Evaluation of non-carcinogenic risks due to fluoride and nitrate contaminations in a groundwater of an urban part (Coimbatore region) of south India

Geochemistry of some fluoride and nitrate enriched water resources from the Oriental Basin: a prospective health risk hotspot from eastern-central Mexico

In attention to the Sustainable Development Goal 6, the quality evaluation of water resources in Mexico is limited compared to other regions. This study provided new data from Oriental Basin, an important socio-economic region with up to 20% population growth over the last decade by assessing groundwater from the Libres-Oriental aquifer (Ca-Mg-HCO3 facies; F-: 2.5-9.9 mg/L; NO3-: up to 75.3 mg/L) and water from the Totolcingo Lake (Na-Cl facies; F-: 12.7-13.2 mg/L; NO3-: < 0.75 mg/L). Fluoride content grouped about 80% groundwater samples as promotor of dental and skeletal fluorosis. Nitrate Pollution Index suggested moderate pollution in 20% and very significant pollution in 10% groundwater samples. Possible exposure of older adults and elderly pregnant women to fluorosis from all the groundwater samples (Hazard Quotient > 1) from the Oriental Basin and 55% of them might also be causing fluorosis in infants suggest a potential health risk hotspot in the eastern-central Mexico. Even though all the groundwater samples did not contain enough NO3- to cause methemoglobinemia, their boiling for drinking could enhance nitrate content beyond the WHO limit. Thus, the mitigation techniques might diminish the health risks in consuming population.

Spatiotemporal variability of groundwater chemistry, source identification and health risks in the southern Chinese Loess Plateau

Groundwater pollution of the loess plateau regions has become a global concern due to its vulnerability to natural and anthropogenic influences. In this study, 146 water samples were investigated to identify the spatiotemporal variability in groundwater chemistry, pollution sources and nitrate health risks in two interconnected river basins of a typical loess region. The results showed that except for bicarbonate, spatiotemporal variability of hydrochemical components in Malian River Basin (ML) was generally greater than that in Upper Jinghe River basin (JH-U) due to the hydrogeological conditions, and the hydrochemical facies in two river basins transformed from SO4·Cl and Cl·SO4 types to HCO3 and HCO3·SO4 types. The results of integrated-weight quality index (IWQI) showed that 77.8 % (1970s), 33.3 % (2004), 34.3 % (2015) of samples in ML exceeded the standard limits of Class IV groundwater quality, displaying a high pollution level with an improvement trend, while groundwater quality in JH-U indicated a very low pollution level with a deterioration trend. The geogenic source was identified as a main factor affecting groundwater quality, with contributions of 59.2 % and 48.7 % in JH-U and ML (2015), respectively. The anthropogenic sources including agricultural activities (20.7 % and 21.8 % in JH-U and ML) and coal mining activities (20.1 % and 29.5 % in JH-U and ML) also played a role in affecting groundwater quality. The nitrate health risk assessment demonstrated that 39.1 % and 20.3 % of groundwater samples (2015) significantly exceeded the standard threshold (Hazard Index = 1), implying a higher health risk to children than adults, and the nitrate health risk in ML was obviously greater than that in JH-U. This study provides novel insight into the spatiotemporal variability in groundwater chemistry, quality and health risk in loess regions under the influence of geogenic and anthropogenic factors.

Perfluorooctanoic acid transport and fate difference driven by iron-sulfide minerals transformation interacting with different types of groundwater

Perfluorooctanoic acid (PFOA) is an emerging persistent organic pollutant that threatens human health and ecosystems. However, the intricate mechanism of the change in PFOA transport behavior that interacts with FexSy minerals under groundwater-type differences is not clear. To address this knowledge gap, multi-scale experiments and multi-process reaction models were constructed to investigate the underlying mechanisms. The results showed that different groundwater (NO3-, Cl--Na+, SO42-, and HCO3- types) had significant effects on PFOA transport. NO3-, Cl--Na+, SO42-, and HCO3- decreased the retardation effect of PFOA in the FexSy media. Compared to other groundwater types, the adsorption sites of FexSy were the least occupied in the NO3- groundwater. This observation was supported by the least inhabition of λ in FexSy-NO3- interaction system, which demonstrated that more PFOA was in a high reaction zone and electrostatic repulsion was weakest. The surface tension of different ion types in groundwater provided evidence explaining the lowest inhibition in the FexSy-NO3- system. The 2D spatiotemporal evolution results showed that in FexSy with NO3- system, the pollutant flux (6.00 ×10-5 mg·(m2·s)-1) was minimal. The pollutant flux in the SO42- groundwater system was 9.95-fold that in FexSy with the NO3- groundwater. These findings provide theoretical support for understanding the transport and fate of PFOA in FexSy transformations that interact with different types of groundwater.

Pan India fluoride hazard assessment in groundwater

Fluoride (F¯) contamination in groundwater in India has gained global attention due to human health hazards. India's hydrogeological heterogeneity, spatio-temporal variability of F¯, and health hazards due to geogenic and geo-environmental control pose unique challenges. Addressing these with only a single region-specific study is not possible. Therefore, this study provides an in-depth, holistic analysis of pan India F¯ contamination, controlling factors, and health hazards using a coupled advanced geostatistical and geospatial approach. Alarming F¯ contaminations are identified in Rajasthan, Telangana, Western Andhra Pradesh, Eastern Karnataka, Parts of Haryana, Gujarat, Madhya Pradesh, Tamil Nadu, Uttar Pradesh, Jharkhand, Bihar, and Chhattisgarh. Probabilistic health-risk evaluation using hot-spot, showed similar spatio-temporal distribution of F¯ contamination. The hazard quotient (HQ) for high F¯ shows more adversity to children than adults. Nationally, 8.65 % and 7.10 % of pre- and post-monsoon sites exceed the recommended safe limit of 1.50 mg/L. The highest average F¯ concentration is in Rajasthan. Very high-risk skeletal fluorosis is possible at around ≤ 2 %, whereas dental caries due to deficiency in F¯ concentration is approximately 40 %. A decisive hierarchy of lithology, geomorphology, soils, and lineaments control are identified on F¯ contamination. Climatic conditions are pivotal in governing all these controlling variables. Thus, in arid/semi-arid dry western regions, F¯ contamination is much higher than in the humid areas. Integration of strengths, weaknesses, opportunities, and threats (SWOT) analysis with the results can aid policymakers and government authorities in achieving sustainable remedial measures for future adaptability.

Assessing variability and hydrochemical characteristics of groundwater fluoride contamination and its associated health risks in East Singhbhum district of Jharkhand, India

Groundwater pollution caused by fluoride is a significant concern for the global population owing to its toxicity, which has negative health consequences. Industrial discharges, agricultural practices, and improper waste disposal are primary concerns in evaluating the degree of fluoride contamination in the selected districts of Eastern India. In a targeted area sampling approach, exactly 196 samples were collected during pre- and post-monsoon, and precise fluoride detection was performed using Ion-Selective Electrodes. Fluoride levels in pre-monsoon water were observed within a range of 0.02 to 2.7 mg/L, with an average abundance of 0.4 ± 0.50. In post-monsoon, the concentration ranged from 0.02 to 4.7 mg/L (mean 0.53 ± 0.60). The study found that 97 % of groundwater samples had acceptable fluoride levels within the 1.5 mg/L limit during pre and post-monsoon. Moreover, approximately 87 % of the samples exhibit fluoride content below the 1 mg/L limit. The hazard quotient was observed to be 0.17 to 0.58 in adults, 0.23 to 0.79 in children and 0.36 to 1.26 in infants during pre-monsoon, whereas 0.05 to 0.55 in adults, 0.12 to 0.74 in children and 0.11to 1.19 in infants during post monsoon. The above data indicates that infants had the highest risk of fluoride exposure, with a significant negative correlation between fluoride and calcium ions. Fluoride had minimal to no link with other ions, a modest positive correlation with sulfate, and a weak negative relationship with overall hardness and alkalinity across both seasons. The present study contributes towards the identification of fluoride levels in various areas, making society aware of water contamination and its health impacts.

Coordinated analysis of groundwater spatiotemporal chemical characteristics, water quality, and potential human health risks with sustainable development in semi-arid regions

The emergence of large-scale time-series data and advancements in computational power have opened new avenues for analyzing the spatiotemporal evolution of groundwater chemistry, water quality, and human health risks. This paper utilizes hydrogeochemical methods to elucidate the controlling factors of water chemical components based on the test results of 124 groundwater samples collected from 31 monitoring wells in Fuxin City, Liaoning Province, China, from 2018 to 2021. By integrating the Random Forest and Enhanced Water Quality Index methods for water quality assessment and employing the Human Health Risk Assessment (HHRA) model to analyze human health risks, our findings indicate that the groundwater is mildly alkaline, with SO4·Cl-Ca·Mg and HCO3-Ca·Mg as the dominant hydrochemical types, primarily derived from the dissolution of carbonate and silicate minerals such as dolomite, limestone, and andesite, and cation exchange reactions. The EI_RF water quality evaluation model reveals that the overall water quality in the study area is poor, with Class I and II water quality zones mainly located in the northeastern and central parts of the study area, showing a gradual transition from Class I and II in the northeast to Classes IV and V in the southwest, significantly influenced by NO3-, TH, TDS, and SO42-. The HHRA model results indicate that the potential non-carcinogenic risk of groundwater nitrates has a severe impact on infants, with the spatial distribution being low in the northeast and high in the southwest. Due to industrial activities, agricultural practices, and population growth, certain areas in developing countries such as China and India exhibit nitrate concentrations significantly higher than those in most international regions, highlighting global environmental and public health challenges. This underscores the importance of enhancing groundwater monitoring and implementing measures to mitigate pollution. These research outcomes hold significant implications for the government in formulating rational protection and management measures to ensure the sustainable utilization of groundwater resources.

Geospatial interpolation and hydro-geochemical characterization of alluvial aquifers in the Thal Desert, Punjab, Pakistan

This study seeks to assess the hydrogeochemical characteristics of groundwater in the southern part of Thal Desert of Pakistan. The primary focus lies in identifying potential sources of contamination and evaluating their impact on groundwater and the ecosystem. Groundwater samples were collected from diverse sources including shallow hand pumps, tubewells, and dug wells, with depths ranging from 11 to 28 m. A comprehensive analysis was performed to scrutinize the physical, chemical, and microbial attributes of the samples. Utilizing visual aids like the Piper, Durov, and Gibbs diagrams, as well as Pearson correlation, scatter plots, Schoeller diagrams, and pie charts, the study evaluated the groundwater quality and its suitability for consumption. Results indicate that mineral infiltration from rainfall, domestic waste, and industrial effluents significantly affects groundwater quality, leading to widespread salinity. Weathering processes and ion exchange were identified as key factors contributing to elevate levels of bicarbonates, sodium, magnesium, and chloride ions. Employing the Water Quality Index (WQI) on 40 groundwater samples, findings reveal that 52.5% of samples demonstrated poor to not suitable quality, with 27.5% categorized as poor, 2.5% as very poor, and 22.5% not suitable consumption. Conversely, 47.5% of samples showcased good to excellent quality, with 25% rated as good and 22.5% as excellent. These findings provide valuable insights for hydrogeologists to develop appropriate strategies for water treatment and address any concerns related to groundwater quality.

Hydrogeochemical appraisal, sources, quality and potential health risk assessment in Holocene and Pleistocene aquifers in Bangladesh

This study integrated hydrochemical analysis, isotopic analysis, the integrated water quality index (IWQI), and the health risk assessment model to analyze hydrochemical characteristics, quality, and nitrate health risks in a typical agricultural and industrial (i.e., Holocene and Pleistocene) simultaneously affected by anthropogenic activities, as well as to explore the recharge mechanisms of the groundwater. The shallow groundwater is mainly Ca-HCO3- and deep groundwater is mainly Na-HCO3- types. In shallow and intermediate aquifers (Holocene), rainfall recharge is seen, but in deep aquifers (Holocene) and the Madhupur tract (Pleistocene), there is no evidence of recent recharge from the stable isotopic (δ2H‰ and δ18O‰) composition of groundwater. Anthropogenic sources significantly impacted the groundwater chemistry of shallow and intermediate aquifers more than geogenic sources. Most metalloids, and metals (As, and Cr, Fe, Ni, Pb, and Mn) and NO3- exceed the WHO-2011 and BD acceptable limit from shallow and intermediate groundwater. PCA analysis revealed the contamination of shallow and intermediate aquifers by metalloids, metals and from various anthropogenic activities. Based on the IWQI, HPI, HEI, and DC, groundwater samples from shallow and intermediate aquifers are unsuitable for oral consumption. The NPI shows that the metalloids, and metals are responsible for groundwater pollution in a descending order of As > Fe > Pb > Ni > Cr > Mn. Health risk assessment indicates oral and dermal consumption of contaminated water from shallow and intermediate aquifers can pose carcinogenic and non-carcinogenic health risks for both the adults and the children. The HQ and HI values of shallow and intermediate groundwater indicates higher non-carcinogenic risk. Carcinogenic risk through oral and dermal consumption follows an order of As > Ni > Cr > Pb and Ni > Cr > As > Pb, respectively. Compared to adults, children are more susceptible to both carcinogenic and non-carcinogenic risks. Potential threats to the health of people living in the study region need immediate attention from the public, government, and the scientific community.

Assessment of groundwater fluoride and human health effects in a hard rock province of south India: Implications from Pollution Index Model (PIM) and Geographical Information System (GIS) techniques

This research examines whether the groundwater in the Sivakasi Region of South India is suitable for consumption, and assesses the possible health hazards for various age demographics including infants, children, teenagers, and adults. A total of 77 groundwater samples were gathered, covering a total area of 580 km2 and analyzed for major and minor ions. The hydrogen ion concentration (pH) of the samples indicates neutral to marginally alkaline. The total dissolved solids (TDS) fluctuate from 255 to 2701 mg/l and electrical conductivity varies from 364 to 3540 µS/cm. A wide range of fluoride concentration was detected (0.1 to 3.2 mg/l) with nearly 38% groundwater samples surpassing the proposed limit (1.5 mg/l) suggested by the World Health Organization in 2017. Gibbs plot analysis suggested that most of the samples were influenced by geogenic factors, primarily rock weathering in this region. Correlation analysis showed that most of the samples were impacted by both natural and human sources. The pollution index of groundwater (PIG) fluctuated from 0.67 to 2.60 with approximately 30% and 53% of samples falling into insignificant and low pollution categories, respectively. Furthermore, 10% and 5% of total samples were characterized as moderate and high pollution levels, and 2% as very high pollution category. Spatial analysis using GIS revealed that 440.63 km2 were within safe fluoride levels according to the WHO standards, while 139.32 km2 were identified as risk zone. The principal component analysis (PCA1) showed strong positive loadings on EC (0.994), TDS (0.905), Mg2+ (0.910), Cl- (0.903) and HCO3- (0.923) indicating rock water interaction. PCA2 accounts the high positive factor loading on HCO3- (0.864) indicating ion exchange and mineral leaching. The PCA1 and PCA2 indicated that variables such as mineral leaching and rock water interaction are the major mechanisms contributing to the chemical signatures in groundwater, which may support for the elevated fluoride levels in certain areas. Risk assessments, including Hazard Quotient results showed that 71%, 61% 38%, and 34% of groundwater samples exceeded the permissible THI limit (THI > 1) for infants, children, teenagers, and adults, respectively. The study recommends implementing measures such as denitrification, defluorination, rainwater harvesting, and improved sanitation infrastructure to enhance the health conditions in the study region. Additionally, it suggests introducing educational programs in rural areas to create awareness about the health dangers due to consumption of water with high fluoride levels.

Emerging nitrate contamination in groundwater: Changing phase in a fast-growing state of India

The consumption of nitrate-contaminated groundwater is often associated with potential health risks, particularly in children. This study aimed to assess the hydrochemistry and nitrate contamination in groundwater of Kerala state, India for the years 2010 and 2018 and evaluate the potential human health risks due to nitrate exposure in adults, and children through oral ingestion and dermal contact pathways. Nitrate-contaminated zones were identified by spatial mapping of nitrate concentration based on groundwater quality data of 324 wells. Groundwater is typically acidic to slightly alkaline, and the electrical conductivity (EC) varied from 33 to 1180 μS/cm in 2010 and 34.6-2500 mg/L in 2018 indicating a noticeable increase over the years. Most samples fall within low salt enrichment category. The nitrate concentration in groundwater varied from 0 to 173 mg/L with a mean of 15.4 mg/L during 2010 and 0 to 244 with a mean of 20.3 mg/L during 2018. Though nitrate concentrations show uneven spatial distributions due to both natural and anthropogenic sources, the spatial clustering of higher concentrations remains almost same in both periods. In 2010, non-carcinogenic risk, as measured by Health Index Total (HITotal) values in groundwater for the investigated region, ranged from 0.005 to 4.170 (mean of 0.349) for males, 0.005 to 4.928 (mean of 0.413) for females, and 0.008 to 7.243 (mean of 0.607) for children, while in 2018, the corresponding values varied from 0.001 to 5.881 (mean of 0.501) for males, 0.002 to 6.950 (mean of 0.592) for females, and 0.003 to 10.215 (mean of 0.870) for children, indicating a substantial increase in risk, for females and children. Greater health risk is observed in children during both the periods. The findings emphasize the need for proper water quality management, especially in regions with higher vulnerability to nitrate pollution, to safeguard human health and well-being.

Hydrogeochemical evolution processes, groundwater quality, and non-carcinogenic risk assessment of nitrate-enriched groundwater to human health in different seasons in the Hawler (Erbil) and Bnaslawa Urbans, Iraq

The main objectives of this research are to assess groundwater, a primary source of drinking water in the urban areas of Hawler (Erbil) and Bnaslawa in northern Iraq, and the non-carcinogenic human health risks of nitrate contamination associated with drinking water quality. For this purpose, twenty-seven groundwater samples were collected from wells to assess the hydrogeochemical characteristics and groundwater quality for both natural and anthropogenic purposes during the wet (May 2020) and dry (September 2020) seasons. During the wet and dry seasons, NO3- in groundwater ranged from 14.00 to 61.00 mg/L and 12.00 to 60.00 mg/L, with an average value of 35.70 and 29.00 mg/L, respectively. Approximately 25.92% of the samples exceeded the permissible limit of the WHO (2011) drinking water standard. The ratios of NO3-/Na+ vs. Cl-/Na+ and SO42-/Na+ vs. NO3-/Na+ indicate the effect of agricultural activities and wastewater leaking from cesspools or septic tanks on the quality of groundwater during the wet and dry seasons. The entropy weighted water quality index method ranked 62.5% and 75% of the urban groundwater as not recommended for drinking, and the remaining samples are moderately suitable in both wet and dry seasons. The non-carcinogenic human health risk assessment displayed that during the wet and dry seasons, 29.6% and 25.9% of adults, 48% and 30% of children, and 48.1% and 29.6% of infants were exposed to increased concentrations of nitrate in groundwater. Due to high nitrate in drinking water, non-carcinogenic human health risk levels vary as infant > child > adults. The main findings obtained from this study can assist policymakers in better understanding the hydrogeochemical properties of groundwater in terms of drinking water safety, thereby facilitating the management of water resources to take the necessary measures.

Safeguarding drinking water: A brief insight on characteristics, treatments and risk assessment of contamination

Water pollution stands as a critical worldwide concern, bearing extensive repercussions that extend to human health and the natural ecosystem. The sources of water pollution can be diverse, arising from natural processes and human activities and the pollutants may range from chemical and biological agents to physical and radiological contaminants. The contamination of water disrupts the natural functioning of the system, leading to both immediate and prolonged health problems. Various technologies and procedures, ranging from conventional to advanced, have been developed to eliminate water impurities, with the choice depending on the type and level of contamination. Assessing risks is a crucial element in guaranteeing the safety of drinking water. Till now, research is continuing the removal of contaminates for the sake of supplying safe drinking water. The study examined physical, inorganic, organic, biological and radiological contaminants in drinking water. It looked at where these contaminants come from, their characteristics, the impact they have and successful methods used in real-world situations to clean the contaminated water. Risk assessment methodologies associated with the use of unsafe drinking water as future directives are also taken into consideration in the present study for the benefit of public concern. The manuscript introduces a comprehensive study on water pollution, focusing on assessing and mitigating risks associated with physical, inorganic, organic, biological and radiological contaminants in drinking water, with a novel emphasis on future directives and sustainable solutions for public safety.

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.

Probabilistic modelling is superior to deterministic approaches in the human health risk assessment: an example from a tribal stretch in central India

This case drew national attention in 2018. About 100 people died and more than 300 hospitalized in a span of few years in a village of 1200 people in a tribal stretch in central India. Medical teams visiting the area reported severe renal failure and blamed the local eating and drinking habits as causative factors. This human health assessment based on geochemical investigations finds nitrate (NO3-) and fluoride (F-) pollution as well in village's groundwater. Both deterministic and probabilistic techniques are employed to decipher the contamination pathways and extent of contamination. Source apportionments of NO3- and F- and their relationship with other ions in groundwater are carried out through chemometric modelling. Latent factors controlling the hydrogeochemistry of groundwater too are explored. While hazard quotients ([Formula: see text]) of the chemical parameters ([Formula: see text] and [Formula: see text]) identify ingestion as the prominent pathway, the calculated risk certainty levels (RCL) of the hazard index (HI) values above unity are compared between the deterministic and probabilistic approaches. Deterministic model overestimates the HI values and magnify the contamination problems. Probabilistic model gives realistic results that stand at infants ([Formula: see text] = 34.03%, [Formula: see text] = 24.17%) > children ([Formula: see text] = 23.01%, [Formula: see text] = 10.56%) > teens ([Formula: see text] = 13.17%, [Formula: see text] = 2.00%) > adults ([Formula: see text] = 11.62%, [Formula: see text] = 1.25%). Geochemically, about 90% of the samples are controlled by rock-water interaction with Ca2+-Mg2+-HCO3- (~ 56%) as the dominant hydrochemical facies. Chemometric modelling confirms Ca2+, Mg2+, HCO3-, F-, and SO42- to originate from geogenic sources, Cl- and NO3- from anthropogenic inputs and Na+ and K+ from mixed factors. The area needs treated groundwater for human consumption.

Evaluation of water from Lake Coatetelco in central-south Mexico and surrounding groundwater wells for drinking and irrigation, and the possible health risks

Due to an increasing reduction of hydrological resources across Mexico and their growing contamination from global warming and anthropogenic activities, this study evaluated water from the perennial Lake Coatetelco (Ca-Mg-HCO3) in tropical central-southern Mexico and groundwater (Ca-Mg-HCO3 and Na-HCO3-Cl) from the surrounding wells for drinking as well as irrigation qualities. Comparison with the WHO guidelines and the estimated water quality indices (DWQI and IWQI) grouped almost all the samples collected after the warm season rainfall in excellent and good categories (DWQI < 100) for drinking, even though fluoride remained > 1.5 mg/L in 50% samples. Except for one groundwater sample, all showed > 25% permeability (classes I and II) in Donnen classification indicating their suitability for irrigation. USSL and Wilcox classifications, however, catalogued some in the high-salinity hazard group and some as doubtful for irrigating regular plants. Samples from about 53% wells were also in high and severe restriction categories of IWQI for the irrigation. Total Hazard Quotient Index (THQI) for estimating the non-carcinogenic risk (HQfluoride > 1) showed that at least one lake water sample and 53% of groundwater might expose the adult and child population to dental and skeletal fluorosis. This water quality assessment data posterior to the rainfall season could be useful as a baseline for both the short- and long-term monitoring in attention to the United Nation's Sustainable Development Goal 6.

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-.

A multi-model study for understanding the contamination mechanisms, toxicity and health risks of hardness, sulfate, and nitrate in natural water resources

Several water quality contaminants have attracted the attention of numerous researchers globally, in recent times. Although the toxicity and health risk assessments of sulfate and water hardness have not received obvious attention, nitrate contamination has gained peculiar research interest globally. In the present paper, multiple data-driven indexical, graphical, and soft computational models were integrated for a detailed assessment and predictive modeling of the contamination mechanisms, toxicity, and human health risks of natural waters in Southeast Nigeria. Majority of the tested physicochemical parameters were within their satisfactory limits for drinking and other purposes. However, total hardness (TH), SO₄, and NO₃ were above stipulated limits in some locations. A nitrate health risk assessment revealed that certain areas present a chronic health risk to children, females, and males due to water intake. However, the dermal absorption route was found to have negligible health risks. SO₄ in some locations was above the 100 mg/L Nigerian limit; thus, heightening the potential health effects due to intake of the contaminated water resources. Most samples had low TH values, which exposes users to health defects. There are mixed contamination mechanisms in the area, according to graphical plots, R-mode hierarchical dendrogram, factor analysis, and stoichiometry. However, geogenic mechanisms predominate over human-related mechanisms. Based on the results, a composite diagrammatic model was developed. Furthermore, predictive radial basis function (RBF) and multiple linear regression (MLR) models accurately predicted the TH, SO₄, and NO₃, with the RBF outperforming the MLR models. Insights from the RBF and MLR models were useful in validating the results of the hierarchical dendrogram, factor, stoichiometric, and graphical analyses.

Assessment of groundwater quality and human health risks of nitrate and fluoride contamination in a rapidly urbanizing region of India

Groundwater contamination studies are important to understand the risks to public health. In this study, groundwater quality, major ion chemistry, sources of contaminants, and related health risks were evaluated for North-West Delhi, India, a region with a rapidly growing urban population. Groundwater samples collected from the study area were analysed for physicochemical parameters - pH, electrical conductivity, total dissolved solids, total hardness, total alkalinity, carbonate, bicarbonate, chloride, nitrate, sulphate, fluoride, phosphate, calcium, magnesium, sodium and potassium. Investigation of hydrochemical facies revealed that bicarbonate was the dominant anion while magnesium was the dominant cation. Multivariate analysis using principal component analysis and Pearson correlation matrix indicated that major ion chemistry in the aquifer under study is primarily due to mineral dissolution, rock-water interactions and anthropogenic factors. Water quality index values showed that only 20% of the samples were acceptable for drinking. Due to high salinity, 54% of the samples were unfit for irrigation purposes. Nitrate and fluoride concentrations ranged from 0.24 to 380.19 mg/l and 0.05 to 7.90 mg/l, respectively due to fertilizer use, wastewater infiltration and geogenic processes. The health risks from high levels of nitrate and fluoride were calculated for males, females, and children. It was found that health risk from nitrate is more than fluoride in the study region. However, the spatial extent of risk from fluoride is more indicating that more people suffer from fluoride pollution in the study area. The total hazard index for children was found to be more than adults. Continuous monitoring of groundwater and application of remedial measures are recommended to improve the water quality and public health in the region.

Assessment of groundwater geochemistry for drinking and irrigation suitability in Jaunpur district of Uttar Pradesh using GIS-based statistical inference

The quality of groundwater in the Jaunpur district of Uttar Pradesh is poorly studied despite the fact that it is the only supply of water for both drinking and irrigation and people use it without any pre-treatment. The evaluation of groundwater quality and suitability for drinking and irrigation is presented in this study. Groundwater samples were collected and analysed by standard neutralisation and atomic emission spectrophotometry for major anions (HCO₃^-, SO₄^2-, Cl^-, F^-, NO₃^-), cations (Ca²⁺, Mg²⁺, Na⁺, K⁺), and heavy metals (Cd, Mn, Zn, Cu, and Pb). The geographic information system (GIS) and statistical inferences were utilised for the spatial mapping of the groundwater's parameters. The potential water abstraction (i.e. taking water from sources such as rivers, streams, canals, and underground) for irrigation was assessed using the sodium absorption ratio (SAR), permeability index (PI), residual sodium carbonate (RSC), and Na percentage. According to the findings, the majority of the samples had higher EC, TDS, and TH levels, indicating that they should be avoided for drinking and irrigation. The positive correlation coefficient between chemical variability shows that the water chemistry of the studied region is influenced by geochemical and biological causes. According to the USSL (United States Salinity Laboratory) diagram, most of the samples fall under the C2-S1 and C3-S1 moderate to high salt categories. Some groundwater samples were classified as C4-S3 class which is unfit for irrigation and drinking. This study suggests that the groundwater in the study area is unfit for drinking without treatment. However, the majority of the samples were suitable for irrigation.

Groundwater chemistry and health hazard risk valuation of fluoride and nitrate enhanced groundwater from a semi-urban region of South India

Evaluation of groundwater chemistry and its related health hazard risk for humans is a prerequisite remedial measure. The semi-urban region in southern India was selected to measure the groundwater quality to know the human health risk valuation for different age groups of adults and children through oral intake and skin contact with elevated concentrations of fluoride ([Formula: see text]) and nitrate ([Formula: see text]) groundwater. Groundwater samples were collected from the semi-urban region for pre- and post-rainfall periods and resolute its major ion chemistry. The pH values showed the water is alkaline to neutral in nature. Total dissolved solid (TDS) ranged from 201 to 3612 mg/l and 154 to 3457 mg/l. However, [Formula: see text] concentration ranges from 0.28 to 5.48 mg/l and 0.21 to 4.43 mg/l; and NO₃^- ranges from 0.09 to 897.28 mg/l and 0.0 to 606.10 mg/l elevating the drinking water standards of [Formula: see text] in 32% and 38% samples and for [Formula: see text] about 62% and 38% during pre- and post-rainfall seasons, respectively. The fluoride-bearing minerals are the main sources of elevated concentrations of [Formula: see text] and excessive use of chemical fertilizers as the chief source of NO₃^- concentration in the aquifer regime. Water quality index (WQI) ranged from 18.3 to 233 and 12.97 to 219.14; 20% and 22% showed poor water quality for pre- and post-rainfall seasons with WQI ≥ 200. Piper plot suggests that 46% and 51% of samples signify carbonate water type ([Formula: see text]), and 32% and 28% of groundwater samples show ([Formula: see text]) type water for pre- and post-rainfall seasons respectively. Gibbs' plot suggests the dominance of water-rock interaction in the aquifer system. Further, the principal component analysis (PCA) revealed three and four components which explain 74.85% and 79.30% of the variance in pre- and post-rainfall seasons with positive loading of EC, TDS, Ca²⁺, Na⁺, Mg²⁺, K⁺, [Formula: see text], Cl^-, and [Formula: see text] due to mineral weathering and water-rock interactions altering the chemistry for an elevated concentration of [Formula: see text] and [Formula: see text] in groundwater. Cluster analyses of chemical variables observed four clusters with a linkage distance of 5 to 25 with a linkage between different variables displaying predominant ion exchange, weathering of silicate and fluoride-rich minerals, salinization of the water, and a high value of [Formula: see text] concentration, resulting from fertilizers. The hazard quotient (HQ) through ingestion (HQ_ing) and dermal (HQ_der) pathways of F^- and NO₃^- was observed higher than its acceptable limit of 1.0 for different age groups indicating the non-carcinogenic effect on human health. Effective strategic measures like defluoridation, denitrification, safe drinking water supply, sanitary facilities, and rainwater harvesting structures are to be implemented in the area for improvement of human health conditions and also bring awareness to the local community about the health hazard effects of using high concentrated [Formula: see text] and [Formula: see text] water for daily uses.

Judging the sources of inferior groundwater quality and health risk problems through intake of groundwater nitrate and fluoride from a rural part of Telangana, India

Evaluation of groundwater quality and related health hazards is a prerequisite for taking preventive measures. The rural region of Telangana, India, has been selected for the present study to assess the sources and origins of inferior groundwater quality and to understand the human health risk zones for adults and children due to the consumption of nitrate ([Formula: see text])- and fluoride (F^-)-contaminated groundwater for drinking purposes. Groundwater samples collected from the study region were determined for various chemical parameters. Groundwater quality was dominated by Na⁺ and [Formula: see text] ions. Piper's diagram and bivariate plots indicated the carbonate water type and silicate weathering as a main factor and man-made contamination as a secondary factor controlling groundwater chemistry; hence, the groundwater quality in the study region is low. According to the Groundwater Quality Index (GQI) classification, 48.3% and 51.7% of the total study region are excellent (GQI: < 50) and good (GQI: 50 to 100) water quality types, respectively, for drinking purposes. However, [Formula: see text] ranged from 0.04 to 585 mg/L, exceeding the drinking water quality limit of 45 mg/L in 34% of the groundwater samples due to the effects of nitrogen fertilizers. This was supported by the relationship of [Formula: see text] with TDS, Na⁺, and Cl^-. The F^- content was from 0.22 to 5.41 mg/L, which exceeds the standard drinking water quality limit of 1.5 mg/L in 25% of the groundwater samples. The relationship of F^- with pH, Ca²⁺, Na⁺, and [Formula: see text] supports the weathering and dissolution of fluoride-rich minerals for high F^- content in groundwater. They were further supported by a principal component analysis. The Health Risk Index (HRI) values ranged from 0.20 to 20.10 and 0.36 to 30.90 with a mean of 2.82 and 4.34 for adults and children, respectively. The mean intensity of HRI (> 1.0) was 1.37 times higher in children (5.70) than in adults (4.16) due to the differences in weight size and exposure time. With an acceptable limit of more than 1.0, the study divided the region into Northern Safe Health Zone (33.3% for adults and 28.1% for children) and Southern Unsafe Health Zone (66.7% for adults and 71.9% for children) based on the intensity of agricultural activity. Therefore, effective strategic measures such as safe drinking water, denitrification, defluoridation, rainwater harvesting techniques, sanitary facilities, and chemical fertilizer restrictions are recommended to improve human health and protect groundwater resources.

Nitrate concentration analysis and prediction in a shallow aquifer in central-eastern Tunisia using artificial neural network and time series modelling

Agricultural activities have become a major source of groundwater nitrate contamination. In this context, this study aims to analyse nitrate concentrations in a shallow aquifer of Mahdia-Kssour Essef in central-eastern Tunisia, identify the assignable sources, and predict the future levels using artificial neural network (ANN) and autoregressive integrated moving average (ARIMA) models. The results showed that nitrate concentrations measured in 21 pumping wells across the plain ranged from 17 to 521 mg L^-1. A total of 67% of the monitoring points greatly exceed the standard guideline value of 50 mg L^-1. The main relevant anthropogenic and natural factors, such as soil texture, land use, fertilizers application rates, livestock waste disposal, and groundwater table, are positively correlated with groundwater nitrate concentration. The ANN model showed good fitting between measured and simulated results with coefficient of determination (R²), root-mean-square error (RMSE), and mean absolute error (MAE) values of 0.88, 53.95, and 39.64, respectively. The ARIMA applied on annual average nitrate concentrations from 1998 to 2017 revealed that the best fitted model (p, d, q) is (1, 2, 1). The R² value is approximately 0.36, and the Theil inequality coefficient and bias proportion values are small and close to zero. These results proved the ARIMA model's adequacy in forecasting annual average nitrate concentrations of 116 mg L^-1 in 2025. These findings may be useful in making groundwater management decisions, particularly in rural and semi-arid areas, and the proposed ARIMA model could be used as a managed tool to monitor and reduce the nitrate intrusion into groundwater.

Estimation of groundwater pollution levels and specific ionic sources in the groundwater, using a comprehensive approach of geochemical ratios, pollution index of groundwater, unmix model and land use/land cover - A case study

This study aimed to evaluate the degree of groundwater pollution and to assess the contribution of specific ionic sources to groundwater, thereby helping to identify the changes in groundwater chemistry and also in groundwater quality from a rural part of Telangana, India, using the comprehensive understanding of geochemical ratios (GR), pollution index of groundwater (PIG), unmix model (UM), and land use/land cover. Groundwater samples collected (22) from the study area were analysed for pH, EC, TDS, Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃^-, Cl^-, SO₄^2-, NO₃^-, and F^-_. The hydrogeochemical diagram showed the dominant groundwater type of Ca²⁺- Mg²⁺- HCO₃^- due to the water-soil-rock interactions. GR, chloro-alkaline indices, and saturation indices revealed the groundwater chemistry that explains the mineral weathering and dissolution, ion exchange, and evaporation processes as the chief geogenic origin, and also the contamination of surface water due to the influence of household wastewater, septic tank leaks, irrigation-return-flows, chemical composts, etc. as the secondary anthropogenic sources on the aquifer system. Changes in groundwater quality from the recharge area to the discharge area and the correlation coefficient of chemical variables further supported the sources of geogenic and anthropogenic origins. According to PIG's calculations, the present study area was classified as the insignificant pollution zone (5.89%), which shows all chemical variables within their drinking water quality limits, and the low pollution zone (43.34%), medium pollution zone (27.48%), high pollution zone (17.34%), and very high pollution zone (5.95%), which exhibit the TDS, Mg²⁺, Na⁺, K⁺, HCO₃^-, Cl^-, NO₃^-, SO₄^2-, and F^-contents above the drinking water quality standards. This indicates the gradual increase in the intensity of pollution activity. UM also classified the contribution of specific ions (>50%) into three sources: Source I (K⁺) measures the poor sewage conditions and potash fertilizers; Source II (SO₄^2-, Mg²⁺, NO₃^-, Na⁺, and Ca²⁺) specifies the poor sewage conditions, irrigation-return-flows, and chemical fertilizers (gypsum and nitrate); and Source III (F^- and HCO₃^-) represents the dissolution of fluoride minerals as a major contributor to groundwater chemistry. Furthermore, the land use/land cover observations had also supported the assessment of groundwater pollution levels and the contribution of specific ionic sources made by PIG and UM. As a result, the present study clearly indicated that groundwater quality of a geogenic origin is primarily overcome the impact of anthropogenic sources. Therefore, the present study suggested strategic measures to control groundwater pollution and improve groundwater quality.

Consumption of water contaminated by nitrate and its deleterious effects on the human thyroid gland: a review and update

Nowadays, the nitrates have been established as carcinogenic components due to the endogenous formation of N-nitroso compounds, however, the consumption of water contaminated with nitrates has only been strongly related to the presence of methemoglobinemia in infants, as an acute effect, leaving out other side effects that demand attention. The thyroid gland takes relevance because it can be altered by many pollutants known as endocrine disruptors, which are agents capable of interfering with the synthesis of hormones, thus far, it is known that nitrates may disrupt the amount of iodine uptake causing most of the time hypothyroidism and affecting the metabolic functions of the organism in all development stages, resulting in an important health burden for the exposed population. Here, this review and update highlighted the impact of consumption of water contaminated with nitrates and effects on the thyroid gland in humans, concluding that nitrates could act as true endocrine disruptor.

Identifying influencing groundwater parameter on human health associate with irrigation indices using the Automatic Linear Model (ALM) in a semi-arid region in India

Quality of water for the purposes of irrigation is a serious threat to the sustainable development of the agriculture sector. The main objective of this study is to evaluate the suitability of groundwater for irrigation purposes using various irrigation indices such as: Sodium Absorption Ratio (SAR), Residual Sodium Carbonate (RSC), Percentage Sodium (%Na), Magnesium Hazards (MH), Permeability Index (PI), Potential Salinity (PS), Residual Sodium Bicarbonate (RBSC), Kelly's Ratio (KR), Synthetic Harmful Coefficient (K), and Exchangeable Sodium Percentage (ESP). A total of 30 samples were collected from the bore well of agricultural farmland and analysed for cations and anions. MH reveal that 53.33 % of samples exceed the permissible level. PS shows that 43.33 % of samples are marginally affected and 33.33 % of samples are unsuitable for use in irrigation. About 76 % of the groundwater samples were suitable for irrigation and the remainder require treatment before use. Automatic Linear Modelling (ALM) is used to predict the major influence parameter for MH and PS are RBSC, RSC and K value of groundwater. ALM shows that excess magnesium concentration and salinity are the primary factors that affect the suitability of groundwater for irrigation use. This integrated technique showed that water from approximately 25 % of the sample locations would require treatment before use. This study will improve the pattern of irrigation, identify sources of contamination and highlight the importance of organic fertilizers to develop and enhance the sustainable practices in the study region.

Appraisal of vulnerable zones of non-cancer-causing health risks associated with exposure of nitrate and fluoride in groundwater from a rural part of India

The present investigation carried out from a rural part of Nalgonda district, Telangana, India was to know the general groundwater quality and also to measure the vulnerable zones of non-cancer-causing health risks with respect to infants, children, and adults due to the consumption of nitrate and fluoride contaminated groundwater. Groundwater samples were collected from the study area and analyzed for the major physicochemical parameters. Nitrate and fluoride contents ranged from 2 to 700 mg/L and 0.3 to 4.7 mg/L, in which 59.09% and 31.82% of the groundwater samples exceed the safe drinking water limits of 45 mg/L and 1.5 mg/L, which spread over an area of 77.59% and 25.41%, respectively. Domestic wastes, septic tank spillages, animal wastes, and nitrate composts are the prime sources of nitrate, while the fluoride-bearing minerals and phosphate fertilizers are the main sources of fluoride in the aquifer regime. Individual non-cancer-causing health index obviously suggested the nitrate as the higher health risk than fluoride. The total non-cancer-causing health index was observed to be more than the acceptable limit of 1.0 in 95.5% of the total groundwater samples concerning infants, children, and adults. The vulnerable intensity of this index appeared to be higher in infants than in children and adults due to the differences in their body weights. The spatial coverage area of very health risk is more in infants (37.45%) than that of children (36.78%) and adults (30.34%). Thus, the present study suggested suitable measures for the improvement of groundwater quality and consequently the health conditions of the locals.

Investigation of health risks related with multipath entry of groundwater nitrate using Sobol sensitivity indicators in an urban-industrial sector of south India

In the present study, we used a variance decomposition based global sensitivity index to evaluate the sensitivity of input variables and their contribution for non-carcinogenic health risks via intake and dermal pathways. Groundwater samples were collected from an industrial sector (Tiruppur region) of south India during the month of January 2020. These samples were analysed for nitrate, which varied from 10 to 290 mg L^-1 having the mean of 87 mg L^-1. Nearly 58% of the samples surpassed the permissible limit (45 mg L^-1) defined by the World Health Organization. Total hazard index (THI) ranged from 0.29 to 8.52 for children, 0.28 to 8.26 for women, and 0.24 to 6.99 for men. The first-order effect (FOE) and second-order effect (SOE) were derived for the three different age groups using Sobol sensitivity approach. The FOE scores showed that nitrate concentration in groundwater is the most sensitive parameter followed by exposure frequency for children, men and women via oral pathway. The SOE scores showed that nitrate concentration along with ingestion rate had greater sensitiveness in the oral input model. The higher SOE was obtained for the interaction of nitrate with skin surface area for children via dermal pathway, but it was not significant for women and men. These results suggest that epidemiology due to nitrate risk should be studied taking into account of concentration of nitrate, exposure frequency, fraction of contact and body weight. Additionally, ingestion rate and skin surface area were considered for the assessment of health risks for children.

Anthropogenic nitrate in groundwater and its health risks in the view of background concentration in a semi arid area of Rajasthan, India

An increased nitrate (NO₃^-) concentration in groundwater has been a rising issue on a global scale in recent years. Different consumption mechanisms clearly illustrate the adverse effects on human health. The goal of this present study is to assess the natural and anthropogenic NO₃^- concentrations in groundwater in a semi arid area of Rajasthan and its related risks to human health in the different groups of ages such as children, males, and females. We have found that most of the samples (n = 90) were influenced by anthropogenic activities. The background level of NO₃^- had been estimated as 7.2 mg/L using a probabilistic approach. About 93% of nitrate samples exceeded the background limit, while 28% of the samples were beyond the permissible limit of 45 mg/L as per the BIS limits. The results show that the oral exposure of nitrate was very high as compare to dermal contact. With regard to the non-carcinogenic health risk, the total Hazard Index (HI_Total) values of groundwater nitrate were an average of 0.895 for males, 1.058 for females, and 1.214 for children. The nitrate health risk assessment shows that about 38%, 46%, and 49% of the samples constitute the non-carcinogenic health risk to males, females, and children, respectively. Children were found to be more prone to health risks due to the potential exposure to groundwater nitrate.

Groundwater quality evolution based on geochemical modeling and aptness testing for ingestion using entropy water quality and total hazard indexes in an urban-industrial area (Tiruppur) of Southern India

This study used geochemical modeling to understand the chemical evolution of groundwater, entropy water quality index to assess the aptness of groundwater for human consumption, and total hazard index to determine the possible non-carcinogenic risks among children, women, and men in an urban-industrial area (Tiruppur region) of southern India. For the above purposes, 40 groundwater samples were collected from tube and dug wells, and they were tested for various physicochemical parameters. Fluoride and nitrate levels ranged from 0.10 to 2.70 mg/l and 10 to 290 mg/l, respectively. Nearly, 50% of the fluoride samples and 58% of the nitrate samples exceeded the WHO limits of 1.5 and 45 mg/l, respectively. The majority of the groundwater samples (22.5%) represented Ca²⁺-Na⁺-Cl^- water type while the remaining samples exhibited mixed water types. Approximately, 85% of the samples indicated high levels of salinization since they had Revelle index > 0.5 meq/l. The saturation index (SI) revealed that mineral weathering; dissolution of halite, gypsum, and anhydrite; and precipitation of calcite and dolomite contributed to groundwater chemistry. Based on the entropy water quality index (EWQI), none of the groundwater samples was characterized as excellent or good water quality while 57.5% of the samples had medium water quality, and 32.5% and 10% of the samples exhibited poor and extremely poor water qualities, respectively. The last two categories are designated as unfit for consumption. The cumulative health risk (nitrate and fluoride together) ranged from 0.97 to 11.16 for children, 0.60 to 10.54 for women, and 0.39 to 6.92 for men. These values represent health risks among 88%, 80%, and 73% of the groundwater samples for children, women, and men, respectively. Therefore, proper measures should to be done to reduce the health risks associated with high nitrate and fluoride in the groundwater of the study area, which is used for drinking purposes.

Appraisal of subsurface hydrogeochemical processes in a geologically heterogeneous semi-arid region of south India based on mass transfer and fuzzy comprehensive modeling

The main aim of the present study was to examine the quality of the groundwater and decipher the sources of groundwater fluoride through mass balance modeling based on fluoride exposure in a geologically heterogeneous semi-arid region of southern India. This was achieved by hydrogeochemical analysis, graphical methods, and mass transfer modeling approaches. Fuzzy comprehensive technique was applied to evaluate the quality of groundwater for groundwater management. In this regard, 61 groundwater samples were obtained from open wells and bore wells and analyzed for different physicochemical parameters. The major cation and anion abundances follow the order Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ and Cl^- > HCO₃^- > SO₄^2- > NO₃^- > PO₄^3-. About 88.4% and 34.4% of the total water samples were dominated with Na⁺ and Cl^- ions in this region, respectively. The fluoride level in groundwater ranged from 0.10 to 3.30 mg/l with a mean value of 1.04 mg/l. Nearly 25% of the groundwater samples collected from 15 villages showed fluoride concentrations exceeding the maximum permissible limit of 1.5 mg/l as per the World Health Organization recommendations for human intake. More than 85% of the samples fell under strong acid (Cl^- and SO₄^2-) type. The amount of groundwater salinization in this region was 70.5% since the Revelle index (RI) was excess in the groundwater samples (RI > 0.5 meq/l). Silicate weathering, cation exchange, and gypsum dissolution were the dominant geogenic processes in the aquifer system influencing groundwater chemistry and nullified the possibility of carbonate dissolution. Saturation indices revealed the contribution of sequestration of CaCO₃ in F^- enrichment. Total dissolved solids showed strong positive correlations with Na⁺, Ca²⁺, Mg²⁺, Cl^-, SO₄^2- and NO^3- indicating the contribution of anthropogenic inputs to groundwater chemistry in addition to geogenic sources. The results of the fuzzy comprehensive method indicated that 33% of the groundwater samples fell under fair water type, 2% and 11% of the samples fell under poor and very poor quality water types, respectively. Therefore, this work will be helpful for the decision-makers to plan for the sustainable management of groundwater resources.

Evaluation of chromium in vegetables and groundwater aptness for crops from an industrial (leather tanning) sector of South India

The main objective of the present study is evaluation of groundwater aptness for crops and chromium concentration in vegetables from an industrial (leather tanning) sector of South India using geospatial techniques. Seventy groundwater samples were collected from the open and tube wells during November 2017, February 2018, May 2018 and September 2018 to represent northeast (NE) monsoon (October-December), post-monsoon (winter) (January-February), pre-monsoon (summer) (March-May) and southwest (SW) monsoon (June-September) seasons, respectively. In addition, vegetables were also collected during the above-mentioned seasons from the market to assess the level of chromium content in them. All the groundwater samples were tested in the chemical laboratory using the American Public Health Association norms for various physicochemical parameters, viz. TDS, pH, sodium, potassium, calcium, magnesium, bicarbonate, chloride, sulfate, nitrate, fluoride and chromium. Northeast and southwest monsoon season samples mostly represented 'high to very high saline' and 'low alkaline' categories of irrigation water. However, post- and pre-monsoon samples represented 'high to very high saline' and 'low to medium alkaline' categories. 'High saline and low alkaline' water could be used for irrigation in all types of soil with less problem of exchangeable sodium. However, 'very high saline' water should not be applied for the crops having poor salt tolerance and soils having poor internal drainage. The concentration of chromium in groundwater and vegetables was within the permissible limits for human intake prescribed by the World Health Organization standards.

Spatial distribution of quality of groundwater and probabilistic non-carcinogenic risk from a rural dry climatic region of South India

Having safe drinking water is a fundamental human right, which affects directly the human health. In view of this, an effort has been made for understanding the spatial distribution of quality of groundwater in a rural dry climatic region of Andhra Pradesh, South India, and associated health risks with respect to pollutants of NO₃^- and F^-, which cause the potential production of non-carcinogenic risk, using entropy-weighted water quality index (EWWQI) and total chronic hazard index (TCHI), where the population rely on the groundwater resource for drinking purpose. Groundwater quality observed from the present study region has an alkaline character with brackish type. The concentrations of K⁺, HCO₃^-, TDS, Na⁺, NO₃^-, F^-, Mg²⁺ and Cl^- come under the non-permissible limits in 100%, 100%, 96.67%, 90%, 73.33%, 46.67%, 13.33% and 6.67% of the groundwater samples, which deteriorate the groundwater quality, causing the health disorders. The overall groundwater quality computed, using EWWQI, ranges from 53.64 to 216.59 (122.22), which classifies the region spatially into 55%, 10% and 35% due to influences of the geogenic and anthropogenic pollutants, which are the respective medium, poor and very poor groundwater quality types prescribed for potable water. According to the TCHI evaluated with respect to pollutants of NO₃^- and F^-, the values of TCHI for men (1.194 to 4030), women (1.411 to 4.763) and children (1.614 to 5.449) are more than its acceptable limit of one. So, the health risk of non-carcinogenic is spatially in the decreasing order of children > women > men, depending upon their sensitiveness to pollutants and also their body weights. Further, the spatial distributions of both TCH1 and EWWQI are more or less similar, following the pollution activities, which help for establishment of the fact to recognize the intensity of various vulnerable zones. Therefore, the present study suggests the suitable environmental safety measures to control the NO₃^-- and F^--contaminated drinking water and subsequently to increase the health conditions.

Human health risks associated with multipath exposure of groundwater nitrate and environmental friendly actions for quality improvement and sustainable management: A case study from Texvalley (Tiruppur region) of India

The present research was attempted to examine the human health risks due to nitrate contamination in the groundwater of Texvalley (Tiruppur region) of southern India. Groundwater samples (n = 40) were picked up from open wells (shallow aquifer) and tube wells (deep aquifer) during January 2020, and laboratory examination was conducted for various major physicochemical constituents. Nitrate concentration varied from 10 to 290 mg/l with a mean of 83.45 mg/l. About 58% (n = 23) of the wells exceeded the recommended limit (>45 mg/l) of World Health Organisation, which spread over an area of 335.16 km². Among this, 45% of the samples (n = 18) represented shallow aquifers (depth < 15 m), and 13% of them (n = 5) represented deep aquifers (depth > 15 m). Synthetic fertilizers, cow dung and sheep manure, industrial discharge, septic tank leakage and municipal solid waste disposal are the major sources of nitrate pollution in this region. The USEPA health risk assessment model was applied in this study to assess hazard quotients (HQ) according to the NO₃^- exposure in various age groups of inhabitants through two different pathways such as drinking (HQ_oral) and skin contact (HQ_dermal). Eventually, total hazard index (THI) was obtained for all the groundwater samples for different age groups. According to THI, 87%, 78%, 66%, 60%, 56% and 48% of the samples contain health risks (THI >1) for infants, kids, children, teens, adults and aged people, respectively. The study finally recommended seven environmental friendly actions for the groundwater quality improvements and for the sustainable health management.

Revealing drinking water quality issues and possible health risks based on water quality index (WQI) method in the Shanmuganadhi River basin of South India

The aim of the study is to address the issues and associated health risks due to consumption of high-fluoride water supplied for drinking in a rural part of Shanmuganadhi River basin, Tamil Nadu, India. In this study, 61 groundwater samples were gathered from various tube and open wells and analysed for fluoride and other physicochemical parameters. The abundance of cations is Na⁺ > Ca²⁺ > Mg²⁺ > K⁺, and that of anions is HCO₃^- > SO₄^2- > Cl^- > F^-. The fluoride concentration in drinking groundwater varied from 0.10 to 3.3 mg/l. According to the WHO standards, about 26% of the samples were unfit for drinking requirements (16 out of 61 samples) Water quality index (WQI) method was adopted to categorize the water into different classes to understand its suitability for drinking requirements. WQI signified that nearly 52% of the samples denoted poor, very poor and not suitable categories, whereas 48% of samples denoted good and excellent categories for consumption. Health risks associated with high-fluoride drinking water were assessed for various age groups of inhabitants such as children, teens and adults. The hazard quotient estimated based on the oral intake ranged from 0.00E+00 to 5.50E+00, from 0.00E+00 to 4.22E+00 and from 0.00E+00 to 3.45E+00 for children, teens and adults, respectively. It suggested that the health risks are associated with 75%, 59% and 43% of samples, respectively, among children, teens and adults. Therefore, children are more inclined towards risk than teens and adults in this region based on the intake of fluoride-rich drinking water. To improve the present scenario, groundwater should be either treated before drinking water supply or must be artificially recharged to lower the concentration of ions.

Fluoride Geochemistry and Exposure Risk Through Groundwater Sources in Northeastern Parts of Rajasthan, India

Exposure to fluoride concentrations above a threshold of 1.5 mg/L can cause joint pains, restricted mobility, skeletal and dental fluorosis. This study aims to determine the hydrochemical evolution of the fluoride-rich groundwater and estimate the risk of fluoride exposure to the residents of semi-arid northeastern part of Rajasthan, India. The methodology involves measurement of fluoride and other ionic concentrations in groundwater using ion chromatography, followed by an estimation of the cumulative density function and fluorosis risk. The fluoride concentration in water samples varied from 0.04 to 8.2 mg/L with 85% samples falling above the permissible limit. The empirical cumulative density function was used to estimate the percentage and degree of health risks associated with the consumption of F^- contaminated water. It is found that 55% of the samples indicate risk of dental fluorosis, 42% indicate risk of deformities to knee and hip bones, and 18% indicate risk of crippling fluorosis. In addition, instances of high nitrate concentrations above the permissible limit of 45 mg/L are also found in 13% of samples. The fluoride rich groundwater is mainly associated with the Na-HCO₃-Cl type water facies while low fluoride groundwater shows varied chemical facies. The saturation index values indicate a high probability of a further increase in F^- concentration in groundwater of this region. The calculated fluoride exposure risk for the general public in the study area is 3-6 times higher than the allowed limit of 0.05 mg/kg/day. Based on the results of this study, a fluorosis index map was prepared for the study area. The northern and northeastern parts are less prone to fluorosis, whereas the south-central and southwestern parts are highly vulnerable to fluorosis. The inferences from this study help to prioritize the regions that need immediate attention for remediation.

Seasonal and Spatial Variation of Groundwater Quality Vulnerable Zones of Yellareddygudem Watershed, Nalgonda District, Telangana State, India

Evaluation of seasonal and spatial variations in vulnerable zones for poor groundwater quality is essential for the protection of human health and to maintain the crop yields. With this objective, groundwater samples were collected seasonally (i.e., pre- and post-monsoon) from the Yellareddygudem watershed of Telangana, India. These samples were analysed for major chemical parameters (pH, TDS, Ca²⁺, Mg²⁺, Na⁺, K⁺, [Formula: see text], Cl^-, [Formula: see text], [Formula: see text], and F^-). Geographical information system (GIS) tools were used to delineate the seasonal and spatial variations for vulnerable zones related to the drinking groundwater quality index (DGQI) and irrigation groundwater quality index (IGQI). Geochemical facies and relations, Piper diagrams, and principal component analysis indicated that the weathering, dissolution, leaching, ion exchange, and evaporation were the primary processes controlling the groundwater quality seasonally. Human influences were the secondary factors. The TDS, Na⁺, K⁺, Cl^-, [Formula: see text], and F^- parameters were observed to be within the drinking water quality standard limits in most post-monsoon groundwater samples. However, the DGQI showed an increase in the number of samples with unsuitable quality for drinking in the post-monsoon period compared with the pre-monsoon period. The IGQI demonstrated that the number of samples with unsuitable quality for irrigation increased in the post-monsoon period compared to the pre-monsoon period. The differences in the vulnerable zones between the pre- and post-monsoon periods were due to variations in groundwater recharge, following the topography. Thus, the present study will help decision makers to plan groundwater treatment measures within vulnerable zones.

Groundwater Pollution and Human Health Risks in an Industrialized Region of Southern India: Impacts of the COVID-19 Lockdown and the Monsoon Seasonal Cycles

Samples of groundwater were collected during a post-monsoon period (January) and a pre-monsoon period (May) in 2020 from 30 locations in the rapidly developing industrial and residential area of the Coimbatore region in southern India. These sampling periods coincided with times before and during the lockdown in industrial activity and reduced agricultural activity that occurred in the region due to the COVID-19 pandemic. This provided a unique opportunity to evaluate the effects of reduced anthropogenic activity on groundwater quality. Approximately 17% of the wells affected by high fluoride concentrations in the post-monsoon period returned to levels suitable for human consumption in samples collected in the pre-monsoon period. This was probably due to ion exchange processes, infiltration of rainwater during the seasonal monsoon that diluted concentrations of ions including geogenic fluoride, as well as a reduction in anthropogenic inputs during the lockdown. The total hazard index for fluoride in the post-monsoon samples calculated for children, adult women, and adult men indicated that 73%, 60%, and 50% of the groundwater samples, respectively, had fluoride levels higher than the permissible limit. In this study, nitrate pollution declined by 33.4% by the pre-monsoon period relative to the post-monsoon period. The chemical facies of groundwater reverted from the Na-HCO3-Cl and Na-Cl to the Ca-HCO3 type in pre-monsoon samples. Various geogenic indicators like molar ratios, inter-ionic relations along with graphical tools demonstrated that plagioclase mineral weathering, carbonate dissolution, reverse ion exchange, and anthropogenic inputs are influencing the groundwater chemistry of this region. These findings were further supported by the saturation index assessed for the post- and pre-monsoon samples. COVID-19 lockdown considerably reduced groundwater pollution by Na+, K+, Cl-, NO3¯, and F- ions due to shutdown of industries and reduced agricultural activities. Further groundwater quality improvement during lockdown period there is evidence that the COVID-19 lockdown by increased HCO3¯ ion concentration. Overall results illustrate the positive benefits to groundwater quality that could occur as a result of measures to control anthropogenic inputs of pollutants.

Groundwater chemistry, distribution and potential health risk appraisal of nitrate enriched groundwater: A case study from the semi-urban region of South India

In recent years, an elevated concentration of nitrate in groundwater has been a growing problem on a global scale. It directly shows the adverse effects on human health via various intake pathways. Herein, the aim of the present study was to evaluate the nitrate concentration in groundwater and its associated human health risk in various age groups (females, males and children) in the investigated region. For this purposes, thirty groundwater samples were collected and analyzed physico-chemical parameters including nitrate concentration. The results showed that, the concentration of nitrate ranges from 14 to 82 mg/L and about 43.3% of these groundwater samples beyond the safe level of 45 mg/L according to Indian guidelines. The higher nitrate contamination is observed in the vicinity of Sarvepalli and Timmapur villages where groundwater chemistry is majorly influenced by anthropogenic sources. Health risks were assessed through oral/ingestion and dermal contact exposure routes for females, males and children population in the study region. Oral exposure was much higher than dermal contacts. For the non-carcinogenic risk, the HI_Total values of groundwater in the investigated region varied from 0.313 to 1.976 (mean of 0.941) for males, 0.370 to 2.336 (mean of 1.112) for females and 0.443 to 2.694 (mean of 1.314) for children. The health risk assessment for nitrate divulged that 60%, 57% and 50% of groundwater samples pose a non-carcinogenic health risk for children, females and males, respectively.

Appraisal of Groundwater Quality with Human Health Risk Assessment in Parts of Indo-Gangetic Alluvial Plain, North India

Groundwater contamination in the Indo-Gangetic alluvial plain has reportedly been affected by various factors, such as mineral dissolution, overexploitation, precipitation, and ion exchange. This study was designed to interpret the hydrochemical fluctuations in the groundwater sources of a rural area in Raebareli district. Groundwater is slightly alkaline and affected by the issues of fluoride, salinity, hardness, and nitrate. The Pollution Index of Groundwater significantly categorize 57% and 79% of the samples under the "insignificant pollution" category during pre-monsoon and post-monsoon periods. The Health risk assessment indicated the high susceptibility of children toward health risks. It also indicated that fluoride had greater impact than nitrate in the study area. The multivariate statistical analysis indicates that anthropogenic activities, such as agricultural practices, including excessive fertilizer application and improper domestic and cattle waste management, are probable causes of groundwater contamination through NO₃^-, Cl^-, Na⁺, and K⁺. Furthermore, the base exchange index classified 71.43% samples in pre-monsoon and 78.57% in post-monsoon as Na-HCO₃ type. The meteoric genesis index suggested that 78.57% and 85.71% of the samples belong to shallow meteoric water percolation type during pre- and post-monsoon periods, respectively. The Piper plots revealed that HCO₃-Ca·Mg and SO₄·Cl-Na + K type are the prominent facies in the area, with dominance of alkalis and weak acids. According to Gibbs plot, majority of the samples fall under "rock dominance" suggesting that "rock-water" interaction was the dominant natural process controlling the groundwater chemistry.

Characterization of the hydrochemistry of water resources of the Weibei Plain, Northern China, as well as an assessment of the risk of high groundwater nitrate levels to human health

This study aimed to evaluate the hydrochemistry of the water resources of the Weibei Plain, Northern China, as well as the risks posed by high groundwater nitrate concentrations to human health. Groundwater and surface water samples numbering 168 and 14, respectively, were collected during the dry and wet seasons. Water in the study area was weakly alkaline, falling into a hard-fresh or hard-brackish category. The groundwater chemical types were mainly SO₄·Cl-Ca·Mg (59.5%) and HCO₃-Ca·Mg (28.6%), whereas the dominant chemistry type of surface water was SO₄·Cl-Na (78.6%). Groundwater showed relatively high concentrations of NO₃^-, with average dry and wet season concentrations of 212 mg·L^-1 and 223 mg·L^-1, respectively, whereas surface water had a low NO₃^- content. The major processes affecting water chemistry were determined to be rock weathering, such as silicate weathering and evaporative dissolution, as well as cation exchange. NO₃^- in groundwater was found to mainly originate from anthropogenic inputs such as agricultural production and domestic sewage. The entropy-weight water quality index (EWQI) assessment showed that although the quality of surface water was generally good, more than half of the groundwater samples failed drinking water standards, with NO₃^- identified as being the most problematic parameter affecting the water quality evaluation. Risk assessment of high groundwater nitrate concentrations indicated that long-term domestic use of groundwater in the study area can put the health of residents at great risk. Totals of 81% and 75% of the groundwater samples exceeded the acceptable limit for non-carcinogenic risk (HI = 1) to infants during the dry and wet seasons, respectively, whereas 75% and 71.3% of samples exceeded the acceptable limit for children, respectively. Future management of water in the Weibei Plain should prioritize the control groundwater nitrate pollution.

Hydrogeochemistry and fluoride contamination in Jiaokou Irrigation District, Central China: Assessment based on multivariate statistical approach and human health risk

Too little and too much fluorine are potentially hazardous for human health. In the Jiaokou Irrigation District, ionic concentrations, hydrogeochemistry, and fluoride contaminations were analyzed using correlation matrices, principal component analysis (PCA), and health risk assessment. The patterns for the average cation and anion concentrations were Na⁺ > Mg²⁺ > Ca²⁺ > K⁺ and SO₄^2- > HCO₃^- > Cl^- > NO₃^- > CO₃^2-. The fluoride concentrations ranged between 0.29 and 8.92 mg/L (mean = 2.4 mg/L). 5% of the samples displayed lower than the recommended limit of 0.5 mg/L fluoride content, while 69% exceeded the allowable limits of 1.5 mg/L for drinking. The low F^- content is distributed in a small part of the southeast, while elevated F^- mainly in the central area of the study region. The PCA results indicated three principal components (PC), PC1 having the greatest variance (45.83%) and affected by positive loadings of TDS, Cl^-, SO₄^2-, Na⁺, and Mg²⁺, PC2 accounting for 17.03% and dominated by Ca²⁺, pH, HCO₃^-, and K⁺, and PC3 representing 12.17% and mainly comprising of CO₃^2-. High fluoride groundwater is of the SO₄-Cl-Na type, followed by HCO₃-Na type. Evaporation and ion exchange play important roles in producing high fluoride groundwater. Furthermore, saturation index and anthropogenic activities also promote the high fluoride concentrations. The values of the total hazard quotient of 93% groundwater samples were greater than 1 for infants, followed by 85% for children, 68% for teenagers, and 57% for adults. Non-carcinogenic health risks to infants may occur over the entire study area, while for adults, health risks are mainly found in Weinan and Pucheng. High fluorine may have a potential negative influence on neurodevelopment, especially for infants and children. Adults in this region have serious dental fluorosis and skeletal fluorosis because of long-term drinking of high fluoride groundwater. Therefore, measures, including using organic fertilizers, strengthening defluoridation process, and optimizing water supply strategies, are necessary in this area.