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

Prediction of nitrate concentration and the impact of land use types on groundwater in the Nansi Lake Basin

Groundwater faces a pervasive threat from anthropogenic nitrate contamination worldwide, particularly in regions characterized by intensive agricultural practices. This study examines groundwater quality in the Nansi Lake Basin (NSLB), emphasizing nitrate (NO3--N) contamination. Utilizing 422 groundwater samples, it investigates hydrochemical dynamics and the impact of land use on groundwater composition. Key methods include hydrogeochemical analysis, PCA, and the Duncan comparison method. The innovative aspect lies in using Multilayer Perceptron Artificial Neural Networks (MLP-ANNs) to predict NO3--N contamination. The results showed that NO3--N levels ranged from 0.004 to 177.72 mg/L, with approximately 43.6 % of the samples exceeding the safe drinking water limit of 10 mg/L (WHO 2022). Substantial spatial variability in the concentrations of major ions within aquifers, with NO3--N exhibiting the most significant fluctuations. The factors responsible for the hydrochemical composition of groundwater include recharge sources, water-rock interaction, prevailing groundwater environment, land use patterns, and related anthropogenic activities. Notably, land use types, primarily farmland and rural areas, exhibited a strong association with NO3--N. The MLP-ANNs achieved high prediction accuracy for NO3--N, with an AUC of 0.85. The MLP-ANN model identified heightened susceptibility to nitrate contamination in the central and southeastern regions, characterized by dense shallow wells (<60 m). Key factors include nitrogen-based fertilizer overuse, agricultural runoff, domestic wastewater discharge, and septic system leakage. The vulnerability is exacerbated by highly permeable loose rock pore water systems underlying intensively cultivated agricultural lands. This study elucidates the complex interrelation between natural processes and anthropogenic activities that influence groundwater quality, providing valuable perspectives that could guide the formulation of policies and practices aimed at promoting sustainable groundwater utilization and environmental conservation.

Hydrogeochemical processes regulating groundwater quality and its suitability for drinking purposes in the recent alluvial plain, Blue Nile Region, Sudan

Groundwater is becoming a critical freshwater source in the Blue Nile Region, Sudan. However, overexploitation and contamination increasingly threaten its sustainability. This study evaluates the hydrogeochemical processes influencing groundwater and its suitability for drinking purposes in the recent alluvial plain. A total of 342 groundwater samples were collected from domestic wells and monitoring boreholes in 2022 for hydrochemical and multivariate statistical analysis. The results revealed that the groundwater is predominantly of HCO3-Ca·Mg and HCO3-Ca·Na facies, reflecting the influences of natural processes like mineral dissolution and ion exchange. The key factors affecting groundwater quality include rock-water interactions and anthropogenic influences. Most groundwater samples complied with the World Health Organization (WHO, WHO. (2022). Fourth edition incorporating the first and second addenda Guidelines for drinking-water quality) and Sudanese drinking water standards. However, F- concentrations exceeding permissible levels were detected in northeastern and southwestern boreholes, posing potential health risks. Elevated total dissolved solids (TDS) were linked to mineral dissolution and agricultural runoff. The Water Quality Index (WQI) categorized 39.42% of samples as excellent, 50.72% as good, and 9.57% as poor to very poor, with 0.29% unsuitable for drinking. Areas with low human activities exhibited better water quality, while compromised samples correlated with nitrate contamination, salinity, and poor waste management practices. This study provides a robust foundation for developing sustainable groundwater management strategies to mitigate contamination risks and secure safe drinking water access.

Hydrogeochemical properties, source provenance, distribution, and health risk of high fluoride groundwater: Geochemical control, and source apportionment

This study evaluated high fluoride (F-) levels, source distribution, provenance, health risk, and source apportionment in the groundwater of Sargodha, Pakistan. Therefore, 48 groundwater samples were collected and analyzed by ion-chromatography (DX-120, Dionex). The lowest concentration of F- was 0.1, and the highest was 5.8 mg/L in the aquifers. In this study, 43.76% of the samples had exceeded the World Health Organization's allowable limit of 1.5 mg/L. The hydrogeochemical facies in Na-rich and Ca-poor aquifers showed NaCl (66.6%), NaHCO3 (14.5%), mixed CaNaHCO3 (8.3%), CaCl2 (8.3%), mixed CaMgCl2 (2%), and CaHCO3 (2%) type water. Alkaline pH, high Na+, HCO3- concentrations, and poor Ca-aquifers promoted F- dissolution in aquifer. The significant positive correlations between Na⁺ and F- suggested cation exchange, where elevated Na⁺ occurs in Ca-poor aquifers. The cation exchange reduces the availability of Ca2+ would lead to higher F- concentrations. Meanwhile, the correlation between HCO₃- and F- indicates that carbonate minerals dissolution helps in increasing pH and HCO₃- as a result F- triggers in aquifers. Groundwater chemistry is primarily governed by the weathering of rock, water-rock interaction, ion-exchange, and mineral dissolution significantly control groundwater compositions. Cluster analysis (CA) determined three potential clusters: less polluted (10.4%), moderately polluted (39.5%), and severely polluted (50%) revealing fluoride toxicity and vulnerability in groundwater wells. Mineral phases showed undersaturation and saturation determining dissolution of minerals and precipitation of minerals in the aquifer. PCAMLR model determined that high fluoride groundwater takes its genesis from F-bearing minerals, ion exchange, rock-water interaction, and industrial, and agricultural practices. The health risk assessment model revealed that children are at higher risk to F- toxicity than adults. Thus, groundwater of the area is unsuitable for drinking, domestic, and agricultural needs.

Integrated assessment of groundwater quality dynamics and Land use/land cover changes in rapidly urbanizing semi-arid region

Rapid urbanization worldwide, poses numerous environmental challenges between escalating land use land cover (LULC) changes and groundwater quality dynamics. The main objective of this study was to investigate the dynamics of groundwater quality and LULC changes in Sargodha district, Punjab, Pakistan. Groundwater hydrochemistry reveals acceptable pH levels (<8) but total dissolved solids (TDS), electrical conductivity (EC) and HCO3- showed dynamic fluctuations by exceeding WHO limits. Piper diagrams, indicated dominance by magnesium and bicarbonate types, underscoring the influence of natural processes and anthropogenic activities. Major ion relationships in 2010, 2015, and 2021 showed a high correlation (R2 > 0.85) between Na+ and Cl-, suggesting salinization. whereas, the poor correlation (<0.17) between Ca2+ and HCO3- does not support calcite dissolution as the primary process affecting groundwater composition. The examination of nitrate contamination in groundwater across the years 2010, 2015, and 2021 was found to be high in the municipal sewage zone, suggesting a prevailing issue of nitrate contamination attributed to urban activities. The Nitrate Pollution Index (NPI) reveals a concerning trend, with a higher proportion of samples classified under moderate to high pollution categories in 2015 and 2021 compared to 2010. The qualitative assessment of nitrate concentration on spatiotemporal scale showed lower values in 2010 while a consistent rise from 2015 to 2021 in north-east and western parts of district. Likewise, NPI was high in the north-eastern and south-western regions in 2010, then reduced in subsequent years, which may be attributed to effective waste management practices and alterations in agricultural practices. The health risk assessment of 2010 indicated Total Health Hazard Quotient (THQ) within the standard limit, while in 2015 and 2021, elevated health risk was observed. This study emphasizes the need to use multiple approaches to groundwater management for sustainable land use planning and regulations that prioritize groundwater quality conservation.

Integrated geophysical and geospatial techniques for surface and groundwater modeling

An integrated approach using geophysical and geospatial techniques was employed to model the surface and subsurface water-bearing strata and assess aquifer vulnerability in the Sehnsa town, Kotli district, State of Azad Kashmir, Pakistan. The inadequate scientific studies in the hilly terrain with such complex geological conditions has led to the failure of the boreholes for groundwater extraction. For the evaluation of groundwater potential and subsurface lithology, 30 vertical electrical soundings (VES) stations utilizing the Schlumberger electrode configuration were completed, modeled and analyzed spatially. Numerous geoelectrical parameters like true resistivity, thickness of subsurface layers and Dar-Zarrouk parameters were evaluated. The subsurface lithology delineated comprised topsoil, clayey sand, sandstone, and boulder clays which closely resemble to the borehole lithologs available in the study area. The inversion model confirms the presence of patches of high-resistivity sandstone in the southwestern part of the study area with the maximum thickness of the aquifer up to 140 m. Most aquifers were classified as unconfined with Q-type resistivity curves. The protective overburden capacity of the aquifers is rated as poor at VES 1, 3-5, 8, 10-16, 18, 19, 22-25, 27 and 30 whereas the moderate category was found at VES 2, 9 and 20 and excellent at VES 7 and 28, respectively. Therefore, the VES stations with poor and moderate ratings of overburden protective capacity are vulnerable for surface contaminants. The aquifer recharge was associated with rainfall and partly from the Poonch River. The effective integration of geophysical and geospatial techniques in this study provides sufficient information about the regional water resources and gives a preliminary model that can facilitate efficient water resource management in the area. These approaches can be successfully applied to diverse geographical and hydrogeological sites due to their versatility and reliability.

Hydrogeochemical evolution and heavy metal characterization of groundwater from southwestern, Nigeria: An integrated assessment using spatial, indexical, irrigation, chemometric, and health risk models

This study examines the hydrogeochemical and heavy metal parameters of groundwater in Ojo District to determine its suitability for use, potential sources, and human health implications. Ten groundwater samples were assessed, and hydrogeochemical modelling was performed via the Aquachem software. The chemical ions were in the following order: EC > (107.78-448.65 μS/cm) > TDS (182.02-320.77 mg/l) > TH (46.22-182.45 mg/l) > pH (5.55-6.35); HCO3 - (64.13-125.82 mg/l) > Na+ (36.87-96.49 mg/l) > Ca2+ (47.65-58.88 mg/l) > SO4 2- (19.94-53.67) > NO3 - (15.55-44.25 mg/l) > Cl- (20.43-27.16 mg/l) > Mg2+ (11.09-16.87 mg/l) and K+ (2.55-7.86 mg/l). The concentrations of heavy metals in groundwater were in the range of: Fe (0.11-0.27 mg/l) > Mn (0.003-0.16 mg/l) > Ni (0.05-0.12 mg/l) > Zn (0.003-0.05 mg/l) > Pb (0.001-0.03 mg/l) > As (0.001-0.005 mg/l) > Cr (0.002-0.005 mg/l) > Cd (0.001-0.003 mg/l) and Cu (0.001-0.0002 mg/l), with Pb, Mn, and Ni exceeding their allowable limits. The Schoeller and Gibbs plots revealed that the major mechanisms controlling the aquifer groundwater in Ojo region are geological rock weathering and mineralization, with a minimal influence of saltwater intrusion. The piper trilinear diagram also revealed that none of the cation was dominant while the anions were strongly dominated by HCO3 - (weak acids). The hydrogeochemical facies which describes the geochemical characteristics of the groundwater were classified into 3 types; "Ca2+-Mg+-HCO3 - (65 %)", "mixing zones (30 %)", and "Na+-K+-Cl--HCO3 - (5 %)". The hydrogeochemical modelling revealed that the groundwater is characterized by forward cation exchange, while rock-water interactions (silicate dissolution) were heavily involved in the geochemical processes. The single pollution index showed that Pb, Ni, and Mn contributed significantly to contamination, and the multi-pollution indices showed that the groundwater was slightly-moderately polluted. The integrated groundwater quality index revealed that only 10 % were clean, 50 % were poor or moderately unclean, 30 % were highly unclean, and only 10 % were extremely unclean (unfit for utilization). The water pollution index showed that 70 % of the groundwater was good. The irrigation indices suggest that the groundwater would enhance soil quality and support plant growth. Multivariate analysis revealed that the groundwater is being influenced by geogenic factors and anthropogenic activities. The health risk assessment (Hazard Quotient and Hazard Index) showed that exposure of adults to the investigated groundwaters could result in noncarcinogenic adverse effects. The cancer risk values also exceeded the minimum limit (1.0 x 10-6) and thresholds (1.0 x 10-4) for adults, indicating the carcinogenic potential of the groundwater.

Macrophyte assisted phytoremediation and toxicological profiling of metal(loid)s polluted water is influenced by hydraulic retention time

The present study reports findings related to the treatment of polluted groundwater using macrophyte-assisted phytoremediation. The potential of three macrophyte species (Phragmites australis, Scirpus holoschoenus, and Typha angustifolia) to tolerate exposure to multi-metal(loid) polluted groundwater was first evaluated in mesocosms for 7- and 14-day batch testing. In the 7-day batch test, the polluted water was completely replaced and renewed after 7 days, while for 14 days exposure, the same polluted water, added in the first week, was maintained. The initial biochemical screening results of macrophytes indicated that the selected plants were more tolerant to the provided conditions with 14 days of exposure. Based on these findings, the plants were exposed to HRT regimes of 15 and 30 days. The results showed that P. australis and S. holoschoenus performed better than T. angustifolia, in terms of metal(loid) accumulation and removal, biomass production, and toxicity reduction. In addition, the translocation and compartmentalization of metal(loid)s were dose-dependent. At the 30-day loading rate (higher HRT), below-ground phytostabilization was greater than phytoaccumulation, whereas at the 15-day loading rate (lower HRT), below- and above-ground phytoaccumulation was the dominant metal(loid) removal mechanism. However, higher levels of toxicity were noted in the water at the 15-day loading rate. Overall, this study provides valuable insights for macrophyte-assisted phytoremediation of polluted (ground)water streams that can help to improve the design and implementation of phytoremediation systems.

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

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

Integrated Approach to Hydrogeochemical Assessment of Groundwater Quality in Major Industrial Zone of Punjab, Pakistan

Groundwater contamination with arsenic (As) is a significant concern in Pakistan's Punjab Province. This study analyzed 69 groundwater samples from Faisalabad, Gujranwala, Lahore, and Multan to understand hydrogeochemistry, health impacts, contamination sources, and drinking suitability. Results revealed varying as concentrations across districts, with distinctive cation and anion orders. Faisalabad exhibited Na+ > Mg2+ > Ca2+ > K+ > Fe2+ for cations and SO42- > Cl- > HCO3- > NO3- > F- for anions. Gujranwala showed Na+ > Ca2+ > Mg2+ > K+ for cations and HCO3-  > SO42- > Cl- > NO3-  > F- for anions. In Lahore, demonstrated: Na+ > Ca2+ > Mg2+ > Fe > K+ for cations and HCO3-  > SO42- > Cl- > NO3-  > F- for anions. Multan indicated K+ > Ca2+ > Mg2+ > Na+ > Fe for cations and HCO3-  > SO42- > Cl- > F- > NO3- ) for anions. Hydrochemical facies were identified as CaHCO3 and CaMgCl types. Principal Component Analysis (PCA), highlighted the influence of natural processes and human activities on groundwater pollution. Water Quality Index (WQI) result reveal that most samples met water quality standards. The carcinogenic risk values for children exceeded permissible limits in all districts, emphasizing a significant cancer risk. The study highlights the need for rigorous monitoring to mitigate (As) contamination and protect public health from associated hazards.

Identification of hydrochemical fingerprints, quality and formation dynamics of groundwater in western high Himalayas

Identifying hydrochemical fingerprints of groundwater is a challenge in areas with complex geological settings. This study takes the Gilgit-Baltistan, a complex geological area in west high Himalayas, Pakistan, as the study area to get insights into the hydrochemcial genesis and quality of groundwater in complex geological mountainous regions. A total of 53 samples were collected across the area to determine the hydrochemical characteristics and formation of groundwater. Results revealed groundwater there is characterized by slightly alkaline and soft fresh feature. Groundwater is dominated by the hydrochemical facies of HCO3·SO4-Ca·Mg type. The factor method yields three components (PCs) of principal component analysis, which together explain 75.71% of the total variances. The positive correlation of EC, TDS, Ca2+, SO42-, K+ in PC1, and NO3-, Cl- in PC2 indicate that a combination of natural and anthropogenic activities influences groundwater hydrochemistry. Water-rock interaction is the main mechanism governing the natural hydrochemistry of groundwater. The negative correlation of Cl-, SO42-, Ca2+, and Na+ with NDVI attributes to inorganic salt uptake by plant roots. Groundwater chemical composition is also affected by the type of land use. Groundwater is characterized as excellent and good water quality based on the entropy-weighted water quality index assessment, and is suitable for drinking purposes except for very few samples, while aqueous fluoride would pose potential health threats to water consumers in western high Himalayas, and infants are most at risk compared to other populations. This study will help to deepen the hydrochemial formation mechanism and exploitation suitability of groundwater resources in the mountainous areas that undergone the combined actions of nature and human activities, and provide insights into the characteristics of water environmental quality in western Himalayas area.

Groundwater quality characterization using an integrated water quality index and multivariate statistical techniques

This study attempts to characterize and interpret the groundwater quality (GWQ) using a GIS environment and multivariate statistical approach (MSA) for the Jakham River Basin (JRB) in Southern Rajasthan. In this paper, analysis of various statistical indicators such as the Water Quality Index (WQI) and multivariate statistical methods, i.e., principal component analysis and correspondence analysis (PCA and CA), were implemented on the pre and post-monsoon water quality datasets. All these methods help identify the most critical factor in controlling GWQ for potable water. In pre-monsoon (PRM) and post-monsoon (POM) seasons, the computed value of WQI has ranged between 28.28 to 116.74 and from 29.49 to 111.98, respectively. As per the GIS-based WQI findings, 63.42 percent of the groundwater samples during the PRM season and 42.02 percent during the POM were classed as 'good' and could be consumed for drinking. The Principal component analysis (PCA) is a suitable tool for simplification of the evaluation process in water quality analysis. The PCA correlation matrix defines the relation among the water quality parameters, which helps to detect the natural or anthropogenic influence on sub-surface water. The finding of PCA's factor analysis shows the impact of geological and human intervention, as increased levels of EC, TDS, Na+, Cl-, HCO3-, F-, and SO42- on potable water. In this study, hierarchical cluster analysis (HCA) was used to categories the WQ parameters for PRM and POR seasons using the Ward technique. The research outcomes of this study can be used as baseline data for GWQ development activities and protect human health from water-borne diseases in the southern region of Rajasthan.

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

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

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.

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.

Groundwater Quality, Health Risk Assessment, and Source Distribution of Heavy Metals Contamination around Chromite Mines: Application of GIS, Sustainable Groundwater Management, Geostatistics, PCAMLR, and PMF Receptor Model

Groundwater contamination by heavy metals (HMs) released by weathering and mineral dissolution of granite, gneisses, ultramafic, and basaltic rock composition causes human health concerns worldwide. This paper evaluated the heavy metals (HMs) concentrations and physicochemical variables of groundwater around enriched chromite mines of Malakand, Pakistan, with particular emphasis on water quality, hydro-geochemistry, spatial distribution, geochemical speciation, and human health impacts. To better understand the groundwater hydrogeochemical profile and HMs enrichment, groundwater samples were collected from the mining region (n = 35), non-mining region (n = 20), and chromite mines water (n = 5) and then analyzed using ICPMS (Agilent 7500 ICPMS). The ranges of concentrations in the mining, non-mining, and chromite mines water were 0.02-4.5, 0.02-2.3, and 5.8-6.0 mg/L for CR, 0.4-3.8, 0.05-3.6, and 3.2-5.8 mg/L for Ni, and 0.05-0.8, 0.05-0.8, and 0.6-1.2 mg/L for Mn. Geochemical speciation of groundwater variables such as OH^-, H⁺, Cr⁺², Cr⁺³, Cr⁺⁶, Ni⁺², Mn⁺², and Mn⁺³ was assessed by atomic fluorescence spectrometry (AFS). Geochemical speciation determined the mobilization, reactivity, and toxicity of HMs in complex groundwater systems. Groundwater facies showed 45% CaHCO₃, 30% NaHCO₃, 23.4% NaCl, and 1.6% Ca-Mg-Cl water types. The noncarcinogenic and carcinogenic risk of HMs outlined via hazard quotient (HQ) and total hazard indices (THI) showed the following order: Ni > Cr > Mn. Thus, the HHRA model suggested that children are more vulnerable to HMs toxicity than adults. Hierarchical agglomerative cluster analysis (HACA) showed three distinct clusters, namely the least, moderately, and severely polluted clusters, which determined the severity of HMs contamination to be 66.67% overall. The PCAMLR and PMF receptor model suggested geogenic (minerals prospects), anthropogenic (industrial waste and chromite mining practices), and mixed (geogenic and anthropogenic) sources for groundwater contamination. The mineral phases of groundwater suggested saturation and undersaturation. Nemerow's pollution index (NPI) values determined the unsuitability of groundwater for domestic purposes. The EC, turbidity, PO₄^-3, Na⁺, Mg⁺², Ca⁺², Cr, Ni, and Mn exceeded the guidelines suggested by the World Health Organization (WHO). The HMs contamination and carcinogenic and non-carcinogenic health impacts of HMs showed that the groundwater is extremely unfit for drinking, agriculture, and domestic demands. Therefore, groundwater wells around the mining region need remedial measures. Thus, to overcome the enrichment of HMs in groundwater sources, sustainable management plans are needed to reduce health risks and ensure health safety.

Fluoride and nitrate in groundwater: a comprehensive analysis of health risk and potability of groundwater of Jhunjhunu district of Rajasthan, India

Groundwater contamination is a major concern in front of the scientific community because it is directly related to human health, especially in arid and semi-arid regions. Therefore, a comprehensive study was engaged to evaluate the water quality, potability, and human health risk assessment due to the consumption of fluoride- and nitrate-contaminated water in Jhunjhunu district of Rajasthan. In order to assess the water quality, samples were collected from 87 locations in the study region, and a total of 16 parameters were analyzed as per the standard methods. The results showed that the value of the number of quality parameters consisting of pH, EC, TDS, fluoride, chloride, nitrate, sulfate, total hardness, calcium, magnesium, and total alkalinity was higher than the recommended limit of BIS and WHO. The fluoride in 11% and nitrate in 6% of samples were observed to exceed the permissible limit of WHO. The results of risk assessment due to fluoride and nitrate revealed that hazard index values of 71% of groundwater samples for males, 78% of groundwater samples for females, and 75% of groundwater samples for children were greater than 1, indicating the significant health hazard due to consumption of groundwater. The water quality index (WQI) found that 39% of groundwater samples belong to categories that cannot be used for drinking purposes. Principal component analysis (PCA) reduced the large number of variables affecting the overall quality and chemistry of groundwater and determined four major components which account for 69.50% variance in the data. PCA concluded that both geogenic and anthropogenic sources of contamination influenced the groundwater of the study area.

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).

Chromium Transport and Fate in Vadose Zone: Effects of Simulated Acid Rain and Colloidal Types

Chromium (Cr) can enter groundwater through rainfall infiltration and significantly affects human health. However, the mechanisms by which soil colloids affect chromium transport are not well investigated. In this study, column experiments were conducted to simulate the chromium (Cr) transport mechanism in two typical soils (humic acid + cinnamon soil and montmorillonite + silt) in the vadose zone of a contaminated site and the effects of acid rain infiltration conditions. The results showed that Mt colloids have less influence on Cr. The fixation of Cr by colloid mainly occurs in the cinnamon soil layer containing HA colloid. The adsorption efficiency of Cr was increased by 12.8% with the addition of HA. In the HA-Cr system, the introduction of SO42- inhibited the adsorption of Cr, reducing the adsorption efficiency from 31.4% to 24.4%. The addition of Mt reduced the adsorption efficiency of Cr by 15%. In the Mt-Cr system, the introduction of SO42- had a promoting effect on Cr adsorption, with the adsorption efficiency increasing from 4.4% to 5.1%. Cr release was inhibited by 63.88% when HA colloid was present, but the inhibition owing to changes in acidity was only 14.47%. Mt colloid promotes Cr transport and increases the leaching rate by 2.64% compared to the absence of Mt. However, the effect of acidity change was not significant. Intermittent acid rain will pose a higher risk of pollutant release. Among the influencing factors, the type of colloid had the most significant influence on the efficiency of Cr leaching. This study guides the quantitative assessment of groundwater pollution risk caused by Cr in the vadose zone.

Evolution Mechanism of Arsenic Enrichment in Groundwater and Associated Health Risks in Southern Punjab, Pakistan

Arsenic (As) contamination in groundwater is a worldwide concern for drinking water safety. Environmental changes and anthropogenic activities are making groundwater vulnerable in Pakistan, especially in Southern Punjab. This study explores the distribution, hydrogeochemical behavior, and pathways of As enrichment in groundwater and discusses the corresponding evolution mechanism, mobilization capability, and health risks. In total, 510 groundwater samples were collected from three tehsils in the Punjab province of Pakistan to analyze As and other physiochemical parameters. Arsenic concentration averaged 14.0 μg/L in Vehari, 11.0 μg/L in Burewala, and 13.0 μg/L in Mailsi. Piper-plots indicated the dominance of Na+, SO42-, Ca2+, and Mg2+ ions in the groundwater and the geochemical modeling showed negative saturation indices with calcium carbonate and salt minerals, including aragonite (CaCO3), calcite (CaCO3), dolomite (CaMg(CO3)2), and halite (NaCl). The dissolution process hinted at their potential roles in As mobilization in groundwater. These results were further validated with an inverse model of the dissolution of calcium-bearing mineral, and the exchange of cations between Ca2+ and Na+ in the studied area. Risk assessment suggested potential carcinogenic risks (CR > 10-4) for both children and adults, whereas children had a significant non-carcinogenic risk hazard quotient (HQ > 1). Accordingly, children had higher overall health risks than adults. Groundwater in Vehari and Mailsi was at higher risk than in Burewala. Our findings provide important and baseline information for groundwater As assessment at a provincial level, which is essential for initiating As health risk reduction. The current study also recommends efficient management strategies for As-contaminated groundwater.

Non-Carcinogenic Health Risk Evaluation of Elevated Fluoride in Groundwater and Its Suitability Assessment for Drinking Purposes Based on Water Quality Index

Fluoride (F^-) contamination in drinking groundwater is a significant human health risk in Pakistan. Moreover, high fluoride pollution in drinking water causes a variety of disorders, including dental, neurological, and skeletal fluorosis. The aim of this research was to evaluate the health risk of elevated fluoride in groundwater and its suitability assessment for drinking purposes. The total of (n = 37) samples were collected from community tube wells of Quetta Valley, Balochistan, Pakistan. The results show a mean pH value of 7.7, TDS of 404.6 mg/L, EC of 500 µs/cm, depth of 96.8 feet, and turbidity of 1.7 nephelometric turbidity units. The mean values of HCO₃^-, Ca²⁺, Mg²⁺, and Na⁺, were 289.5, 47.5, 30.6, and 283.3 mg/L, respectively. The mean values of SO₄^2-, NO₃^-, K⁺, Cl^-, and Fe²⁺, were 34.9, 1.0, 1.6, 25.6, and 0.01 mg/L, respectively. The F^- concentration in the groundwater varied between 0.19 and 6.21, with a mean value of 1.8 mg/L, and 18 samples out of 37 were beyond the WHO recommended limit of 1.5 mg/L. The hydrochemical analysis results indicated that among the groundwater samples of the study area, 54% samples were Na-HCO₃ type and 46% were mixed CaNaHCO₃ type. The saturation indices of the mineral phases reveal that the groundwater sources of the study area were saturated with CaCO₃ and halide minerals due to their positive (SI) values. Such minerals include calcite, dolomite, gypsum, and fluorite. The principal component analysis results reveal that the groundwater sources of the study area are contaminated due to geological and anthropogenic actions. The health risk assessment results of the F^- concentrations show the ranges of ADD_ingestion for children, females, and males in the Quetta Valley, and their mean values were observed to be 0.093052, 0.068825, and 0.065071, respectively. The HQ_ingestion mean values were 1.55086, 1.147089, and 1.084521 for children, females, and males, respectively. It was noticed that children had the highest maximum and average values of ADD_ingestion and HQ_ingestion in the research area, indicating that groundwater fluoride intake poses the greatest health risk to children. The water quality index (WQI) analyses show that 44% of the samples belong to the poor-quality category, 49% were of good quality, and 8% of the samples of the study area belong to the excellent category.

Geochemical Characterization of Natural Groundwater on the Southern Slopes of the Caucasus Mountains on the Russian Black Sea Coast

The Mzymta and Sochi watersheds, located on the southern slopes of the Caucasus Mountains on Russia’s Black Sea coast, are characterized by a remarkably complex geological setting. The predominant rocks are mudstones, siltstones, and shales, with smaller amounts of carbonate and clay-carbonate rocks, and occasionally igneous rocks. The area is also characterized by the occurrence of polymetallic, gold, sulfide, rare metal, and rare-earth mineralizations in addition to hosting a thermal hydrogen sulfide groundwater aquifer. The objective of this study was to determine groundwater genesis patterns in an area with such contrasting geological and hydrogeological structures. Based on the chemical analysis of 33 natural groundwater springs, five chemical types of water were identified dictated by the composition of the host rock as well as the occurrence of mineralizations, seepage of mineralized water, and local geochemical features of the host rock. The high sodium concentration and mineralization of groundwater near the thermal hydrogen sulfide groundwater aquifer are due to the infiltration of seawater. The consistent presence of excessive amounts of rare-earth elements (REEs) in all groundwaters in the area is a reflection of the regional geochemical specialization of the rocks. Groundwater, like the terrestrial components of the natural environment, inherits rare-earth fractionation patterns from the rocks that make up the area. Thus, rare-earth totals and fractionation patterns can be used as a reliable criterion to interpret the regional specificity of groundwater.