Dissolution Of Sulfate Minerals Research Articles

Evaluation of groundwater quality with multi-source pollution based on source identification and health risks

Groundwater is a crucial water supply source in Chengdu City, western China, a region experiencing significant water scarcity. The sources of inorganic pollutants in groundwater and their potential health risks are of great concern. In this study, based on 156 groundwater samples collected in 2021 in the study area were analyzed for hydrochemical characterization and controlling factors. The Positive Matrix Factorization (PMF) model was used for contaminant source analysis, and Monte Carlo Simulation (MCS) combined with the Health Risk Evaluation Model (HREM) was used to quantify the health risks. The results indicate that the groundwater in the study area is predominantly of the Ca·Na-SO4·HCO3, Ca·Na-HCO3·SO4 and Ca-HCO3·SO4 types, mainly influenced by the combination of evaporation-concentration-crystallization and rock leaching-weathering. K+, Na+, and Cl− mainly originate from the weathering and dissolution of potassium feldspar and rock salt, while Ca2+, Mg2+, HCO3−, and SO42− primarily come from the weathering and dissolution of sulfate minerals. The main sources of groundwater pollution and their contributions are as follows: domestic pollution (25.6 %), dissolution-filtration-evaporation-concentration action (22.8 %), hydrogeochemical evolution (15.8 %), water-rock interactions (12.8 %), primary geologic context (12.1 %), and agricultural non-point source pollution (11.0 %). Cl− and As are the primary contributors to non-carcinogenic and carcinogenic risks, respectively. Non-carcinogenic risks are below USEPA standards, while the average carcinogenic risk for arsenic exceeded the maximum acceptable risk level thresholds by 23 and 109 times for adults and children, respectively. Non-carcinogenic and carcinogenic health risks were mainly influenced by pollutant concentrations. The primary geological background and domestic pollution contributed the most to the non-carcinogenic risk for adults (50.3 %) and children (77.1 %), and 38.2 % and 10.3 %, respectively. This study highlights the necessity of establishing a comprehensive groundwater pollution monitoring system, enhancing industrial waste management practices, and raising public awareness to mitigate contamination and ensure the sustainable use of groundwater resources in Chengdu City.

Hydrochemical Characterization and Quality Assessment of Groundwater in the Southern Plain of Hebei Province, China

The purpose of this research was to understand the hydrogeochemical characteristics and assess the quality of phreatic and confined groundwater in southern Hebei Province. A total of 107 groundwater samples were collected, representing different aquifer conditions over the study area. Multivariate statistical analysis, hydrochemical maps, ionic ratio coefficients, geographic information system (GIS) and geochemical simulation were comprehensively and systematically used to reveal the hydrochemical characteristics of groundwater and its controlling mechanism. The results revealed that both phreatic (pH = 7.02–9.08) and confined groundwater (pH = 7.00–10.60) were slightly alkaline. The hydrochemical types were mainly present as the HCO3-Ca-Mg type in the western premontane area and mixed Ca-Mg-SO4-Cl and Na-Cl-SO4 types in the eastern plains. The hydrochemical composition was dominated by water–rock interactions of natural processes, including silicate weathering, dissolution of sulfate minerals (gypsum, anhydrite), and cation-exchange adsorption. Anthropogenic activities were the main factor causing NO3− content in some groundwater samples to exceed the geochemical baseline. The hydrogeochemistry of groundwater in different aquifers was significantly varied. The average contents of TH, TDS, Na+, Ca2+, Mg2+, Cl− and SO42− in phreatic aquifers were significantly higher than those in confined aquifers. The Entropy Weighted Water Quality Index (EWQI) results revealed that 17.78% of phreatic and 50% of confined water samples were meeting the purpose of drinking water. The groundwater samples with EWQI values exceeding 100 were mainly situated in the Handan urban area and the eastern region of Xingtai City, which should be avoided for direct utilization and needs to be improved through protection and management measures, to enhance the quality of groundwater. Correlation analysis showed that groundwater quality was significantly dominated by TH, TDS, Na+, Mg2+, Cl− and SO42− concentrations.

Hydrogeochemical and biological assessment of spring and stream water quality for its suitability for drinking in Kanglung locality, Trashigang, Bhutan

Abstract Springs are important water sources for domestic and agricultural uses in eastern Himalayas. This study describes the water quality scenario and major geochemical processes of the springs utilized for drinking in Kanglung locality, Bhutan. Water samples were collected at two end-user taps and three spring sources from October 2020 through April 2021 for laboratory analyses. Water samples analyzed met the WHO drinking water quality standard except for turbidity and thermotolerant coliform in some samples. The Water Quality Index (WQI) values of the spring water ranged from 5.75 to 41.64, majority falling under excellent class demonstrating potability of springs tapped. The order of anion and cation chemistry were HCO3− >Cl− >SO42−, and Na+ >Ca2+>Mg2+>K+, respectively. The scatter diagrams and molar ratios of major ions indicated silicate and carbonate weathering controlling the spring water chemistry. The piper diagram indicated that springs are predominantly Ca-Mg-Cl and Na-Cl types. Gibbs diagrams inferred that spring/stream chemistry is mainly controlled by rainwater followed by water-rock interaction. Statistical analyses indicated different sources of dissolved ions including carbonate and silicate weathering, atmospheric precipitation, dissolution of sulphate minerals, and oxidation of sulphides.

Hydrogeochemical Characteristics Refine the Conceptual Model of Groundwater Flow in Wood Buffalo National Park, Canada

Wood Buffalo National Park (WBNP), the largest national park of Canada, has unique and complex ecosystems that depend on specific water quantity and quality. We characterize groundwaters and surface waters in WBNP by determining their chemical compositions and water types, the dominant hydrochemical processes affecting their compositions, and their hydrochemical characteristics in relation to interpreted groundwater flow systems. Total Dissolved Solid concentrations in groundwaters and surface waters range from ≤10 mg/L to ≥300,000 mg/L. Four distinct water type groups are found: (1) Ca-SO4-type waters occur in multiple clusters across the area in outcrop areas of Devonian evaporites; (2) Na-Cl-type waters predominantly occur in the Salt plains region along the central eastern boundary, overlapping evaporite and carbonate-dominated bedrock formations; (3) Ca-HCO3-type waters dominate the Peace-Athabasca Delta-region in the south and most of the central region; and (4) “mixed” waters. Solutes in the waters originate from three main processes: dissolution of halite, dissolution of sulphate minerals, and dissolution of carbonates. The spatial occurrence of hydrochemical characteristics correlate with hypothesized groundwater flow systems, i.e., Ca-SO4 and Na-Cl-type waters coincide with discharge areas of intermediate to regional groundwater flow paths, and Ca-HCO3-type waters overlap with recharge areas. The findings of this study contribute to advancing knowledge on the hydrochemical characteristics of this remote and highly protected region of Alberta, Canada, and are important components of any further, comprehensive assessment of the natural water conditions.

Evolution of pyrite oxidation from a 10-year kinetic leach study: Implications for secondary mineralisation in acid mine drainage control

Acid rock drainage (ARD) is generated when mineral sulfides, primarily pyrite (FeS2), are exposed to weathering. Pyrite oxidation and dissolution may also result in the precipitation of secondary sulfate minerals, commonly found in weathered mine wastes, that release ‘stored acidity’ on subsequent dissolution. To better understand the release of this stored acidity, a kinetic leach column experiment using a synthetic pyritic (5 wt%) mine waste was conducted for a period of 524 weeks. The first 260 weeks watering/flushing was carried out using Milli-Q water during which the leachate pH decreased from 6.0 to 2.0, pyrite passivation layers present initially were removed and secondary sulfate minerals formed. The rate at which acidity was generated from secondary sulfate mineral dissolution was significantly greater than from pyrite oxidation after the calcite-saturated silicate water treatment during the period from 260 to 440 weeks. This suggests that in weathered pyritic wastes, both the amount of acidity and the rate at which it is released may be dominated by acid sulfate minerals rather than residual pyrite. Importantly, it was found that passivation strategies appropriate for reducing pyrite oxidation rates were not effective for reducing the rate of acid release from secondary mineralisation. Significant amounts of lime-saturated water (with high alkalinity) were required to dissolve the secondary sulfate minerals containing the stored acidity before circum-neutral conditions necessary for pyrite passivation could be achieved. It follows therefore that it is necessary to quantify the amount of stored acidity in secondary minerals so that appropriate remediation and acid management strategies can be designed and implemented to achieve long-term sustainable ARD control and mine closure.

Hydrogeochemical characteristics and risk evaluation of potential toxic elements in groundwater from Shanmughanadhi, Tamilnadu, India

Hydrogeochemical and Health Risk Assessments of trace elements are integral to groundwater resource assessment, utilization, and human health. Investigation of groundwater chemistry and trace elemental impact on local inhabitants were attempted in Shanmuganadhi basin, Tamilnadu, India. About 60 groundwater samples were collected during the pre-monsoon period and analyzed for hydrochemical composition, including major and trace elements (Fe, Cr, Ni, Cu Pb, Mn, and As) to isolate chemical characteristics and human health risk assessment. Groundwater geochemistry is prejudiced by geochemical reactions uniting cation exchange, dissolution and precipitation, adsorption, and anthropogenic contributions. About thirty-two percent of groundwater samples recorded higher F−(>1.5 mg/L) than the prescribed limit suggests sources from rock weathering and silicate dissolution. Nitrates (>45.0 mg/L) suggest sources from agricultural influences. Water types indicate alkalis (Na+ + K+) dominating alkali earth (Ca2+ - Mg2+) and strong acids (Cl− and SO42−) looming weak acid (CO32− and HCO3−) irrespective of water samples. The geochemical stability diagram suggests precipitation of silica, carbonate, and magnesium and dissolution of sulphate minerals along the groundwater flow path. Significant correlation between major ions and trace elements (Pb, Mn, Ni, and Cu) suggests origin from rock weathering, human impacts, and cultivation practices. Non-carcinogenic human risk for trace elements was higher in children compared with adults via ingestion and dermal exposure. The carcinogenic result suggests that Cr in CHK (7.1 × 10−2) and HBG (4.3 × 10−2) have the most excellent chance of cancer risk. The environmental risk category attempted using Comprehensive risk factor (CRI) suggests Pb (3.2-CHK, 2.6-HBG) with potential cancer risk. The comprehensive evaluation index recommends environmental damage between mild to moderate, indicating continuous exposure of traceable elements might result in cancer cause to the inhabitants. The study suggests water quality seems to be prejudiced by various geological and anthropogenic causes and endorses counteractive measures and proper execution of existing laws to protect groundwater resources in the study area.

Multi-isotopic (O, H, C, S, Sr, B, Li) characterization of waters in a low-enthalpy geothermal system in Havza (Samsun), Turkey

In this study, multi-isotopic (O, H, C, S, Sr, B, Li) compositions were used to perform geochemical characterization, determine the source and reservoir rocks, and explain the water-rock interaction mechanisms for geothermal fluids in the low-enthalpy Havza (Samsun) geothermal field (HGF) in Turkey. The geothermal water of Na-HCO3 water type has a wellhead temperature of 53°C, pH of nearly 7.7 and an EC value of 1140 µS/cm. The geothermal springs of Ca-HCO3 water type have an EC value of nearly 667 µS/cm and a temperature of nearly 26°C. The reservoir temperatures of the HGF geothermal system were calculated as 60–90°C and 108–160°C by silica and SO4-H2O oxygen isotope geothermometers, respectively. Stable isotope compositions (δ2H and δ18O) show that the geothermal well water is mixed with deeply circulated waters fed from higher elevations (∼ 830–1260 m), while the geothermal spring water is mixed with shallow cold water. The positive δ13C value (+3.01‰) indicates that the dissolved inorganic carbon (DIC) in the geothermal well water has no contribution from the atmospheric CO2 but originates in the metamorphic CO2 and marine limestones. However, the DIC in the geothermal springs is derived from C3 plants and silicate weathering. The values of 34SCDT show that the sulfate in the geothermal waters is due to the dissolution of sulfate minerals. The values of δ11B (-1.12 to +9.37 ‰) in the geothermal well and spring waters reflect both leaching of surrounding rocks and mantle-derived B. The reservoir rock may be Late Cretaceous-Permian limestones and Jurassic sandstones considering 87Sr/86Sr ratios (0.707108–0.707688) and δ7Li values (-7.44 to +6.18 ‰), whereas it might be Jurassic sandstones based on δ11B values. The strontium isotope composition of the geothermal spring water indicates the mixing of deep geothermal waters and cold groundwaters.

Secondary Sulfate Minerals from Thallium Mineralized Areas: Their Formation and Environmental Significance

Thallium is a highly toxic metal and is predominantly hosted by sulfides associated with low-temperature hydrothermal mineralization. Weathering and oxidation of sulfides generate acid drainage with a high concentration of thallium, posing a threat to surrounding environments. Thallium may also be incorporated into secondary sulfate minerals, which act as temporary storage for thallium. We present a state-of-the-art review on the formation mechanism of the secondary sulfate minerals from thallium mineralized areas and the varied roles these sulfate minerals play in Tl mobility. Up to 89 independent thallium minerals and four unnamed thallium minerals have been documented. These thallium minerals are dominated by Tl sulfosalts and limited to several sites. Occurrence, crystal chemistry, and Tl content of the secondary sulfate minerals indicate that Tl predominantly occurs as Tl(I) in K-bearing sulfate. Lanmuchangite acts as a transient source and sink of Tl for its water-soluble feature, whereas dorallcharite, Tl-voltaite, and Tl-jarosite act as the long term source and sink of Tl in the surface environments. Acid and/or ferric iron derived from the dissolution of sulfate minerals may increase the pyrite oxidation process and Tl release from Tl-bearing sulfides in the long term.

Hydrogeochemical changes during managed aquifer recharge (MAR) in a salinised coastal aquifer

The southern part of the Plana de Castellón aquifer (Spanish Mediterranean coast) has experienced persistent seawater intrusion over the last 50 years. The salinisation process is related to the lateral advance of the saline wedge and saline upconing as a result of intensive local groundwater pumping. In this context, managed aquifer recharge (MAR) was performed to aid in the recovery of this coastal aquifer. The artificial recharge water (ARW) was characterised by very low mineralisation, as evidenced by a mean electrical conductivity of 330 μS/cm, whereas native groundwater (NGW) was brackish, with EC values of approximately 3000–3500 μS/cm.The dynamics of the injected water and physicochemical changes to groundwater during the MAR event were evaluated using a combination of hydrogeochemical methods. EC, chloride ions, nitrate ions, and stable water isotopes (oxygen-18 and deuterium) were used as tracers to quantify the presence of injected water in groundwater (mixing ratios).Hydrochemical analysis (of major cations and anions) was used to determine changes to water characteristics and hydrogeochemical processes associated with the mixing of ARW and NGW and water-rock interactions. The injection significantly reduced groundwater salinity: EC and major ions rapidly and continuously declined after the first days of recharge. Percentage decreases in electrical conductivity of 80–90% and 30% were detected at 80 and 450 m from the recharge wells (values of 350–550 μs/cm), respectively.The principal process occurring in the aquifer during injection was dilution due to the displacement of NGW and mixing of ARW and NGW. Carbonate and sulfate mineral dissolution, cation exchange, and redox reactions were also identified, and their magnitudes were estimated. In quantitative terms, cation exchange was the most important geochemical process occurring during the MAR event.

A Forty-Year Karstic Critical Zone Survey (Baget Catchment, Pyrenees-France): Lithologic and Hydroclimatic Controls on Seasonal and Inter-Annual Variations of Stream Water Chemical Composition, pCO2, and Carbonate Equilibrium

The long-term trends and seasonal patterns of stream water chemical composition in a small remote forested karst catchment, were investigated from 1978 to 2018. Calcium, magnesium, and bicarbonates, the dominant ions, increased over the period together with temperature, while sulfates decreased. Carbonate and sulfate mineral dissolution was the main source of these elements. These trends and the seasonal opposite patterns of discharge vs. temperature, calcite saturation index vs. pCO2 and bicarbonate vs. sulfates, suggested the influence of discharge, of reduced long-range atmospheric pollution, and of increasing air temperature on biological activity and carbonate dissolution. Furthermore, the hydrological regime controlled the seasonal stream water chemical composition and fluxes by: (i) a dilution during the high discharge period, (ii) a change in the contribution rate of the waters draining different lithological areas in the catchment, e.g., the increased sulfates to bicarbonates ratio during summer low flows, with a maximum alkalinity decrease of 24%, and (iii) a “piston” and a “flushing” effects of dissolved elements stored in soils and epikarst with the first autumn heavy rains. Long-term stream water hydrochemical surveys of karst system have proved to be powerful indicators of biogeochemical processes, water sources and pathways under variable natural and anthropogenic environmental pressure conditions.

Application of the analytic hierarchy process to weight the criteria used to determine the Water Quality Index of groundwater in the northeastern basin of the Sidi Bouzid region, Central Tunisia

The Sidi Bouzid and El Hjal Wadi basins together comprise one of the most important agricultural regions in Central Tunisia. Exploitation of the groundwater in this region is increasing exponentially. In this work, hydrochemical characteristics and the analytic hierarchy process (AHP) were used to assess the suitability of the groundwater in the aquifer for use in irrigation. Concentrations of total dissolved solids in the groundwater ranged from 1500 to 5000 mg/L. The most abundant chemical species in the water were SO42− and Cl−, with mean concentrations of 1010 mg/L and 641 mg/L, respectively. The high levels of these species can be explained by sulfate mineral dissolution and the leaching of evaporitic formations into the groundwater flow. Quality criteria weighting using the AHP was employed to generate a map of groundwater suitability for irrigation. This method categorized water samples as either excellent, good, or permissible for irrigation based on the Water Quality Index (WQI). Most of the water samples (76.5%) in the study area were found to contain water that would be good for irrigation, although the groundwater quality deteriorated towards the areas with low elevation.

Origin of sulfate-rich fluids in the Early Triassic Montney Formation, Western Canadian Sedimentary Basin

Abstract This study investigates diagenetic and geochemical processes that control regional distribution and formation of sulfate minerals (i.e., anhydrite and barite) in the Early Triassic Montney Formation in the Western Canadian Sedimentary Basin. The generation of H2S in hydrocarbon reservoirs is often associated with the dissolution of sulfate minerals, as a major source of sulfate required for sulfate-reducing reactions. The formation of pervasive late diagenetic anhydrite and barite in the high H2S zone of the Montney Formation is therefore contrary to the normal paragenetic sequence of sour gas reservoirs. Petrographic observations revealed early and late anhydrite and barite cement. The early fine-crystalline anhydrite cement is dominant in northeastern British Columbia (low H2S zone), while the late-stage coarse-crystalline cement and fracture/vug-filling anhydrite are dominant in Alberta (high H2S zone). The bulk isotopic values (δ34S: +2.9 to +24.7‰ V-CDT, δ18O: −11.2 to +15.7‰ V-SMOW) suggest that sulfate-rich fluids originated mainly from modified Triassic connate water was the origin of early anhydrite. In contrast, the SIMS isotopic values of late anhydrite (δ34S: +18.5 to +37‰ V-CDT, δ18O: +12 to +22‰ V-SMOW) and barite cement (δ34S: +23.3 to +39‰ V-CDT, δ18O: +13.2 to +18.7‰ V-SMOW) as well as fracture/vug-filling anhydrite (δ34S: +23.5 to +24.7‰ V-CDT, δ18O: +13.3 to +14.7‰ V-SMOW) from Alberta represents a mixed isotopic signature of Triassic connate water and contribution of dissolved sulfate-rich fluids derived from dissolution of Devonian evaporites. The 87Sr/86Sr isotope ratios of the fracture/vug-filling anhydrite (0.7092–0.7102) are highly radiogenic suggesting extensive water/rock interactions between sulfate-rich fluids and siliciclastic and basement rocks. The similar isotopic composition of the late anhydrite/barite and fracture/vug-filling anhydrite in western Alberta with Devonian evaporites isotopic signature, and the highly radiogenic 87Sr/86Sr ratio further supports sulfate-bearing fluids were mainly originated from underlying Devonian evaporites and migrated upwards through deep-seated faults/fractures to the Montney Formation.

Hydrochemical and isotopic characteristics of surface water in the Lhasa River basin

In this study, 36 surface water samples were collected to investigate the hydrochemical and isotopic characteristics of the surface water in the Lhasa River basin using mathematical statistics, a Piper diagram, Gibbs plots, ratio graphs of ions and factor analysis. The dominance of the cations and anions in the surface water was Ca2+ > Mg2+ > Na+ > K+ and HCO3− > SO42− > Cl−. The mean concentrations of the cations and anions of the surface water were low in the study area. Human activities have a certain influence on the hydrochemical components of surface water in the study area. HCO3·SO4 (SO4·HCO3)-Ca·Mg (Mg·Ca) types of surface water were dominant in the study area. Water-rock interactions play a dominant role in controlling the surface water chemistry in the Lhasa River basin, mainly the weathering of silicate and carbonate, as well as the dissolution of sulfate minerals and cation exchange. Isotopic analysis indicated that the surface water was of meteoric and glacial/snow meltwater origin.

Evaluation of Meltwater Quality Using Dissolved Ions Chemistry and Multivariate Statistical Methods: A Case Study of the Manimahesh Glacier, Ravi Basin, Himachal Pradesh, India

The hydrogeochemical study on glacial meltwater gives important information about the quality of meltwater and weathering processes controlling dissolved ions chemistry in the glacierized area. Anionic abundance in the Manimahesh Glacier meltwater shows a trend of HCO3− > SO42− > Cl− = NO3−, whereas cationic abundance in the meltwater shows a trend of Ca2+ > Mg2+ > K+ > Na+. On the basis of high equivalent ratios of (Ca + Mg) versus (Na + K) and (Ca + Mg) versus TZ+ (total cations) and low equivalent ratio of (Na + K) versus TZ+, carbonate-type weathering has been identified as a major hydrogeochemical process regulating solute chemistry of the Manimahesh Glacier meltwater followed by silicate weathering. About 80% of bicarbonate in the meltwater of investigation area was mainly generated from carbonate weathering, whereas 20% of bicarbonate was produced from silicate weathering. The result of statistical methods (correlation, principal component and cluster analysis) shows that meltwater quality of the Manimahesh Glacier is mainly governed by carbonate and silicate-type weathering, oxidation of pyrite, dissolution of sulphate minerals and atmospheric input. The average value of suspended sediment concentration (SSC) in the glacier meltwater was calculated to be 46 mg/l and 63 mg/l during the month of June and July 2014, respectively, showing higher concentration of SSC during the month of July (peak-flow period) followed by June (low-flow period).

A hydrochemistry and multi-isotopic study of groundwater origin and hydrochemical evolution in the middle reaches of the Kuye River basin

The Kuye River basin lays in an economically and ecologically important area, therefore, the groundwater quality issues are of growing concern in this semi-arid region. In the present study, the combination of techniques (i.e. piper diagram, ionic ratios, Gibbs diagrams, multiple isotopic analyses etc.) provided an efficient way for analyzing the groundwater origin and hydrochemical processes that affected water chemistry. The groundwater type was CaHCO3 in low TDS values and NaCl/SO4 in high TDS values in both shallow unconfined and deep Cretaceous-Jurassic semi-confined aquifer. And, furthermore, Na+, Cl−, SO42− and F− were the dominated parameters deteriorating the groundwater quality. In general, groundwater was of meteoric origin and the more depleted δ18O and δD features of CJY groundwater samples indicated that the groundwater was formed during the wetter and colder climate. The rock weathering in conjunction with the cation exchange absolutely predominated in geochemical evolution and deuterium excess method quantified that mineral dissolution contributed most of the salinity (67–92%) of the groundwater. The SO42− of the groundwater was primary from the dissolution of sulfate minerals, next was the atmospheric precipitation. In addition, bacterial sulfate reduction was an important reaction affecting the SO42− concentration in the groundwater from CJY aquifer. The hydrochemical type of high fluoride groundwater in the study area was NaHCO3 or NaCl/SO4 and it was mainly from the dissolution of fluoride bearing minerals. NaHCO3 water was favorable for F− enrichment due to CaF2 solubility and NaCl/SO4 type water may favor the F− enrichment by lower its activity in groundwater. The results of this study will facilitate understanding of groundwater origin and quality status to enable effective management and utilization of groundwater.

Assessment of groundwater quality and 222Rn 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 SO42- 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.

Hydrogeochemistry of high-altitude lake: a case study of the Chandra Tal, Western Himalaya, India

Major ion chemistry of lake water provides important information about the sources of dissolved ions, weathering, and hydrogeochemical processes as well as anthropogenic activities taking place in the lake environment. Surface water samples were collected from 23 different locations of the Chandra Tal (Lake) situated in the Western Himalaya and analyzed for 12 different physicochemical parameters for understanding hydrogeochemistry of the study area. The average value of pH in the lake water was measured to be 8.1, showing alkaline nature. HCO3− was the most dominant anion and Ca2+ and Mg2+ were major cations in the Chandra Tal water. The high ratios of (Ca2+ + Mg2+)/TZ+ (total cations), (Ca2+ + Mg2+)/(Na+ + K+), Ca2+/Na+, Mg2+/Na+, and HCO3−/Na+ show the dominancy of carbonate weathering as a major source of dissolved ions in the lake water of the study area. On the other hand, equivalent ratios of Na+/Cl− and K+/Cl− are significantly higher than the sea aerosol indicating relatively minor contribution of these ions from atmospheric fallout to the chemical composition of the Chandra Tal water. The carbon dioxide partial pressure (Pco2) of the lake water (10–2.9 atm) was significantly higher than Pco2 value of the atmosphere (10–3.5 atm), showing disequilibrium with respect to the atmosphere and open system weathering in the catchment. The correlation and R-mode principal component analysis indicate that Chandra Tal water chemistry is mainly controlled by weathering processes such as carbonate and silicate weathering, oxidation of pyrite, dissolution of sulphate minerals along with small contribution from atmospheric precipitation, and anthropogenic activities.

Effect of sulfidogenesis cycling on the biogeochemical process in arsenic-enriched aquifers in the Lanyang Plain of Taiwan: Evidence from a sulfur isotope study

This study evaluated the biogeochemical interactions between arsenic (As) and sulfur (S) in groundwater to understand the natural and anthropogenic influences of S redox processes on As mobilization in the Lanyang Plain, Taiwan. Cl− and the sulfate isotopic composition δ34S[SO4] were selected as conservative tracers. River water and saline seawater were considered as end members in the binary mixing model. Thirty-two groundwater samples were divided into four types of groundwater (I, pyrite-oxidation; II, iron- and sulfate-reducing; III, sulfate-reducing; and IV, anthropogenic and others). The binary mixing model coupled with discriminant analysis was applied to yield a classification with 97% correctness, indicating that the DO/ORP values and δ34S[SO4] and Fe2+ concentrations are effective redox-sensitive indicators. Type I groundwater is mostly located in a mountainous recharge area where pyrite oxidation is the major geochemical process. A high 18O enrichment factor ε[SO4–H2O] and high 34S enrichment factor ε34S[FeS2–SO4] indicate that disproportionation and dissimilatory sulfate reduction are both involved in Type II and Type III groundwater. The process of bacterial sulfate reduction may coprecipitate and sequester As, a mechanism that is unlikely to occur in Type II groundwater. The presence of high As and Fe2+ concentrations and enriched δ34S[SO4] in Type II groundwater suggest that biogeochemical reactions occurred under anaerobic conditions. The reductive dissolution of As-bearing Fe oxyhydroxides together with microbial disproportionation of sulfur explains the substantial correlations among the high As concentration and enriched δ34S[SO4] and Fe2+ concentrations in the iron- and sulfate-reducing zone (Type II). The As concentration in Type III groundwater (sulfate-reducing) is lower than that in Type II groundwater because of bacterial sulfate reduction and coprecipitation with As. Furthermore, the dissolution of sulfate minerals is not the major source of aqueous SO4, based on the sulfur isotopic composition of solid-phase sulfate (δ34S[sulfate mineral]). Finally, the anthropogenic influence of fertilizers with wide S isotopic ranges is proposed as the plausible sulfate budget in Type IV groundwater. The results of this study suggest that the As release into groundwater involves the reductive dissolution of As-bearing Fe-hydroxides, bacterial sulfate reduction, and microbial disproportionation in the Lanyang Plain.

Hydrogeochemistry of Meltwater of the Chaturangi Glacier, Garhwal Himalaya, India

A hydrochemical analysis of meltwater draining from Chaturangi glacier was conducted to determine the dissolved ions chemistry and to evaluate the geochemical processes controlling major ions chemistry of the study area. Ca2+, Mg2+ and SO4 2− are the dominant ions in the glacier meltwater. The ratio of (Ca + Mg) versus TZ+ varied from 0.79 to 0.86 with an average value of 0.82 ± 0.02 indicating larger contribution of Ca and Mg to the total cations. (Ca + Mg)/(Na + K) ratio is also high, varying from 3.77 to 6.33 with an average value of 4.77 ± 0.79. This shows the dominancy of carbonate weathering in the study area. The scatter diagram between (Ca + Mg) versus SO4 2− shows a linear trend throughout the range of data, indicating the dissolution of sulphate minerals as one of the possible source of SO4 2− in the Chaturangi glacier meltwater. The C-ratio of meltwater of the study area shows that sulphide oxidation is the major proton producing mechanism. Correlation matrix and principal component analysis (factor analysis) were applied for identification of various processes controlling solute acquisition in the Chaturangi glacier meltwater.

Hydrochemical Characterization of a Groundwater Aquifer and its Water Quality in Relation to Irrigation in the Jinghuiqu Irrigation District of China

The Jinghuiqu irrigation district is located in the semi-arid regions of northwestern China, where groundwater is the most important natural source for local industry, agriculture and residents. The present work was conducted in the Jinghuiqu irrigation district to characterize the groundwater aquifer, which has undergone long-term flood irrigation for over 2000 years. Isotopic and hydrochemical analyses, along with geological and hydrogeological tools, were used to determine the chemical properties and evolutionary processes of the groundwater aquifer. Results showed that the groundwater chemistry had changed significantly from 1990 to 2009. Water with concentrations of CaMgSO4 had decreased significantly, from 60% to 28% of the total water samples, during the period, while water with concentrations of NaSO4 and NaCl increased significantly, from 28% to 72%. The salinity of the groundwater increased rapidly and the affected area had expanded to most of the irrigation district. Stable isotope studies showed that most of the groundwater concentrations were derived from sulfate mineral dissolution. The minerals saturation indices (SI), ion ratios and oxygen isotope values of the groundwater indicated that the shallow groundwater had mainly experienced mineral dissolution, cation exchange, and mixing of the irrigated surface waters and groundwater. The groundwater quality had continuously evolved toward salinization as concentrations of SO4(2-) and Na+ grew to dominate it. Water quality risk analyses showed that most of the saline groundwater is not suitable for domestic and irrigation uses, especially in the middle and eastern parts of the irrigation district. These findings indicate that the irrigation district should strengthen the groundwater resources management.