Hydrogeochemical Characterization and Suitability Assessment of Groundwater: A Case Study in Central Sindh, Pakistan

Arsenic-contaminated groundwater of the Western Banat (Pannonian basin): Hydrogeochemical appraisal, pollution source apportionment, and Monte Carlo simulation of source-specific health risks

Due to rapid urbanization and industrial growth, groundwater globally is continuously deteriorating, posing significant health risks to humans. This study employed a comprehensive methodology to analyze groundwater in the Western Banat Plain (Serbia). Using Piper and Gibbs plots, hydrogeochemistry was assessed, while the entropy-weighted water quality index (EWQI) was used to evaluate groundwater quality. Pollution sources were identified using positive matrix factorization (PMF) accompanied by Pearson correlation and hierarchical cluster analysis, while Monte Carlo simulation assessed health risks associated with groundwater consumption. Results showed that groundwater, mainly Ca-Mg-HCO3 type, is mostly suitable for drinking. Geogenic pollution, agricultural activities, and sewage were major pollution sources. Consumption of contaminated groundwater poses serious non-carcinogenic and carcinogenic health risks. Additionally, arsenic from geogenic source was found to be the main health risks contributor, considering its worryingly elevated concentration, ranging up to 364 μg/L. These findings will be valuable for decision-makers and researchers in managing groundwater vulnerability. PRACTITIONER POINTS: Groundwater is severely contaminated with As in the northern part of the study area. The predominant hydrochemical type of groundwater in the area is Ca-Mg-HCO3. The PMF method apportioned three groundwater pollution sources. Monte Carlo identified rock dissolution as the primary health risk contributor. Health risks and mortality in the study area are positively correlated.

Assessment of landcover impacts on the groundwater quality using hydrogeochemical and geospatial techniques

Groundwater quality is influenced by urbanization and land use land cover (LULC) changes. This study investigated their impact on groundwater quality in Quetta City, Pakistan, from 2015 to 2021. About 58 groundwater samples from monitoring wells were analyzed using hydrogeochemical and statistical methods. The water quality index (WQI), Wilcox, USSL, and various agricultural indices were employed to assess water quality trends. LULC analysis and NDVI using Sentinel-2 imagery revealed increased urban and agricultural areas and decreased barren land. Rapid urbanization was evident, with the buildup class expanding by 7.50% during this period. NDVI findings emphasized monitoring vegetation health and water quality for environmental assessments. The groundwater in Quetta was primarily classified as Cl-Ca·Mg, Cl-Ca, and Cl-Na according to the Piper diagram, with water-rock interactions and rock weathering evident. Most groundwater samples were suitable for irrigation according to the Wilcox and USSL diagrams. The WQI demonstrated overall safety for human consumption, but declining WQI values in northern parts due to urbanization are concerning. The results also revealed a moderate positive relationship between landcover classes and WQI values. It can be concluded that urbanization and excessive use of pesticides contributed to declining agricultural land quality. The spatial overlay of agricultural indices with landcover class suggested that barren land was most suitable, followed by build-up and agriculture were suitable for drinking and agriculture purposes. Moreover, agricultural indices moderately declined due to excessive fertilizers and pesticides in the agriculture landcover class. Thus, effective water resource management is crucial to address challenges. This comprehensive study serves as a baseline for future research and recommends larger-scale studies to implement efficient management strategies, urbanization planning, and safe irrigation and drinking water practices to prevent groundwater pollution.

Fluoride Contamination in Groundwater of Community Tube Wells, Source Distribution, Associated Health Risk Exposure, and Suitability Analysis for Drinking from Arid Zone

Fluoride (F−) pollution in potable groundwater (GW) is a serious environmental concern in Pakistan with substantial human health hazard reports. The research on F− pollution in GW resources in Sindh Province is still incomplete. To explore the realistic conditions, the present research aimed to investigate the GW quality of community tube wells concerning F− contamination in Tharparkar, Sindh, Pakistan. A total of 53 samples were collected and examined for F−, along with other physicochemical parameters. The F− values observed varied from 0.2–4.2 mg/L, with a mean value of 1.63 mg/L. Among the 53 samples, 46% had F− levels that were higher than the World Health Organization’s (WHO) recommended limit (1.5 mg/L). The water type of the studied region was Ca-HCO3 type, which can be attributed to fresh recharged water. The interaction of rock–water contact controls the hydrochemistry of GW. The GW resources of the research zone were highly saturated with fluorite minerals. Human health risk calculation outcomes exposed that 21 samples showed high HQ values for children and 7 samples showed high values for adults in the research zone. Children are at high risk in the study area from drinking F−-contaminated GW. WQI results showed that 31 samples were not suitable for drinking.

COVID-19 pandemic lockdown modulation of physico-chemical parameters of surface water, Karamana river basin, Southwest India: A weighted arithmetic index and geostatistical perspective

The coronavirus disease or COVID-19 pandemic continues imposing restrictions on the human population from full-scale normal/routine activities all over the world. This study primarily spotlights the consequences of the COVID-19-pandemic-lockdown on physicochemical parameters of water (samples) of the Karamana river system (KRS) during the pre-monsoons (or January) of 2021 and 2022, using the Weighted Arithmetic Index method and Geostatistical analysis (ArcMap 10.2). Even though the Karamana river supported the water needs of the people during the past several decades, the quality of water deteriorated due to the rising population and consequent anthropogenic activities. Hence, it is imperative to evaluate the water quality during the post-COVID-19 lockdowns and document the spatial distribution of parameters listed in the BIS (Bureau of Indian standard) IS10500, 2012. This was accomplished by establishing a water quality index (WQI), Geostatistical analysis, and weighted overlay analysis (WOA). The estimated WQI suggested that about 45.11km2 (6.43%) area has declined from the excellent category of water quality between 2021 and 2022. Similarly, WOA results deciphered that the area under the poor category has drastically and negatively changed from 27.85 km2 (4.0%) to 60.42 km2 (8.6%) after revoking of lockdown restrictions. The lessons learned from syn-Covid-19, the spike or uptrend of the water quality compared to the past decades, offer ample scientific basis to policymakers, administrators, and environmentalists for restoration of river system health from huge anthropogenic stress.

Groundwater fluoride and nitrate contamination and associated human health risk assessment in South Punjab, Pakistan

Consumption of high fluoride (F^-) and nitrate (NO₃^-) containing water may pose serious health hazards. One hundred sixty-one groundwater samples were collected from drinking wells in Khushab district, Punjab Province, Pakistan, to determine the causes of elevated F^- and NO₃^- concentrations, and to estimate the human health risks posed by groundwater contamination. The results showed pH of the groundwater samples ranged from slightly neutral to alkaline, and Na⁺ and HCO₃^- ions dominated the groundwater. Piper diagram and bivariate plots indicated that the key factors regulating groundwater hydrochemistry were weathering of silicates, dissolution of evaporates, evaporation, cation exchange, and anthropogenic activities. The F^- content of groundwater ranged from 0.06 to 7.9 mg/L, and 25.46% of groundwater samples contained high-level fluoride concentration (F^-  > 1.5 mg/L), which exceeds the (WHO Guidelines for drinking-water quality: incorporating the first and second addenda, WHO, Geneva, 2022) guidelines of drinking-water quality. Inverse geochemical modeling indicates that weathering and dissolution of fluoride-rich minerals were the primary causes of F^- in groundwater. High F^- can be attributed to low concentration of calcium-containing minerals along the flow path. The concentrations of NO₃^- in groundwater varied from 0.1 to 70 mg/L; some samples are slightly exceeding the (WHO Guidelines for drinking-water quality: incorporating the first and second addenda, WHO, Geneva, 2022) guidelines for drinking-water quality. Elevated NO₃^- content was attributed to the anthropogenic activities revealed by PCA analysis. The high levels of nitrates found in the study region are a result of various human-caused factors, including leaks from septic systems, the use of nitrogen-rich fertilizers, and waste from households, farming operations, and livestock. The hazard quotient (HQ) and total hazard index (THI) of F^- and NO₃^- showed high non-carcinogenic risk (> 1) via groundwater consumption, demonstrating a high potential risk to the local population. This study is significant because it is the most comprehensive examination of water quality, groundwater hydrogeochemistry, and health risk assessment in the Khushab district to date, and it will serve as a baseline for future studies. Some sustainable measures are urgent to reduce the F^- and NO₃^- content in the groundwater.

Identification and Risk Assessment of Priority Control Organic Pollutants in Groundwater in the Junggar Basin in Xinjiang, P.R. China

The Junggar Basin in Xinjiang is located in the hinterland of Eurasia, where the groundwater is a significant resource and has important ecological functions. The introduction of harmful organic pollutants into groundwater from increasing human activities and rapid socioeconomic development may lead to groundwater pollution at various levels. Therefore, to develop an effective regulatory framework, establishing a list of priority control organic pollutants (PCOPs) is in urgent need. In this study, a method of ranking the priority of pollutants based on their prevalence (Pv), occurrence (O) and persistent bioaccumulative toxicity (PBT) has been developed. PvOPBT in the environment was applied in the screening of PCOPs among 34 organic pollutants and the risk assessment of screened PCOPs in groundwater in the Junggar Basin. The results show that the PCOPs in groundwater were benzo[a]pyrene, 1,2-dichloroethane, trichloromethane and DDT. Among the pollutants, benzo[a]pyrene, 1,2-dichloroethane and DDT showed high potential ecological risk, whilst trichloromethane represented low potential ecological risk. With the exception of benzo[a]pyrene, which had high potential health risks, the other screened PCOPs had low potential health risks. Unlike the scatter distribution of groundwater benzo[a]pyrene, the 1,2-dichloroethane and trichloromethane in groundwater were mainly concentrated in the central part of the southern margin and the northern margin of the Junggar Basin, while the DDT in groundwater was only distributed in Jinghe County (in the southwest) and Beitun City (in the north). Industrial and agricultural activities were the main controlling factors that affected the distribution of PCOPs.

Geochemical fingerprint and spatial pattern of mine water quality in the Shaanxi-Inner Mongolia Coal Mine Base, Northwest China

The spatial distribution of mine water quality and geochemical controls must be investigated for water safety and ecosystem protection in Shaanxi-Inner Mongolian Coal Mine Base (SICMB). Based on 122 mine water samples collected from 14 mining areas, self-organizing maps (SOM) combining with principal component analysis (PCA) derived that the mine water samples were classified into seven clusters. Clusters 1 and 3 (C1 and C3) samples were dominant by HCO3-Ca and mixed types, which were distributed in the recharge area of the middle SICMB. In this area, the active groundwater circulation contributed to the good water quality. Cluster 2 (C2) samples were characterized by HCO3-Na type, mainly distributed in the discharge area of the middle SICMB. These samples were threatened by heavy fluorine contamination and high residual sodium carbonate (RSC) because of slow groundwater flow in this area. Clusters 4 and 5 (C4 and C5) samples, distributed in the northeast and middle SICMB, were characterized by high Cl- concentration and light fluorine contamination. They were influenced by anthropogenic input through faults or underground mining. In contrast, Clusters 6 and 7 (C6 and C7) samples with high salinity and sulfate were distributed in the southwest SICMB. The deep groundwater circulation enhanced water-rock interaction and contributed to poor water quality. These findings are beneficial to the management of mine water resources in the SICMB and provide an insight to investigate the mine water quality in large spatial scale.

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 100 µg/L, with an average value of 21.38 µg/L. Forty-two samples were beyond the acceptable limit of 10 µg/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^- > SO4^2- > 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).

Subsurface groundwater aquifer mapping and quality characterization in Matiari district, Sindh, Pakistan

Groundwater, is an alternative resource, is used as a supplement for irrigation as well as drinking purposes in Pakistan. This paper aims to determine the quantum and quality of groundwater in Matiari district of Sindh, Pakistan, through Electrical Resistivity Survey (ERS). The ERS was conducted at 52 location points using the ABEM Terrameter SAS 4000. The quantity of good quality groundwater has also been evaluated with ArcGIS interpolation techniques, i.e., the maximum percentage of fresh groundwater is 34% the marginal fresh groundwater 43% at the depth of with few patches of saline groundwater aquifers. Moreover, at 50-m depth, the percentage of fresh groundwater reduces to 21% and the marginal has increased to 48%. However, groundwater below the depth from 50 to 100 m was found only 8% fresh groundwater, 29% marginal, 49% salt water, and 14% high salt water. Analysis of groundwater samples for quality showed a good agreement with the quality obtained from VES results. In addition, a socio-economic survey of 55 tube well owners were conducted through interviews related to groundwater suitability and usage. According to the survey, about 62% of respondents are using good quality groundwater; however, 36% consuming the marginal and the remaining 2% are utilizing the hazardous quality of groundwater. The consumer satisfaction survey showed most farmers (89%) were satisfied with the groundwater usage, while 11% were unsatisfied due to poor-quality groundwater. The crop productivity could be enhanced through awareness and conjunctive use of marginal quality groundwater with the canal water.

Hydrochemical evaluation of water quality and its influencing factors in a closed inland lake basin of Northern China

Understanding the water quality and its influencing factors of different water bodies is essential for managing water resources in closed inland lake basins in semi-arid regions. However, generally, groundwater or surface water is assessed separately, and the differences among different water bodies are neglected. This study assessed the water quality and its influencing factors of different water bodies in the Daihai Lake Basin (a closed inland lake basin in a semi-arid region) by analysing the hydrochemical data of groundwater, and spring, river, and lake waters in the dry and wet seasons. The dominant hydrochemical type of groundwater (81.48%), spring water (80%), and river water (83.33%) was HCO3–Ca•Mg, while that of lake water was Cl-Na (100%). Groundwater, spring water, and river water were suitable for drinking and agricultural irrigation; however, the groundwater quality was worse in the wet season than in the dry season. Na+ and Cl– majorly affected the lake water quality. The mean NO3– concentration in groundwater was 28.39 mg/L, and its non-carcinogenic hazard quotient indicated that high risk areas were mainly distributed in Tiancheng and northern Maihutu. The hydrochemical compositions of groundwater, spring water, and river water were mainly influenced by rock (silicate and carbonate) weathering and cation exchange, and agricultural activities were the main sources of groundwater NO3–. Moreover, the lake hydrochemical composition was mainly affected by evaporation and halite dissolution. Thus, groundwater NO3– pollution and lake water salinisation should be prioritised. These findings provide a more thorough understanding of water quality and its influencing factors in the closed inland lake basin in the semi-arid region, and can be used to develop the protection of ecosystems and water resources management strategies in the Daihai Lake Basin.

Evaluation of Shallow Groundwater Quality at Regional Scales Using Adaptive Water Quality Indices

Groundwater, which is the main source of water for human consumption in many rural areas, has its quality determined by the complex interaction of environmental factors and anthropogenic activities. The present study evaluated the quality of shallow groundwater (1 to 25 m depth) in the rural area of the Târgovişte Plain, a densely populated area (200 inhabitants/km²) using 80 water samples collected from public wells. In order to explain the spatial distribution of the concentrations of the 19 physicochemical parameters considered (including heavy metals), the evaluation of groundwater quality for human consumption and potential impact on human health was conducted using the Water Quality Index (WQI), Integrated Weight Water Quality Index (IwWQI), Total Hazard Index (THI), and cumulative carcinogenic risk (CCR). For the WQI/IwWQI the comparative analysis of the two indices showed that for the WQI, it is important to select an optimal set of parameters, because use of a large number of physicochemical parameters can eclipse the values that exceed WHO guideline limits. In contrast, the use of entropy in the calculation of the IwWQI did not lead to eclipsing of exceedance, no matter the number of parameters used. Areas with poor and very poor groundwater quality according to the WQI/IwWQI overlapped, with a moderate risk to human health (THI > 1) for noncarcinogenic contaminants and also a risk of developing cancer according to the CCR average value (1.15 × 10^-2). The health of 43% of the rural population in the Târgovişte Plain can be affected if they drink contaminated groundwater, and it is estimated that about 600 people can develop cancer during their lifetime. If the risk of developing cancer is reduced only in the rural population that does not have access to a water source from a centralized and verified network, the results suggest that 385 people (1.15%) can develop cancer as a result of consuming groundwater contaminated with heavy metals based on the average value of CCR. This value is lower than the general mortality rate in areas with high CCR and below the average number of cancer patients in Romania (2.65%). The quality of groundwater and the risk of developing diseases and cancer due to water consumption is directly proportional to the intensity of agricultural land use and inversely proportional to the depth of the groundwater layer, the distance from the main hydrographic network and the reservoirs, and the distance from the main city, Târgovişte. The complex and integrated analysis of groundwater quality using quality indices and indicators of health risk for the population, validated by hot-spot analysis and compared to the mortality rate, is an approach with practical applicability. This integrated approach allows public authorities, policymakers, and health services to implement an efficient monitoring program and optimize anthropogenic activities in order to prevent groundwater contamination and finally improve the quality of life for the residents in the area of this study.

Characterisation of Hydro-Geochemical Processes Influencing Groundwater Quality in Rural Areas: A Case Study of Soutpansberg Region, Limpopo Province, South Africa

Groundwater is often the main or only source of fresh water supply in arid to semi-arid rural areas owing to decreasing rainfall patterns, reduced availability of surface water and socioeconomic activities. It is important to understand the hydro-geochemical processes influencing groundwater quality for improved management and sustainability of resources and to improve rural livelihoods. To understand the hydro-geochemical process influencing the hydro-geochemistry of the Soutpansberg region, this study assessed groundwater quality data from 12 boreholes and 2 geothermal springs collected between 1995 and 2017. This study indicated that the majority of the samples were classified as fresh groundwater dominated by Ca-HCO3 and mixed Ca-Mg-Cl types. Gibbs diagrams, Pearson correlations, bivariate plots and saturation indexes suggested that rock dominance processes, such as weathering of silicates, dissolution of carbonates and halite minerals and ion exchange processes, were the main hydro-geochemical processes influencing the groundwater quality in the Soutpansberg region. The high concentration of F− in the geothermal spring was attributed to the dissolution of fluorite mineral. Point source anthropogenic inputs from fertilisers were attributed to the high concentration of NO3− in the groundwater. This study recommends that research outputs should be used to influence and support policy change and groundwater allocation in arid to semi-arid rural environments for improved management of resources and livelihoods. This study further recommends that suitable deflouridation and denitrification techniques be applied to improve the quality of groundwater for drinking purposes.

A modified approach to quantify aquifer vulnerability to pollution towards sustainable groundwater management in Irrigated Indus Basin

The quality of groundwater in the study watershed has worsened because of industrial effluents and residential wastes from the urbanized cities; therefore, there is an important need to explore the aquifer vulnerability to pollution for sustainable groundwater management in the Irrigated Indus Basin (IIB). This study proposed a novel methodology to quantify groundwater vulnerability using two fully independent methodologies: the first by reintroducing an improved recharge factor (R) map and the second by incorporating three different weight and rating schemes into a traditional DRASTIC framework to improve the performance of the DRASTIC approach. In the current study, we composed a recharge map from Soil and Water Assessment Tool (SWAT) output (namely SWAT recharge map) with a drainage density map to retrieve an improved composite recharge map (SWAT-CRM). SWAT-CRM along with other thematic layers was combined using weightage overlay analysis to prepare the maps of groundwater vulnerability index (VI). The weight scale (w) and rating scale (r) were assigned based on a survey of available literature, and we then amended them using the analytical hierarchy process (AHP) and a probability frequency ratio (PFR) technique. Results depicted that the region under high groundwater vulnerability was found to be 5-22% using traditional recharge maps, while those are 9-23% using improved SWAT-CRM. The area under the curve (AUC) revealed that groundwater vulnerability zones predicted with SWAT-CRM outperformed the DRASTIC model applied with the traditional recharge map. Groundwater electrical conductivity (EC) was>2500 mS/cm in the high groundwater vulnerability zones, while it was <1000 mS/cm in the low groundwater vulnerability zones. The outcomes of this study can be used to improve the sustainability of the groundwater resources in IIB through proper land-use management practices.

Global diagnosis of nitrate pollution in groundwater and review of removal technologies

Clean water and sanitation for the world population is one of the most important challenges established by the Sustainable Development Goals of the United Nations since worldwide, one in three people do not have access to safe drinking water. Groundwater, one of the main sources of fresh water, has been considerably damaged by human activities. Nevertheless, while numerous plants are globally aimed at removing pollutants from surface waters, a much scarcer number of facilities have focused on groundwater remediation. Nowadays, there is increasing concern about the presence of nitrates (NO₃^-) in groundwaters as a consequence of the intensive use of fertilizers and other anthropogenic sources, such as sewage or industrial wastewater discharge. In this context, the selection and development of highly effective and low-cost solutions for the sustainable management of groundwater resources need to be addressed. Thus, this work collects data from the literature regarding the presence of nitrates in groundwater, and, simultaneously, it reviews the main alternatives available to remove NO₃^- from groundwater sources. A total of 292 sites have been analyzed categorized by continents, carefully discussing the possible origins of nitrate pollution. In addition, a discussion is carried out of the different technologies currently employed to treat groundwater, highlighting the progress made and the main challenges to be overcome. Finally, the review gathers the data available in the literature for nitrate treatment plants at full-scale.

Hydrogeochemical Assessment of Groundwater and Suitability Analysis for Domestic and Agricultural Utility in Southern Punjab, Pakistan

Groundwater is a critical water supply for safe drinking water, agriculture, and industry worldwide. In the Khanewal district of Punjab, Pakistan, groundwater has severely deteriorated during the last few decades due to environmental changes and anthropogenic activities. Therefore, 68 groundwater samples were collected and analyzed for their main ions and trace elements to investigate the suitability of groundwater sources for drinking and agricultural purposes. Principal component analysis (PCA) and cluster analysis (CA) were employed to determine the major factors influencing groundwater quality. To assess the groundwater’s appropriateness for drinking and irrigation, drinking and agricultural indices were used. The pH of the groundwater samples ranged from 6.9 to 9.2, indicating that the aquifers were slightly acidic to alkaline. The major cations were distributed as follows: Na+ > Ca2+ > Mg2+ > K+. Meanwhile, the anions are distributed as follows: HCO3− > SO42− > Cl− > F−. The main hydrochemical facies were identified as a mixed type; however, a mixed magnesium, calcium, and chloride pattern was observed. The reverse ion exchange process helps in exchanging Na+ with Ca2+ and Mg2+ ions in the groundwater system. Rock weathering processes, such as the dissolution of calcite, dolomite, and gypsum minerals, dominated the groundwater hydrochemistry. According to the Weight Arithmetic Water Quality Index (WAWQI), 50% of the water samples were unsafe for drinking. The Wilcox diagram, USSL diagram, and some other agricultural indices resulted in around 32% of the groundwater samples being unsuitable for irrigation purposes. The Khanewal’s groundwater quality was vulnerable due to geology and the influence of anthropogenic activities. For groundwater sustainability in Khanewal, management strategies and policies are required.

Hydrogeochemical Investigation of Elevated Arsenic Based on Entropy Modeling, in the Aquifers of District Sanghar, Sindh, Pakistan

Arsenic (As) contamination in drinking groundwater is a common environmental problem in Pakistan. Therefore, sixty-one groundwater samples were collected from various groundwater sources in District Sanghar, Sindh province, Pakistan, to understand the geochemical behavior of elevated As in groundwater. Statistical summary showed the cations and anions abundance in decreasing order of Na+ > Ca2+ > Mg2+ > K+, and HCO3− > Cl− > SO42− > NO3−. Arsenic was found with low to high concentration levels ranging from 5 µg to 25 µg/L with a mean value of 12.9 µg/L. A major water type of groundwater samples was mixed with NaCl and CaHCO3 type, interpreting the hydrochemical behavior of rock–water interaction. Principal component analysis (PCA) showed the mixed anthropogenic and natural sources of contamination in the study area. Moreover, rock weathering and exchange of ions controlled the hydrochemistry. Chloro-alkaline indices revealed the dominance of the reverse ion exchange mechanism in the region. The entropy water quality index (EWQI) exposed that 17 samples represent poor water, and 11 samples are not suitable for drinking.

Shallow Groundwater Quality Assessment and Its Suitability Analysis for Drinking and Irrigation Purposes

For shallow groundwater, hydrogeochemical processes and quality assessment must be addressed because shallow groundwater is freely available in many parts of the globe. Due to recent anthropogenic activities and environmental changes in Sakrand, Sindh, Pakistan, the groundwater is extremely vulnerable. To provide safe drinking and agricultural water, hydrogeochemical analysis is required. Ninety-five groundwater samples were analyzed using agricultural and drinking indices to determine the hydrogeochemical parameters using multivariate analysis such as Pearson correlations, principal component cluster analysis, as well as Piper diagrams and Gibbs plot for drinking and agricultural indices. An abundance of ions was observed through the statistical summary; however, cations and anions were recorded in the orders Na+ > Ca2+ > Mg2+ > K+ and HCO3− > Cl− > SO42− > NO3− > F−. The hydrogeochemical process used to quantify the major reactions occurring in the groundwater system showed rock dominance; the Piper diagrams evaluated the water type. A mixed pattern of calcium, magnesium, and chloride ions (Ca2+−Mg2+−Cl− type) was observed. Additionally, the ion exchange method showed an excess of bicarbonate ions due to carbonic acid weathering. The water quality index (WQI) resulted 32.6% of groundwater being unsuitable for human consumption; however, the United States Salinity Laboratory (USSL) diagram showed 60% of samples were unsuitable for irrigation due to high salinity and the Wilcox diagram depicted 5% of samples lying in the unsuitable region. Most of the water samples were suitable for drinking; only a few samples were unsafe for drinking purposes for children due to the high hazard index.

Identification of Natural and Anthropogenic Geochemical Processes Determining the Groundwater Quality in Port del Comte High Mountain Karst Aquifer (SE, Pyrenees)

The Port del Comte Massif (SE, Pyrenees) contains one of the most important vulnerable and strategic karst aquifers for supplying freshwater to the city of Barcelona (Spain). It is a fragile system, whose possible environmental impact is highly conditioned by land use. To improve the hydrogeological knowledge of the system, between September 2013 and October 2015, a detailed fieldwork was carried out for the revision of the geological model, the inventory of water points, and the in situ physico-chemical characterization on major elements and isotopes of up to a total of 43 springs, as well as precipitation water. This paper focuses on the characterization of the geochemical processes that allow explanation of the observed chemical variability of groundwater drained by the pristine aquifer system to determine the origin of salinity. The results show that the main process is the dissolution of calcite and dolomite, followed by gypsum and halite, and a minor cation exchange-like process. Sulfur and oxygen isotopes from dissolved sulfate in the studied springs point out a geogenic origin related to the dissolution of gypsum from Triassic and Tertiary materials, and that the contribution from anthropogenic sources, like fertilizers, is lower. Nitrate in groundwater is not an important issue, with a few localized cases related with agricultural activities. The multidisciplinary approach has allowed the development of a consistent hydrogeological conceptual model of the functioning of the aquifer system, which can be replicated in other places to understand the geogenic character of the hydrogeochemistry.

Occurrence, Geochemistry and Speciation of Elevated Arsenic Concentrations in a Fractured Bedrock Aquifer System

The presence of elevated arsenic concentrations (≥ 10 µg L^-1) in groundwaters has been widely reported in areas of South-East Asia with recent studies showing its detection in fractured bedrock aquifers is occurring mainly in regions of north-eastern USA. However, data within Europe remain limited; therefore, the objective of this work was to understand the geochemical mobilisation mechanism of arsenic in this geologic setting using a study site in Ireland as a case study. Physicochemical (pH, Eh, d-O₂), trace metals, major ion and arsenic speciation samples were collected and analysed using a variety of field and laboratory-based techniques and evaluated using statistical analysis. Groundwaters containing elevated dissolved arsenic concentrations (up to 73.95 µg L^-1) were characterised as oxic-alkali groundwaters with the co-occurrence of other oxyanions (including Mo, Se, Sb and U), low dissolved concentrations of Fe and Mn, and low Na/Ca ratios indicated that arsenic was mobilised through alkali desorption of Fe oxyhydroxides. Arsenic speciation using a solid-phase extraction methodology (n = 20) showed that the dominant species of arsenic was arsenate, with pH being a major controlling factor. The expected source of arsenic is sulphide minerals within fractures of the bedrock aquifer with transportation of arsenic and other oxyanion forming elements facilitated by secondary Fe mineral phases. However, the presence of methylarsenical compounds detected in groundwaters illustrates that microbially mediated mobilisation processes may also be (co)-occurring. This study gives insight into the geochemistry of arsenic mobilisation that can be used to further guide research needs in this area for the protection of groundwater resources.

Hydrogeochemical facies and pollution status of groundwater resources of Owerri and environs, Southeastern Nigeria

The aim of the study was to assess the status of groundwater quality of Owerri and environs, for drinking and irrigation purposes. Twenty-two (22) groundwater samples were collected and analyzed for both chemical and physical compositions. The result of the study showed that groundwater in the area is of good quality for drinking purposes, except for pH and Fe, which had higher concentrations in some areas. A weak correlation matrix within the sampled parameters of the groundwater was observed. Hydrogeochemical studies revealed that 91% of the samples are within the geochemical zone of 4 (strong acids (SO₄ + Cl) exceed weak acids (CO₃ + HCO₃)), while 9% are of the geochemical zone of 3 (weak acids (CO₃ + HCO₃) exceed strong acids (SO₄ + Cl)). The study shows an ionic trend of Cl^-  > Ca²⁺  > HCO₃^-  > Na⁺  + K⁺  > Mg²⁺  > SO₄^2- and hydrogeochemical facies of Na-Cl, Ca-Cl, Ca-CO₃, Mg-Cl, and Mg-HCO₃ of 45.5%, 36.4%, 4.5%, 4.5%, and 9.1% respectively. Chloro-alkaline values were negative except for B4 which was positive. The water quality index (WQI) revealed water quality status of excellent (4.5%), good (27.3%), poor (40.9%), and very poor (27.3%). Contamination factor (CF) reveals that the groundwater is slightly polluted while the pollution load index (PLI) revealed no noticeable pollution. Gibbs diagram revealed that the entire samples are within the rock dominance zone. Irrigation suitability studies showed that SAR of the groundwater was of excellent quality; %Na had good quality (27.3%), permissible quality (45.4%), and doubtful quality (27.3%); MH had 86.4% of the groundwater suitable, while 13.6% are not suitable; KR had suitable groundwater (59.1%) and unsuitable (40.9%); while the Wilcox diagram had 72.7% excellent water for irrigation and 27.3% permissible for irrigation. A routine check of groundwater in the study area is recommended.

Evaluation of Groundwater Using an Integrated Approach of Entropy Weight and Stochastic Simulation: A Case Study in East Region of Beijing

Groundwater is an important source of water in Beijing. Hydrochemical composition and water quality are the key factors to determine the availability of groundwater. Therefore, an improved integrated weight water quality index approach (IWQI) combining the entropy weight method and the stochastic simulation method is proposed. Through systematic investigation of groundwater chemical composition in different periods, using a hydrogeochemical diagram, multivariate statistics and spatial interpolation analysis, the spatial evolution characteristics and genetic mechanism of groundwater chemistry are discussed. The results show that the groundwater in the study area is weakly alkaline and low mineralized water. The south part of the study area showed higher concentrations of total dissolved solids, total hardness and NO3--N in the dry season and wet season, and the main hydrochemical types are HCO3--Ca and HCO3--Ca-Mg. The natural source mechanism of the groundwater chemical components in Chaoyang District includes rock weathering, dissolution and cation exchange, while the human-made sources are mainly residents and industrial activities. Improved IWQI evaluation results indicate that water quality decreases from southwest to northeast along groundwater flow path. The water quality index (WQI) method cannot reflect the trend of groundwater. Sensitivity analysis indicated that the improved IWQI method could describe the overall water quality reliably, accurately and stably.

Groundwater quality for potable and irrigation uses and associated health risk in southern part of Gu'an County, North China Plain

The study area is a part of the North China Plain, where groundwater is heavily abstracted for drinking and irrigation purposes. Groundwater quality is adversely affected due to rapid economic development and urbanization. Therefore, the purposes of this study were to evaluate the suitability of groundwater for drinking and irrigation purposes and to quantify the associated human health risks in the southern part of Gu'an County, North China Plain. The matter-element extension method based on entropy weight was used to evaluate the water quality for drinking, while sodium adsorption ratio, sodium percentage (%Na), residual sodium carbonate and magnesium hazard were used to evaluate the water quality for irrigation. Non-carcinogenic and carcinogenic health risks via different exposure ways were evaluated for different age groups. The study found that the quality of both deep and shallow groundwater in this area was generally suitable for drinking. Deep water quality has better quality than the shallow water. However, 8.70% and 73.92% of water samples pose non-carcinogenic health risks on adults and children, respectively. Children and adults are also at cancer risk due to Cr⁶⁺ and As in drinking groundwater in this area. The main responsible parameters for non-carcinogenic risk are Cr⁶⁺, F^- and Fe, and Cr⁶⁺ is also responsible for carcinogenic risk. These toxic elements are mainly from industries. Therefore, deterioration of groundwater quality can be prevented by strengthening the sewage management of various industries.

Hydrogeochemical and health risk evaluation of arsenic in shallow and deep aquifers along the different floodplains of Punjab, Pakistan

The current study delineated the distribution, (hydro)geochemical behavior and health risk of arsenic (As) in shallow (depth < 35 m; handpumps and electric pumps) and deep (depth > 35 m; tube wells) aquifers in five areas along the Indus River (Bhakar, Kallur Kot), Jhelum River (Jhelum) and Chenab River (Hafizabad, Gujranwala) floodplains of Punjab, Pakistan. Relatively, greater As concentration was observed in deep wells (mean: 24.3 µg L^-1) compared to shallow wells (19.4 µg L^-1), with groundwater As spanning 0.1-121.7 µg L^-1 (n = 133) in three floodplains. Groundwater from Hafizabad (Chenab River floodplain) possessed the highest As (121.7 µg L^-1), Na⁺ (180 mg L^-1), Ca²⁺ (95 mg L^-1), Cl^- (101 mg L^-1) and SO₄^2- (1353 mg L^-1) concentrations. Arsenic health risk modeling indicated the potential carcinogenic (value > 10^-4) and non-carcinogenic (hazard quotient > 1.0) risks for groundwater of all areas, with the utmost risk estimated for Chenab floodplain and deep aquifers. Positive saturation index values for Fe oxide mineral phases may suggest their potential role in As mobilization/release in these aquifer environments. This study provides critically-important and baseline knowledge for a widespread groundwater As examination along these three floodplains, which is vital for launching suitable As mitigation and remediation programs to reduce the potential health risk.

Groundwater Quality Characterization in an Overallocated Semi-Arid Coastal Area Using an Integrated Approach: Case of the Essaouira Basin, Morocco

In this study, hydrogeochemical analyses were combined with geographic information system (GIS) tools to investigate salinization sources of groundwater in the downstream part of the Essaouira basin, and to analyze the spatiotemporal trends in groundwater quality. To assess groundwater suitability for drinking purposes, the quality of sampled water was compared with the World Health Organization (WHO) and the Moroccan guidelines. Wilcox and US salinity laboratory (USSL) diagrams were used to evaluate groundwater suitability for irrigation. Hydrogeochemical analyses revealed that groundwater is of Na-Cl and Ca-Mg-Cl types. The analyses of the correlation between the chemical elements showed that the water–rock interaction and the reverse ion exchange are the major processes impacting groundwater degradation in the study area. The study of groundwater suitability for drinking and irrigation purposes shows that groundwater quality in the study area is permissible, but not desirable for human consumption. Additionally, groundwater is permissible for agricultural use but with high-salinity hazards. The spatial distribution of the physicochemical elements shows a general upward gradient from the north to the south and from the east to the west. The trend in groundwater quality during the last five years shows a shifting in the quality from the mixed Ca-Mg-Cl to the Na-Cl type.

Hydrochemical composition and potentially toxic elements in the Kyrgyzstan portion of the transboundary Chu-Talas river basin, Central Asia

Water chemistry and the assessment of health risks of potentially toxic elements have important research significance for water resource utilization and human health. However, not enough attention has been paid to the study of surface water environments in many parts of Central Asia. Sixty water samples were collected from the transboundary river basin of Chu-Talas during periods of high and low river flow, and the hydrochemical composition, including major ions and potentially toxic elements (Zn, Pb, Cu, Cr, and As), was used to determine the status of irrigation suitability and risks to human health. The results suggest that major ions in river water throughout the entire basin are mainly affected by water-rock interactions, resulting in the dissolution and weathering of carbonate and silicate rocks. The concentrations of major ions change to some extent with different hydrological periods; however, the hydrochemical type of calcium carbonate remains unchanged. Based on the water-quality assessment, river water in the basin is classified as excellent/good for irrigation. The relationship between potentially toxic elements (Zn, Pb, Cu, Cr, and As) and major ions is basically the same between periods of high and low river flow. There are significant differences between the sources of potentially toxic elements (Zn, Pb, Cu, and As) and major ions; however, Cr may share the same rock source as major ions. The risk assessment revealed low non-carcinogenic and carcinogenic risks for human health; however, the maximum carcinogenic risk for As exceeded the allowable value, which requires further consideration. These results provide a scientific basis for the management of agricultural irrigation uses and also infill existing gaps regarding the hydrochemical composition in the Chu-Talas river basin, Central Asia.

Hydrochemical Characterization and Suitability Assessment of Groundwater Quality in the Saboba and Chereponi Districts, Ghana

Hydrochemical data of groundwater samples obtained from the mudstones, sandstones, and siltstones aquifer units that underlie the study area have been characterized. The aim of this study was to assess the suitability of groundwater for drinking, domestic, and agricultural purposes. The physico-chemical parameters were initially compared with the World Health Organization (WHO) standards for potable water. They were further subjected to various hydrochemical techniques to assess the overall water quality for drinking purposes. Conventional methods of assessing irrigation water suitability were also adopted. The results indicate that, with the exception of HCO3− characterized as unsuitable for drinking water, most of the parameters are within the WHO permissible limits and are thus characterized as suitable for drinking water. A few samples however show slight deviation. The results also show that the abundance of major cations in groundwater is in the order: Na+ > Ca2+ > Mg2+ > K+. However, the abundance of the major anions is in the order: HCO3− > Cl− > SO42−. Na-HCO3 is thus inferred as the dominant water type in the area. Analyses of the overall Water Quality Index (WQI) and irrigation water assessment indices suggest that groundwater in the area is generally suitable for drinking, domestic, and irrigation purposes.

Heavy Metals and Related Human Health Risk Assessment for River Waters in the Issyk-Kul Basin, Kyrgyzstan, Central Asia

The water resources of Central Asia play an important role in maintaining the fragile balance of ecosystems and the sustainable development of human society. However, the lack of research on the heavy metals in river waters has a far−reaching influence on public health and the sustainable development in Central Asia. In order to reveal the possible sources of the heavy metals and to assess the associated human health risks, thirty−eight water samples were collected from the rivers of the Issyk−Kul Basin during the period with low river flow (May) and the period with high river flow (July and August), and the hydrochemical compositions and major ions of heavy metals were analyzed. No changes in hydrochemical facies were observed between the two periods and the river water type was calcium bicarbonate. Carbonate dissolution and silicate weathering controlled the variation of cations and anions in river waters from the Issyk−Kul Basin. There were some differences in the sources of heavy metals in water bodies between the two periods. During the period with low river flow, heavy metals (Cr) were closely clustered with major ions, indicating that they were mainly affected by water–rock interactions. During the period with high river flow, all heavy metals studied in this paper had different sources of major ions, and the heavy metals maybe influenced by human activities. From the human health risk assessment, the hazard quotients for all samples were less than 1, reflecting that there was no noncarcinogenic risk in the river waters of the Issyk−Kul Basin during the two sampling periods. However, the water samples with carcinogenic risk of arsenic exceeding the threshold (10⁻⁴) accounted for 21.1% of the total, indicating that there were some certain carcinogenic hazards for human health via water drinking with direct oral ingestion. The results are of certain significance for the utilization and protection of water resources in the basin as well as the protection of public health.

Stable H-O Isotopic Composition and Water Quality Assessment of Surface Water and Groundwater: A Case Study in the Dabie Mountains, Central China

In order to understand the water cycle and assess the water quality for irrigation purposes in the Upper Pi River Basin (UPRB), which is the northern slope of the Dabie Mountains, 68 surface water and groundwater samples were collected and analyzed for H-O isotopes and hydrochemistry during the high-flow season in 2017 and 2018. The results show that ranges of hydrogen and oxygen isotopic composition (δ²H: −68.8‰ to −40.8‰, δ¹⁸O: −10.05‰ to −5.05‰) are controlled by the medium latitude and high altitude of the UPRB. Among different types of water, the δ²H and δ¹⁸O values can be ordered as follows: reservoir water < spring water ≈ river water < pond water. The water of the upstream medium and small reservoir is enriched with lighter isotopes that is likely related to more exchange with rainwater and less residence time; however, large reservoirs are similar to the upstream river and spring in terms of the H-O isotopic composition. Hydro-chemical facies are dominated by the Ca-HCO₃ type in the UPRB, which reflects fresh recharged water from rainfall, and few samples are of the Ca-Cl type that is caused by intensive evaporation. The water quality for irrigation purposes was also evaluated. According to the Wilcox diagram, United States Salinity Laboratory (USSL) diagram, magnesium hazard, and Kelly’s ratio, all water samples have been considered suitable for irrigation water.