Spatial variability of groundwater quality and its suitability for drinking and irrigation in the Amik Plain (South Turkey)

In this study, it is determined physicochemical properties of the groundwater and the spatial variability of physicochemical properties of the groundwater in the Amik plain and as well as assess its suitability for drinking and irrigation. A total 92 groundwater samples were collected from drilled well in June 2012. In addition, the 42 of 92 drilled wells were also sampled in September 2012 to evaluate the changes of groundwater properties. According to t test values, the mean Ca²⁺, SO₄ ^2?, Mg²⁺ and TH values in the June period were significantly lower than those of the September period. On the other hand, the mean (CO ₃ ^2?  + HCO₃ ^?) and RSC and MR values in the June period were significantly higher than those of the September period. The order of relative abundance of major cations in the groundwater (in mg L^?1) is in order Na⁺ > Mg²⁺ > Ca²⁺ > K⁺. The order of the anions abundance (mg L^?1) is SO₄ ^2? > Cl^? > HCO₃ ^? > CO₃ ^2? in this research. Log and square-root transformation were carried out for the most of the water properties before the calculation of semivariance. The nugget ratio showed all the variables were strongly spatial dependent except for K⁺ and Mg²⁺ and (CO₃ ^2? + HCO₃ ^?) which showed moderate spatial dependence (ratio ranging from 28 to 49.9 %). Spatial distribution analysis of groundwater quality indicated that The EC, TDS values and Na and Cl^? contents which is important water quality parameters increase from northern towards southern. The total hardness values increase also from northwestern towards southwestern.     

Geochemistry and quality of groundwater of Gummanampadu sub-basin, Guntur District, Andhra Pradesh, India

Groundwater survey has been carried out in the area of Gummanampadu sub-basin located in Guntur District, Andhra Pradesh, India for assessing the factors that are responsible for changing of groundwater chemistry and consequent deterioration of groundwater quality, where the groundwater is a prime source for drinking and irrigation due to non-availability of surface water in time. The area is underlain by the Archaean Gneissic Complex, over which the Proterozoic Cumbhum rocks occur. The results of the plotting of Ca²⁺ + Mg²⁺ versus HCO₃ ^? + CO₃ ^2?, Ca²⁺ + Mg²⁺ versus total cations, Na⁺ + K⁺ versus total cations, Cl^? + SO₄ ^2? versus Na⁺ + K⁺, Na⁺ versus Cl^?, Na⁺ versus HCO₃ ^? + CO₃ ^2?, Na⁺ versus Ca²⁺ and Na⁺: Cl^? versus EC indicate that the rock–water interaction under alkaline condition is the main mechanism in activating mineral dissociation and dissolution, causing the release of Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃ ^?, CO₃ ^2?, SO₄ ^2? and F^? ions into the groundwater. The ionic relations also suggest that the higher concentrations of Na⁺ and Cl^? ions are the results of ion exchange and evaporation. The influences of anthropogenic sources are the other cause for increasing of Mg²⁺, Na⁺, Cl^?, SO₄ ^2? and NO₃ ^? ions. Further, the excess alkaline condition in water accelerates more effective dissolution of F^?-bearing minerals. Moreover, the chemical data plotted in the Piper’s, Gibbs’s and Langelier–Ludwig’s diagrams, computed for the chloro-alkaline and saturation indices, and analyzed in the principal component analysis, support the above hypothesis. The groundwater quality is, thus, characterized by Na⁺ > Ca²⁺ > Mg²⁺ > K⁺: HCO₃ ^? + CO₃ ^2? > Cl^? > SO₄ ^2? > NO₃ ^? > F^? facies. On the other hand, majority of groundwater samples are not suitable for drinking with reference to the concentrations of TDS, TH, Mg²⁺ and F^?, while those are not good for irrigation with respect to USSL’s and Wilcox’s diagrams, residual sodium carbonate, and magnesium hazard, but they are safe for irrigation with respect to permeability index. Thus, the study recommends suitable management measures to improve health conditions as well as to increase agricultural output.     

Hydrogeochemical investigation and groundwater quality assessment of Pratapgarh district,Uttar Pradesh

Hydogrochemical investigation of groundwater resources of Paragraph district has been carried out to assess the solute acquisition processes and water quality for domestic and irrigation uses. Fifty-five groundwater samples were collected and analyzed for pH, electrical conductivity, total dissolved solids, hardness, major anions (F^?, Cl^?, NO₃, HCO₃ ^?, SO₄ ^2?) and cations (Ca²⁺, Mg²⁺, Na⁺, K⁺). Study results reveal that groundwater of the area is alkaline in nature and HCO₃ ^?, Cl^?, Mg²⁺, Na⁺ and Ca²⁺ are the major contributing ions to the dissolved solids. The hydrogeochemical data suggest that weathering of rock forming minerals along with secondary contributions from agricultural and anthropogenic sources are mainly controlling the groundwater composition of Pratapgarh district. Alkaline earth metals (Ca²⁺+Mg²⁺) exceed alkalis (Na⁺+K⁺) and weak acid (HCO₃ ^?) dominate over strong acids (Cl^?+SO₄ ^2?) in majority of the groundwater samples. Ca-Mg-HCO₃ and Ca-Mg-Cl-HCO₃ are the dominant hydrogeochemical facies in the groundwater of the area. The computed saturation indices demonstrate oversaturated condition with respect to dolomite and calcite and undersaturated with gypsum and fluorite. A comparison of groundwater quality parameters in relation to specified limits for drinking water shows that concentrations of TDS, F^?, NO₃ ^? and total hardness exceed the desirable limits in many water samples. Quality assessment for irrigation uses reveal that the groundwater is good for irrigation. However, values of salinity, sodium adsorption ratio (SAR), residual sodium carbonate (RSC), %Na and Kelley index are exceeding the prescribed limit at some sites, demanding adequate drainage and water management plan for the area.     

Hydrogeochemical characterization and quality assessment of groundwater around Umrer coal mine area Nagpur District,Maharashtra, India

Quality assessment as well as hydrogeochemical characterization of 45 representative groundwater samples around Umrer coal mine area was undertaken. The pH of the water lies in the normal range i.e. from 7.5 to 8.5, the electrical conductivity varies from 826 to 1,741, the total hardness varies from 289 to 1,302 and the TDS values range from 528.6 to 1,114.2 mg/l which reflects variation in lithology and thus, the distinction in hydrogeological regime. The cation chemistry is dominated by Ca²⁺ and Mg²⁺ while anion chemistry is dominated by Cl^? and HCO₃ ^?. Out of total ten hydrochemical facies, the two dominant facies are Mg–Ca–HCO₃ (37.7 %) and Ca–Mg–SO₄–HCO₃ (17.7 %). The groundwater in the study area, in general, is useful for drinking and domestic use; however, it has marginal utility for irrigation purpose. Standard US Salinity Laboratory classification shows that water of the study area belongs to C2–S1 and C3–S1 classes. The concentration of 9 trace elements analysed from 18 samples did not exceed the desirable limit.     

An appraisal of groundwater quality in Seymour and Blaine aquifers in a major agro-ecological region in Texas,USA

Aquifer-based groundwater quality assessment offers critical insight into the major hydrochemical processes, and aids in making groundwater resources management decisions. The Texas Rolling Plains (TRP), spanning over 22 counties, is a major agro-ecological region in Texas from where highest groundwater nitrate (NO₃ ^?) levels in the state have been reported. In this study, we present a comparative assessment of major hydrochemical facies pertaining to NO₃ ^? contamination and a host of species such as sulfate (SO₄ ^2?), chloride (Cl^?), and total dissolved solids (TDS) in different water use classes in the Seymour and Blaine aquifers, underlying the TRP. Aquifer-stratified groundwater quality information from 1990 to 2010 was obtained from the Texas Water Development Board and aggregated over decadal scale. High groundwater salinization was found in the municipal water use class in the Blaine aquifer with about 100, 87 and 50 % of observations exceeding the secondary maximum contaminant level for TDS, SO₄ ^2?, and Cl^?, respectively in the 2000s (2000–2010). The NO₃-contamination was more alarming in the Seymour aquifer with 82 and 61 % of observations, respectively, exceeding the maximum contaminant level (MCL) in the irrigation and municipal water use classes in the 2000s. Salinization was more influenced by SO₄ ^2? and Cl^? in the Blaine aquifer and by NO₃ ^? in the Seymour aquifer. High NO₃ ^? (>MCL) observations in the Seymour aquifer occurred in the Ca–HCO₃ and Ca–Mg–HCO₃ facies, the domains of fresh water recharge and anthropogenic influences (e.g., agricultural activities, waste disposal). High SO₄ ^2?, Cl^? and TDS observations in the Blaine aquifer dominated the Ca–Cl, Na–Cl, and mixed Ca(Mg)–SO₄(Cl) facies indicating evaporite dissolution, mixing and solute exchange, and lack of fresh recharge.     

Environmental geochemistry and quality assessment of mine water of Jharia coalfield,India

A long mining history and unscientific exploitation of Jharia coalfield caused many environmental problems including water resource depletion and contamination. A geochemical study of mine water in the Jharia coalfield has been undertaken to assess its quality and suitability for domestic, industrial and irrigation uses. For this purpose, 92 mine water samples collected from different mining areas of Jharia coalfield were analysed for pH, electrical conductivity (EC), major cations (Ca²⁺, Mg²⁺, Na⁺, K⁺), anions (F⁻, Cl⁻, HCO₃ ⁻, SO₄ ²⁻, NO₃ ⁻), dissolved silica (H₄SiO₄) and trace metals. The pH of the analysed mine water samples varied from 6.2 to 8.6, indicating mildly acidic to alkaline nature. Concentration of TDS varied from 437 to 1,593 mg L⁻¹ and spatial differences in TDS values reflect the variation in lithology, surface activities and hydrological regime prevailing in the region. SO₄ ²⁻ and HCO₃ ⁻ are dominant in the anion and Mg²⁺ and Ca²⁺ in the cation chemistry of mine water. High concentrations of SO₄ ²⁻ in the mine water of the area are attributed to the oxidative weathering of pyrites. Ca–Mg–SO₄ and Ca–Mg–HCO₃ are the dominant hydrochemical facies. The drinking water quality assessment indicates that number of mine water samples have high TDS, total hardness and SO₄ ²⁻ concentrations and needs treatment before its utilization. Concentrations of some trace metals (Fe, Mn, Ni, Pb) were also found to be above the desirable levels recommended for drinking water. The mine water is good to permissible quality and suitable for irrigation in most cases. However, higher salinity, residual sodium carbonate and Mg-ratio restrict its suitability for irrigation at some sites.     

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.     

Hydrogeochemical assessment of surface and groundwater resources of Korba coalfield,Central India: environmental implications

The present study assesses the impact of coal mining on surface and groundwater resources of Korba Coalfield, Central India. Accordingly, water samples collected from various sources are analyzed for major ions, trace elements, and other mine effluent parameters. Results show that the groundwater samples are slightly acidic, whereas river water and mine water samples are mildly alkaline. Elevated concentrations of Ca²⁺, Na⁺, HCO₃ ^?, and SO₄ ^2? alongside the molar ratios (Ca²⁺+Mg²⁺)/(SO₄ ^2?+HCO₃ ^?) <1 and Na⁺/Cl^? >1 suggest that silicate weathering (water-rock interaction) coupled with ion exchange are dominant solute acquisition processes controlling the chemistry of groundwater in the study area. The overall hydrogeochemistry of the area is dominated by two major hydrogeochemical facies (i.e., Ca–Cl–SO₄ and Ca–HCO₃). Analysis of groundwater and river water quality index (GRWQI) elucidates that majority (82%) of samples are of “excellent” to “good” category, and the remaining 12% are of “poor” quality. Similarly, the effluent water quality index (EWQI) indicates that 6 out of 8 samples belong to excellent quality. Concentration of trace element constituents such as As, Zn, Cu, Cr, and Cd is found to be well within the stipulated limits for potable use, except for Fe, Mn, and Pb. Suitability of water samples for irrigation purpose, established using standard tools like Wilcox and USSL diagrams, reveal “excellent to permissible” category for majority of the samples. The present study also substantiates the effectiveness of the measures implemented for the treatment of mine effluent water.     

Investigation of the quality and physical-geochemical characteristics of the drinking water in Gümüşhane (Turkey) city central

The physical (turbidity, color, smell, taste, pH, and conductivity) and geochemical properties (Ca, Mg, Na, Fe, Mn, Al, K, Cl^?, HCO₃ ^?, SO₄ ^2?, Fe, Cu, Co, Ni, Zn, Cd, Pb, and Cr) of the drinking water in Gümü?hane city center were determined. This city center constitutes the study area. The pH levels of the water samples ranged from 6.3 to 8.2, and their conductivities ranged between 240 and 900 μS. These findings were concordant with the drinking water standards of the Turkey Standard Institute and the World Health Organization. The hardness of the water samples in the study area was between 18.1 and 115.1 °Fr. These samples were classified as extremely hard, hard, and quite hard. In addition, an assessment using the criteria for Inland Surface Water Classification indicated that considering certain parameters (pH levels, amount of Na, SO₄ ^2?, Fe, Mn, Al, Co, Ni, Cu, and Cr), the samples belonged to class I (high quality) water. When Cl^? amount and conductivity were considered, the samples belonged to the first and second classes (less polluted) of water. The water in the study area was generally classified as carbonated and sulfated (Ca + Mg > Na + K) water classes. This water contained more weak acids than strong acids (HCO₃ ^? + CO₃ ^2? > Cl^? + SO₄ ^2?). The pH levels (6.3–8.2) of the water in the study area were unrelated to the varying concentrations of metals in the water. Elements such as Fe, Ni, Cd, Pb, Zn, and Cu increase in the water through the water–rock interaction in the area in which water rises or through the mixture of water with either mine or industrial wastes. In addition, several water samples belonged to an acceptable water class for drinking and usage.     

Variation of groundwater hydrochemical characteristics in the plain area of the Tarim Basin,Xinjiang Region,China

Groundwater hydrochemistry could reveal the interaction mechanism between groundwater and the environment, which provides a scientific basis for environmental resources management. In this study, Shukaliefu’s classification method and Piper diagram were adopted to determine the hydrochemical types of groundwater in the Tarim Basin of Xinjiang, China. The method of “one^-vote veto” was applied to evaluate the quality of groundwater. Phreeqc software was used to calculate the saturation indices of calcite and fluorite in groundwater. By comparing groundwater quality data of 2003 and 2011, we characterized the variations in hydrochemical types and water quality types, salinization of groundwater and fluoride geochemistry of the plain area of the Tarim Basin. Results show that the primary anion in phreatic water in the plain area of the Tarim Basin changed from HCO₃ ^? to SO₄ ^2? or Cl^?. On the contrary, the primary anion in confined water changed from SO₄ ^2? or Cl^? to HCO₃ ^?. In 2003, 63.1 % of the sampling points in the study area exceeded the Class III water quality standard of China. In 2011, the proportion increased to 82.5 %. In addition, severe groundwater salinization was found at 19.7 % of the sampling points. Some of the deep groundwater samples were salinized as well. In the Aksu area at the north-west part of the Tarim Basin, F^? concentration exceeding the standard limit (1 mg/L) was found to be 55.0 % of the groundwater samples tested. Based on these findings, it is concluded that the phreatic water in the study area was severely influenced by the industrial wastewater and domestic sewage related to human activities, while the confined water was less affected. The general quality of groundwater was in an aggravation trend, and the groundwater salinization was in a severe condition in this area. The Ca²⁺–Na⁺ ionic exchange, the unsaturated fluorite and oversaturated calcite in the aquifer of the Aksu area are proposed to cause F^? enrichment in groundwater of this area.     

Hydrogeochemical processes and quality assessment of groundwater in Dumka and Jamtara districts, Jharkhand, India

The hydrogeochemical study of groundwater in Dumka and Jamtara districts has been carried out to assess the major ion chemistry, hydrogeochemical processes and groundwater quality for domestic and irrigation uses. Thirty groundwater samples were collected and analyzed for pH, electrical conductivity, total dissolved solids (TDS), total hardness, anions (F^?, Cl^?, NO₃ ^?, HCO₃ ^?, SO₄ ^2?) and cations (Ca²⁺, Mg²⁺, Na⁺, K⁺). The analytical results show the faintly alkaline nature of water and dominance of Mg²⁺ and Ca²⁺ in cationic and HCO₃ ^? and Cl^? in anionic abundance. The concentrations of alkaline earth metals (Ca²⁺?+?Mg²⁺) exceed the alkali metals (Na⁺?+?K⁺) and HCO₃ ^? dominates over SO₄ ^2??+?Cl^? concentrations in the majority of the groundwater samples. Ca?CMg?CHCO₃ is the dominant hydrogeochemical facies in 60?% of the groundwater samples, while 33?% samples occur as a mixed chemical character of Ca?CMg?CCl hydrogeochemical facies. The water chemistry is largely controlled by rock weathering and ion exchange processes with secondary contribution from anthropogenic sources. The inter-elemental correlations and factor and cluster analysis of hydro-geochemical database suggest combined influence of carbonate and silicate weathering on solute acquisition processes. For quality assessment, analyzed parameter values were compared with Indian and WHO water quality standards. In majority of the samples, the analyzed parameters are well within the desirable limits and water is potable for drinking purposes. Total hardness and concentrations of TDS, Cl^?, NO₃ ^? _, Ca²⁺ and Mg²⁺ exceed the desirable limits at a few sites, however, except NO₃ ^? all these values were below the highest permissible limits. The calculated parameters such as sodium adsorption ratio, percent sodium (%Na) and residual sodium carbonate revealed excellent to good quality of groundwater for agricultural purposes, except at few sites where salinity and magnesium hazard (MH) values exceeds the prescribed limits and demands special management.     

Major ion chemistry,weathering processes and water quality assessment in upper catchment of Damodar River basin,India

The chemical characteristics of surface, groundwater and mine water of the upper catchment of the Damodar River basin were studied to evaluate the major ion chemistry, geochemical processes controlling water composition and suitability of water for domestic, industrial and irrigation uses. Water samples from ponds, lakes, rivers, reservoirs and groundwater were collected and analysed for pH, EC, TDS, F, Cl, HCO₃, SO₄, NO_3, Ca, Mg, Na and K. In general, Ca, Na, Mg, HCO₃ and Cl dominate, except in samples from mining areas which have higher concentration of SO₄. Water chemistry of the area reflects continental weathering, aided by mining and other anthropogenic impacts. Limiting groundwater use for domestic purposes are contents of TDS, F, Cl, SO₄, NO₃ and TH that exceed the desirable limits in water collected from mining and urban areas. The calculated values of SAR, RSC and %Na indicate good to permissible use of water for irrigation. High salinity, %Na, Mg-hazard and RSC values at some sites limit use for agricultural purposes.     

Characteristics of the geothermal water in Changbai Mountain volcanic region,northeast of China

Geothermal water is plentiful in Changbai Mountain region, northeastern China, due to the volcanic activities and widespread faults. For the exploration of geothermal resources, this study uses quartz and cation geothermometer to estimate the temperatures of the geothermal reservoir and uses the tubular models to evaluate the thermal gradient. The hydrogeochemical characteristics of the geothermal resources were also evaluated by hydrogeochemical analysis. The results showed that the geothermal reservoir temperatures of the four major thermal springs in Changbai Mountain region range from 72 to 169 °C. The average geothermal reservoir temperatures of Jinjiang hot springs, Changbai hot springs I, Xianrenqiao hot springs, and Changbai hot springs II are 129.25, 169, 89, and 73.67 °C, respectively. The geothermal gradient values of the four major thermal springs have different characteristics. The geothermal gradient values of Jinjiang hot springs and Changbai hot springs I are 4.6 and 3.1 °C/100 m, respectively. The geothermal gradient values of Xianrenqiao thermal springs and Changbai thermal springs II are both lower than 1.5 °C/100 m, with the values of 1.1 and 1.4 °C/100 m. And the geothermal gradients are influenced by Changbai Mountain Tianchi volcano. In addition, the water chemical analyses showed that the geothermal water types are HCO₃-Na with higher concentrations of Na⁺, Cl^?, SO₄ ^2?, TDS, and HCO₃ ^? than the non-thermal waters, which suggested a deep and long water cycle of the thermal water, and therefore a sufficient water-rock interaction.     

Dissolution sequestration mechanism of CO<Subscript>2</Subscript> at the Shiqianfeng saline aquifer in the Ordos Basin,northwestern China

This study focused on the target injection layers of deep saline aquifers in the Shiqianfeng Fm. in the Carbon Capture and Sequestration (CCS) Demonstration Projects in the Ordos Basin, northwestern China. The study employed a combination method of experiments and numerical simulation to investigate the dissolution mechanism and impact factors of CO₂ in these saline aquifers. The results showed (1) CO₂ solubility in different types of water chemistry were shown in ascending order: MgCl₂-type water < CaCl₂-type water < Na₂SO₄-type water < NaCl-type water < Na₂CO₃-type water < distilled water. These results were consistent with the calculated results undertaken by TOUGHREACT with about 5% margin of error. CO₂ solubility of Shiqianfeng Fm. saline was 1.05 mol/L; (2) compared with distilled water, the more complex the water’s chemical composition, the greater the increase in HCO₃ ^?concentration. While the water’s composition was relatively simple, the tested water’s HCO₃ ^?concentrations were in close accord with the calculated value undertaken by the TOUGHREACT code, and the more complex the water’s composition, the poorer the agreement was, probably due to the complex and unstable HCO₃ ^? complicating matters when in an aqueous solution system including both tested HCO₃ ^?concentration and calculated HCO₃ ^?concentration; (3) the CO₂ solubility in the saline at the temperature conditions of 55 °C and 70 °C were 1.17 and 1.02 mol/L. When compared with the calculated value of 1.20 and 1.05 mol/L, they were almost the same with only 1 and 3% margin of error; concentrations of HCO₃ ^? were 402.73 mg/L (0.007 mol/L) and 385.65 mg/L (0.006 mol/L), while the simulation results were 132.16 mg/L (0.002 mol/L) and 128.52 mg/L (0.002 mol/L). From the contrast between the tested data and the calculated data undertaken by the TOUGHREACT code, it was shown that TOUGHRACT code could better simulate the interaction between saline and CO₂ in the dissolution sequestration capacity. Therefore, TOUGHREACT code could be used for the inter-process prediction of CO₂ long-term geological storage of CO₂; (4) The Ca²⁺ concentration and SO₄ ^2?concentration in saline water had less effect on the solubility of CO₂ and HCO₃ ^?concentration. In addition, TDS and pH values of saline affected not only the solubility of CO₂, but also the conversion of CO₂ to HCO₃ ^? due to that they can affect the activity and acid-base balance. So in fact, we just need to consider that the TDS and pH values are main impact factors in the dissolution sequestration capacity of CO₂ geological sequestration in deep saline aquifers.     

Hydrogeochemical assessment of groundwater quality along the coastal aquifers of southern Tamil Nadu,India

Hydrogeochemical investigation of groundwater has been carried out in the coastal aquifers of southern Tamil Nadu, India. Seventy-nine dug well samples were collected and analyzed for various physicochemical parameters. The result of the geochemical analysis indicates the groundwater in the study area is slightly alkaline with moderate saline water. The cation and anion concentrations confirm most of the groundwater samples belong to the order of Na⁺ > Mg²⁺ > Ca²⁺ > K⁺ and Cl^? > SO₄ ^2? > HCO₃ ^?. Thereby three major hydrochemical facies (Ca–Cl, mixed Ca–Mg–Cl and Na–Cl) were identified. Based on the US Salinity diagram, majority of the samples fall under medium to very high salinity with low to high sodium hazard. The cross plot of Ca²⁺ + Mg²⁺ versus chloride shows 61 % of the samples fall under saline water category. Higher EC, TDS and Cl concentrations were observed from Tiruchendur to Koodankulam coastal zone. It indicates that these regions are significantly affected by saltwater contamination due to seawater intrusion, saltpan deposits, and beach placer mining activities.     

Hydrochemical characteristics and quality assessment of regolith aquifers in Enugu metropolis, southeastern Nigeria

Twenty groundwater samples were collected from Enugu metropolis over two seasonal periods in order to characterize the groundwater and to determine its quality for domestic and irrigation purposes. The results show that groundwater of the area is strongly acidic to slightly alkaline in nature and varied from “soft water” to “moderately hard” water type. The major ionic trend is in the order Cl^? > Na⁺ > HCO₃ ^? > K⁺ > Mg²⁺ > Ca²⁺ > SO₄ ^2?and Mg²⁺ > Cl^? > Na⁺ > K⁺ > Ca²⁺ > HCO ₃ ^?  > SO₄ ^2? in abundance for dry and rainy seasons, respectively. The results also reveal that there is an increase in trend of the ionic concentrations during the dry season, which arises from weathering of the host rocks and anthropogenic activities. Two hydrochemical facies were identified, namely, Na⁺ –K⁺ –Cl^? –SO₄ ^2?and Ca²⁺ –Mg²⁺ –Cl^? –SO₄ ^2? _, with Na⁺ –K⁺ –Cl^? –SO₄ ^2? as the dominant facies for the two seasons. Groundwater quality ranges from “very poor water” to “good water” and “water unsuitable for drinking purposes” to “good water” for the dry season and rainy season investigations, respectively. The groundwater is suitable for irrigation purposes for the two seasons.     

Ion chemistry of groundwater and the possible controls within Lhasa River Basin,SW Tibetan Plateau

In order to study the major ion chemistry and controls of groundwater, 65 groundwater samples were collected and their major ions measured from wells within Lhasa River Basin. Groundwater has the characteristics of slightly alkaline and moderate total dissolved solid (TDS). TDS concentration ranged from 122.0 to 489.9 mg/L with a median value of 271.2 mg/L. Almost all the groundwater samples suited for drinking and irrigation. The major cations of groundwater are Ca²⁺ and Mg²⁺, accounting for 59.6 and 31.3% of the cations, respectively. Meanwhile, HCO₃^? and SO₄^2? constituted about 56.7 and 36.9% of the anions, respectively, in Lhasa River Basin. The hydrochemical type of groundwater is HCO₃-SO₄-Ca-Mg. The chemical composition of groundwater samples located in the middle of Gibbs model, which indicates that the major chemical process of groundwater is controlled by rock weathering. Carbonate weathering was the dominant hydro-geochemical process controlling the concentration of major ions in groundwater within Lhasa River Basin, but silicate weathering also plays an important role.     

Hydrogeochemical characterization and groundwater quality assessment in Al-Hasa,Saudi Arabia

Fifty groundwater samples were collected from Al-Hasa to analyze the pH, electrical conductivity (EC, dS m^?1), total dissolved solids (TDS), major anions (HCO₃^?, CO₃^2?, Cl^?, SO₄^2?, and NO₃^?), major cations (Ca²⁺, Mg²⁺, Na⁺, and K⁺), and total hardness. The analyzed data plotted in the Piper, Gibbs, and Durov diagrams, and water quality index (WQI) were calculated to evaluate the groundwater geochemistry and its water quality. The results reveal that most of the investigated samples are Ca²⁺, Mg²⁺, SO₄^2?, Cl^? and Na⁺, and HCO₃^? water types using the Piper diagram. Na⁺?>?Ca²⁺?>?Mg²⁺ are the dominant cations, while Cl^??>?HCO₃^??>?SO₄^2??>?CO₃^2? are the dominant anions. Sodium adsorption ratio (SAR) values varied from 0.79 to 10; however, the Kelly ratio (KR) ranged between 0.1 and 2.2. The permeability index (PI) showed that well water is suitable for irrigation purposes with 75% or more of maximum permeability. The US salinity diagram revealed that the water quality classes of studied waters were CIII-SI, CIII-SII, and CIV-SII, representing height hazards of salinity and medium- to low-sodium hazard. The water quality index (WQI) results indicated that total dissolved solids are out of the drinking water standard limits in Saudi Arabia. The WQI revealed that 38% of the studied wells were considered as poor water (class III), 52% are found as very poor water class (IV), and 10% are unsuitable water for drinking class (V).     

Hydrochemical and isotopic study of groundwater in the Yinchuan plain, China

The Yinchuan plain is located in the arid climate zone of NW China. The western margin of the plain is the Helan mountain connecting a series of normal slip faults. The eastern margin of the plain connects with the Yellow River and adjacents with the Ordos platform. The south of the plain is bordered by the EN fault of the Niushou mountain. The bottom of the plain is the Carboniferous, Permian, or Ordovician rocks. Based on the analysis of groundwater hydrochemical and isotopic indicators, this study aims to identify the groundwater recharge and discharge in the Yinchuan plain, China. The hydrochemical types of the groundwater are HCO₃–SO₄ in the west, HCO₃–Cl in the middle, and Cl–SO₄ in the east. The hydrochemical types are HCO₃–SO₄ in the south, HCO₃–Cl and SO₄–HCO₃ in the middle. The hydrochemical types are complex in the north, mainly SO₄–HCO₃ and Cl–SO₄. Deuterium, ¹⁸O, and tritium values of groundwater indicate that groundwater recharge sources include precipitation, bedrock fissure water, and irrigation return water. Groundwater discharges include evaporation, abstraction, and discharge to surface water. According to the EW isotopic profile, the groundwater flow system (GFS) in the Yinchuan plain can be divided into local flow systems (LFS) and regional flow systems (RFS). Groundwater has lower TDS and higher tritium in the southern Yellow River alluvial plain and groundwater age ranges from 6 to 25 years. The range of groundwater renewal rates is from 11 to 15 % a^?1. The depth of the water cycle is small, and groundwater circulates fast and has high renewal rates. Groundwater has higher TDS and lower tritium in the northern Yellow River alluvial plain. The range of groundwater age is from 45 to 57 years, and renewal rate is from 6 to 0.1 % a^?1. The depth of the water cycle is larger. Groundwater circulates slowly and has low renewal rates.     

Chemical characteristics of coastal rainwater from Puducherry to Neithavasal,Southeastern coast of India

The chemistry of the rainwater indirectly reflects the composition of the ions in the atmosphere. The study of the rainwater gains its own importance as it forms the basis for the agricultural, domestic and drinking water. Twelve rainwater samples were collected along the southeastern coast of India during southwest monsoon. The samples were analyzed for the major anions (Cl^?, SO₄ ^2?, PO₄ ^3? and HCO₃ ^?) and cations (Na⁺, K⁺, Ca²⁺ and Mg²⁺). The majority of the samples reflect acidic pH. The general dominance of the cations is in the order of Na⁺ > Ca²⁺ > K⁺ > Mg²⁺ and that of anions is HCO₃ ^? > Cl^? > SO₄ ^2? > PO₄ ^3?. The water is classified as calcium bicarbonate to sodium bicarbonate type. The decrease of pH value also increases the pCO₂. In order to study the impact of acidic and alkaline species on rainwater, correlation coefficients were determined for establishing the relationship between different ions. Good correlation was established between cations, and sulfate has no correlation with other ions and pH. Factor analysis reveals that land use pattern, marine source and methanogenesis from the tidal influenced mangroves play a major role in determining the rainwater chemistry of the region.