Groundwater quality assessment of the Takelsa phreatic aquifer (Northeastern Tunisia) using geochemical and statistical methods: implications for aquifer management and end-users

Multi-model exploration of groundwater quality and potential health risk assessment in Jajpur district, Eastern India

The presence of fluoride and nitrate is a serious groundwater quality issue in India impacting human health. In the present study, 14 different hydrochemical parameters for 76 groundwater samples collected from the Jajpur district of Odisha, India, were evaluated. Entropy-weighted water quality index (EWQI), fixed-weight groundwater quality index (GWQI), principal component analysis (PCA), and rotated factor loading-based water quality index (PCWQI) were employed to assess groundwater quality. About 65.79 ± 4.68%, 33.55 ± 3.95%, and 0.66 ± 0.76% of the samples were rated as "excellent," "good," or "medium" quality, respectively, across the four different water quality indices, with a nominal rating discrepancy of 13.15%. Though 86% of samples consistently received excellent or good ratings across all WQI frameworks, concentrations of F- and NO3- in 36.8% and 11.84% of the samples exceeded the WHO permissible limit. In health risk assessment, about 38.15% of samples surpassed the F- hazard quotient (HQ > 1) posing non-carcinogenic health risks for children. The non-carcinogenic health risks due to NO3- were evident in 55.26% and 11.84% of samples for children and adults, respectively. The higher concentration of NO3- in some of the water samples, together with its positive correlation with HCO3-, may worsen groundwater pollution. The moderate correlation between Ca2+ and HCO3- (r = 0.410) and the insignificant correlation between Mg2+ and HCO3- (r = 0.234) suggests calcite dissolution is far more common than dolomite.

Analysis of hydrochemical characteristics and assessment of organic pollutants (PAH and PCB) in El Fahs plain aquifer, northeast of Tunisia

The availability of good quality groundwater constitutes a major concern in many developing countries. The El Fahs shallow aquifer, northeastern Tunisia, is an important source of water supply for various economic sectors in the agricultural region. The intensive exploitation of this groundwater has led to its quality degradation. In fact, assessment of water quality degradation is very useful in planning the conservation and management practices of water resources in this watershed. This research aims to evaluate the groundwater quality and its suitability for irrigation uses, identify the main processes to assess their chemical composition, and investigate the potential sources of persistent organic pollutants (POPs). The hydrogeochemical investigation is thus conducted by collecting groundwater samples and analyzing their physicochemical characteristics. Polycyclic aromatic hydrocarbons (16 PAHs) and polychlorinated biphenyls (7 PCBs) were determined in groundwaters from nine stations. The sampling took place in July 2020. The relative abundance of ions was Na > Mg > Ca > K for cations and Cl > SO4 > HCO3 for anions. The groundwater exhibits two predominant hydrochemical facies: Ca-Mg-Cl/SO4 and Na-Cl. The relevant recorded pollutant is nitrate, which was generally far above values of pollution thresholds indicating the influence by the intensive agricultural activity. The suitability for irrigation purposes was assessed using several parameters (EC, SAR, %Na, TH, PI, Mh, and Kr). As a matter of fact, the results mentioned that the majority of the samples are unsuitable for irrigation uses. An analysis of the organic pollutants indicates that the total PAH and PCB concentrations are above the permissible values. Therefore, a considerable predominance of naphthalene and PCB28 was observed in order to discriminate between pyrolitic and petrogenic PAH sources; low-molecular-weight (LPAH)/high-molecular-weight (HPAH) ratio was calculated. Results showed that PAHs were mainly of petrogenic origin. The results revealed also that the chemical composition of groundwater is influenced by evaporation process, ion exchange, and water-rock interaction during the flow. A high risk of organic contamination has been highlighted linked to anthropogenic activities which have exerted increasing pressure on groundwater quality. The presence of organic pollutants in groundwater is becoming a serious threat to the environment and human health.

Application of stable isotope of water and a Bayesian isotope mixing model (SIMMR) in groundwater studies: a case study of the Granvillebrook and Kingtom dumpsites

The increase in groundwater salinity of the two major dumpsites in Sierra Leone has been a major concern for stakeholders. Therefore, this study employed geochemical and stable water isotope analyses to investigate the factors controlling groundwater salinity. The proportional sources of the groundwaters were also evaluated using the Bayesian isotope mixing model. The geochemical analysis showed that the groundwater chemistry in the Granvillebrook dumpsite is controlled by water-rock interaction and evaporation while that of the Kingtom is dominated by water-rock interaction and precipitation. The biplot of deuterium (δ²H) versus oxygen (δ¹⁸O) composition relative to the global meteoric water line confirms that the groundwaters of the study areas are of meteoric origin. The linear plot of electrical conductivity versus δ¹⁸O depicts that mineralization is the major factor impacting the groundwater salinity in the study areas. The stable isotope mixing model in R (SIMMR) suggests that 96.5% of the groundwaters in the study areas are recharged by precipitation while only 3.5% originated from surface water. The SIMMR model also depicts that groundwaters in the Granvillebrook dumpsite have been bridged by leachate (33.0%) and domestic wastewater (15.2%) while for the Kingtom dumpsite, 13% and 21.5% are contaminated by leachate and domestic wastewaters. Contrary to other previous studies, this research confirms the feasibility of using the Bayesian isotope mixing model to quantify the factors influencing groundwater salinity.

Groundwater quality enumeration and health risk in the extended part of Chhotanagpur granite gneiss complex of India

The majority of people on the earth bank largely on groundwater to quench their thirst. In the era of rapid population growth, the over-exploitation of groundwater gives rise to water scarcity, and people find themselves in distress to manage safe drinking water. In this backdrop, the present study is carried out in the terrain of Pre-Cambrian igneous and high- to low-graded metamorphic rocks, to assess the groundwater potential zones (GWPZs) and evaluation of groundwater quality. The map of GWPZ is produced employing the multi-criteria decision-making model and geospatial technology. It unveils that around 29% area of the watershed enjoys good GWPZ, whereas around 43% area experiences low GWPZ. The overall accuracy of the simulated model is 92%. The water quality index indicates that 68% of water samples belong to excellent to good water quality. A significant proportion of water samples (24%) are found to be unsuitable for drinking, which may be due to groundwater contamination by the process of leaching of mineral-rich weathered rocks. The presence of fluoride (F^-) beyond the maximum permissible limit (1.5 mg L^-1) of WHO is recorded among 18% samples of the watershed, where 24,963 souls including 3457 children aged between 0 and 6 years lived and might have ingested F^- through drinking water. Hence, the health risk of those people is quite high. Children are at a more non-carcinogenic health risk of F^- than adults. The study also confirms no statistically significant difference (p ˃ 0.05) is observed between low and high GWPZ with respect to groundwater quality. The study recommends adopting a sustainable outlook to explore GWPZ, and an assessment of drinking water quality must be done before drinking.

Assessment of groundwater vulnerability in coastal zone using SI method and GIS: case study of Bouficha aquifer (northeast Tunisia)

Nowadays, groundwater is under stress due to contamination, over-exploitation, seawater intrusion, climate change, etc. The groundwater contamination is the major problem which can engender the total deterioration of the aquifer. The groundwater vulnerability assessment may contribute to predicate and to delimitate the areas affected by contamination or any future pollution. This research aims to zoning the potential pollution of the Bouficha shallow aquifer, located in the northeast Tunisia, using the SI model and GIS. Five parameters are presented in the SI model: depth to groundwater (D), recharge (R), aquifer media (A), topography (T), and land use (LU). The different parameters were collected from diverse sources for assess groundwater vulnerability. The net recharge map was generated using GIS-based multi-criteria analysis method based on different parameters (slope, lithology, LU, soil, and drainage density). The generated vulnerability map shows three vulnerability classes: low vulnerability (< 45), moderate vulnerability (45-64), and high vulnerability (64-84) which represent 3.14%, 76.8%, and 20.06% of the total area, respectively. The SI vulnerability represent a moderate positive correlation with the measured nitrate concentrations (R² = 0.76). The sensitivity analysis shows that the land use parameter is the most influential parameter for groundwater vulnerability in BFC.

Hydrogeochemistry, identification of hydrogeochemical evolution mechanisms, and assessment of groundwater quality in the southwestern Ordos Basin, China

Understanding the evolution process of hydrogeochemistry and groundwater quality is essential for water supply and health in the southwestern Ordos Basin, where groundwater is a vital source for drinking. This study systematically illustrates the hydrogeochemical characteristics and evolution mechanism based on the groundwater samples (n = 67) collected from Loess area by integrating multivariate statistical methods and hydrogeochemical methods. Furthermore, the entropy water quality index (EWQI) and water quality indices combined with spatial analysis were employed to evaluate the suitability of groundwater for drinking and irrigation purposes and analyze the spatial variation of water quality. The hierarchical cluster analysis and principal component analysis classified groundwater dataset into four clusters and four components which were examined using a Piper diagram and Gibbs diagram, representing different hydrogeochemical characteristics and controlling factors. Based on results, the groundwater chemistry was characterized by representative water types: freshwater (cluster 1, cluster 2), low salinity (half of cluster 3), high salinity (half of cluster 3, cluster 4), and the main controlling factors of hydrogeochemistry revealed by Gibbs diagram were evaporation crystallization (cluster 3, cluster 4) and water-rock interactions (cluster 1, cluster 2). Moreover, the Gaillardet diagram, chloro-alkaline indices, binary diagram, and saturation index further comprehensively illustrate that the silicate and evaporite weathering, ion exchange, dissolution of halite, gypsum, and anhydrite are responsible for hydrogeochemical process. Based on EWQI and ArcGIS, the groundwater quality is categorized as excellent (47.0%), good (31.8%), medium (4.5%), poor (6.1%), and extremely poor (10.6%) types, and the quality in the south of the study area is better than north. Additionally, the USSL diagram shows that most of samples belong to C3S1 (high-salinity hazard and low-sodium hazard) and C2S1 (medium-salinity hazard and low-sodium hazard), and Wilcox diagram shows that 77.2% of samples are suitable for irrigation.

Groundwater Quality Evaluation for Potable Use and Associated Human Health Risk in Gaobeidian City, North China Plain

The groundwater in Gaobeidian city is used for drinking, irrigation, industrial production, and other purposes. With the rapid development of the economy and urbanization, groundwater quality has been seriously affected. The main purposes of this paper are to evaluate the groundwater quality in the study area on the basis of understanding the hydrochemical characteristics of the study area and assess the possible health risks of groundwater to children and adults. In this paper, the entropy weight method was used to determine the weight of each evaluation parameter, and on this basis, groundwater quality evaluation was carried out, and the spatial distribution map of groundwater quality was drawn according to the evaluation results. The results show that the weight values of the five parameters of NO2–, Fe, As, Cr6+, and NO2–N are more than 0.1 among the total of fifteen parameters, and the concentration of these five parameters can be considered as the main influencing parameters of groundwater quality. The calculation results of the entropy weighted water quality index (EWQI) show that all the groundwater quality in the study area is class 1 water, which is Excellent Water. However, the EWQI value is the highest in the southwest of the study area, showing a trend of deterioration of groundwater water quality. Since all groundwater samples were evaluated as “excellent water,” it was speculated that the natural environment had more influence on groundwater chemical characteristics than human factors. The study found that 7.407% and 55.556% of the water samples posed a noncarcinogenic health risk to adults and children, respectively. The main responsible parameters for noncarcinogenic risk are F−, NO2−, NO3−, and Cr6+. The carcinogenic risk for adults ranged from 0 to 6.91E-04, with a mean of 1.00E-04. The carcinogenic risk for children ranged from 0 to 1.03E-03, with a mean of 1.55E-04. These toxic elements are mainly from industries. Therefore, the deterioration of groundwater quality can be prevented by strengthening the sewage management of various industries.

Comparative Water Qualities and Blending in the Ogallala and Dockum Aquifers in Texas

Within the US Southern High Plains, it is known that the Ogallala Aquifer (OA) has been over pumped since large-scale agriculture began making use of the water in the 1950s. One option to address the decline is to find new water sources. The last 10–15 years have seen an increase in drilling large capacity, deeper wells in the co-located Dockum Aquifer in the Texas Panhandle. This lower aquifer is separated from the OA by low hydraulic conductivity sediment and is thus generally considered independent from the OA. We examined the suitability of the Dockum to supplement OA water by comparing recent water chemistries where the aquifers coexist. We also examined historical information on well yield, well development, and water quality. We found that water quality is equivalent to the Ogallala in some places but in others it is saltier, softer, and more sodic. Use of PCA and hydrochemical facies revealed that even in this small area Dockum water quality is highly variable. We used USGS-PHREEQC to model water blending at ratios of 0–>100% Ogallala. We show that there is irrigation water quality risk no matter the blend, that risks differ according to location, and that the most frequent risks are salinity, sodicity, and nitrate. We conclude that growers can manage these risks if they use blending to choose the risks they feel most apt to mitigate.

Groundwater quality assessment for different uses using various water quality indices in semi-arid region of central Tunisia

The Hajeb Layoun-Jelma basin, located in the central Tunisia, is the principal source of water supply for Sidi Bouzid and Sfax region. The over-abstraction from this groundwater, since 1970, and the intensive agriculture activities led to the degradation of the water quantity and quality. The quality evaluation for this groundwater is very important tool for sustainable development and decision for water management. A total of 28 groundwater samples, from shallow, springs, and deep aquifers, were collected, storage and analyzed to evaluate its quality suitability for domestic and agriculture purposes using geographic information system and geochemical methods. For the both aquifers, the abundance of cations: Na > Mg > Ca > K, and of anions in the order: Cl > HCO₃ > SO₄. The dominant hydrochemical facies, for the shallow aquifer and springs, are Na-Cl and Ca-Mg-Cl; for the deep aquifer, the geochemical facies are Na-Cl, Ca-Mg-Cl, and Ca-Cl. The comparison of the major parameters and the chemical data with the World Health Organization standards and the national standards indicate that this groundwater is suitable for drinking, except in some samples, with high salinity concentrations. The water quality was assessed, for drinking uses, using "water quality index," "entropy," and "improved water quality index." The results mentioned that the improved water quality index is the best method which indicated that the poor water quality coincide with the Na-Cl water type. The entropy method and the water quality index present the optimistic methods. The irrigation suitability assessment was made using various parameters (SAR, TH, % Na, PI, MH, KR, EC). The results revealed that the majority of samples in Hajeb Layoun-Jelma basin are not appropriate for irrigation uses.

Assessment of groundwater quality for drinking purpose with special emphasis on salinity and nitrate contamination in the shallow aquifer of Guenniche (Northern Tunisia)

Monitoring the groundwater quality situation and identifying the various pollution loads' sources are a prerequisites to finding solutions. In many areas, nitrate and salinity are one of the prime pollutants in the groundwater. This investigation is carried to present the results of a monitoring study focusing on 20 wells samples collected from the shallow groundwater of Guenniche plain (North Tunisia) during the wet season of May 2016, to present its suitability for drinking purposes with emphasis on the assessment of the presence of nitrate and salinity elements. Nitrate levels' results show that 55% of the samples exceeded the National Tunisian standard limit (NT) and the World Health Organization standard limit (WHO). The salinity results, measured as total dissolved solids (TDS), show that 95% of the samples exceed the international standard, and 25% exceed the national standard. A total of 20% of the wells exceeded the nitrite standards. The total hardness levels indicate that 90% of the samples present very hard water. The Guenniche shallow groundwater average concentrations are categorized as follows: Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ for the cations and Cl^- > SO₄^2- > HCO₃^- > NO₃^- for the anions. Nitrate and salinity variations during the period 2006-2015 follow the rainfall fluctuation patterns. The assessment of water quality using Water Quality Index revealed that 95% of the wells' water classes ranged between "poor", "very poor," and "unsuitable for drinking purposes". Therefore, these wells are affected by anthropogenic and/or natural factors and they are inadvisable for drinking purposes, unless the water from these wells undergoes appropriate treatment before use.