74°37?? to 74°58?? E longitude, positioned in the midst of Belgaum district, in the northern part of Karnataka. Since the quantity and quality of water available for irrigation in India is variable from place to place, groundwater quality in the Markandeya River basin was evaluated for its suitability for drinking and irrigation purposes by collecting 47 open and bore-well samples during the post-monsoon period of 2008. The quality assessment was made by estimating pH, electrical conductivity, total dissolved solids, hardness, and alkalinity besides major cations (Na^?+?, K^?+?, Ca^2?+?, and Mg^2?+?) and anions (HCO $_{3}^{\,\,-}$ , Cl^???, SO $_{4}^{\,\,2-}$ , PO $_{4}^{\,\,3-}$ , F^???, and NO $_{3}^{\,\,-}$ ). Based on these analyses, irrigation quality parameters like, sodium absorption ratio, %Na, residual sodium carbonate, residual sodium bicarbonate, chlorinity index, soluble sodium percentage, non-carbonate hardness, potential salinity, permeability index, Kelley??s ratio, magnesium hazard/ratio, index of base exchange, and exchangeable sodium ratio were calculated. According to Gibbs?? ratio, majority of water samples fall in the rock dominance field. The groundwater samples were categorized as normal chloride (95.75%), normal sulfate (95.75%), and normal bicarbonate (61.70%) water types based on Cl, SO₄, and HCO₃ concentrations. Based on the permeability index, majority of the samples belongs to classes 1 and 2, suggesting the suitability of groundwater for irrigation. The negative index of base exchange indicates the existence of chloro-alkaline disequilibrium (indirect base exchange reaction) existing in majority of the samples (68.08%) from the study area.     

The hydrochemistry of groundwater in the Densu River Basin, Ghana

Hydrochemical analyses of groundwater samples were used to establish the hydrochemistry of groundwater in the Densu River Basin. The groundwater was weakly acidic, moderately mineralized, fresh to brackish with conductivity ranging from of 96.6 μS cm^???1 in the North to 10,070 μS cm^???1 in the South. Densu River basin have special economic significance, representing the countries greatest hydrostructure with freshwater. Chemical constituents are generally low in the North and high in the South. The order of relative abundance of major cations in the groundwater is Na^?+??> Ca^2?+??> Mg^2?+??> K^?+? while that of anions is Cl^????> HCO $_{3}^{-} >$ SO $_{4}^{2-} >$ NO $_{3}^{-}$ . Four main chemical water types were delineated in the Basin. These include Ca–Mg–HCO₃, Mg–Ca–Cl, Na–Cl, and mixed waters in which neither a particular cation nor anion dominates. Silicate weathering and ion exchange are probably the main processes through which major ions enter the groundwater system. Anthropogenic activities were found to have greatly impacted negatively on the quality of the groundwater.     

Source evaluation of physicochemically contaminated groundwater of Dera Ismail Khan area, Pakistan

Groundwater samples collected from Dera Ismail Khan, Pakistan, in 15 different stations were analyzed to determine the status of concentration of different physicochemical parameters. The samples were collected around a sugar mill in the study area. Sample location was selected on the basis of the flow of sugar mill effluents and groundwater. The samples were collected at random intervals in different villages. The physicochemical parameters such as pH, electrical conductivity (EC), total dissolved salts (TDS), TH, HCO₃, NO₃, SO₄, PO₄, Na, K, Ca, Mg, Fe, F, and Pb have been analyzed. The results showed that values of the tested parameters for EC, TDS, TH, HCO₃, SO₄, and Na near the sugar mill were very high, which indicate the descent of standard norms of quality and protection procedures for the groundwater around this area.     

Preliminary assessment of groundwater hydrogeochemistry within Gilan,a northern province of Iran

In four basins of Gilan province, groundwater samples were collected from 127 piezometric wells to investigate the hydrogeochemistry of groundwater, and additionally its suitability for drinking and irrigation purposes. The average concentrations of major cations and anions follow the order of Ca²⁺?>?Na⁺?>?Mg²⁺?>?K⁺ and \( {\mathrm{HCO}}_3^{-}>{\mathrm{Cl}}^{-}>{\mathrm{SO}}_4^{2-}>{\mathrm{CO}}_3^{2-} \), respectively. Using Piper diagram delineation, CaMgHCO₃ was determined as the main hydrogeochemical facies of groundwater. According to Piper diagrams, Gibbs plots, and ionic ratios, silicate weathering and ion exchange are the major processes regulating the groundwater hydrochemistry. Furthermore, saturation indices (SIs) revealed that carbonate precipitation also plays an important role in aquifers. Among the processes, weathering of silicate minerals seems to be the dominant process. Comparing the analyzed major ions and physicochemical parameters with the WHO guideline values indicates that the potability of most groundwater samples is generally acceptable. Electrical conductivity (EC) and total dissolved solid (TDS) measurements along with sodium percentage (SP), sodium adsorption ratio (SAR), Kelley’s index (KI), and residual sodium carbonate (RSC) calculations suggest that groundwater in many areas is suitable for irrigation use. Nonetheless, total hardness (TH) values ranging as high as 650.0 mg/l reveal many groundwater samples to be classified as hard and very hard, indicating a requirement for long-term monitoring and further evaluation. The present study shows that the groundwater quality in Lahijan, Astaneh, and to a lesser extent Fouman drainage basins is lower than in Talesh. Therefore, intense monitoring programs towards enhanced water management practices are recommended before poorer quality groundwater is further utilized.     

Quality of Shallow Groundwater and Drainage Water in Irrigated Agricultural Lands in A Mediterranean Coastal Region of Turkey

Spatial and seasonal differences in water quality of drainage water and unconfined shallow groundwater were related to irrigation in Samandağ, a Mediterranean coastal region. Eighteen wells, seven drainage points and Orontes River were monitored bimonthly for one year for analyses of electrical conductivity (EC), total dissolved solids (TDS), sodium adsorption ratio (SAR), cations (Na, K, Ca + Mg) and anions (CO₃, HCO₃, Cl and SO₄). Agricultural irrigation using saline groundwater decreased water quality of Orontes River during the irrigation season (May to September) more than during the non-irrigation season (October to April). Seasonal fluctuations in water quality of shallow groundwater were greater during the irrigation season than the non-irrigation season in the study area. Excessive use of groundwater resulted in a decline in the water table levels in the irrigation season. Water table level rose up to the soil surface in areas where there was a lack of drainage or poor drainage, due to the impact of precipitation in the winter. SAR and pH values of drainage water increased in the irrigation season, while the other properties of drainage water decreased. Irrigation water quality of Orontes River was classified as C₃S₁ in both seasons. Irrigation water quality of shallow groundwater and drainage water varied from C₂S₁ to C₄S₂ in one year. Drainage and well waters were found to be different on yearly basis in terms of Na, SAR (p<0.01) and Ca + Mg concentrations (p<0.001). Ca + Mg concentrations for both sources were different for all sampling dates (p<0.001).     

Groundwater geochemistry in the Alisadr, Hamadan, western Iran

The chemical composition of 59 well water samples throughout the Alisadr area, Hamadan, western Iran was determined in order to describe the background ion concentration and to identify the major hydrogeochemical processes that control the observed groundwater chemistry. The hydrochemical types, Ca–HCO₃, Ca–SO₄, dominate the largest part of the groundwater followed by water types Ca–Cl and Mg–HCO₃. Total hardness indicated that 30% of groundwater samples fell in the very hard water category. Ninety-seven percent of the water samples showed nitrate ( ${\rm NO}_{3}^{-})$ concentrations above the human affected value (13 mg l^???1 ${\rm NO}_{3}^{-})$ , while 15% exceeded the maximum acceptable level (50 mg l^???1 ${\rm NO}_{3}^{-})$ according to WHO regulations. With respect to sodium adsorption ratio, the groundwater can be used for irrigation on almost all soils with little danger of the developing harmful levels of exchangeable Na^?+?. But with respect to electrical conductivity, the water quality for irrigation was low to medium, providing the necessary drainage to avoid the buildup of toxic salt concentrations. Geochemical modeling using PHREEQC enabled prediction of the saturation state of minerals and indicated the dissolution and precipitation reactions occurring in the groundwater. Groundwaters were undersaturated with respect to amorphous silica. Stability diagram indicated that the dominant cluster of groundwater samples fell into the K-feldspar field.     

Natural and anthropogenic factors affecting the shallow groundwater quality in a typical irrigation area with reclaimed water,North China Plain

In this study, the hydrochemical characteristics of shallow groundwater were analyzed to get insight into the factors affecting groundwater quality in a typical agricultural dominated area of the North China Plain. Forty-four shallow groundwater samples were collected for chemical analysis. The water type changes from Ca·Na-HCO₃ type in grass land to Ca·Na-Cl (+NO₃) type and Na (Ca)-Cl (+NO₃+SO₄) type in construction and facility agricultural land, indicating the influence of human activities. The factor analysis and geostatistical analysis revealed that the two major factors contributing to the groundwater hydrochemical compositions were the water-rock interaction and contamination from sewage discharge and agricultural fertilizers. The major ions (F, HCO₃) and trace element (As) in the shallow groundwater represented the natural origin, while the nitrate and sulfate concentrations were related to the application of fertilizer and sewage discharge in the facility agricultural area, which was mainly affected by the human activities. The values of pH, total dissolved solids, electric conductivity, and conventional component (K, Ca, Na, Mg, Cl) in shallow groundwater increased from grass land and cultivated land, to construction land and to facility agriculture which were originated from the combination sources of natural processes (e.g., water-rock interaction) and human activities (e.g., domestic effluents). The study indicated that both natural processes and human activities had influences on the groundwater hydrochemical compositions in shallow groundwater, while anthropogenic processes had more contribution, especially in the reclaimed water irrigation area.     

Assessment of hydrogeochemical characteristics of groundwater in parts of Hindon–Yamuna interfluve region,Baghpat District,Western Uttar Pradesh

The present study has been carried out to assess groundwater quality in parts of Hindon–Yamuna interfluve region of western Uttar Pradesh. Fifty-five groundwater samples were collected from hand pumps in post-monsoon 2005 and pre-monsoon 2006 period, respectively, covering an area of about 1,345 km². Physical and chemical parameters of groundwater such as electrical conductivity, pH, total dissolved solid, Na, K, Ca, Mg, HCO₃, Cl, and SO₄ were determined. Concentration of the chemical constituents in groundwater of the study area varies spatially and temporarily. Interpretation of analytical data of major ion chemistry helps to identify three chemical types of groundwater i.e. ‘mixed’, ‘mixed bicarbonate’ and ‘alkali bicarbonate’ types. The species likely to occur in groundwater of the study area are Ca-HCO₃, Mg-HCO₃, Ca-SO₄, Na-Cl, Na-SO₄, Na-HCO₃, K-Cl, and some other possible species of K, depending on its abundance. The groundwater of the study area comes under the category of moderately hard to very hard, mildly acidic to slightly alkaline in nature. There is anomalously high concentration of major ions, particularly, Na, K, SO₄, and Cl. High SO₄ and K values may be related to anthropogenic influences, rather than through some natural process. Sodium along with Cl may be added to the system through sewage pollution and leachate percolation.     

Identification of the hydrogeochemical processes in groundwater using major ion chemistry: a case study of Penna–Chitravathi river basins in Southern India

Hydrogeochemical studies were carried out in the Penna–Chitravathi river basins to identify and delineate the important geochemical processes which were responsible for the evolution of chemical composition of groundwater. The area is underlain by peninsular gneissic complex of Archaean age, Proterozoic meta-sediments, and strip of river alluvium. Groundwater samples were collected covering all the major hydrogeological environs in pre- and post-monsoon seasons. The samples were analyzed for major constituents such as Ca^2?+?, Mg^2?+?, Na^?+?, K^?+?, CO₃ ^???, HCO₃ ^???, Cl^???, SO₂ ^???4, NO₃ ^???, and F^???. The groundwater in general is of Na^?+?–Cl^???, Na^?+?–HCO₃ ^???, Ca^2?+?–Mg^2?+?–HCO₃ ^???, and Ca^2?+?–Mg^2?+?–Cl^??? types. Na^?+? among cations and Cl^??? and/or HCO₃ ^??? among anions dominate the water; Na^?+? and Ca^2?+? are in the transitional state with Na^?+? replacing Ca^2?+? and HCO₃ ^??? Cl^??? due to physiochemical changes in the aquifer and water–rock interactions. The Ca^2?+?–Mg^2?+?–Cl^??? HCO₃ ^??? type water in one third samples suggest that ion exchange and dissolution processes are responsible for its origin. Change in storage of aquifer in a season does not influence the major geochemical makeup of groundwater. Gibbs plots indicate that the evolution of water chemistry is influenced by water–rock interaction followed by evapotranspiration process. The aquifer material mineralogy together with semiarid climate, poor drainage system, and low precipitation factors played major role in controlling groundwater quality of the area.     

Evaluation of groundwater suitability for domestic,irrigational, and industrial purposes: a case study from Thirumanimuttar river basin,Tamilnadu, India

The Thirumanimuttar sub-basin forms an important groundwater province in south India, facing serious deficiency in both quality and quantity of groundwater due to increased demand associated with rapid population explosion, agricultural growth and industrial activities. A total of 194 groundwater samples were collected and 15 water quality parameters were analyzed using standard procedures. Na⁺, Cl⁻, Ca^2 +, HCO₃^-_{3}^{-}, Mg^2 + and SO₄^2-_{4}^{2-} concentration ions are more dominant in both seasons. The total dissolved solids and electrical conductivity was observed good correlation with Na⁺, Cl⁻, HCO₃^-_{3}^{-}, Ca^2 +, Mg^2 +, Cl⁻, PO₄^3-_{4}^{3-} and NO₃^- _{3}^{- } ions indicating dominance of plagioclase feldspar weathering, anthropogenic input and over drafting of groundwater irrespective of seasons. The Hill–Piper diagram indicates alkaline earths exceed the alkalis, an increase of weak acids was noted during both the seasons. For assessing the groundwater for irrigation suitability parameters like total hardness, sodium adsorption ratio, residual sodium carbonate (RSC), permeability index, and sodium percentage are also calculated. Permanent hardness was noted in higher during both the seasons due to discharge of untreated effluents and ion exchange process. The RSC indicates 56% of the samples are not suitable for irrigation purposes in both seasons, if continuously used will affect the crop yield. From the results, nearly 72% of the samples are not suitable for irrigation.     

Hydrogeochemical characteristics and assessment of drinking water quality in Zeuss�CKoutine aquifer, southeastern Tunisia

Zeuss?CKoutine aquifer, located in southeastern Tunisia, has been used intensively as a primary source to meet the growing needs of the various sectors. Detailed knowledge of the geochemical evolution of groundwater and water quality can enhance understanding of the hydrochemical system, promoting sustainable development and effective management of groundwater resources. To this end, a hydrochemical and statistical investigation was conducted. Groundwater samples have been collected from 13 wells from 1995 to 2005; to understand the sources of dissolved ions and assess the chemical quality of the groundwater. Results demonstrate that among the cations, only the mean concentrations of Na^?+? exceed guideline values set by the World Health Organization (WHO). Regarding the analyzed anions, the concentration of SO $_{4}^{2-}$ and Cl^??? are above the WHO allowable concentrations. Total dissolved solids in most groundwater samples are greater than 1,000 mg l^???1, the limit set by the WHO, indicating slightly saline or moderately saline water. In general, a significant increase in the degree of water mineralization was observed in the direction of southwest to northeast following the regional flow direction. Calculated saturation indices show that all water samples were oversaturated with respect to aragonite, calcite, and dolomite, and undersaturated with respect to anhydrite, gypsum, and halite. Based on hydrochemical facies, two types of water predominate in the study area. The first is Ca?CNa?CSO₄?CCl in type and located in the southwest which corresponds to the recharge part of the aquifer. The second type is Na?CCa?CCl?CSO₄ and located in the east, which corresponds to the discharge part.     

Hydrogeochemical characterization of fluoride rich groundwater of Wailpalli watershed, Nalgonda District, Andhra Pradesh, India

The groundwater of Nalgonda district is well known for its very high fluoride content for the past five decades. Many researchers have contributed their scientific knowledge to unravel causes for fluoride enrichment of groundwater. In the present paper, an attempt has been made to relate the high fluoride content in the groundwater to hydrogeochemical characterization of the water in a fracture hard rock terrain—the Wailpally watershed. Groundwater samples collected from all the major geomorphic units in pre- and post-monsoon seasons were analyzed for its major ion constituents such as Ca^2?+?, Mg^2?+?, Na^?+?, K^?+?, CO $_{3}^{-}$ , HCO $_{3}^{-}$ , Cl^???, SO $_{4}^{-2}$ , NO $_{3}^{-}$ , and F^???. The groundwaters in the watershed have the average fluoride content of 2.79 mg/l in pre-monsoon and 2.83 mg/l in post-monsoon. Fluoride concentration in groundwater does not show perceptible change neither with time nor in space. The ionic dominance pattern is in the order of Na^?+? > Ca^2?+??> Mg^2?+??> K^??? among cations and HCO $_{3}^{-}\:\,>$ Cl^????> SO $_{4}^{-2} >$ NO $_{3}^{-} >$ F^??? among anions in pre-monsoon. In post-monsoon, Mg replaces Ca^2?+? and NO $_{3}^{-}$ takes the place of SO $_{4}^{-2}$ . The Modified Piper diagram reflect that the water belong to Ca^?+?2–Mg^?+?2–HCO $_{3}^{-}$ to Na^?+?–HCO $_{3}^{-}$ facies. Negative chloralkali indices in both the seasons prove that ion exchange between Na^?+? and K^?+? in aquatic solution took place with Ca^?+?2 and Mg^?+?2 of host rock. The interpretation of plots for different major ions and molar ratios suggest that weathering of silicate rocks and water–rock interaction is responsible for major ion chemistry of groundwater in Wailpally watershed. Chemical characteristics and evolution of this fluoride-contaminated groundwater is akin to normal waters of other hard rock terrain; hence, it can be concluded that aquifer material play an important role in the contribution of fluoride in to the accompanying water. High fluoride content in groundwater can be attributed to the continuous water–rock interaction during the process of percolation with fluorite-bearing country rocks under arid, low precipitation, and high evapotranspiration conditions.     

Precipitation Chemistry and Occurrence of Acid Rain Over Dhanbad, Coal City of India

The present study investigated the chemical composition of wet atmospheric precipitation over Dhanbad, coal city of India. The precipitation samples were collected on event basis for three years (July 2003 to October 2005) at Central Mining Research Institute. The precipitation samples were analyzed for pH, conductivity, major anions (F, Cl, NO₃, SO₄) and cations (Ca, Mg, Na, K, NH₄). The pH value varied from 4.01 to 6.92 (avg. 5.37) indicating acidic to alkaline nature of rainwater. The pH of the rainwater was found well above the reference pH (5.6), showing alkalinity during the non-monsoon and early phase of monsoon, but during the late phase of monsoon, pH tendency was towards acidity (<5.6~pH) indicating the non-availability of proper neutralizer for acidic ions. The observed acidic events at this site were 91, (n = 162) accounting 56% for the entire monitoring months. The (NO₃ + Cl)/SO₄ ratio in majority of samples was found below 1.0, indicating that the acidity is greatly influenced by SO₄. The calculated ratio of (Ca + NH₄)/(NO₃ + SO₄) ranges between 0.42–5.13 (average 1.14), however in most of the samples, the ratio is greater than unity (>1.0) indicating that Ca and NH₄ play an important role in neutralization of acidic ions in rainwater. Ca and SO₄ dominate the bulk ionic deposition and these two ions along with NH₄ accounts 63% of the annual ionic deposition.     

A pragmatic approach to study the groundwater quality suitability for domestic and agricultural usage,Saq aquifer,northwest of Saudi Arabia

The present study deals with detailed hydrochemical assessment of groundwater within the Saq aquifer. The Saq aquifer which extends through the NW part of Saudi Arabia is one of the major sources of groundwater supply. Groundwater samples were collected from about 295 groundwater wells and analyzed for various physico-chemical parameters such as electrical conductivity (EC), pH, temperature, total dissolved solids (TDS), Na⁺, K⁺, Ca²⁺, Mg²⁺, CO₃ ^?, HCO₃ ^?, Cl^?, SO₄ ^2?, and NO₃ ^?. Groundwater in the area is slightly alkaline and hard in nature. Electrical conductivity (EC) varies between 284 and 9,902?μS/cm with an average value of 1,599.4 μS/cm. The groundwater is highly mineralized with approximately 30 % of the samples having major ion concentrations above the WHO permissible limits. The NO₃ ^? concentration varies between 0.4 and 318.2 mg/l. The depth distribution of NO₃ ^? concentration shows higher concentration at shallow depths with a gradual decrease at deeper depths. As far as drinking water quality criteria are concerned, study shows that about 33 % of samples are unfit for use. A detailed assessment of groundwater quality in relation to agriculture use reveals that 21 % samples are unsuitable for irrigation. Using Piper’s classification, groundwater was classified into five different groups. Majority of the samples show Mix-Cl-SO₄- and Na-Cl-types water. The abundances of Ca²⁺ and Mg²⁺ over alkalis infer mixed type of groundwater facies and reverse exchange reactions. The groundwater has acquired unique chemical characteristics through prolonged rock-water interactions, percolation of irrigation return water, and reactions at vadose zone.     

Assessment of groundwater quality and <Superscript>222</Superscript>Rn distribution in the Xuzhou region,China

Evaluation of groundwater quality represents significant input for the development and utilization of water resources. Increasing exploitation of groundwater and man-made pollution has seriously affected the groundwater quality of the North China Plain, such as in the Xuzhou region which is the target of this investigation. The assessment of the groundwater quality and sources in the region was based on analyses of water chemistry and ²²²Rn activity in samples collected from wells penetrating unconfined and confined aquifers. The results indicate that most of the untreated groundwater in the region is not suitable for the long-term drinking based on permissible limits of the Chinese Environmental Agency and the World Health Organization. However, the groundwater can be used as healthy source of drinking water when they can pass the biological test and softening water treatment. Most of the groundwater is suitable for irrigation. Excessive amounts of SO₄^2? and NO₃^? are attributed to mainly influence of wastewater, irrigation, and dissolution of sulfate minerals in local coal strata. The major source of the groundwater is meteoric recharge with addition from irrigation and wastewater discharges. Variability of the water quality seems to be also reflecting the type of aquifers where the highest concentration of HCO₃^? occurs in water of the carbonate fractured aquifer, while the highest Cl^? concentration in the unconfined aquifer. Source of ²²²Rn activity is mainly related to the rock-water interaction with possible addition from the agricultural fertilizers. Protection of groundwater is vital to maintain sustainable drinking quality through reducing infiltration of irrigation water and wastewater.     

Assessment of geospatial and hydrochemical interactions of groundwater quality,southwestern Nigeria

Groundwater pollution resulting from anthropogenic activities and poor effluent management is on the rise in Nigeria. Hence, groundwater used for domestic purposes is questionable and therefore calls for scientific scrutiny. Investigation of hydrochemical interactions and quality of groundwater resource is essential in order to monitor and identify sources of water pollutants. As a result, groundwater samples were collected from 21 locations in Abeokuta South, Nigeria and analyzed for physicochemical parameters using standard methods. Results obtained were subjected to hydrochemical and geospatial analyses. Water quality parameters investigated exhibited wide variations from location to location. Fe²⁺, Mg²⁺, SO₄^2?, Cl^?, total hardness (TH), Mn, Na⁺, NO₃^?, SiO₂, and alkalinity exhibited the highest levels of variation with coefficients of variation of 131.3, 92.8, 83.9, 76.7, 65.9, 64.3, 57.6, 57.2, 57.0, and 52.5, respectively. The average pH value was 6.76 with 71% of the water samples being slightly acidic. Na²⁺, Mg²⁺, Fe²⁺, and EC contents exhibited the most violation of drinking water standards with percent violations of 100, 52.4, 47.6, and 47.6%, respectively. Parameters, such as Mn, Ca²⁺, NO₃^?, and CO₃^2?, were within the WHO guideline values for drinking water in all the samples. The highest level of significant correlation was found to exist between Na⁺ and Cl^? (r?=?0.84, α?=?0.01). Six principal components, which explained 83.5% of the variation in water quality, were extracted with the first (34.1%) and second components (15.7%) representing the influence of mineral dissolution and anthropogenic practices, respectively, on the hydrochemistry of the area. Four hydrochemical clusters were identified with distinctly partitioned water quality. Further analysis revealed that 38, 29, 24, and 9% of the samples were the Na-K-HCO₃, Na-K-Cl-SO₄, Ca-Mg-HCO₃, and Ca-Mg-Cl-SO₄ types, respectively. Anthropogenic activities are increasing threat to groundwater quality in the study location and therefore call for urgent attention. There is also a need for routine monitoring of groundwater in Abeokuta.