Groundwater Characterisation in Urbanising Hard‐Rock Aquifers: Insights From Rock–Water Interactions in a Sub‐Humid Region of Central Kerala, India

Groundwater quality in Sargodha City, Pakistan: Comprehensive research of geochemical modeling, groundwater quality assessment, and risk evaluation

The aim of this study was to evaluate groundwater quality the Marvdasht aquifer using the Groundwater Quality Index (GWQI), which was determined using a conventional method and also predicted using three machine learning algorithms: Artificial Neural Network (ANN), Support Vector Machine (SVM) and Random Forest (RF). For this purpose, groundwater quality parameters (pH, EC, TDS, TH, Na⁺, Ca2⁺, Mg2⁺, Cl⁻, HCO₃⁻, SO₄2⁻, and K⁺) were measured. The GWQI was calculated based on WHO drinking-water standards, and a spatial map was generated in ArcGIS. Results showed that TDS, EC, Na⁺, Cl⁻, and Mg2⁺ were the most influential parameters controlling groundwater quality. The groundwater quality was classified as hard to very hard and not suitable for drinking purposes in the southern and southeastern areas of the study site, while the northern area showed good quality due to limestone formations and recharge from a dam. Results also revealed that Na-Cl was the dominant water type, which indicates the groundwater evolution through rock-water interaction, dissolution, and evaporation. TDS mean variation index of 27.8 and EC with mean variation index of 15.7 were selected as the most sensitive quality parameters in GWQI calculation. Among the applied models, the ANN provided the highest accuracy (R2 = 0.999; RMSE = 1.02), followed by SVM and RF for predicting GWQI from groundwater quality parameters. It was concluded that the integration of GWQI, ANN, and GIS effectively captured spatial variations and provided a reliable framework for groundwater monitoring in arid regions.

Located in a semi-arid climate, Cumra (Konya) plain is one of the most important agricultural regions in Turkey. Groundwater is the major source for agricultural, domestic, and other water-related activities due to the insufficiency of surface water. As groundwater is the only major source of water in this area, it is important to know the effects of geological formations and anthropogenic activities on groundwater chemistry. This study was carried out with the objective of identifying the hydrogeochemical characteristics and processes controlling the groundwater chemistry in Cumra Plain, Central Anatolia, Turkey. The study area is comprised of two main aquifers which are the semi-confined aquifer of the Neogene age and the unconfined aquifer of the Quaternary age. To identify the hydrogeochemical characteristics of groundwater in two aquifer systems and to understand the major factors and mechanisms controlling the groundwater chemistry, graphical plots, mineral saturations, and multivariate statistical analysis of chemical constituents in the groundwater were used. Study results show that groundwater is generally neutral to slightly alkaline in nature with a pH ranging from 6.67 to 8.10, and the dominance of ions is in the order of Ca2+ > Mg2+ > Na+ > K+ for the Neogene aquifer and HCO3 − > SO4 2− > Cl− > NO3 −; Mg2+ > Ca2+ > Na+ > K+ and SO4 2− > HCO3 − > Cl− > NO3 − for the Quaternary aquifer. While the chemical composition of groundwater in the Neogene aquifer is mainly controlled by water–rock interaction including dissolution of carbonates and gypsum, calcite precipitation, and de-dolomitization, the main geochemical processes in the Quaternary aquifer are reverse ion exchange, evaporation, dissolution of carbonates, gypsum and soil salts, calcite precipitation, and silicate weathering. The mechanism controlling groundwater chemistry in the Neogene aquifer is actually regulated by the geogenic processes (water–rock interaction) rather than by anthropogenic activities. However, the mechanism controlling groundwater chemistry in the Quaternary aquifer is regulated by both geogenic processes and anthropogenic activities. In addition, anthropogenic nitrogen pollution in the study area is currently not serious, but evaporation and leaching of soil salts due to anthropogenic activities increase the concentrations of ions in the Quaternary aquifer.

The zeolite minerals characterized with hydrated aluminosilicates, negative ionic charge and 3D framework structure are well known for purifying the groundwater occurring in basaltic aquifer systems. However, the filtering mechanism at in situ field conditions is a complex process, which is rarely studied, and hence, it needs to be demonstrated. This paper explores the mechanism of hydrochemical processes and evolution of natural zeolites associated with basaltic rock to enhance groundwater quality. We present the hydrochemical findings and evolution processes derived from 46 groundwater samples (Nt = 46) belong to zeolitic (Nz = 25) and non-zeolitic (Nnz = 21) zones of a micro-watershed (4.4 km2) beset over basaltic terrain, Deccan Volcanic Province (DVP), India. The groundwater samples collected for one hydrological cycle (pre- and post-monsoons) are examined for major ion chemistry to determine the aqueous solution mechanism and ion-exchange process occurred in zeolitic and non-zeolitic zones. Further, the hydrochemical parameters are appraised by means of dominancy of ions, rock–water interactions, silicate weathering, chloro-alkaline indices, cation-exchange bivariate plots and the mechanism controlling groundwater chemistry. The results show that: 1) the purifying efficiency of zeolites for total ionic strength is observed as 63.85 and 68.58% during pre- and post-monsoons, respectively, 2) the significant reduction (36.51%) in total hardness attributed to the positive trend of chloro-alkaline indices depicting the ion-exchange phenomenon between Na+ and K+ (alkalies) and Ca2+ and Mg2+ (alkali-earth) elements in the zeolitic zone, 3) Gibbs plot shows the rock–water interaction as the predominant mechanism controlling groundwater chemistry in the zeolitic zone, and 4) the groundwater quality parameters from zeolitic zone are found within the permissible limit of WHO drinking water standards.

Water is a valued resource, which is increasingly being threatened by mining activity. Monitoring of surface water and groundwater quality around gold mine is essential in terms of heavy metals and toxic substances. The northern zone of Cote d’Ivoire where located Tongon is a highly mineralised zone, with extensive mining of gold. The quality of water resources in this region may be affected by the activity of the Tongon mine, which is the main gold mine in the region. The objectives of this study were to determine the concentration of heavy metals and the Heavy Metal Pollution Index (HPI) in surface water and groundwater around Tongon mine. The concentrations of As, Zn, Pb, Cd, Cr, Cu, and Mn have been evaluated at 21 surface water and 16 groundwater sampling stations. The concentration of these metals were analysed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for heavy metal pollution indexing. The concentrations of As, Pb, Cr, Cu and Mn in surface water were found to be above the highest desirable limit of WHO drinking water standard with mean concentrations of 5.761, 0.016, 0.178, 2.939, and 0.684 mg/L, respectively. Excepted As (2.95 mg/L) and Mn (0.67 mg/L), the metal concentrations in groundwater were well below the permissible limits of WHO drinking water standard. The Heavy Metal Pollution Index was used to evaluate surface water and groundwater quality. The results showed that, in the groundwater samples, HPI values (48.56-72.49) were less than 100, indicating a low-level heavy metal. Concerning surface water, HPI values of Poungbe River are well below the index limit of 100, which suggest that it is generally no contaminated with respect to these metals. The mining activity of Tongon is carried out while protecting water quality against heavy metals. The quality of water resources in the area must be regularly monitored to avoid any dramatic situation.

In the present study, we approach the geochemical processes affecting the hydrochemistry and resulting in elevated concentrations of hexavalent chromium (Cr6+) in groundwater of the Psachna basin, central Euboea, Greece. Sixty-five groundwater samples and 16 topsoil (5-20cm) samples were studied in order to examine groundwater and soil quality in relation to geogenic processes and anthropogenic activities. Specifically, the origin of Cr and Cr6+ in groundwater was investigated by co-evaluating (a) hydrochemical cross plots of major ions; (b) spatial distribution maps of Cl-, Mg2+, NO3-, and Cr6+; (c) multivariate statistical analyses such as factor analysis (FA) and hierarchical cluster analysis (HCA) of groundwater geochemistry; (d) chemical analyses of soil samples; and (e) chemical analyses of fertilizers. The major factors that control the hydrochemistry of the study area are reverse ion exchange, dissolution of silicate minerals, and intense agricultural activities. According to FA, three factors explain 73.2% of the total variance of data, whereas according to HCA, the groundwater samples were classified into three groups indicating both geogenic (water-rock interaction) and anthropogenic (agricultural activities) impact. The high concentration of NO3-, up to 540mgL-1; the strong positive correlation between NO3- and Cr as well as between NO3- and other parameters such as SO42- and Mg2+ in groundwater samples; and the very high content of P, up to 2444mgkg-1, in soil samples of the Psachna basin, imply the synergistic, although commonly neglected, role of the use of fertilizers in groundwater quality.

Understanding factors influencing groundwater quality is critical to the development of best management practices at the large watershed scale. In this study, the shallow groundwater (10–20 m depth) in the Su-Xi-Chang region, eastern China, was investigated as part of a monitoring program from 2007 to 2008 to analyze the regional groundwater quality as well as the hydrogeochemical processes and their controlling factors. Conventional physicochemical water parameters (pH, turbidity, electrical conductivity, dissolved oxygen, total phosphorus), major cations (Na+, Ca2+, Mg2+ and NH4+) and anions (Cl−, NO3− and SO42−) were measured. Hydrochemical methods and multivariate statistical methods were applied to analyze the hydrogeochemical signatures, origins, the similarities among the variables and to identify the main pollution sources in the groundwater. The results showed that (1) the concentrations of TDS (224.89–1086.70 mg/L) and turbidity (0.1–18.60 NTU) were higher than the class II groundwater quality standards in China and the WHO drinking water standards, (2) there were extremely high concentrations of ammonia (0.01–32.90 mg/L), with a mean value of 0.72 mg/L and (3) the nitrate concentrations (average value of 22.07 mg/L) exceeded the class III groundwater quality standards. The study also provided evidence that weathering, dissolution of carbonate, halite and silicate and cation exchange were the possible primary hydrogeochemical control mechanisms in the groundwater. The sources of ammonia, total phosphorus, sulfates and nitrates included rock–water interactions and anthropogenic activities. The groundwater administration of pollution sinks and sources, long-term legal frameworks and economic incentives should be improved to optimize watershed scale management in the context of rapid development in China.

A qualitative approach, including geochemical and multivariate statistical approaches, is applied to evaluate the groundwater quality and human health risk, based on analytical data of 72 samples collected from a semi-arid region of eastern Maharashtra, India. The shifting of hydrochemical type from Ca2+-Na+-[Formula: see text] to Na+-Ca2+-Cl- type was observed along different flow paths. The main controlling processes observed from the chemical characterisation of the groundwater are water-rock interactions, dedolomitisation and reverse ion exchange. Simulation analysis (mass transfer) exposes the dissolution of dolomite, gypsum, halite, k-feldspar and CO2 down the simulated pathways. Around 77% of the total variance was observed from the first three principal component analyses. The high positive loadings of EC, TDS, Na+, K+, Ca2+, Cl-, [Formula: see text] and [Formula: see text] of PC1 revealed silicate weathering and reverse ion exchange followed by human activities as the contamination sources. The sources identified for high positive loadings on [Formula: see text] and [Formula: see text] of PC2 are soil CO2 and human activities. The high loadings of pH and F- in PC3 revealed fluorite dissolution and calcite precipitation. The human health risk calculated for [Formula: see text] revealed that 58% and 44% of the total groundwater samples surpassed the tolerance limit for non-carcinogenic risk of 1.0 in children and adults. The human health risk assessment for fluoride showed high hazard index values in 40% and 23% of the total groundwater samples for children and adults, respectively. The study suggests some management measures for protection of groundwater resources.

Evaluating groundwater quality reveals its condition, supports water resource management, and minimizes health risks; yet, such studies in the Gidabo watershed remain limited. This study analyzes 30 groundwater samples from 15 sampling stations collected in the wet (October 2024) and dry (January 2025) seasons to assess spatiotemporal variations in physicochemical parameters and hydrochemical evolution. The parameters analyzed include temperature (T), pH, total dissolved solids (TDS), electrical conductivity (EC), and all major ions measured: Na+, Ca2+, Mg2+, K+, Fe2+, HCO3−, SO42−, Cl−, NO3−, CO32−, F−, and total hardness (TH). Results showed that most parameters met the WHO drinking water standards. Ion concentrations were lower in the wet season, and TDS levels were lower in the northern and southeastern parts of the watershed. Groundwater in the study area was largely of the Ca–Na–HCO3 type but exhibited a gradual shift toward more chemically evolved mixed types, including Ca–Na–Mg–HCO3 and Na–Ca–Mg–Cl–HCO3, with its chemistry primarily governed by rock–water interactions. This study provides valuable information for environmentalists and decision-makers in developing strategies for sustainable groundwater management.

This study explores the utility of silica concentration in deciphering geological controls and hydrogeochemical processes affecting groundwater quality in Mount Cameroon’s volcanic terrain. Fifty water samples from wells, boreholes, springs, and rivers were analysed for hydrochemical properties (EC, pH, temperature, TDS) and major ion concentrations (Ca2+ > Mg2+ > K +> Na+ and HCO3− > Cl −> NO3− > SO42−). The groundwater exhibits low mineralization, with a dominance of Ca2+, Mg2+, HCO3−, and SiO2, reflecting minimal water–rock interaction and short residence times. Spatial variations in hydrochemistry suggest diverse water–rock interactions and potential mixing processes (76% of samples in rock dominance zone). Silica concentrations (5.8–58.7 mg/L) and estimated chalcedony temperatures (> 60 ℃ at five sites) indicated depths exceeding 1000 m. This research highlights silica’s effectiveness in tracking water–rock interactions across diverse geological settings, regardless of flow depth or interaction time variations. Mineral saturation indices pointed towards supersaturation with silicate minerals (quartz) but undersaturation with carbonates, sulphates, and halides. These findings contribute to a better understanding of groundwater evolution in Mount Cameroon, valuable insights into the hydrogeochemical processes shaping groundwater quality, aiding sustainable water resource management practices that can benefit local communities by ensuring a reliable source of freshwater. However, opportunities exist to improve future studies and water resource management. For a more comprehensive understanding, future analyses should include a broader range of geochemical tracers, such as nitrate (NO3−) and phosphate (PO43−), to assess potential agricultural or anthropogenic contamination. The study also found elevated levels of chloride and sodium, suggesting potential anthropogenic influences on groundwater quality, such as agricultural practices and waste disposal.

Assessment of Bangladesh groundwater for drinking and irrigation using weighted overlay analysis

Summary The long‐term sustainability of forest soils may be affected by the retention of exchangeable nutrient cations such as Ca 2+ and the availability of potentially toxic cations such as Al 3+ . Many of our current concepts of cation exchange and base cation saturation are largely unchanged since the beginnings of soil chemistry over a century ago. Many of the same methods are still in use even though they were developed in a period when exchangeable aluminium (Al) and variable charge were not generally recognized. These concepts and methods are not easily applicable to acid, highly organic forest soils. The source of charge in these soils is primarily derived from organic matter (OM) but the retention of cations, especially Al species, cannot be described by simple exchange phenomena. In this review, we trace the development of modern cation exchange definitions and procedures, and focus on how these are challenged by recent research on the behaviour of acid forest soils. Although the effective cation exchange capacity (CECe) in an individual forest soil sample can be easily shown to vary with the addition of strong base or acid, it is difficult to find a pH effect in a population of different acid forest soil samples. In the very acidic pH range below ca 4.5, soils will generally have smaller concentrations of adsorbed Al 3+ . This can be ascribed to a reduced availability of weatherable Al‐containing minerals and a large amount of weak, organic acidity. Base cation saturation calculations in this pH range do not provide a useful metric and, in fact, pH is modelled better if Al 3+ is considered to be a base cation. Measurement of exchangeable Al 3+ with a neutral salt represents an ill‐defined but repeatable portion of organically complexed Al, affected by the pH of the extractant. Cation exchange in these soils can be modelled if assumptions are made as to the proportion of individual cations that are non‐specifically bound by soil OM. Future research should recognize these challenges and focus on redefining our concepts of cation retention in these important soils.

Solid waste dump where leachate generated is allowed to escape to the surrounding and underlying water body is a major threat to borehole water. This study was designed to assess the impact of solid waste dumps on ground water quality and the current status of the quality of borehole water in Calabar municipality. Randomly selected boreholes around Lemna road where the final dump site of solid waste in Calabar is located, Etta Agbor area where there are no major dumpsites but a few sporadic dumps and Satellite town where there are relatively no dumpsites were thoroughly examined. Physicochemical properties of water quality were determined following standard analytical procedure and metal content by atomic absorption Spectrophotometry using Shimadzu atomic absorption spectrophotometer (model AA6800, Japan). Metal content and other physicochemical parameters generally displayed the trend Lemna road > Etta Agbor road > Satellite town. The differences were found to be statistically significant (ANOVA, p < 0.05), suggesting that solid waste dumpsites have reasonable influence on the quality of ground water in Calabar municipality. A significant (p < 0.01) positive correlation was observed between each of the metals and between the metals and most of the physicochemical parameters, suggesting that a similar source is responsible for their presence at the concentration determined. When ompared with WHO drinking water standards, borehole water in the study area especially Lemna road was seriously implicated. The study thus concludes that solid waste dumps in Calabar municipality have significant influence on the quality of ground water and that continuous use of borehole water from the study area for drinking or other domestic purposes without any form of physical or chemical treatment could pose serious toxicological risk. It was therefore recommended that ground water in Calabar municipality should be put under surveillance in other to protect it from further degradation and safeguard public health.

The main drawback in the utilization of geothermal resources arises from the precipitation of secondary minerals within wells, pipelines, steam separators, turbines and other surface equipment in form of scales. Scale formation is an outcome of the alteration of various rocks dissolved in geothermal fluids that find their way into a reservoir. Once geothermal fluids ascend to the surface, hydrostatic pressure decreases toward a phase separation level that permits the dissolved gases such as CO2, H2S and H2, and steam to separate from the liquid phase by “boiling”. Stripping of these volatiles may increase fluid pH, leading to precipitation and deposition of secondary minerals. The study sought to establish the relationship between water-rock interaction and secondary mineral precipitates at the surface and deep fluid at different temperatures during depressurisation boiling and cooling. Samples were collected from selected Olkaria wells; OW-38A, OW-910 and OW-910A. The analysis of the results outlined deep fluid Alkali-Chloride waters and surface steam-heated Alkali-Bicarbonate and acidic Sulphate-Chloride waters. Various models suggested adiabatic boiling, conductive cooling and possible mixing and dilution in the wells. Hydrothermal alteration minerals were found to be in equilibrium with the geothermal fluids at varying temperatures, and the secondary minerals controlled the chemistry of the reservoir. Silica-saturated solutions precipitated silica in OW-910 and OW-910A, which may have resulted from rapid cooling following mixing with cold surface water.

The proposed study aims to assess groundwater quality and suitability of the Upper and Middle Cheliff plains (northwest of Algeria) for irrigation and drinking. Here the groundwater is the main source for domestic, agricultural and industrial activities similarly to any other region of the world. The suitability for drinking and for irrigation was evaluated on the basis of water quality index, salinity risk, hardness risk, sodium risk, magnesium risk, permeability index, water infiltration rate, Kelly index and Wilcox and Richards diagrams. The aquifer system is mainly composed of alluvium (gravel, sand, silt, clay, …) from the Mio-Plio-Quaternary. The results of this study highlighted that the majority of the chemical elements analyzed exceed the WHO's drinking water standards and FAO's irrigation water standards. Based on the GroundWater Quality Index (GWQI) results, the Upper and Middle Cheliff groundwater plains shows Doubtful class in most of the plains. In addition, the GroundWater Quality Index for Irrigation (GWQII) shows the predominance of the Good/Permissible groundwater quality class in most of the plains. According to these results, drinking water can cause health problems (a danger) for the human consumption making necessary a proper treatment be able to use it. As for irrigation water, it does not present a danger for irrigating for the vast fields of the region, with the exception of sensitive crops such as: garlic, onion, beans and strawberry. The proposed approach demonstrated to be appropriate in assessing the groundwater quality for irrigation and drinking water supply since it can be easy applicable and suitable in humid, arid or semi-arid regions around the world.