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

Patterns of spatiotemporal variations in the hydrochemistry and controlling factors of bedrock aquifers in the northern region of the Linhuan mining area

Systematically studying the hydrochemical evolution of bedrock groundwater in mining areas during mining process is crucial for effective groundwater resource management and coal mine production. The spatiotemporal characteristics and hydrochemical evolution patterns of the Permian fractured sandstone aquifer (PA) and the Carboniferous Taiyuan Formation limestone aquifer (CTA), both of which are directly associated with coal mining in the northern Linhuan mining area, China, were investigated using multivariate statistical analyses, hydrochemical graphical methods, ion ratio analysis, and a conceptual model. 72 groundwater samples, collected before and after mining, were classified into four groups by hierarchical cluster analysis (HCA). Principal component analysis (PCA) and ion ratio analysis indicated that water-rock interactions involve mineral dissolution (carbonates, gypsum, dolomite, silicates), cation exchange, and common ion effects. Hydrochemical evolution is influenced by bedrock paleotopography, aquifer hydraulic conductivity, and mining drainage. Paletopographic differences significantly influence water-rock interactions and spatial variability in hydrochemistry, with ion concentrations in groundwater increasing as paleotopographic elevation decreases. The pattern of hydraulic conductivity reflects the control exerted by variations in aquifer characteristics on mineral dissolution, leading to minor changes in hydrochemical characteristics. Mining activities disrupt the aquifer's reducing environment, resulting in a significant increase in groundwater SO42- concentration. These findings provide insights and a solid theoretical foundation for studying the hydrochemical variations patterns of groundwater and these control mechanisms in the hidden coal fields of North China.

Hydrogeochemistry and prediction of arsenic contamination in groundwater of Vehari, Pakistan: comparison of artificial neural network, random forest and logistic regression models

Arsenic contamination in the groundwater occurs in various parts of the world due to anthropogenic and natural sources, adversely affecting human health and ecosystems. The current study intends to examine the groundwater hydrogeochemistry containing elevated arsenic (As), predict As levels in groundwater, and determine the aptness of groundwater for drinking in the Vehari district, Pakistan. Four hundred groundwater samples from the study region were collected for physiochemical analysis. As levels in groundwater samples ranged from 0.1 to 52 μg/L, with an average of 11.64 μg/L, (43.5%), groundwater samples exceeded the WHO 2022 recommended limit of 10 μg/L for drinking purposes. Ion-exchange processes and the adsorption of ions significantly impacted the concentration of As. The HCO3- and Na+ are the dominant ions in the study area, and the water types of samples were CaHCO3, mixed CaMgCl, and CaCl, demonstrating that rock-water contact significantly impacts hydrochemical behavior. The geochemical modeling indicated negative saturation indices with calcium carbonate and other salt minerals, encompassing aragonite, calcite, dolomite, and halite. The dissolution mechanism suggested that these minerals might have implications for the mobilization of As in groundwater. A combination of human-induced and natural sources of contamination was unveiled through principal component analysis (PCA). Artificial neural networks (ANN), random forest (RF), and logistic regression (LR) were used to predict As in the groundwater. The data have been divided into two parts for statistical analysis: 20% for testing and 80% for training. The most significant input variables for As prediction was determined using Chi-squared analysis. The receiver operating characteristic area under the curve and confusion matrix were used to evaluate the models; the RF, ANN, and LR accuracies were 0.89, 0.85, and 0.76. The permutation feature and mean decrease in impurity determine ten parameters that influence groundwater arsenic in the study region, including F-, Fe2+, K+, Mg2+, Ca2+, Cl-, SO42-, NO3-, HCO3-, and Na+. The present study shows RF is the best model for predicting groundwater As contamination in the research area. The water quality index showed that 161 samples represent poor water, and 121 samples are unsuitable for drinking. Establishing effective strategies and regulatory measures is imperative in Vehari to ensure the sustainability of groundwater resources.

Hydrochemistry, quality, and integrated health risk assessments of groundwater in the Huaibei Plain, China

Groundwater is an essential freshwater resource utilized in industry, agriculture, and daily life. In the Huaibei Plain (HBP), where groundwater significantly influences socio-economic development, information about its quality, hydrochemistry, and related health risks remains limited. We conducted a comprehensive groundwater sampling in the HBP and examined its rock characteristics, water quality index (WQI), and potential health risks. The results revealed that the primary factors shaping groundwater hydrochemistry were rock dissolution and weathering, cation exchange, and anthropogenic activities. WQI assessment indicated that only 73% of the groundwaters is potable, as Fe2+, Mn2+, NO3-, and F- contents in the water could pose non-carcinogenic hazards to humans. Children were more susceptible to these health risks through oral ingestion than adults. Uncertainty analysis indicated that the probabilities of non-carcinogenic risk were approximately 57% and 31% for children and adults, respectively. Sensitivity analysis further identified fluoride as the primary factor influencing non-carcinogenic risks, indicating that reducing fluoride contamination should be prioritized in future groundwater management in the HBP.

Geospatial assessment of groundwater quality using entropy-based irrigation water quality index and heavy metal pollution indices

Groundwater contamination has become a serious environmental threat throughout the world in the era of Anthropocene. Thus, the present study examined the groundwater quality for irrigation purposes based on the entropy method and heavy metal pollution indices. To compute the entropy-based groundwater irrigation quality index (EIWQI), physicochemical parameters such as pH, chloride (Cl-) and nitrate (NO3-), irrigation indices including electrical conductivity (EC), sodium absorption ratio (SAR), sodium percentage (%Na), soluble sodium percentage (SSP), residual sodium carbonate (RSC), magnesium hazard (MH), Kelley's ration (KR), permeability index (PI) and heavy metals such as manganese (Mn), iron (Fe), zinc (Zn) and arsenic (As) have been employed for the 37 sample wells of the Damodar fan delta (DFD), India, which is a semi-critical agriculture-dominated region. Shannon's entropy method has been used to assign the weights of the different parameters for constructing the EIWQI. The results portray a spatial variation of the irrigation water quality in the DFD. The EIWQI revealed that 27.03%, 59.46%, 8.11%, 2.7% and 2.7% of the sample wells, respectively, contain excellent, good, moderate, poor and very poor quality of irrigation water. On the other hand, heavy metal pollution indices (modified degree of contamination, pollution load index, Nemerow index and modified heavy metal pollution index) show that 15-20% of sample wells of the DFD are contaminated by heavy metal pollution. The pockets of pollution are concentrated in the southwestern, northeastern and central parts of the DFD. The study found that the spatial variation in groundwater quality is controlled by the higher sodium concentration, carbonate weathering and expansion of agricultural and urban-industrial areas.

Groundwater chemistry and entropy weighted water quality index of tsunami affected and ecologically sensitive coastal region of India

Quality groundwater is the most essential prerequisite for the better livelihood of the coastal villages and a vital resource for a safe living. Seawater interaction and coastal inundation modify hydro geochemical cycles leading to gross utility as a challenge. Poor quality water intake causes diseases and seriously affects human health. In this study, the suitability of shallow drinking water sources (10-15 m) has been studied with a focus on coastal village in south west of India (Alappad coast, Kollam, Kerala) which is a host of huge placer mineral reserve of the country. This coastal stretch has good deposition of Late Quaternary sediments of heavy mineral placers subjected to severe seawater interactions. Mineralogically, garnet and heavy minerals comprises the beaches and most coastal plains of the Alappad. A concerted geological process where moving water and waves causes erosion, leads to lowering of the earth's surface -is prominent in this fragmented land. This study critically evaluates the temporal-spatial impact of these interactions in an age of varying climatic conditions and hence for reference beyond. Water quality index analysis has been attempted using the entropy weighted water quality index (EWQI) method for a total of 45 samples (15 samples season-wise). It aims to ascertain better choices of groundwater sources for domestic uses for isolated settlers endowed with estuaries, and old coastal plains with barrier beaches. Irrigation suitability was evaluated using sodium adsorption ratio (SAR) and Na%. Observed EWQ Indices (38.2 ± 14.5) for post-monsoon (80% samples), (66.1 ± 77.7) for monsoon (66% samples), and (71.4 ± 71.3) for pre-monsoon (53% samples) fall in excellent category. Post-monsoon is most favoured for a better quality groundwater as evidenced by WQI of 80% among the samples tested. Ca-HCO3 is the dominant hydrochemical type observed. The mean value of iron (0.9 ± 1.3 mg/L) exceeded the permissible limit of 0.3 mg/L during monsoon season due to mineral-water interactions. In pre-monsoon season the parameters Na+ (95.9 ± 200.7 mg/L), Cl- (173.4 ± 510.2 mg/L), EC (1559.3 ± 2510.6 μS/cm), and TDS (492.5 ± 629.7 mg/L) were observed in higher ranges. Significant correlation (p < 0.05) prevailed between EWQI, and parameters-conductivity (0.75), TDS (0.75), Iron (0.59), Ca2+ (0.66), and Mg2+ (0.74). Principal component analysis (PCA) on chemical parameters accounted for the total variance of 84.2% in pre-monsoon, 89.9% in monsoon and 82.9% in post-monsoon. Groundwater quality is influenced by geochemical processes, salt intrusion, and human activities like fertiliser application and domestic sewage discharge. Hierarchical cluster analysis (HCA) grouped the samples into three clusters. Cluster 3 represents poor quality water (13%) in pre-monsoon (EWQI ranged 32.2-192.7), and monsoon (EWQI ranged 171.8-309.7). Cluster 3 in post-monsoon (20%) indicating good water quality (EWQI ranged 51.4-72.6). Ultimate finding is that post-monsoon groundwater is more suitable for drinking and domestic purposes for the selected coastal area.

An appraisal to hydrochemical characterization, source identification, and potential health risks of sulfate and nitrate in groundwater of Bemetara district, Central India

Gypsum-enriched aquifers (GEA) and intensive agriculture regions (IAR) in semi-arid regions are responsible for very high amounts of sulfate and nitrate in many groundwater systems of the world, respectively. However, in such regions, the problem of nitrate pollution and its associated health risk has been increasing and emerging as a global issue. However, along with nitrate, sulfate contamination and its potential health risks are often neglected worldwide in these regions. Therefore, considering sulfate along with nitrate as a significant threat to water quality in such regions, this study aimed to characterize hydrochemistry, factors controlling groundwater quality, and assessment of risk to human health. To accomplish this objective, 116 groundwater samples were collected over pre-monsoon (PRM) and post-monsoon (POM) (2019) seasons in Bemetara district. As per Bureau of Indian standards (BIS) for drinking, SO42- (28 and 19%) and NO3- (7 and 35%) exceeded the permissible limits in PRM and POM seasons, respectively; thereby, groundwater was not suitable for drinking. SO42- and NO3- pollution sources were identified and mainly attributed to gypsum dissolution and agricultural activities as well as domestic sewage discharge, respectively. In addition, SO42-and NO3- risk assessment results show that total 20% to 46% of all samples surpassed the permissible limit (HQ = 1) of risk to children and adults, over both seasons. To ensure drinking water security in this region, sustainable management of agricultural activities and treatment should be done to reduce the potential health risks due to SO42- and NO3-.

Assessment of Bacteriological Quality and Physiochemical Parameters of Domestic Water Sources in Jenin Governorate: A Case Study

Water quality of drinking water is a concern in Palestine due to possible pollution sources. There is a demand for investigating the quality of municipal water supply. This study aimed to assess the quality of domestic water in Jenin Governorate located in the north of the West Bank. The methodology of this research was based on field sampling and laboratory standard testing. The tested parameters included (1) physicochemical parameters of electrical conductivity, turbidity, total hardness, salinity, pH, and total alkalinity, (2) chemical contents including the contents of nitrate, nitrite, sulfate, chloride, sodium, potassium, aluminum, and fluoride, and (3) biological contents including total coliforms and fecal coliforms. The water quality parameters were compared with the acceptable limits set by local and international standards. The findings confirm that most of the values of the investigated parameters are within the acceptable standard limits. No pollution of heavy metals is detectable. On the other hand, there are limited pollution contents in terms of the total dissolved solid (TDS), total hardness, and calcium. Furthermore, the biological parameters indicate that there are low to very high risks in a fraction of the water quality samples in terms of total coliforms and fecal coliforms. This is believed to be due to the presence of septic tanks in the neighborhoods of the sampling locations. For these cases, biological disinfection treatments are recommended before human use with an essential need for the construction of urban sewer systems. Furthermore, water treatment for harness removal may be required.

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.

Groundwater quality, heavy metal pollution, and health risk assessment using geospatial techniques and index methods in Eber wetland and surroundings (Afyonkarahisar/Turkey)

The continuous increase in the demand for water and the scarcity of water to be used as drinking water have made groundwater even more important. The study area, Eber wetland, is located in the Akarçay river basin, which is one of the most important river basins in Turkey. The groundwater quality and heavy metal pollution were investigated in the study using index methods. In addition, health risk assessments were performed. Ion enrichment was determined at locations E10, E11, and E21 related to water-rock interaction. In addition, nitrate pollution was observed in many samples due to agricultural activities and also fertilizer application in the areas. The water quality index (WOI) values of the groundwaters vary between 85.91 and 201.77. In general, groundwater samples located around the wetland were in the "poor water" class. According to the values for the heavy metal pollution index (HPI), all the groundwater samples are suitable for use as drinking water. They are also classified as "low pollution" according to the heavy metal evaluation index (HEI) and the value/degree of contamination (Cd). In addition, since the water is been used for drinking by the people in the area, a health risk assessment was performed to ascertain As and NO₃. It was determined that the R_cancer values calculated for As were considerably higher than the tolerable/acceptable values for both adults and children. The results obtained clearly show that the groundwater should not be used as drinking water.

Assessment of water quality, trace metal pollution, source apportionment and health risks in the groundwater of Chakwal, Pakistan

Groundwater quality evaluation is the main concern in the regions like Chakwal where it is major source of water for drinking and irrigation due to low storage capacity of the surface water and lack of proper irrigation system. The aim of the present study was to evaluate various physicochemical parameters (pH, EC, TDS, DO, TA, TH and chlorides) and selected essential/toxic trace metal concentrations (Na, K, Ca, Mg, Sr, Li, Ag, Zn, Fe, Cu, Co, Mn, Cr, Cd, and Pb) in order to explore their distribution, correlation, spatial variations and health risk assessment. Average concentration of some trace metals (Co, Cd and Pb) and physicochemical parameters (EC, TDS, and alkalinity) were found to exceed the national/international standards. Multivariate methods of analysis showed strong associations among Fe-Li-K, Sr-Mg-Ca, Cd-Mn, Cu-Zn, Ag-Co, and Cr-Pb-Na which were significantly contributed by anthropogenic activities. Irrigation water quality index exhibited intermediate suitability of the groundwater for irrigation purpose. Health risk evaluation of the trace metals revealed significant non-carcinogenic risks for Cd, Co and Pb (HQ_ing > 1) especially for children. Similarly, significant carcinogenic risk was found to be associated with Pb and Cr which exceeded the safe limit, suggesting the lifetime carcinogenic risk associated with these metals in the groundwater. The present health risk problems should be considered on top priority and immediate actions should be taken to safeguard the water quality in the study area.

Tracking anthropogenic nitrogen-compound sources of surface and groundwater in southwestern Nile Delta: hydrochemical, environmental isotopes, and modeling approach

This research aims to assign the specific and potential sources that control migration and transformation mechanisms of ammonium/nitrate contaminants of surface and groundwater systems in the southwestern Nile Delta, Egypt. To achieve that, an integration of hydrogeochemistry, multiple environmental stable isotopes (δ²H-H₂O, δ¹⁸O-H₂O, δ¹⁵N-NH₄, and δ¹⁵N-NO₃) coupled with three-dimensional nitrogen transport numerical model (MODFLOW-MT3D) was done. A set of representative water samples (20 canals and drainage water) and 14 groundwater samples were collected and analyzed for physical, chemical, and stable isotope analysis. NH₄⁺ and NO₃^- concentrations in surface water samples varied from 0.29 to 124 mg/l and 0.52 to 39.67 mg/l, respectively. For groundwater samples, NH₄⁺ and NO₃^- concentrations varied from 0.21 to 1.75 mg/l and 0.33 to 32.8 mg/l, respectively. Total risk quotient (THQ) level of nitrate (oral and dermal effects) from drinking water exceeds unity for all water samples indicating a potential noncancer risk for the southwestern Nile Delta residents. The potential sources of nitrogen compound pollution are water from sewage treatment plants used for irrigation, sludge and animal manure, septic tanks, soil nitrogen, and artificial fertilizers according to results of δ¹⁵N values. Results of ammonium/nitrate modeling in shallow groundwater aquifers are compared with observed concentrations and are found to be in good agreement. Some recommendations are given to decrease nitrogen loads in the study area through suggested a need for adoption of N-fertilizer management practices and treatment of sewage water before to application in agricultural activities.

Covalently Functionalized Cellulose Nanoparticles for Simultaneous Enrichment of Pb(II), Cd(II) and Cu(II) Ions

Cellulose nanoparticles are sustainable natural polymers with excellent application in environmental remediation technology. In this work, we synthesized cellulose nanoparticles and covalently functionalized them with a multi-functional group possessing ligands. The hybrid material shows excellent adsorption properties for the simultaneous extraction of multiple metal ions in the sample preparation technique. The sorbent shows excellent sorption capacity in the range of 1.8-2.2 mmol/g of material. The developed method was successfully employed for the simultaneous extraction of Pb(II), Cd(II) and Cu(II) from real-world samples (industrial effluent, river water, tap and groundwater) and subsequently determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). The method shows a preconcentration limit of 0.7 ppb attributes to analyze the trace concentration of studied metal ions. The detection limit obtained for Pb(II), Cd(II) and Cu(II) is found to be 0.4 ppb.

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).

Water quality and probabilistic non-carcinogenic health risk of groundwater: a half decadal scenario change in Vadodara

Groundwater is essential to secure the safety of water supply in Vadodara, Gujarat. In this study, groundwater samples were collected from various part of the city which separated in 12 wards. The present study contains analyses of 720 groundwater samples gathered from various tube and open wells and analyzed for fluoride and other physicochemical parameters during 2014 and 2019. The results indicated that fluoride and TDS were high and the overall water quality was poor in the study area. Gastrointestinal and other health-related issues increased due to higher TDS in east, north and northeast regions. Likewise, hierarchical cluster analysis also indicated that TDS and chloride-rich water. Fluoride concentration was observed in the range of 0.66-1.61 mg/l (2014) and 0.86-1.77 mg/l (2019) which indicates that 62% samples are unfit for drinking purpose, which could cause dental and skeletal fluorosis. The water quality index (WQI) indicated lack of excellent water in the studied area in the last half-decade. As per WQI calculation suggest that 82.12% (2014) and 69.00% (2019) of groundwater samples represent poor, very poor and unsuitable categories, whereas remaining 17.85% (2014) and 31.00% (2019) of the samples represent good category for drinking purposes in entire Vadodara, Gujarat. Marginal improvement in the groundwater quality is reported due to good rainfall in 2019. Health risks associated with high fluoride drinking water were assessed for various age groups of inhabitants such as children, infants and adults. The non-carcinogenic hazard quotient estimated by oral intake was 1.38-3.36 (2014) and 1.79-3.70 (2019) for infants; 0.69-1.68 (2014) and 0.90-1.85 (2019) for children, whereas 0.07-0.18 (2014) and 0.10-0.20 (2019) for adults. Therefore, infant and children are relatively at higher health risk due to the intake of fluoride-rich drinking water than adult in the studied region. Both indices were indicated contaminated water or closer to contamination which induced non-carcinogenic health risk on citizens. Thus, the comprehensive results of present study can be used as a baseline data and valuable tool for government authorities for long-term monitoring, health monitoring and sustainable development of Vadodara, Gujarat.

A unified multivariate statistical approach for the assessment of deep groundwater quality of rapidly growing city of Maharashtra Province, India, with potential health risk

The main aim of this research is to assess the consequences of natural and anthropogenic processes on the groundwater quality of 65 deep aquifers of Nagpur city, Maharashtra Province, India, using a unified multivariate statistical approach. The dominant groundwater type recognized is Ca-HCO₃ (recharge waters) in 43.1 and 38.5% of groundwater samples of pre- and post-monsoon seasons, followed by mixed water types. The seasonal distribution of physicochemical parameters shows increase in the concentration of EC, TDS, TH, Mg²⁺, SO₄^2-, and NO₃^- signifying the high mineralization and anthropogenic loading from pre- and post-monsoon season respectively. The entropy-weight water quality index categorizes the 84.6% and 75.4% of total samples from pre- and post-monsoon seasons into moderate quality. The multiple linear regression and PCA analysis reveal the masking of rock weathering mechanism by anthropogenic activities. The % of PCA Variance varies from 79 to 83.7% from pre- to post-monsoon season. The high contributions of EC (0.76, 0.72), TDS (0.79, 0.73), TH (0.97, 0.962), Ca²⁺ (0.84, 0.78), Mg²⁺ (0.79, 0.83), Cl^- (0.73, 0.75), and NO₃^- (0.78, 0.68) in PC1 components expose high salinity and hardness in urban groundwater that signifies the consequences of urbanization on the groundwater regime. About 55.4 and 70.8% of children population as compared to the adult female (53.8%, 69.2%) and male (32.3%, 46.1%) population in PRM and POM respectively were at high non-carcinogenic health threat of NO₃^--enriched groundwater. The study is beneficial for understanding the variation in groundwater composition due to unplanned urbanization and is very useful for protecting groundwater resources in urban areas.

Development of function-specific indices for assessing water quality based on the proposed modifications of the expected conflicts on existing information entropy weights

Water serves numerous purposes besides drinking, such as irrigation and industrial usage. Most water quality indices developed have primarily focused on drinking water quality. However, assessing other functionalities of water bodies is also equally essential. The present study proposes a novel technique to measure water quality for two highly specific water use, i.e., assessing heavy metal contamination and irrigation suitability. The ambiguities in the current practice of entropy weights were identified, and a novel method was proposed, considering a three-dimensional approach instead of the conventional two-dimensional procedure. Weights to different parameters were assigned based on the probability estimates obtained from the frequency of observed values within acceptable limits. The proposed method's reliability, correctness, and applicability were tested using Deepor Beel's water quality dataset. Results were highly consistent with the experimental values and correlated well with other established methods. The efficacy of the method was determined by employing sensitivity analyses. Both indices showed high reliability and correctness, as no single parameter was found to be highly sensitive compared to others. Therefore, the proposed methodology proved to be the most reasonable, incorporating all the factors required for a reliable water quality monitoring program.

Estimating adults and children's potential health risks to heavy metals in water through ingestion and dermal contact in a rural area, Northern Tunisia

High concentrations of heavy metals (HMs) in water (e.g., As, Cr, and Cd) are harmful to human health, especially to children. HMs' (As, Cd, Mn, Fe, Cu, Hg, Zn, Cr, and Se) values have been determined from the water of the Guenniche plain (Tunisia); then the carcinogenic risk (CR) and non-carcinogenic Risk (N-CR) were estimated through ingestion and dermal contact for adults and children. The analysis results show that the Hg, As, and Cd in 50% of the ephemeral streams (ESs) exceeded one of the WHO and NT guidelines for safe water, as is the case with Hg and Cd in 25% of the shallow groundwater wells (SGW). In all samples, the N-CR of all HMs, and the CR due to the dermal contact controlled by As, for both age brackets, are deemed to fall far short of the threshold set by USEPA. The CR due to the ingestion pathway caused by As, Cr, and Cd contamination indicates a "high" to "very high" risk on its users in roughly 50% of all the samples (ESs and SGW) for both age brackets by exceeding 10^-5. Overall, the SGW samples close to the floodplain area of the ESs pose a real CR to both age groups, which is more serious for children. Therefore, the SGW are not recommended for drinking use, with an urgent call for a solution by the policy-makers to improve the water quality of the region.

Groundwater Quality and Associated Human Health Risk in a Typical Basin of the Eastern Chinese Loess Plateau

Groundwater is an important source for drinking, agricultural, and industrial purposes in the Linfen basin of the Eastern Chinese Loess Plateau (ECLP). To ensure the safety of drinking water, this study was carried out to assess the quality using the water quality index (WQI) and potential health risks of groundwater using the human health risk assessment model (HHRA). The WQI approach showed that 90% of the samples were suitable for drinking, and Pb, TH, F−, SO42−, and TDS were the most significant parameters affecting groundwater quality. The non-carcinogenic health risk results indicated that 20% and 80% of the samples surpassed the permissible limit for adult females and children. Additionally, all groundwater samples could present a carcinogenic health risk to males, females, and children. The pollution from F−, Pb, and Cr6+ was the most serious for non-carcinogenic health risk. Cd contributed more than Cr6+ and As to carcinogenic health risks. Residents living in the central of the study area faced higher health risks than humans in other areas. The research results can provide a decision-making basis for the scientific management of the regional groundwater environment and the protection of drinking water safety and public health.

Spatial and seasonal variation of water quality indices in Gomal Zam Dam and its tributaries of south Waziristan District, Pakistan

This study investigated the quality of water and its seasonal variation in the Gomal Zam Dam and tributaries, south Waziristan District, Pakistan. For this purpose, water samples were collected from the Gomal Zam Dam and its tributaries in the winter and summer seasons (n = 24 in each season). Water samples were analyzed and found within drinking water guidelines set by the World Health Organization (WHO), except turbidity. Water characteristics were evaluated for the water quality index (WQI) and sodium hazards. Based on WQI and sodium hazards, the water of Gomal Zam Dam and its tributaries were observed as good and in permissible levels for drinking and irrigation, respectively. The winter season has slightly poor water quality compared to the summer season due to higher contamination. Gibbs's and Piper's models showed that the water quality of Gomal Zam Dam and its tributaries was mainly characterized by the weathering of bedrocks. The studied water is classified as Na-Cl type and Mg-HCO₃ types in the summer and winter seasons, respectively. Statistical analyses revealed that geogenic sources of rock weathering are the dominant factor for controlling the water quality of the area.

Characterization of drinking groundwater quality in rural areas of Inner Mongolia and assessment of human health risks

Groundwater is an important natural resource of drinking water in rural areas in Inner Mongolia, China. In this study, 4438 drinking groundwater samples were collected from the rural areas of 81 counties in Inner Mongolia, and were analyzed for 16 parameters, including pH, total hardness (TH), chemical oxygen demand (COD), total dissolved solids (TDS), sulfate (SO42-), chloride (Cl-), fluoride (F-), iron (Fe), manganese (Mn), arsenic (As), cadmium (Cd), hexavalent chromium (Cr), lead (Pb), aluminum (Al), cuprum (Cu), zinc (Zn). The groundwater quality was evaluated with water quality index (WQI) and human health risk assessment (HRA). Monte Carlo simulation were applied for the uncertainty and sensitivity analysis in the health risk assessment. The spatial map was employed based on the inverse distance weighted (IDW) interpolation technique. The results reveal that while the hazard quotient (HQ) suggests that the risk of single element contamination is feeble, the hazard index (HI) indicates a potential health risk for the local population. The observed cumulative carcinogenic risk (CCR) indicates a probable risks of carcinogenic health hazards in the study area. The sensitivity analysis revealed that daily ingestion rate (IR), exposure frequency (EF), and the concentrations of As, Mn, F-, and Cr are the most influential parameters for health hazards. The highly polluted areas are mainly distributed in the central and western regions of Inner Mongolia, including Xianghuangqi, New Barag Zuoqi, and Togtoh. It is observed that the groundwater may cause a potential health risk after long-term ingestion. The results of this study will contribute to groundwater management and protection in Inner Mongolia.

Distribution, Genesis, and Human Health Risks of Groundwater Heavy Metals Impacted by the Typical Setting of Songnen Plain of NE China

Heavy metals pollution in groundwater and the resulting health risks have always been an environmental research hotspot. However, the available information regarding this topic and associated methods is still limited. This study collected 98 groundwater samples from a typical agricultural area of Songnen Plain in different seasons. The pollution status and sources of ten heavy metals (As, Ba, Cd, Co, Cr (VI), Cu, Fe, Mn, Ni, Pb, and Zn) were then analyzed and compared. In addition, the human health risks assessment (HHRA) model was used to calculate human health risks caused by heavy metals in groundwater. The results revealed that heavy metals were mainly distributed in the northwest of the study area and along the upper reaches of the Lalin river and that the concentrations of heavy metals were higher during the wet season than the dry season. Industrial and agricultural activities and natural leaching are the main sources, and each kind of heavy metal may have different sources. Fe and Mn are the primary pollutants, mainly caused by the native environment and agricultural activities. The exceeding standard rates are 71.74% and 61.54%, respectively based on the Class III of Quality Standard for Groundwater of China (GB/T 14848-2017). The maximum exceeding multiple are 91.45 and 32.05, respectively. The health risks of heavy metals borne by different groups of people were as follows: child > elder > young > adult. Carcinogenic heavy metals contribute to the main risks, and the largest risks sources are Cr and As. Therefore, the government should appropriately restrict the use of pesticides and fertilizers, strictly manage the discharge of enterprises, and control man-made heavy metals from the source. In addition, centralized water supply and treatment facilities shall be established to prevent the harm of native heavy metals.

Seasonal changes in dissolved trace elements and human health risk in the upper and middle reaches of the Bhavani River, southern India

The surface water is a significant feature in the hydrological system and is a vital compound for life growth. Assessment of trace elements in the water bodies is essential since it poses huge threats to aquatic organisms and humans if present in high concentrations. This study was carried out to assess the seasonal changes in the dissolved trace elements concentration in Bhavani river, which is one of the major rivers of Tamil Nadu, southern India and also to assess the human health risk due to its consumption. A total of 46 surface water samples were collected along the river during pre-monsoon and post-monsoon of 2018 and were analyzed for various trace elements such as Zn, Cu, Fe, Ni, and Pb. The variation in trace element concentration is observed spatially, where higher concentration is found in samples from agricultural and urban areas than the samples from the undisturbed natural-mountain terrains. The results highlighted that the concentrations of trace elements differ temporally where the concentration is greater during the monsoon due to increased discharge of sewage and agricultural run off to the river. Multivariate statistical analysis indicates stronger relationship between trace elements and other physio-chemical parameters hinting that natural and anthropogenic sources alters the riverine chemistry. Thus, the rainfall-runoff characteristics along with lithology, topography, and landuse of the basin plays a dominant role in the seasonal variation of dissolved trace elements. The water quality index value shows "good/excellent" during pre-monsoon and "marginal/fair" during monsoon season and the Heavy Metal Pollution Index values were also low during both the seasons. The river water samples which defy these indices were found to be either from urban or agricultural lands. The oral and dermal ingestion health risk to adults was assessed, which indicates that the risks posed to humans by consumption of water were minimal. The trace metal concentration of the river was then compared with the other rivers of world and India, where it shows that Zn, Cu, and Ni concentration was higher in Bhavani than in most of the rivers. Thus, the study highlighted that the urban settlements and agricultural lands have a considerable influence on river quality thereby triggering the increase in trace element concentrations. Therefore, the study necessitates on the continuous monitoring of river along with adoption of stringent discharge protocols.

Investigating sources, driving forces and potential health risks of nitrate and fluoride in groundwater of a typical alluvial fan plain

Groundwater of alluvial fan plains is the foremost water source, especially in arid/semiarid regions. Its contaminants are big issues for water supply and public health concern. To reveal the groundwater chemistry, contaminants sources and health threats in alluvial aquifers, 81 groundwaters were collected from a typical alluvial fan plain of northern China for nitrogen, fluoride and major ions analysis. Statistical analysis and hydrochemical diagrams as well as human health risk assessment were performed. Nitrate is widely distributed and 53% of groundwaters exceed the permissible limit with the maximum concentration up to 326 mg/L. The distributions of nitrite, ammonia and fluoride contaminants are sporadic in spatial, and the concentrations of fluoride in groundwaters are slightly beyond the permissible limit of 1 mg/L. The hydrochemical facies shift from HCO₃-Ca or Mixed HCO₃-Na·Ca type to Mixed Cl-Mg·Ca and ClCa type with the increase of nitrate content. Two factors (Factor-1 and Factor-2) are extracted by factor analysis and account 63% of the total variances. The positive loading of F^- and negative loading of NO₃^- on Factor-2 reveal geogenic and anthropogenic origins, respectively. The significant positive loadings of TDS, TH, SO₄^2-, Cl^-, Ca²⁺, Mg²⁺ on Factor-1 reveal the governing mechanisms on groundwater chemistry by intermixed sources of geogenic origins and anthropogenic inputs. Hydrogeochemical evolution in the study area is driven by both water-rock interaction and anthropogenic forces. Anthropogenic inputs/influences are the dominated forces increasing groundwater nitrate content and salinity in the piedmont zone and the residential and industrial zone of the southeastern lower parts, and would pose potential non-carcinogenic risks to various populations via oral intake pathway. Rational measures should be taken to protect groundwater quality out of the threats of anthropogenic pollution. The geogenic fluoride in groundwater would threat the health of children through oral pathway and should be also concerned. CAPSULE: The driving forces of groundwater chemistry in alluvial fan plains were revealed using integrated approach of factor analysis and geostatistical modelling.

Discussion on the existing methodology of entropy-weights in water quality indexing and proposal for a modification of the expected conflicts

The present research focuses on addressing various ambiguities in the existing method of integrating information entropy and water quality, thereby presenting a novel approach for an entropy-weighted water quality index. A three-dimensional water quality dataset is considered in the proposed method, the third dimension being the sampling frequency factor. The probability of observed values adhering to desirable limits prescribed by a standard code is estimated, leading to the computation of information entropy and, eventually, entropy weights. These weights are then used for the computation of the Modified Entropy-weight Water Quality Index (MEWQI) values. To verify the proposed method's applicability, the water quality dataset of Deepor Beel, India, was considered. IS 10500: 2012 was used for estimating MEWQI values. Results showed an excellent correlation with the observed dataset and their uncertainties of occurrence. The reliability and correctness of the proposed methodology were finally confirmed through both cluster analysis and sensitivity analysis. The cluster analysis showed remarkable associations with the computed MEWQI values, while the sensitivity analysis proved that no particular parameter was accountable for the contribution of MEWQI values; instead, all parameters exhibited equal contributions. The proposed methodology was thus found to be the most reasonable and reliable as it considered both factors, i.e., measured values concerning standard limits and the uncertainty, necessary for a consistent water quality monitoring program.

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.

Hydrogeochemical Features and Genesis of Confined Groundwater and Health Perspectives for Sustainable Development in Urban Hengshui, North China Plain

Groundwater in confined aquifers is the preferred water resource worldwide, and its hydrochemical quality is the premise for sustainable development. A systematic hydrogeochemical research was conducted to get insight into the hydrochemical characteristics, genesis, and potential health threats of confined groundwater, based on analytical data of 45 groundwater samples collected from the urban area of Hengshui, Central North China Plain (NCP). The results showed most groundwater had desirable hydrochemical quality with a nearly neutral to slightly alkaline nature and dominantly soft-fresh Cl-Na face. Solute chemistry was governed by rock-water interaction including minerals dissolution and ion exchange, but out of the anthropogenic influences. All nitrogen pollutants and Zn were within the desirable limit, while F−, Mn, and Fe were beyond the desirable limit recommended by WHO in 28.9%, 15.6%, and 68.9% of samples. Overall chronic health risk from these toxic elements was identified in terms of various populations and mainly contributed by F−. Infants were more prone to the health risks of aqueous pollutants. Differential water supplies based on hydrochemical quality are recommended, and water improvement measures are suggested to be conducted aiming at the harmful fluoride in confined groundwater. The present research could provide valuable references for the health sustainability of confined groundwater utilization in sedimentary plains like NCP worldwide.

Hydrochemical Characteristics and Formation Mechanism of Strontium-Rich Groundwater in Shijiazhuang, North China Plain

Strontium is a kind of trace element. Groundwater containing strontium is called mineral water when its content reaches a level that is beneficial for human physiology. Some groundwater resources in Shijiazhuang are rich in strontium. In this study, groundwater samples collected from 103 sites were studied for the hydrochemical characteristics of strontium and its formation mechanism in the groundwater system in Shijiazhuang City. The methods of source provenance analysis, factor correlation analysis, and runoff condition analysis were carried out in the study. The results showed that the content of strontium in eastern Shijiazhuang is higher than 0.229 mg/L, with a maximum content of 1.942 mg/L. The source of strontium is the dissolution of strontium-containing minerals in carbonate rock, sheet hemp rock, clastic rock, and granite in the Taihang Mountain area of the Hutuo River Basin. Strontium is positively correlated with total dissolved solids, bicarbonate, calcium magnesium, and free carbon dioxide. The erosion ability of groundwater strengthens the dissolution of strontium, and the geochemical action is mainly due to the dissolution. The enrichment and distribution of strontium are related to the conditions of groundwater runoff. Areas with good runoff conditions and strong mining are low in strontium, while areas with poor runoff conditions have high strontium content.

Sources and Consequences of Groundwater Contamination

Groundwater contamination is a global problem that has a significant impact on human health and ecological services. Studies reported in this special issue focus on contaminants in groundwater of geogenic and anthropogenic origin distributed over a wide geographic range, with contributions from researchers studying groundwater contamination in India, China, Pakistan, Turkey, Ethiopia, and Nigeria. Thus, this special issue reports on the latest research conducted in the eastern hemisphere on the sources and scale of groundwater contamination and the consequences for human health and the environment, as well as technologies for removing selected contaminants from groundwater. In this article, the state of the science on groundwater contamination is reviewed, and the papers published in this special issue are summarized in terms of their contributions to the literature. Finally, some key issues for advancing research on groundwater contamination are proposed.

Hydrogeochemical Processes Affecting Groundwater Chemistry in the Central Part of the Guanzhong Basin, China

Groundwater is essential for the sustainable development of the Guanzhong Basin, China, and its quality is mainly controlled by hydrogeochemical processes and anthropogenic pollution. This study used statistical and multivariate statistical analysis approaches to recognize the hydrogeochemical processes and affecting factors of groundwater in the central part of the Guanzhong Basin. Correlations among 14 hydrochemical parameters were statistically examined. Principal component analysis (PCA), factor analysis (FA), and hierarchical cluster analysis (HCA) techniques were applied to analyze the physicochemical variables to understand the affecting factors of groundwater quality in the study area. The correlation analysis results indicate that cation exchange is the dominant process affecting the concentration of Na⁺ and Ca²⁺ in the groundwater. Both the PCA and FA indicate that minerals dissolution/precipitation and human activities are the key factors that affect groundwater quality. All parameters except CO₃^2- and pH increase from C1 to C4 obtained through the Q mode HCA. C4 has a hydrochemical type of SO₄-Na·K, indicating that the sample of this cluster is primarily influenced by anthropogenic processes.

Assessment of groundwater quality and determination of hydrochemical evolution of groundwater in Shillong, Meghalaya (India)

Deterioration of surface water quality in various parts of India due to increasing urbanization has led to the extensive usage of groundwater for various domestic and irrigation needs, thereby raising concerns over its quality. However, there are very few studies focussing over the issue of groundwater quality in North-Eastern region of India. In order to make an assessment of the quality of groundwater for drinking and irrigation purposes, this study was carried out in Shillong—the Capital City of Meghalaya State in North-East India during pre-monsoon and post-monsoon seasons of 2018. Standard sampling and analytical procedures were followed for groundwater quality assessment. Minimal variation was observed in the water quality of pre- and post-monsoon seasons. However, the study found that groundwater samples are having acidic pH and presence of nitrate is also reported. Some of the samples also showed the presence of mercury, nickel, and cadmium. The presence of these contaminants could be attributed to the industrial activities in the state. Overall, the groundwater quality was found suitable for drinking and irrigation purposes after conventional treatment. Hydrochemical studies further inferred that groundwater properties in the region are influenced by the rock weathering along with the atmospheric precipitation.

Groundwater chemistry integrating the pollution index of groundwater and evaluation of potential human health risk: A case study from hard rock terrain of south India

Groundwater is an important resource for drinking and irrigation purposes and also the significant route of human exposure in most of the arid and semi-arid regions of the world. In view of this, 43 groundwater samples were collected and analyzed for various physico-chemical parameters. Particularly, this study integrates the groundwater contamination by comparing it to national guidelines and the impact of fluoride and nitrate on health risk were quantified through the model recommended by the United States Environmental Protection Agency (USEPA). The groundwater of the investigated region is slightly alkaline in nature with hydrochemical facies of groundwater is predominantly characterized by Ca²⁺-Mg²⁺-HCO₃^- and Ca²⁺-Mg²⁺-Cl^- water types. The results show that the concentrations of groundwater nitrate and fluoride range from 2.2 to 165 mg/L and 0.84 to 4.3 mg/L, and 55.81% and 65% of groundwater exceed the national guidelines for drinking purposes, respectively. The pollution index of the groundwater (PIG) method unveiled that low quality and moderate quality of water account for 40% and 4.65% of collected groundwater samples, respectively. The results of non-carcinogenic health risk ranged from 0.63 to 5.31 ± 2.59 for adults, 0.85 to 7.18 ± 3.50 for children and 0.98 to 8.29 ± 4.04 for infants, indicating health risk was higher in infants and children as compared to the adults in the study region.