Cations In Groundwater Research Articles

Heavy-Metal Ions Control on PFAS Adsorption on Goethite in Aquatic Systems.

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous environmental contaminants that often co-occur with heavy metals. Despite their prevalence, the mobility of PFAS in complex, multicomponent systems, particularly at the molecular scale, remains poorly understood. The vast diversity of PFAS and their low concentrations alongside anthropogenic and natural substances underscore the need for integrating mechanistic insights into the sorption models. This study explores the influence of metal cations (Cu(II), Cd(II), and Fe(II)) on the adsorption of four common PFAS (PFOA, PFOS, PFDA, and GenX) onto goethite (α-FeOOH), a common iron (oxyhydr)oxide in both aquatic and terrestrial environments. PFAS adsorption was highly dependent on the PFAS type, pH, and metal ion concentration, with a surface complexation model effectively predicting these interactions. Cu(II) and Cd(II) enhanced PFOS and PFDA adsorption via ternary complexation while slightly reducing PFOA and GenX adsorption. Under anoxic conditions, Fe(II) significantly increased the adsorption of all PFAS, showing reactivity greater than those of Cu(II) and Cd(II). Additionally, natural organic matter increased PFAS mobility, although metal cations in groundwater may counteract this by enhancing PFAS retention. These findings highlight the key role of metal cations in PFAS transport and offer critical insights for predicting PFAS behavior at oxic-anoxic environmental interfaces.

Analysis of the evolution and causes of groundwater chemistry after ecological water replenishment of the Jialu River, China

Ecological water replenishment is an important measure for conserving water sources and improving the water environment. To explore the evolution and causes of groundwater chemistry after ecological water replenishment in the Jialu River, this study utilized groundwater monitoring data from 2015 to 2019 following ecological water replenishment. Various methods, including Piper’s trilinear diagram, Gibbs diagram, principal component analysis, and ion ratio analysis, were employed for research purposes. The results indicate that (1) since the implementation of ecological water replenishment in the Jialu River, there has been a general downwards trend in total dissolved solids (TDS) in groundwater. The dominant cation in groundwater is Ca2+, whereas HCO3− is the dominant anion. The concentration of cations in groundwater has generally decreased, with noticeable reductions in SO42− and Cl− concentrations in the upper reaches of the recharge river contributing to improved groundwater quality. (2) A comparison with 2015 reveals a gradual transition at sampling points from chemical types such as HCO3-Ca·Mg and HCO3·Cl–Ca·Mg to an ecological water replenishment chemical type (HCO3-Ca).

Hydrochemical and Formation Mechanism Studies of Groundwater in Quaternary Aquifer in a Northern Plain of China: An Example of Beijing Plain

Beijing Plain is a very active part of Beijing city regarding the socio-economic and human activities of the region. Over the past four decades, Beijing’s economic development and the continuous drought for nearly 10 years in the 2000s have negatively impacted the groundwater quantity and quality. Therefore, it is necessary to investigate the present situation of groundwater chemistry in this region to develop a comprehensive database and orientation for future research on groundwater quality evaluation. Mathematical statistics, Piper’s trilinear diagram, Gibbs plots, the ion ratio method and PHREEQC software 3.7.3 were used to analyze the groundwater hydrogeochemical characteristics and formation mechanisms of the quaternary aquifers of the Beijing Plain area. Hydrogeochemical results indicated that the groundwater is slightly alkaline, with pH values ranging from 6.76 to 8.65 and an average value of 7.92. The order of major cations in groundwater was Ca2+ > Na+ > Mg2+ > K+ with average values of 66.54 mg/L, 50.58 mg/L, 23.78 mg/L, and 1.81 mg/L, respectively, while the order of major anions was HCO3− > SO42− > Cl− with average values of 284.89 mg/L, 52.1 mg/L and 35.5 mg/L, respectively. The groundwater chemical types are Mg-Ca-Cl-HCO3, Na-Ca-HCO3, Mg-Ca-HCO3 and Mg-Na-HCO3. Research on the main influencing factors and PHREEQC hydrogeochemical inverse simulations results along the four pathways selected confirmed that rock weathering with sulfate, silicate and carbonate rock mineral dissolution and Na+, Mg2+ and Ca2+ ion reaction exchange influenced groundwater hydrogeochemical characteristics of the quaternary aquifers of the Beijing Plain area. Understanding the formation mechanisms of hydrogeochemistry in quaternary plains provides guidance for future studies and, through suggestions and case studies, facilitates decision-making by policy-makers on the sustainable management of groundwater resources.

Hydrochemical characterization and health risk assessment of different types of water bodies in Fenghuang Mountain Area, Northeast China.

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

Groundwater hydrogeochemical processes, water quality index, and probabilistic health risk assessment in an arid and semi-arid environment (Hamedan, Iran)

Groundwater protection requires an understanding of different hydrogeochemical processes and this study synthesised and analysed a large hydrogeochemical dataset (1030 data points over 15 years) of published data in western Iran, to gain a deeper understanding and reveal the main factors controlling groundwater geochemistry. Furthermore, non-carcinogenic effects on human health related to nitrate (NO3−) concentrations were assessed. In terms of the measured parameters, four distinct clusters were identified Ca–HCO3, Na–HCO3, Na–SO4, and Na–SO4–Cl. Cluster 1 (68% of samples) had higher average pH while exhibiting lower average electrical conductivities (ECs), cations, and anions than the other clusters and had a lower average weighted arithmetic than the other clusters. 28.5%, 51.9%, 16.3%, 2.1%, and 1.2% of total water samples rated as excellent, good, poor, extremely poor, and undrinkable, respectively, implying that about 80.4% of the groundwater samples are potable. Multi-linear regression models based on pH and EC values can predict cation and anion concentrations in groundwater with high accuracy. The significance of the findings lies in their potential to facilitate the comprehension, modeling, and eventual forecasting of the fate of anions and cations in semi-arid and arid environments, as well as similar groundwaters, using common water characteristics. In order to lower the non-carcinogenic health risks to the local population, the appropriate actions should be taken. The majority of the region's agricultural areas have primary soil textures that are sandy and prone to NO3− leaching. Therefore, in order to maintain the quality of the groundwater in the study region, excessive use of chemical and organic fertilizers should be avoided. These findings will contribute to understanding and safeguarding groundwater quality, while also informing management strategies in arid and semi-arid regions with similar environmental characteristics.

Diffusion capability of Cs-137 in compacted soil and bentonite under groundwater-saturated condition

Several researches have been studied the diffusion coefficient (Da) of radionuclide in soil samples in varies location around the world; however, the effect of cations in groundwater as a medium of saturation for Cs-137 diffusion in soil and bentonite remains to be accomplished. Compacted soil and bentonite layers are utilized in the construction of radioactive waste disposal sites, which serve to prevent the release of Cs-137 from the repository to the unsaturated zone. The samples used were soil from the prospective disposal site in SP4—Serpong Nuclear Center (SNC) and bentonite taken from Santrijaya, Tasikmalaya. The diffusion coefficient (Da) is used as indicator of Cesium-137 diffusion in the samples. Experimental measurements were conducted on a diffusion column unit that varied in diffusion time and density conditions to determine diffusion coefficients. The samples were cut into slices and analyzed using Multichannel Analyzer (MCA) unit to measure Cs-137 radioactivity. The measurement results were then incorporated into Fick's Law equation to obtain the value of the diffusion coefficient (Da) of Cs-137 in soil and bentonite. The experimental results showed that the diffusion coefficients of samples with groundwater simulation are in the range of 10–12 m2 s−1 for the local soil and bentonite samples, respectively. Compare to the similar experiment that was conducted previously, the results indicated that the groundwater content could slightly impact the increase in the diffusion coefficient value of Cs-137.

Hydrochemical Characteristics and Its Origin of Surface Water and Groundwater in Dianbu River Basin

Chaohu lake is a key water body for water pollution prevention and treatment in our country. However， it has been at a higher eutrophication level recently. Here， the surface water and groundwater in the Dianbu River Basin， a secondary tributary of Chaohu Lake， were taken as the research object. In order to test the hydrochemical composition and hydrogen and oxygen isotope values of different water bodies， 30 groups of surface water samples， 36 groups of groundwater samples， 16 groups of hydrogen and oxygen stable isotope samples， and 18 groups of groundwater hydrogen and oxygen stable isotope samples were collected in August 2021 （wet season）， November 2021 （normal season）， and February 2022 （dry season）. The seasonal and spatial variation characteristics were analyzed to explore the hydrochemical characteristics and formation mechanism of water bodies by means of mathematical statistics， Piper triangular diagram， Gibbs figures， and ion ratios. The following results were obtained： ① precipitation was the main source of surface water and groundwater in Dianbu River Basin， and the evaporation fractionation effect of surface water was more significant than that of groundwater. At different periods， the surface water was more enriched with stable isotopes of hydrogen and oxygen than groundwater. The stable isotopes of hydrogen and oxygen in water showed seasonal variation， relative enrichment in the wet season， and depletion in the dry season. ② Both surface water and groundwater in the Dianbu River Basin were weakly alkaline， and the concentration of ions in surface water was significantly lower than that in groundwater. Ca2+ and Na+ were the main cations in surface water， Ca2+ was the main cation in groundwater， and the dominant anion in all water was HCO3-. The hydrochemical typology of surface water was mainly HCO3·Cl-Na·Ca， and that of groundwater was mainly HCO3-Na·Ca. ③ The concentrations of the main hydrochemical indexes of surface water and groundwater showed certain seasonal and spatial differences. From the wet season to the dry season， the concentrations of TDS， K+， Na+， Ca2+， Mg2+， Cl-， and SO42- in surface water showed an increasing trend on the whole. The concentrations of Na+， Ca2+， and Mg2+ in groundwater showed little change but increased slightly， whereas the concentrations of Cl-， SO42-， and NO3- showed an increasing trend on the whole. The concentrations of Cl-， SO42-， and NO3- in the water showed relatively large seasonal fluctuations. From upstream to downstream， the concentrations of the main hydrochemical indexes in surface water first decreased and then increased， among which the concentration of NO3- increased the most. The concentrations of the main hydrochemical indexes of groundwater in the direction of runoff changed little overall， but the concentration in the discharge area was higher than that in the recharge area. ④ The formation of hydrochemical characteristics of the water was mainly controlled by water-rock interaction but was also influenced by human factors. The water-rock action was mainly the weathering dissolution of silicate rock， salt rock， and carbonate rock. Man-made pollutants such as sewage from a sewage treatment plant， domestic sewage， and feces had obviously changed the hydrochemical characteristics of the local water. ⑤ Compared with that in 2016， the concentration of NO3- in surface water showed a certain degree of reduction. The nitrogen pollution control work carried out by the local government had achieved certain results， but it was still necessary to strengthen the pollution prevention and control of sewage and feces in the downstream of the Dianbu River， some tributaries （such as the Dingguang River and Maqiao River）， and some residential areas.

Hydrogeochemical study of groundwater in arid and semi-arid regions of the Infracenomanian aquifers (Cretaceous Errachidia basin, Southeastern Morocco). Using hydrochemical modeling and multivariate statistical analysis

Groundwater in the Cretaceous Errachidia basin, located in the southern part of Morocco, is crucial in supporting the region's main economic activities, such as farming. This arid region faces multiple challenges, including an average annual rainfall of less than 80 mm/year, intense agricultural activities, high evaporation, and extremely high evapotranspiration rates up to 1580 mm/year. Therefore, the hydrogeochemical study focuses on the Infracenomanian aquifers in the Cretaceous Errachidia basin. The goal is to evaluate the sustainable use of saline lands and brackish water, particularly assessing water resources and sustainable socioeconomic development in southeastern Morocco. In June 2021, 20 samples were collected and analyzed for pH, electrical conductivity (EC), total dissolved solids (TDS) and major ions. The hydrogeochemical parameters were analyzed using multivariate statistical methods. Statistical techniques such as Piper's trilinear diagram analysis of hydrochemistry types, Gibbs diagram analysis, The HFE diagram and ion correlation analysis were used to examine the origins of the main ions in the groundwater and to determine the source of the salinization processes in the groundwater.The findings revealed a strong positive correlation between TDS and the spatial distribution of major ions (Na+, Ca2+, Mg2+, Cl−) and EC, revealing high mineralization in the study area. The main cations in groundwater are Na+ and Ca2+, while the main anions are Cl−. The elevated concentrations of Cl− and Na+ are due to the evapotranspiration of irrigation water. Furthermore, the hydrochemical facies types are predominantly sodium chloride (Na–Cl), followed by calcium chloride (Ca–Cl) and a mix of calcium and magnesium chloride facies (Ca–Mg–Cl). These analyses indicate that the hydrochemistry of groundwater in the study area is primarily influenced by water-rock interactions, such as the dissolution of sedimentary rocks, soil leaching through gravity irrigation, and evaporation in the region. Moreover, the analysis using the Gibbs diagram indicates that evaporation is the primary hydrogeochemical process that shapes the chemical composition of the groundwater in the area under study.

Integrated approach to hydrogeochemical appraisal of groundwater quality concerning arsenic contamination and its suitability analysis for drinking purposes using water quality index

Arsenic (As), contamination in drinking groundwater resources is commonly environmental problem in many developing countries including Pakistan, with significant human health risk reports. In order to examine the groundwater quality concerning As contamination, its geochemical behavior along with physicochemical parameters, 42 samples were collected from community tube wells from District Bahawalpur, Punjab, Pakistan. The results showed the concentration of elevated As, its source of mobilization, and associated public health risk. The As concentration detected in groundwater samples varied from 0.12 to 104 µg/L with an average value of 34.7 µg/L. Among 42 groundwater samples, 27 samples were beyond the permitted limit of 10 µg/L recommended by World Health Organization (WHO), for drinking purposes. Statistical analysis result show that the groundwater cations values are in decreasing order such as: Na+ > Mg2+ > Ca2+ > K+, while anions were HCO3– > SO42– > Cl– > NO3–. Hydrochemical facies result depict that the groundwater samples of the study area, 14 samples belong to CaHCO3 type, 5 samples belong to NaCl type, 20 samples belong to Mixed CaMgCl type, and 3 samples belong to CaCl2 type. It can be accredited due to weathering and recharge mechanism, evaporation processes, and reverse ion exchange. Gibbs diagram shows that rock water interaction controls the hydrochemistry of groundwater resources of the study area. Saturation Index (SI) result indicated the saturation of calcite, dolomite, gypsum, geothite, and hematite mineral due their positive SI values. The principal component analysis (PCA) results possess a total variability of 80.69% signifying the anthropogenic and geogenic source of contamination. The results of the exposure-health-risk-assessment method for measuring As reveal significant potential non-carcinogenic risk (HQ), exceeding the threshold level of (> 1) for children in the study area. Water quality assessment results shows that 24 samples were not suitable for drinking purposes.

Potential environmental pollution study by leachate generation and health risk assessment in the vicinity of bandhwari landfill disposal site, National Capital Region, India

Effects of fast urbanization and development in metropolitan cities is the production of massive amounts of waste from households and industries. Dumping of waste at an unengineered landfill site creates environmental issues. Generated leachate from such landfill is having potential to pollute the surrounding environment including groundwater. To understand the groundwater pollution by the effect of landfill leachate and health risk assessment for humans, four leachate samples and thirty-six groundwater samples were collected from different sources of groundwater from close proximity of Bandhwari Landfill site located in National Capital Region, Delhi. EC and SO42− values of Leachate samples i. e L-1 and L-2 are 42.5 mS/cm and 55.4 mS/cm; 1916.4 mg/l and 1931 mg/l respectively. Leachate pollution Index (LPI) values signifies that landfill leachate is having moderate potential for contamination. The dominance of average ionic species concentration of major cations in groundwater is given as Ca2+>Na+>Mg2+>K+ and major anion as HCO3− > Cl− > SO42− > NO3− > F−. As per Water Quality Index (WQI), 67% of samples lies in excellent category, 17% of samples falling in good category, whereas around 6% of groundwater samples lies in poor category, very poor category and unsuitable category. Landfill leachate and groundwater sample from North East direction are having high concentration of tritium i.e. 8.11 ± 0.40 TU and 3.03 ± 0.29 TU, respectively. Leachate samples from leachate pond-1 and leachate pond-2 are showing quite high Cl−/Br− ratio i. e 342 and 320. 86 respectively. But groundwater samples are exhibiting Cl−/Br− ratio in the range of 173.68 to 108.75. This represents leaching of salts from solid decomposed waste from landfill. Both non-carcinogenic and carcinogenic risk (CRing) were calculated for children and adult. Hazard Index (HI) values are higher than reference value i. e > 1 in the children (in 23% samples) as compare to the adult. These are mainly associated with Co, Cd and Pb. CRing of groundwater sample due to the presence of As, Ni, Cr and Cd falling in the range of 10−6 and 10−4 showing high risk to cancer per 10, 00, 000 million people by ingestion. However there is no significant cancer risk by dermal exposure by all metals in all groundwater samples. Groundwater pollution appears to be limited to the close vicinity in South and North-East direction.

Evaluation of quality and risk to human health of groundwater in a coastal coal-bearing graben basin, North China

Water quality assessments are essential for ensuring human and ecosystem health. This study conducted a water quality assessment on a typical coastal coal-bearing graben basin. Suitability of groundwater quality of the basin for drinking and agricultural irrigation was assessed. Hazards posed to human health by groundwater nitrate were assessed using the objective combined weight water quality index, percent sodium, sodium adsorption ratio, and health risk assessment model. The results indicated groundwater of the basin to be weakly alkaline hard-fresh or hard-brackish, and mean values of pH, total dissolved solids, and total hardness of 7.6, 1464.5 mg/L, and 794.1 mg/L, respectively. The ranks of groundwater cations and anions by abundance were Ca2+>Na+>Mg2+>K+ and HCO3->NO3->Cl->SO42->F-, respectively. The main groundwater type was Cl-Ca, followed by HCO3-Ca. The results of the water quality evaluation indicated that most groundwater in the study area is of a medium quality (38%), followed by poor (33%), and extremely poor (26%). Groundwater quality gradually worsened from inland to the coast. Groundwater of the basin was generally suitable for agricultural irrigation. Groundwater nitrate posed a hazard to over 60% of the exposed population, with infants most at risk, followed by children, adult females, and adult males.

Amphibolite dissolution mechanism under chlorine-rich conditions during freeze-thaw cycles

The low-temperature weathering behavior of amphibolite is vital for revealing the cation source of groundwater and for understanding a wide range of geochemical evolution. This study aims to observe the macroscopic and microscopic characteristics of amphibolite dissolution under the freeze-thaw cycles (-25–25 °C) and chlorides (HCl, NaCl, KCl). The results show that Mg-hornblende was dissolved in chloride solutions of the same pH or concentration before albite. The change rule of the solution composition of freeze-thaw cycles is consistent with the results obtained from the dissolution experiment at room temperature. In addition, in an HCl solution of pH 1 and NaOH solutions of pH 11, 13, and 14, the dissolved amount of quartz in amphibolite can reach 11 wt %. KCl can powerfully dissolve quartz and efficiently dissolve Si in the silica-oxide tetrahedron (especially the T2 site) of Mg-hornblende. However, NaCl significantly dissolves cations in the Mg-hornblende octahedron. Analysis indicates that the leaching of Ca2+ and Mg2+ in proton-promoted dissolution strongly depended on the concentration of H+. At the same time, the release of Mg is closely related to Cl−. The results can help understand chemical element migration in the earth, especially providing a theoretical basis for groundwater cation in the Qaidam Basin.

Hydrogeochemical Characteristics, Water Quality, and Human Health Risks of Groundwater in Wulian, North China

Groundwater shortage and pollution are critical issues of global concern. In Wulian County, a typical hilly area, groundwater is the main source of water supply. This study investigates the current situation of groundwater pollution in Wulian City through the analysis of groundwater water chemistry characteristics, water quality evaluation, and health risk evaluation. After the analysis of the controlling factors of chemical components in groundwater and the analysis of ion sources, the main ion sources in groundwater were determined. The results showed that the major cations in groundwater were Ca2+ and Na+ and the major anions were HCO3− and SO42−. Nevertheless, NO3− exceeded the standard to different degrees in pore water (PW), fissure pore water (FPW), and fissure water (FW). The minimum NO3− concentration exceeded the standard in FW. Under the influence of rock weathering and salt rock dissolution, the main hydrochemical types of groundwater were the HCO3-Ca, HCO3-Ca·Mg, and SO4·Cl-Ca·Mg types. According to the water quality evaluation and health risk assessment, the FW area in the south had the highest water quality, where Class I water appeared and potable water was more widely distributed. The PW and FPW areas in the north had lower water quality, with higher health risks. Category V water gradually appeared in the FPW area, which is not suitable as a water supply source. Factor analysis and ion ratio analysis showed that the study area is strongly affected by anthropogenic factors. These research methods have important reference value to the research of groundwater pollution status.

The Performance of Several Current Interpolation Methods for Variability of cations in Groundwater in Esfarayen Plain, Iran: A Case Study

Acquiring information about groundwater quality is essential in developing management strategies. In this article, spatio-temporal variations of cations in groundwater in Esfarayen plain were investigated using data monitored in 134 groundwater wells, active in 1988, and 47 wells, active in 2019. To evaluate groundwater quality, interpolation methods have been used to interpolate existing limited spatial data. The performance of 8 current interpolation methods on the data for the two selected years (1988 and 2019) was compared. Finding the optimum interpolation method for the considered groundwater quality parameters is essential. Cross-validation and three indexes of R2, mean absolute error (MAE), and root mean square error (RMSE) were used to compare the performance of the methods. By identifying universal kriging (UK) and global polynomial interpolation (GPI) methods as the optimum methods and using those for the selected years (1988 and 2019), spatial variation of the concentration of cations in groundwater across the plain has been presented. In 1988, the maximum concentration of the cations occurred in the southwest of the plain (about 80 mg/L), and the minimum concentration of the cations was observed in the northwest of the plain (approximately 8 mg/L). Similarly, in 2019, the highest concentration of the cations was found in the southwest of the plain (almost 64 mg/L), and its lowest concentration was observed in the northeast of the plain (roughly 13 mg/L). Moreover, temporal variations of the concentration of cations in groundwater from 1988 to 2019 have also been presented. The concentration of the cations increased by approximately 23 mg/L in the northwest and decreased to about 37 mg/L in the southwest of the study area from 1988 through 2019. According to the results, changes in the quality of groundwater are a complex problem and it is necessary to adopt proper strategies to reduce its adverse effects.

Hydrogeochemical characterization and evaluation of subsurface water quality in the Proterozoic Cuddapah Basin, Andhra Pradesh, India.

In the current survey, different hydrogeochemical processes governing the geochemistry of aquifers, the usefulness of groundwater for regular consumption, and agricultural purposes were evaluated around the Tummalapalle area. One hundred forty-four borehole locations were chosen to characterize the major physicochemical components of the aquifer water. The analysis results of pH inferred that the groundwater is nominally acidic to basic, and pH ranged from 6.6 to 8.4. The average concentrations of TDS, Ca2+, Mg2+, total hardness (TH), HCO3-, and total alkalinity (TA) are within the allowable limits of potable water quality as prescribed by the Bureau of Indian Standards (BIS) and WHO. However, the average concentrations of Na+, K+, Cl-, and SO42- were all below the permissible limit. All samples were analyzed with the help of Piper and Chadha charts to determine the dominant hydrogeochemical components of groundwater. The dominance of cations in groundwater in this region is in the sequence of Ca2+ > Na+ > Mg2+ > K+, followed by anions HCO3- > Cl- > SO42-. The Gibbs plot analysis suggested the predominance of rock aquifer interaction as the major hydrogeochemical process governing groundwater geochemistry in this region.The water quality index (WQI) of all groundwater samples in the Tummalapalle region was estimated, with 55% of the samples being potable grade. The different irrigation indices were analyzed for the groundwater samples to estimate their desirability for agriculture. The maximum number of water samples was found to be well-suited for cultivation.

Arsenic Contamination, Water Toxicity, Source Apportionment, and Potential Health Risk in Groundwater of Jhelum Basin, Punjab, Pakistan.

Potable groundwater (GW) contamination through arsenic (As) is a commonly reported environmental issue in Pakistan. In order to examine the groundwater quality for As contamination, its geochemical behavior, and other physicochemical parameters, 69 samples from various groundwater sources were collected from the mining area of Pind Dadan Khan, Punjab, Pakistan. The results showed the concentration of elevated As, its source of mobilization, and linked public health risk. Arsenic detected in the groundwater samples varied from 0.5 to 100µg/L, with an average value of 21.38µg/L. Forty-two samples were beyond the acceptable limit of 10µg/L of the WHO for drinking purposes. The statistical summary showed that the groundwater cation concentration was in decreasing order such as Na+ > Ca2+ > Mg2+ > K+, while anions were as follows: HCO3- > SO42- > Cl- > NO3-. Hydrochemical facies results depicted that groundwater samples belong to CaHCO3 type. Rock-water interactions control the hydrochemistry of groundwater. Saturation indices' results indicated the saturation of the groundwater sources for CO3 minerals due to their positive SI values. Such minerals include aragonite, calcite, dolomite, and fluorite. The principal component analysis (PCA) findings possess a total variability of 77.36% suggesting the anthropogenic and geogenic contributing sources of contaminant. The results of the Exposure-health-risk-assessment model for measuring As reveal significant potential carcinogenic risk exceeding the threshold level (value > 10-4) and HQ level (value > 1.0).

Intrinsic Dependence of Groundwater Cation Hydraulic and Concentration Features on Negatively Charged Thin Composite Nanofiltration Membrane Rejection and Permeation Behavior.

Commercial nanofiltration membranes of different molecular weight cut-offs were tested on a pilot plant for the exploration of permeation nature of Ca, Mg, Mn, Fe, Na and ammonium ions. Correlation of transmembrane pressure and rejection quotient versus volumetric flux efficiency on nanofiltration membrane rejection and permeability behavior toward hydrated divalent and monovalent ions separation from the natural groundwater was observed. Membrane ion rejection affinity (MIRA) dimension was established as normalized TMP with regard to permeate solute moiety representing pressure value necessary for solute rejection change of 1%. Ion rejection coefficient (IRC) was introduced to evaluate the membrane rejection capability, and to indicate the prevailed nanofiltration partitioning mechanism near the membrane surface. Positive values of the IRC indicated satisfactory rejection efficiency of the membrane process and its negative values ensigned very low rejection affinity and high permeability of the membranes for the individual solutes. The TMP quotient and the efficiency of rejection for individual cations showed upward and downward trends along with flux utilization increase. Nanofiltration process was observed as an equilibrium. The higher the Gibbs free energy was, cation rejection was more exothermic and valuably enlarged. Low Gibbs free energy values circumferentially closer to endothermic zone indicated expressed ions permeation.

Assessing salinization of coastal groundwater by tidal action: The tropical Wouri Estuary, Douala, Cameroon

Study regionDouala, Cameroon, West Africa. Study focusSalinity of shallow coastal groundwater in Douala, Cameroon impairs its use for drinking and industrial purposes. Previous studies suggest that salinization is from tidal flooding from the Wouri Estuary. We aimed to test the tidal origin of groundwater salinization by conducting a time series investigation of water level and salinity, and assessed the stable water isotopes (δ¹⁸O and δD) and major cations (Ca²+ and Mg²+) in groundwater and adjacent estuarine tidal creek. During the time series measurements, we pumped groundwater for over 5 tidal cycles to induce flow into a test well. New hydrologic insights for the regionThe time-series groundwater level mimicked water level changes in the estuary. However, the temporal salinity in groundwater did not correspond to tidal salinity changes of estuarine water, indicating that estuarine water did not intrude groundwater. The δ¹⁸O and δD of the groundwater and estuarine samples are collinear and fall along the local meteoric water line of Douala and had d-excesses of >10, indicating a non-evaporated rain recharge of groundwater or lack of salinization by evapoconcentration. The salinity-δ¹⁸O relationship showed that the origin of salinity in the coastal groundwater aquifer is not from seawater intrusion. The Mg²+/Ca²+ ratios of <1 in groundwater compared to 6–8 in estuarine water support the non-seawater origin of groundwater salinity. We conclude that the salinity of coastal groundwater in Douala is not affected by tide-induced salinization from the adjacent Wouri Estuary but by geogenic sources in the aquifer.

Developing persulfate-activator soft solid (PASS) as slow release oxidant to remediate phenol-contaminated groundwater

The research objective was to develop a persulfate-activator soft solid (PASS) as a biodegradable slow-release oxidant to treat phenol-contaminated groundwater. PASS was prepared by graft copolymerization of acrylic acid (AA) and acrylamide (AM) onto 1% (w/v) sodium alginate mixed with 500 mg L−1 sodium persulfate and 5 mg L−1 ferrous sulfate. The physical and chemical properties of PASS were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, the water content and swelling ratio. Various variables, including the ratio of AA/AM, pH, temperature and the type of groundwater cations affecting PS release, were investigated. The maximum PS release in DI water was 98% in the ratio of PASS 1 (AA/AM, 75/25), 96% at pH 3, 83% at 25 °C, and 80% with Na+. The major factors controlling PS release were the AA/AM ratio and pH. PASS 1 can be stable in size and shape for 6–8 days and completely degraded within 34 days. The degradation rates of 10 mgL−1 phenol using PASS produced the highest kobs values for each variable at a ratio of PASS 1 (k=0.1408 h−1), pH 7 (k=0.1338 h−1), 25 °C (k=0.1939 h−1), and Ca2+ (k=0.1336 h−1). The temperature of the groundwater was key to driving the reaction between PS and phenol. PASS 1 was applied in simulated phenol-contaminated groundwater via horizontal tanks containing Ottawa sand. The results indicated 93.2% phenol removal within 72 h in a narrow horizontal flow tank and 41.7% phenol removal in a wide horizontal flow tank with aeration.

Hydrochemical characteristics and pollution source apportionment of the groundwater in the east foothill of the Taihang Mountains, Hebei Province

The east foothill of the Taihang Mountains, Hebei Province, is an important groundwater recharge and transport area in the North China Plain. It is of practical significance to study the groundwater hydrochemical characteristics of this area for rational groundwater regulation. In this study, the Chadha rectangular diagram and Piper trilinear diagram were adopted to identify the relevant hydrochemical processes, and the main groundwater hydrochemical type was the HCO3·SO4–Ca. Descriptive statistical methods, correlation analysis, major ion ratio determination and principal component analysis (PCA) were employed to analyze the formation mechanism of groundwater hydrogeochemical characteristics and to identify the sources of the main groundwater ions in the study area. The results showed that Ca2+ and HCO3− were the dominant groundwater cation and anion, respectively, and the Gibbs diagram demonstrated that the majority of groundwater samples occurred in the rock weathering-dominated area. Bivariate diagrams revealed that mineral dissolution and ion exchange controlled the groundwater geochemistry. The study area was seriously polluted by NO3–, which might be due to the application of farmland fertilizers and leakage of rural domestic sewage and garbage. PCA yielded three principal components (PCs), which represented processes influenced by salinity, human activity and fluoride impacts on the groundwater chemistry. The distribution of high-positive PC scores verified the influences of the various processes on the groundwater study area, which is an effective tool to formulate and implement management strategies for the sustainable development of groundwater areas.