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The migration of a groundwater contaminant plume consisting of light nonaqueous phase liquids (LNAPLs) along the Ionian coastline of Sicily, Italy, has been reported to follow a trajectory that is inconsistent with the regional hydraulic gradient. The influence of several faults affecting the fractured carbonate bedrock aquifer, and groundwater abstraction from a well, were hypothesized to be responsible for the anomalous trajectory of the contaminant plume. A conceptual hydrogeological model was developed for the study area that incorporated structural information derived from geophysical surveys and the mapping of fractures in bedrock outcrops. This conceptual model was incorporated into numerical groundwater flow and solute transport models to simulate the groundwater transport of the light nonaqueous phase liquids. Four model scenarios representing different levels of complexity were tested to assess the relative influence of geological heterogeneity and groundwater abstraction on the migration of the contaminant plume. Results show that underground major discontinuity systems, invoking the presence of the faults in the model domain accounted for the observed migration of the contaminant plume, act as conduits for groundwater flow. Conversely, groundwater abstraction from a well was found to result in relatively minor, localized impacts to the migration of the contamination plume. This study demonstrates the importance of incorporating geological heterogeneity into groundwater modelling and environmental risk assessments associated with the storage of LNAPLs. [ABSTRACT FROM AUTHOR]

Hydrochemical and geophysical methods were used to assess saline paleo-water mass transfer induced by piston flow in the alluvial aquifer of the Oltrepò Pavese plain (northern Italy). The surface aquifer shows salinity contamination from a Tertiary substrate of marine origin, due to mixing of the shallower fresh groundwater with the Po Plain's deep brines. The study also used continuous monitoring of groundwater electrical conductivity, temperature and piezometric levels. Well logging and geophysical imaging, conducted at different times, revealed that the contamination varies over time, and that the water salinity and the depth of the transition zone (between the surface freshwaters and the deep saline waters) are subject to modifications. This is due to a pressure transfer—and, subsequently, mass transfer−from the groundwater circuits of the nearby Apennine mountains. It suggests that a hydraulic connection exists between the fractured Apennine water circuits and the deeper Mio-Pliocene and Tertiary saline-water circuits found below the plain's alluvial aquifer. Coinciding with significant recharge episodes that affect Apennine water circuits (prolonged rainfall and snow melt at mid-high altitudes), there is a pressure transfer transmitted along the water circuits in which saline water resides, providing an impulse to rise along the discontinuities and reach the alluvial aquifer. The conceptual model is supported by evidence that wells constructed in correspondence to hydraulically active tectonic discontinuities are affected by the arrival of saline waters with variable delays, while wells sited in sectors not affected by tectonic discontinuities are diluted by 'fresh' waters connected to alluvial aquifer recharge. [ABSTRACT FROM AUTHOR]

The valorization of Lake Maga for agricultural purposes has not only contributed to the socio-economic development of the study area, but has also modified the surface water (SW) and groundwater (GW) flow regimes. Understanding the interaction between the SW and the shallow Quaternary aquifer, under land use change and soil structure modification, is still a challenge, especially in the semi-arid area. In this study, GW level, hydrogeochemical characterization, and geological features are used to understand, locally, the influence of Lake Maga, its associated hydraulic components, and the other SW bodies on the GW behaviour. GW levels were measured in 51 wells in December 2012 and monitored in February 2013, and in 15 wells (beyond the 51) in June 2017 and December 2018. Physicochemical parameters of SWs and GWs were measured in the field, and 15 water samples were collected for major ion characterization. The GW levels were close (mean value ≈5 m) to the land surface, with zero to very low (< 1 m) water level fluctuations near SW bodies. The GW levels (< 2 m) are influenced more by their proximity to irrigation canals, ponds, and streams than Lake Maga (mean ≈3.5 m). The analysis of electrical conductivity (EC) values and GW levels showed that the weakly mineralized (< 200 µS.cm−1) GW were associated with the shallower GW table level. The moderate GW mineralization (200 < EC < 700 µS.cm−1) were more influenced by the geological texture of the shallow aquifer. The analysis of the geological characteristics of the sub-shallow aquifer structure in the locality of Pouss is mainly sandy, while in the localities of Maga and Guirvidig, clay, clayey-sand and sandy-clay materials dominate. There are no trends in GW chemical evolution from Lake Maga waters towards the shallow groundwater table (SGWT). The mixing-ratios values showed that the SW contributed for more than 65% (mean) to the sub-shallow aquifer in the study area, and the highest SWs (80%) contribution occurred in the locality of Pouss, close to Lake Maga, pond, Logone River, irrigation canal, and seasonal stream, associated with the shallowest GW levels (< 1.5 m). The proximity to SW bodies and the texture of the fluvio-lacustrine deposit of the shallow aquifer strongly influenced GW table levels and their hydrogeochemical characteristics. This work could be a prerequisite to understand how the physicochemical and chemical properties of GW in the shallow aquifer evolve and respond under the influence of SW bodies. [ABSTRACT FROM AUTHOR]

The Maggiore Valley well field plays a fundamental role in supplying drinking water to a large territory of the Piedmont Region (northwestern Italy) and has been intensively exploited since the early twentieth century. This water resource is hosted in a deep, multilayered aquifer system. The main purpose of this study was to characterize the recharge processes of the deep aquifer through hydrochemical and isotopic assessments, as well as the water quality in the recharge and drainage areas. For this purpose, 128 physical–chemical analyses (major ions) and 50 isotopic analyses (δ18O and δ2H) were carried out on samples collected in shallow and deep aquifer complexes in two sampling campaigns in 2021. From the results, a hydrogeological conceptual model of recharge processes was developed. The chemical data confirm the presence of bicarbonate–calcium facies in most samples of the shallow and deep aquifer complexes. Clear hydrochemical differences were observed among the investigated sectors. The recharge areas were identified as (1) far zones, namely the shallow aquifer complex of the Cuneo Plain, and (2) the shallow and deep aquifer complexes with groundwater mixing in the riverside sector of Po Plain in the Turin area. The mixing of waters from the Cuneo Plain and Turin Plain was verified in the well field area. The isotopic values of the artesian well water also confirmed contributions from the Turin and Cuneo Alps. This study clarified the recharge processes, thereby defining potential pollutant pathways, and the results provide additional support for groundwater resource management and protection. [ABSTRACT FROM AUTHOR]

Existing aquifer water abundance evaluation methods employ fixed and constant index weights and overlook variations within major influencing factors as well as interactions among multiple factors. We propose a water abundance index method based on a variable weight model that considers various water abundance influencing factors and their respective weights, and quantitatively determines the weights of the same factor across different state values. This paper establishes a comprehensive system of four categories and 16 subcategories of main influencing factors that describe the distribution pattern of water abundance, considering lithological characters, hydraulic characteristics, structural factors, and geophysical parameters that influence aquifer water abundance. The variable weight model is used along with the K-means clustering method in dynamic clustering to determine the variable weight interval thresholds for each index of the main influencing factor. Additionally, we investigated the construction of the state variable weight vector, determination of weight adjustment parameters, quantitative assessment of the interaction relationship, and relative importance of each main influencing factor in relation to aquifer water abundance. Finally, an evaluation method and mathematical model for the water abundance index based on the variable weight model are developed. This study provides a detailed description of the specific implementation steps of the water abundance index method based on the variable weight model, using the direct water-filled J2z–#2 coal seam roof fissured aquifer in the Xiaojihan coal mine as a case study. The evaluation results were then verified using drainage data from the working face. The findings indicate that a comparison with the traditional constant weight evaluation results demonstrates that the variable weight model better reflects the characteristics of aquifer heterogeneity and achieves higher prediction accuracy. [ABSTRACT FROM AUTHOR]

In arid regions characterized by large variations in groundwater salinity, the data derived from irrigation and domestic water supply wells may exhibit bias, reflecting an overall lower salinity than the true aquifer distribution. This bias stems from the decommissioning, non-use, or disrepair of wells that are frequently sources of higher salinity readings, rendering them unavailable for sampling. Baseflow-fed streams, agricultural drains, seeps, springs issuing into agricultural drains, and randomly located test hole samples tend to manifest higher averages and ranges of salinity when compared to supply wells. Agricultural drain flows, springs, and test holes, if sampled following recommended guidelines, are less susceptible to such bias. This study presents a case of groundwater bias identified through an initial water well sampling program in El Paso (Texas, USA). Subsequent rounds of sampling, incorporating drain samples, spring samples, and test hole samples, revealed a more comprehensive understanding of the salinity dynamics. The dataset not only highlights the existence of bias but also provides evidence for a combined geological and agricultural origin of salinity. Additionally, it demonstrates that drain sampling in an earlier study did not accurately depict a primary salinity source due to incomplete analysis of the data. Recommendations are outlined to mitigate bias, emphasizing the importance of sample control from baseflow-fed drains, springs, water wells, and test hole samples. The study also infers the upwelling of saline groundwater from deeper formations in the study area, contributing to a more comprehensive understanding of groundwater salinity dynamics. [ABSTRACT FROM AUTHOR]

In recent years groundwater contamination through nitrate contamination has increased rapidly in the managementof water research. In our study, fourteen nitrate conditioning factors were used, and multi-collinearity analysis is done. Among all variables, pH is crucial and ranked one, with a value of 0.77, which controls the nitrate concentration in the coastal aquifer in South 24 Parganas. The second important factor is Cl−, the value of which is 0.71. Other factors like—As, F−, EC and Mg2+ ranked third, fourth and fifth position, and their value are 0.69, 0.69, 0.67 and 0.55, respectively. Due to contaminated water, people of this district are suffering from several diseases like kidney damage (around 60%), liver (about 40%), low pressure due to salinity, fever, and headache. The applied method is for other regions to determine the nitrate concentration predictions and for the justifiable alterationof some management strategies. [ABSTRACT FROM AUTHOR]

A common challenge in many cities in Europe is endangerment of natural resources due to soil and water pollution. Despite extensive investigation and remediation measures over decades and current practices of environmental management, residues of pollutants persist in soil and groundwater, reducing the functionality of many urban areas. In complex hydrogeological systems, where contaminated plumes are overlapping and/or diffuse contamination is present, technical and administrative activities have to be thoroughly planned and executed in the long term to secure the recovery of groundwater quality. Communities need a management strategy (MS) to manage soil and groundwater contamination in urban areas, especially where contamination exceeds local scales but does not reach the national level. A MS drives administrations to understand hydrogeological system properties, define new, reachable target values and give practical guidance for the implementation of necessary measures. Implementation of a MS fosters the early involvement of key stakeholders and their contribution to the development of MS itself. The strategy has proven to be an appropriate and flexible tool for the transfer of scientific knowledge to the planning, coordination and implementation necessary for the remediation of large-scale groundwater contamination. [ABSTRACT FROM AUTHOR]

Agricultural activities can generate contaminants that enter underlying granular aquifers and become transported within the groundwater to adjacent streams. This paper reports on estimation of the transit time of groundwater through a saturated granular unconfined aquifer in an agricultural region of Saguenay-Lac-Saint-Jean, Quebec (Canada). A multi-technique approach is applied, integrating analytical, hydrogeochemical, and numerical methods—to determine groundwater flow from a recharge (wetland) to discharge zone (groundwater seep). Fieldwork observations, including borehole drilling, soil/groundwater sampling, and piezometers, were combined with laboratory measurements of soil hydrogeological properties and stable (δ18OH2O and δ2HH2O)/radioactive (3H) isotopes in the collected groundwater. The Dupuit–Forchheimer-based analytical method used here estimated a groundwater transit time of 7.75 years, whereas the hydrogeochemical-based and three-dimensional FEFLOW numerical method produced estimates of 7.34 and 7.27 years, respectively. The similarity of the three estimates highlights the robustness of the approach, which integrates field data to produce accurate assessments of groundwater transit time. This multi-technique approach will help in the sustainable management of groundwater resources and for preparing effective environmental plans for agricultural practices in areas underlain by aquifers. [ABSTRACT FROM AUTHOR]

The study is aimed at evaluating the groundwater accumulations present in Alice using magnetic and electrical resistivity measurements to examine the trends of structural elements and characterize the groundwater resource for borehole drilling. The magnetic maps show a low magnetic linear structure moving northwest to southeast direction, which may be caused by fractures. The linear high intensities were probably caused by dolerite dykes, while dolerite sills caused broader high-intensity areas. The depth slices show that the near-surface magnetic structures are visible to a depth of about 19 m, and the deep-seated structures are found at a depth of about 31 m, possibly deeper. Twenty-five vertical electrical soundings (VES) of the Schlumberger array were measured with AB/2 varying between 1.5 m and 250 m across the study area. The VES interpretation showed four geoelectric layers composed of HK and HA curve types. The geoelectric layer's thicknesses are (1) topsoil from 0.4 to 1.8 m, (2) weathered layer from 0.8 to 17.5 m, and (3) weathered/fractured layer from 9.9 to 143.9 m; the third layer could be the productive water-bearing zones, and (4) bedrock layer has an infinite thickness. The layers have resistivity values of 20-5752 Ωm, 3-51 Ωm, 136-352 Ωm, and 44-60428 Ωm, respectively. A correlation of the VES with the borehole log indicated a well-matched result. The magnetic and electrical resistivity surveys provided a detailed subsurface structure and helped identify possible fractures that could act as a passage for groundwater. [ABSTRACT FROM AUTHOR]

Quaternary glacial aquifers are important water sources for irrigation in many agricultural regions, including eastern Nebraska, USA. Quaternary glacial aquifers are heterogeneous, with juxtaposed low-permeability and high-permeability hydrofacies. Managing groundwater in such aquifers requires a realistic groundwater-flow model parameterization, and characterization of the aquifer geometry, spatial distribution of aquifer properties, and local aquifer interconnectedness. Despite its importance in considering uncertainty during decision-making, hydrofacies probabilities generated from multiple-point statistics (MPS) are not widely applied for groundwater model parameterization and groundwater management zone delineation. This study used a combination of soft data, a cognitive training image, and hard data to generate 100 three-dimensional (3D) conditional aquifer heterogeneity realizations. The most probable model (probability of hydrofacies) was then computed at node spacing of 200 × 200 × 3 m and validated using groundwater-level hydrographs. The resulting hydrofacies probability grids revealed variations in aquifer geometry, locally disconnected aquifer systems, recharge pathways, and hydrologic barriers. The profiles from hydrofacies probability at various locations show spatial variability of the streambed and aquifer connectivity. Groundwater-level hydrographs show evidence of these aquifer characteristics, verifying the general structure of the model. Using the MPS-generated 3D hydrofacies probability and hydrologic data, a novel workflow was developed in order to better define high-resolution groundwater management zones and strategies. In general, the conditional probability of hydrofacies helps improve the understanding of glacial aquifer heterogeneity, the characterization of aquifer-to-aquifer and streambed-aquifer connections, and the delineation of groundwater management zones. This MPS workflow can be adapted to other areas for modeling 3D aquifer heterogeneity using multisource data. [ABSTRACT FROM AUTHOR]

This investigation is aimed at exploring the mobilization and sources of Fe, Mn, and As in aquifers through geochemical characterization, spatial analysis, and statistical approaches. Analytical results showed that the average concentrations of Fe (10.17 mg/L) and Mn (3.6 mg/L) crossed the guideline value but not As in all samples. In this study, the elevated levels of dissolved organic carbon, salinity, total hardness, and log10 pCO2; the lower value of dissolved oxygen; and some oxidizing groups of samples influence the reductive environment of Fe and Mn weathering. The investigation illustrated that the source of both metals on the upper platform is consolidated silty soil and aquifer sediment, whereas, in the river valley, they originate from Fe and Mn-bearing nodules in the rich clay layer and tidal mud. In addition, the frequent fluctuation of river flow, excess water mining, and an unbalanced recharge/discharge ratio are the causes of higher concentrations of both metals. The correlation matrix and factor analysis of Fe and Mn with redox-sensitive water variables confirmed that a favourable reductive situation fosters the Fe and Mn release process. Studies have also shown the significant possibility of forming a metal complex with organic and inorganic substances. The higher dissolution of Fe and Mn minerals causes As to be adsorbed on them, leading to less release of As into groundwater. This investigation provides a basis for the rational use of groundwater and the defense of public health in zones with high Fe and Mn contents. [ABSTRACT FROM AUTHOR]

High-cost remediation of groundwater pollution makes it important to obtain exact information about the source. This is quite difficult to achieve in naturally ill-posed inverse problems of this kind. If the aquifer parameters are also unknown, the problem becomes even more challenging. To address this difficulty, we propose the alternating direction genetic algorithm (ADGA) approach, together with modification of the order of magnitude of the decision variables, to increase the accuracy of the results and computational efficiency. Seven scenarios were designed to test the accuracy of the proposed approach in aquifer with different properties, number of pollution sources, parameters and measurement errors. The results show that combining the ADGA approach with modification of the order of magnitude of the decision variables for identifying both groundwater pollution source and aquifer parameters significantly increases the accuracy of estimated results. The NE value for the estimated results decreased from 9.81% to 58.44% for different cases, and computation time is about half decreased. In addition, the approach is applicable in situations where concentrations of observational data with measurement error, and for multiple source locations and non-uniform media. [ABSTRACT FROM AUTHOR]

The instability of colloidal gas aphrons (CGAs) in aquifers is one of the major obstacles influencing the remediation efficiency of CGAs-flushing. In this study, hydrophobic nano-SiO2 (HN-SiO2) was utilized to enhance the stability of CGAs. The batch experiments were carried out to investigate the effect of hydrogeochemical conditions on the stability of HN-SiO2 stabilized CGAs in aquifers, such as ions, pH, and nitrobenzene (NB); 2-D tank experiments designed with various injection velocities and medium particle sizes were conducted to determine the factors influencing the migration of CGAs in the aquifer; and 1-D column experiments were established to evaluate the remediation efficiency of HN-SiO2 stabilized CGAs flushing for NB removal. The results indicated that HN-SiO2 had a favorable effect on the stability of CGAs, which enhanced the half-life of CGAs from 328 to 1,050 s. HN-SiO2 particles formed a shell film on the gas-liquid interface of CGAs to slow down the gas escape and drainage velocity. The stability of CGAs decreased while pH<6 or pH>8 , whereas this was enhanced with the addition of 0.1 wt.% NaCl. The 2-D tank experiments demonstrated that the HN-SiO2 stabilized CGAs had better stability when they flowed in aquifers compared to sodium dodecyl sulfate (SDS) CGAs. The fine medium and high injection velocity facilitated CGAs forming the larger radius remediation area. The injection pressure was inversely proportional to the medium grain sizes, whereas directly proportional to the injection velocities. In addition, column experiments demonstrated the remediation efficiency of HN-SiO2 stabilized CGAs (81.7%) flushing for NB removal was higher than that of SDS CGAs (61.4%) flushing. Therefore, in comparison with SDS CGAs, HN-SiO2 stabilized CGAs were more efficient reagents for NB removal. CGAs-flushing technique using HN-SiO2 stabilized CGAs is feasible to remedy the contaminated aquifers. The contamination caused by dense nonaqueous phase liquids in aquifers has a great threat to ecosystems and human health. Colloidal gas aphron (CGA) flushing has been proposed as an effective remediation technology for dense nonaqueous liquids contaminated aquifers. However, the instability of colloidal gas aphrons in aquifers is one of the major obstacles influencing remediation efficiency. In this work, the hydrophobic nano-SiO2 was used to improve its stability. Besides, the migration of colloidal gas aphron generated with sodium dodecyl sulfate (SDS) and SDS/SiO2 was investigated, and the remediation efficiency for nitrobenzene removal of SDS/SiO2 colloidal gas aphrons flushing was evaluated. SiO2 had a favorable effect on the stability of colloidal gas aphrons, enhancing the half-life of colloidal gas aphrons from 328 to 1,050 s, and the enhancement effect was more evident with the increasing SiO2 concentration. The tank experiment results indicated that SDS/SiO2 colloidal gas aphron had fine migration performance and wide applicability in aquifer environments. In addition, column experiments demonstrated the remediation efficiency of hydrophobic nano-SiO2 stabilized colloidal gas aphrons flushing for nitrobenzene removal was higher than that of SDS colloidal gas aphrons flushing. Therefore, the colloidal gas aphron flushing technique using SDS/SiO2 colloidal gas aphrons is feasible to remedy the contaminated aquifers. [ABSTRACT FROM AUTHOR]

The largest confined aquifers hydraulically continuous from the Algeria Atlas Mountains as a recharge area to the Tunisian Chotts were discharge area. Is being largely used in the valley of Oued Souf, southeastern of Algeria and part of the northeastern Sahara, composed with sedimentary series ranging from the lower Cretaceous to the Quaternary. These formations have favored several aquifer layers with variable hydrodynamic behavior depending on their facies . The high expansion of the agricultural field needs irrigation from groundwater aquifers in this area. The overexploitation of the shallow aquifer causes severe deterioration of groundwater quality and soil suffusion at arid areas. The high salinity (electrical conductivity exceeds 3600 mS.cm-¹) coupled with groundwater level decline pose serious problems for current irrigation and domestic water supplies. Although, the multi-layers of complex terminal (CT) and continental intercalary (CI) aquifers is used to approve the water supplies. In aim to corroborate the hydrochemical process, and to investigate the water potentialities and mineralization of CT and CI groundwater aquifers, chemical tools namely major elements and trace elements are studied. The isotopic (δ 18O, δ 2H) hydrogeochemical study helps to identify and classify this deep underground water aquifers relationship. The samples isotopic signal shown a current recharge of the CT, according to the regional rainfall signal. [ABSTRACT FROM AUTHOR]

Although chalk aquifers are not too often associated with conduit flow, they are highly productive groundwater systems and, like limestone aquifers, they can be vulnerable to contamination when exposed to land use activities. The Danish carbonate rocks are generally recognized to be highly fractured and covered by thick Quaternary sediments. Fissure flow is pronounced, occurring in the upper 50–100 m due to Pleistocene glaciations. According to recently published maps of the distribution of karst in Europe, Denmark has no karst. However, this study concludes that karstified chalk and limestone aquifers are an important source of freshwater in Denmark. Four national datasets on karst features, groundwater flow, groundwater chemistry, and fish ecological quality ratio (EQR) data now indicate more heterogeneous structures and preferential flow pathways in the chalk and limestone aquifers than had been conceptualized and modelled with a national water resources groundwater/surface-water model in the recent past. This study provides new qualitative evidence that rapid and preferential flow of water and agrochemicals from the surface through thinner parts of the Quaternary cover layers, sinkholes and solution-enlarged fractures may likely impact the vulnerability of chalk and limestone aquifers. Additionally, due to the preferential flow system, some gaining streams discharged by karstified chalk and limestone aquifers show increased fish EQR values when using observed river daily discharge data instead of simulated daily discharge. [ABSTRACT FROM AUTHOR]

Groundwater is an important freshwater resource and hosts specialized microbial assemblages providing fundamental ecosystem services. The current knowledge on the role of aquatic microorganisms in subsurface ecosystems is still limited. This work aimed to explore the links between groundwater hydrogeochemical properties and microbial community traits in a volcanic unconfined aquifer, moderately impacted by anthropic activities. The main physical and chemical parameters of groundwater samples were analyzed, along with microbial biomass (total cell counts, ATP-active biomass concentration), potential metabolic activity, and physiological profiles at the microbial community level (Biolog ™ EcoPlates). The results showed the coexistence of oxidizing and reducing groundwater conditions across the study area. We discriminated two groups of oxidizing/reducing groundwater samples (Ox and Red), each including two subgroups with different chemical conditions attributed to contrasting levels of anthropogenic impact for non-intensive agricultural practices and waste disposal activities (Ox − and Ox + ; Red − and Red +). Although the microbial biomass was likely not affected by changing redox, the microbial metabolic potential and functional diversity changed significantly. In the Ox samples, the community-level physiological profiles were different, mainly owing to the utilization of carboxylic acids (Ox − > Ox +) and carbohydrates (Ox + > Ox −). In the Red samples, a wider set of organic substrates were consumed by the microbial communities, including those less bioavailable (e.g., phenols). Significant differences were also found between Red − and Red + , mainly owing to the relative increase in the utilization of amino acids in Red − , polymers and amines in Red + , along with the active biomass. By reflecting the local redox conditions and moderate levels of anthropogenic impact, the applied approach highlighted changes of microbial metabolic potential and physiological profiles that imply direct repercussions on biogeochemical cycling and the ecosystem services provided by groundwater microorganisms. [ABSTRACT FROM AUTHOR]

DRASTIC is a model used to reliably assess the pollution potential of aquifers at global location. Despite various criticisms of this model or its optimization, sometimes the territorial or geological conditions still must rely on this model approach based on its simplicity. The existence of sinkholes in the alluvial aquifer with an underlying karst aquifer is a clear example of the need to change or optimize the DRASTIC model to improve accuracy of prediction. In this study, the DRASTIC model was changed by adding two factors, the distance to a sinkhole and the sinkhole catchment factors. The modified DRASTIC model was then used to evaluate the pollution potential of Abarkouh aquifer in Yazd province, Central Iran. The intrinsic vulnerability index of Abarkouh aquifer was calculated by the weighted sum method in GIS. The resulting numerical values ranged between 62 and 176 for full study area. Without adding the two layers related to Sin-DRASTIC, the generic DRASTIC Index map showed summed values ranging between 54 and 130. The final Sin-DRASTIC map was divided it into 4 orders very low (<106; 722 km2, 78%), low (107-133; 186 km2, 20%), low to moderate (133-160; 15.3 km2, 1.7%), and moderate vulnerability (161-176; 1.7 km2, 0.3%) vulnerability. Both of the created maps showed high Area Under the Curve values at 76% and 78% for the generic DRASTIC and Sin-DRASTIC respectively. However, the area of the aquifer containing the sinkholes showed low and very low zones of contamination vulnerability on the generic DRASTIC map. The sensitivity analysis showed that the aquifer vulnerability to pollution is mainly controlled by the vadose zone impacts and the sinkhole catchment factor. Therefore, it is concluded that for geologic settings containing sinkholes that are open or contain higher vertical hydraulic conductivity sediment compared to the general matrix of the unconfined aquifer, the Sin-DRASTIC model method yields a superior prediction. Sin-DRASTIC is a modified version of the generic DRASTIC method that used in regions wherein sinkholes occur The Sin-DRASTIC models was applied to intrinsic vulnerability of Abarkouh aquifer, Central Iran. The high AUC values at 76% and 78% for the generic DRASTIC and Sin-DRASTIC respectively, show the accuracy of the results. In the Sin-DRASTIC map the sinkhole areas showed a high potential for groundwater contamination [ABSTRACT FROM AUTHOR]

The present research aims to determine the sources and concentration of uranium in the groundwater of the hard rock aquifer. Two hundred and fifty-four groundwater samples were collected, and the analysis shows the uranium concentrations range from 0.5 to 113 ppb (pre-monsoon) and 0.5 to 120 ppb (post-monsoon). Factor analysis illustrates that the lower concentrations of uranium in the study region may be due to the poor dissolution of minerals in the subsurface. Saturation Index values confirm that the Uraninite mineral is undersaturated, and the U4O9 has dominant distribution during both seasons. During both seasons, four samples have a uranium concentration of more than 60 ppb, which might be due to the fertilizer usage in the agricultural activities in the study area. The GIS technique highlights the uranium-contaminated location and polluted water quality parameters using the Inverse Distance Weighted spatial interpolation plots. [ABSTRACT FROM AUTHOR]

Underground natural gas storage is a promising solution to lowering greenhouse gas emissions and attaining sustainable development goals. However, several issues prevent the application of storage projects on a global scale. An accurate estimation of the delivered amount of natural gas from each storage site might be used for supply and demand. Due to this fact, this study proposed hybrid intelligent models integrating the least square support vector machine (LSSVM), differential evolution (DE), imperialist competitive algorithm (ICA), cultural algorithm (CA) , teaching learning-based optimization (TLBO), genetic algorithm (GA), and particle swarm optimization (PSO) for approximating the deliverability of underground natural gas storage in different geological formations. We have employed vast data sets of 782 reservoirs from depleted fields to train and validate the proposed intelligent models to predict underground natural gas storage deliverability in the USA. The visual and analytical assessments were used to investigate the performance of the developed intelligent systems. The predicted results showed that all of the intelligent models agreed with the recorded data. Moreover, the statistical indicators revealed that the LSSVM coupling TLBO model shows the highest accuracy in predicting the deliverability of natural gas storage in the depleted field among three intelligent models. Also, the optimal intelligent model accurately predicts 880 and 600 data measurements of saline aquifers and salt domes, respectively. The optimal intelligent model yields a root mean square error (RMSE) value of less than 0.022. The correlation factor (R2) is over 0.998, 0.999, and 0.906 for the depleted field, saline aquifers, and salt domes, respectively. The results highlight the importance of combining smart approaches with nature-inspired strategies in forecasting storage site deliverability. In light of these findings, researchers are better equipped to reduce petroleum energy usage and increase community acceptability of natural gas as part of the transition to green energy. [ABSTRACT FROM AUTHOR]

The Mateur multi-aquifer system, consisting of a Quaternary alluvial aquifer and a Campanian limestone aquifer, is one of the most significant aquifer systems in northern Tunisia, providing domestic and agricultural water supply for the entire Mateur region. The present study aims to unveil the various factors and mechanisms controlling the groundwater chemistry of such a system. Indeed, integrated hydrogeochemical and isotopic approaches are used herein to identify the alluvial and limestone aquifer waters mixing and evolution in the Mateur region. Results show that despite the difference in aquifer lithology, there is little difference in the major ion geochemistry and stable isotope ratios of groundwater within the Mateur plain. Waters from the Quaternary alluvial aquifer are classified into two predominant facies: mixed facies (Ca–Na–SO4–Cl and Ca–Na–HCO3–Cl) and Na–Cl facies. Similarly, waters from the limestone aquifer have also mixed facies (Ca–Na–SO4–Cl) and sodium chloride facies (NaCl). Groundwater δ18O and δ²H values show more homogeneous values along the groundwater flow direction, indicating inter-aquifer mixing processes. Tritium contents of the Campanian aquifer are lower than those of the Quaternary aquifer, indicating a relatively older age or mixture with recent waters. This validates a concept of the hydraulic continuity between the Quaternary aquifer and the Campanian aquifer which is consistent with the geochemical analytical results. [ABSTRACT FROM AUTHOR]

Groundwater is an important factor in establishing new urban communities, especially in coastal arid and semi-arid regions. Egypt is one of the world's driest countries, with hyper-arid territory accounting for 86% of the total area and arid and semi-arid terrain accounting for the rest. The present work aims to demonstrate the powerful integration of geophysical techniques to assess groundwater potentiality and suitability in Gara Oasis (GO), which describes a good example of Egypt's strategic southern extension of its arid north-western coast. Geophysical methods, including electrical resistivity and aeromagnetics, were used to evaluate groundwater resources. The study region reduced to pole total magnetic intensity map is subjected to digital filters that include derivatives, analytic signal, and tilt angle. The possible structures controlling the shallow and deep aquifers are delineated and integrated with geoelectric results. Moreover, two magnetic tomography sections are constructed to show the subsurface distribution of magnetic susceptibilities and formation boundaries. Ten vertical electric soundings (VESs) are measured and used in this study to construct four geoelectrical cross-sections. According to the results, Gara's commonly calculated subsurface resistivity model comprises six major resistivity layers. The 5th layer, in particular, is composed of Fractured dolomitic Limestone and represents a possible promising shallow aquifer. Moreover, as evidenced by various magnetic data filters, the shallow (Miocene carbonate) and deep (Nubian sandstone) aquifers are structurally controlled and regulated by a system of faults or contacts. These contacts trends NW-SE, E-W, and NE-SW as common trends emerged from the total derivative and tilt maps. Results suggest that the central part (N-S zone) together with the western side of Gara, have the most notable aquifer possibility demanded future improvement strategies. [ABSTRACT FROM AUTHOR]

The Ganges River delta complex contains a transboundary aquifer system shared between India and Bangladesh. Although it serves as the main freshwater source for the population inhabiting the delta, the aquifer system is severely contaminated with arsenic (As). This study aimed to determine the control of the delta hydrostratigraphy on the regional-scale depth distribution of As within the aquifer system. We developed the first high-resolution, regional-scale, transboundary hydrostratigraphic model of the Ganges River delta and analyzed the patterns of As distribution as a function of the hydrostratigraphy. Model results indicate that, despite the presence of a single aquifer system across the delta, the hydrostratigraphy is spatially variable and can be architecturally divided into three distinct aquifer subsystems from northwest to southeast: a single, thick continuous aquifer (type I); a vertically segregated, semiconfined aquifer subsystem (type II); and a multilayered, nearly confined aquifer subsystem (type III). Results indicate that the spatial distribution of As is characteristically different in each subsystem. In the type I aquifer, As concentrations tend to be homogeneous at all depths, while in type II and type III aquifers, As concentrations sharply decrease with depth. The intervening aquitards in the type II and type III aquifer subsystems appear to act as natural barriers to infiltration of surficial As or organic matter-rich water to the deeper aquifer zones. This delineation of the regional-scale hydrostratigraphic architecture and resulting understanding of its plausible controls on the depth-distribution of As within the delta should significantly aid in the systematic framing of sustainable management plans for the As-safe aquifers within the Ganges River delta aquifer system. [ABSTRACT FROM AUTHOR]

Groundwater from different aquifers in the Zhanjiang area suffers from different degrees of nitrogen pollution, which poses a serious threat to the health of urban and rural residents as well as the surrounding aquatic ecological environment. However, neither the water chemistry and microbial community characteristics in different aquifer media nor the sources of inorganic nitrogen pollution have been extensively studied. This study integrated water quality parameters, dual isotopes (δ15N–NO 3 − and δ18O–NO 3 −), and 16S rRNA data to clarify the hydrochemical and microbial characteristics of loose rock pore water (LRPW), layered bedrock fissure water (LBFW), and volcanic rock pore fissure water (VRPFW) in the Zhanjiang area and to determine inorganic nitrogen pollution and sources. The results show that the hydrochemistry of groundwater in different aquifers is complex and diverse, which is mainly affected by rock weathering and atmospheric precipitation, and the cation exchange is strong. High NO 3 − concentration reduces the richness of the microbial community (VRPFW). There are a large number of bacteria related to nitrogen (N) cycle in groundwater and nitrification dominated the N transformation. A quarter of the samples exceeded the relevant inorganic nitrogen index limits specified in the drinking water standard for China. The NO 3 − content is highest in VRPFW and the NH 4 + content is highest in shallow loose rock pore water (SLRPW). In general, NO 3 −/Cl−, dual isotope (δ15N–NO 3 − and δ18O–NO 3 −) data and MixSIAR quantitative results indicate manure and sewage (M&S) and soil organic nitrogen (SON) are the main sources of NO 3 −. In LRPW, as the depth increases, the contribution rate of M&S gradually decreases, and the contribution rate of SON gradually increases. The results of uncertainty analysis show that the UI 90 values of SON and M&S are higher. This study provides a scientific basis for local relevant departments to address inorganic nitrogen pollution in groundwater. [Display omitted] • Groundwater chemistry mainly reflects an oxidizing environment. • There are a large number of bacteria related to N cycle in groundwater. • Mean 58.0%, 37.0% and 11.5% of the nitrate were contributed from M&S, SON and NF. • In LRPW, the contribution rate of M&S and SON is related to the depth change. • Uncertainties of source contributions decreased in the order: SON > M&S > NF > AP. [ABSTRACT FROM AUTHOR]

This study evaluates the groundwater potential and quality in the parts of Chhotanagpur Gneissic Complex situated in the East Indian Shield. The region has faced groundwater development challenges for several decades. Therefore, in the study area, it is crucial to address the depletion of both groundwater quality and quantity, as this facilitates the identification of potential uncontaminated groundwater zones. The present study interprets the groundwater potential zones (GWPZ) utilizing an analytical hierarchical process (AHP) integrated with hydrogeochemical analysis. Several thematic maps were prepared to delineate the GPWZ. It has been found that ∼0.6% of the study area has a very good potential zone, 14.4% has good, 52% has moderate, and approximately 32% and 0.9% have low to very low prospective groundwater resources, respectively. The authentication of results was found to be excellent (91.4%) with the Area Under Curve (AUC). Analysis of hydrogeochemical data suggests that Mixed Ca–Na–HCO 3 , Mixed Ca–Mg–Cl, Ca–HCO 3 , and Na–Cl are the dominant water types in the study area. The principal component analysis suggests that Na+, Mg2+, Cl−, NO 3 −, and SO 4 2− significantly contribute to groundwater chemistry. The K-means clustering and hierarchical cluster analysis classified groundwater samples into three clusters based on the hydrogeochemical characteristics. It is inferred that silicate weathering and reverse ion reactions through rock-water interaction control geogenic processes for groundwater chemistry. It is also inferred that regions with poor to unsuitable water quality indexes also have low GWPZ. Further, groundwater for irrigation is also accessed and found unsuitable at some locations. This research contributes to comprehending groundwater characteristics in analogous geological regions globally. Additionally, it assists in implementing preventive actions to mitigate groundwater contamination, consequently lowering health risks and formulating sustainable plans for the future. • Remote sensing and GIS, and field data to assess groundwater potential zones (GWPZ) and understand the geochemical behaviour. • Groundwater facies has been comprehended utilizing hydrogeochemical fingerprinting and statistical modeling. • Linked low GWPZ to poor water quality, emphasizing the impact of over-extraction on groundwater deterioration. [ABSTRACT FROM AUTHOR]

The assessment of the level of groundwater protection, formalized by the expression "vulnerability to pollution of aquifers", frequently used since 1980, still faces the problem of identifying a representative index (e.g. DRASTIC, GOD, SINTACS, EPIK, etc.), an index that must reflect the complex characteristics of hydrostructures and contaminants. In order to assess the vulnerability to pollution of phreatic aquifers, a 4D model has been developed, a model that integrates the 3D features of the hydrostructure and time, the fourth dimension of the model. The proposed model is applied for a phreatic aquifer from the arid area of south-eastern Romania. The phreatic aquifers, in the green-schists area of the Central Dobrogea Massif, are accumulated in loessoid deposits with heterogeneous particle size composition and in the altered area of green-schists. These low-resource aquifers are "protected" by a vadose zone with variable thickness, whose transport capacity is determined by the moisture resulting from the precipitation regime. The vulnerability of the phreatic aquifer to pollution is synthesized as the time required for a contaminant to cross the vadose zone (in short: duration time of pass over), the relevant vulnerability index that integrates the characteristics of the vadose zone (thickness, particle size composition, lithology and moisture) and of contaminants. [ABSTRACT FROM AUTHOR]

The goal of the present study is to investigate, delineate, and evaluate the shallow Miocene groundwater aquifer with vertical and lateral facies variations in the Gara oasis, western desert of Egypt. This oasis represents a typical arid region in North Africa. Through grid texture analysis, lineament detection, edge detection, thresholding, and identifying areas of structural complexity from the filtered residual reduced-to-pole magnetic anomaly map, it is possible to outline the fracture zones that principally control the groundwater aquifers and water flow in the area. The groundwater quality and quantity are examined hydro-geochemically through nine groundwater samples that were gathered from wells and springs distributed throughout the area around Gara Lake. Measurements of physio-chemical parameters (TDS, pH, and EC) are carried out and its spatial distribution is critically studied. The results reveal that the ion-exchange process caused by water-rock interaction is the dominant process. Furthermore, the main ions in the groundwater in the study areas were Na and Cl. This might be due to evaporation or halite dissolution with the upward flow of waters through the fractures from the deep aquifer of the Nubian sandstone to the shallow aquifer of the fractured Miocene limestone. [ABSTRACT FROM AUTHOR]

In order to provide a recommendation on the quality of groundwater in the region of Berrechid, Morocco, we analysed the concentration of conductivity as one of the main measures to identify the salinity of the water. We applied artificial intelligence models for predicting the conductivity of water while analysing several physical parameters as input parameters of the models. To achieve this purpose, we exploited and evaluated the Random Forest (RF), Support Vector Regression (SVR), and k-nearest neighbour models using 400 data samples related to ten groundwater quality parameters in the Berrechid aquifer, Morocco. The results revealed that the overall prediction performance of the RF models is higher than the SVR and KNN models. Overall, the developed models are able to predict conductivity with high accuracy. The approaches developed in this study are promising for real-time and low-cost prediction of groundwater quality by using physical parameters as input variables. [ABSTRACT FROM AUTHOR]

In this work, an isotopic analysis of δ18O, δ 13C, and NO3−concentrations was carried out to identify the origin and the processes related to the contamination of an aquifer located in the state of Guanajuato, Mexico. The research identified the possible sources of δ13C in groundwater. During groundwater flow, CO2 participates in different hydrogeochemical reactions in which the dissolution of carbonates or biochemical processes related to biodegradation stand out. Isotopic data of δ13C, δ18O, and the hydrogeochemical behavior of NO3− and HCO3− in water, in addition to isotopic data and the chemical composition of limestones in the study area, were determined to establish the isotopic signature and the processes undergone by the rocks. The isotopic signature of rock and water samples indicated that metamorphic limestones contributed with carbon dioxide to deep groundwater, while in the upper aquifer, bacterial metabolic reactions during nitrification–denitrification could modify the isotopic signature of δ13C in some wells, although atmospheric contribution also plays a role. The modification of the carbon isotopic component is related to the precipitation of calcite in specific regions of the study area, input of atmospheric CO2, and soil (e. g. the possible participation of C4-type plants in the assimilation-release of carbon). This process is not confirmed or completely ruled out in this study since agriculture is excessively developed throughout the region. The joint interpretation of isotopic values and the hydrogeochemical behavior of major and conservative elements help in identifying possible pollution processes in which different carbon sources are related. [ABSTRACT FROM AUTHOR]

The effect of waste dumps on groundwater quality on perched aquifers in Nsukka and environs was investigated by applying multivariate statistical analyses using Statgraphics Centurion XVII, ArcGIS 10.2.2 and Surfer 10 software on hydrochemical parameters from soil (0 cm and 15 cm depth) and groundwater media. Factor analysis, correlation, principal component analysis and cluster analysis reflect biodegradable domestic solid contaminants, automobile contaminants and construction or building contaminants. The significant or positive correlation between parameters was taken at value equal to or greater than 0.5. Chromium showed positive or significant correlation with copper (0.98), cadmium (0.91), nitrate (0.87) and potassium (0.82) indicating that they are from the same source. Zinc showed positive correlation with manganese (0.89) and pH (0.70) showing similar source. The first cluster showed chromium, copper, cadmium, nitrate, potassium and iron which could be attributed to market and domestic biodegradable wastes. The second cluster showed parameter association for lead, EC and mercury which could be attributed to automobile wastes. The third cluster showed zinc, manganese and pH which could be attributed to construction and building wastes. This showed that the third cluster is the major contributor to the soil pH. Based on the Normality Tests (Shapiro-Wilk significance test) to determine P-Value of the analyzed parameters, in the study area; there was no significant spatial variation (@p > 0.05) in the values of parameters such as chromium, iron, pH in the impact zone and the control area. Conversely, the other parameters were statistically significant. For the groundwater analysis, the dendrogram extracted three clusters highlighting the parameter associations according to their possible sources of occurrence. The first cluster showed potassium, sodium, DOI, manganese, and bicarbonate, which could be attributed to construction and building wastes. The second cluster showed parameter association for sulfate, nitrate, calcium and chloride; which could be domestic biodegradable solid waste. The third cluster showed pH, EC, TDS, Cu+, Pb2+, Hg+, Fe2+, Cr2+ and Cd2+ which could be attributed to automobile wastes. [ABSTRACT FROM AUTHOR]

Flow in many bedrock aquifers is through fracture networks. Point to point tracer tests using applied tracers provide a direct measure of time of travel and are most useful for determining effective porosity. Calculated values from these tests are typically between 10−4 and 10−2 (0.01% to 1%), with these low values indicating preferential flow through fracture and channel networks. Tracer tests are not commonly used in site investigations, and specific yield is often used as a proxy for effective porosity. The most popular methods have used centrifuge measurements, water table fluctuations, pumping tests, and packer tests. Specific yield varies substantially with the testing method. No method is as reliable as tracer testing for providing estimates of effective porosity, but all methods provide complementary insights on aquifer structure. Temporal and spatial scaling effects suggest that bedrock aquifers have hierarchical structures, with a network of more permeable fractures and channels, which are connected to less permeable fractures and to the matrix. Consequences of the low effective porosities include groundwater velocities that often exceed 100 m/d and more frequent microbial contamination than in aquifers in unconsolidated sediments. The large uncertainty over the magnitude of effective porosity in bedrock aquifers makes it an important parameter to determine in studies where time of travel is of interest. [ABSTRACT FROM AUTHOR]

We performed a comparative analysis of eight case studies worldwide from the perspective of transboundary aquifer governance efficacy. First, we mapped variation in institutional design, applying institutional design criteria in four dimensions linked to The OECD Principles on Water Governance. We then identified explanatory factors: (1) physical variables, including aquifer size and hydrogeological characteristics; (2) watershed variables, including groundwater exploitation capacity and water transfer infrastructure; and (3) political factors, including international donor support. We found that transboundary aquifer governance efficacy is closely linked to problem structure and less attributable to institutional design in the presence of specific contextual variables. [ABSTRACT FROM AUTHOR]

• High As sediments in the Hetao Basin were from the Yellow River sediments from Northeastern Tibetan Plateau. • Long transportation, recycling of sediments, and warm climate enhanced the silicate weathering in shallow aquifer. • The enhanced silicate weathering increased contents of Fe/Mn oxides and As in shallow aquifer. • Aquatic environmentof sedimentation provided organic matter that drove As enrichment in shallow groundwater. • Geochemical processes and geochemical conditions jointly contributed to As enrichment in groundwater. High arsenic (As) groundwater has been widely observed in the world, but the provenance, chemical weathering, and sedimentary environment of aquifer sediments hosting high As groundwater remain poorly understood. The geochemical and isotopic characteristics of high-resolution aquifer sediments were investigated to unravel the roles of provenance, chemical weathering, and sedimentary environment of the aquifer sediments. The average values of rare earth elements (REEs) showed the enrichment of light REEs and flat heavy REEs in the aquifer and the Yellow River sediments. The chemical index of alteration reflected incipient and moderate weathering (41 to 71). The δ13C SOM (−27.4‰ ± 4.3‰) and C/N values (8.1 ± 5.8) indicated aquatic environment of sedimentation. Shallow aquifer sediments mostly had relatively high ΣREEs contents and negative Eu anomalies, demonstrating that the aquifer sediments were mainly derived from the Yellow River (up to 94.3% ± 5%). Deep aquifer sediments had relatively low ΣREEs contents and positive Eu anomalies, which originated from the Yinshan Mountains (up to 72.2% ± 20.4%) principally with igneous and metamorphic rocks. Moreover, recycling of the Yellow River sediments from Northeastern Tibetan Plateau enhanced the silicate weathering and increased contents of Fe/Mn oxides and As. The δ13C SOM and C/N values evidenced that organisms of paleo-lake or paleo-Yellow River were responsible for abundant sedimentary organic matter. Concentrations of Fe, Mn, and As were high in shallow groundwater from the plain. The As enrichment in the shallow groundwater was jointly controlled by the provenance and chemical weathering of the aquifer sediments (14%), sedimentary environment (10%), reductive dissolution (35%) of Fe/Mn oxides, As desorption under elevated pH (20%), and competitive adsorption of HCO 3 - (21%). This study systematically reveals the roles of provenance, chemical weathering, and sedimentary environment of the aquifer sediments and highlights joint contributions of geochemical processes and geochemical conditions to As enrichment in groundwater. [ABSTRACT FROM AUTHOR]

Radon (222Rn), naturally occurring in subsurface environments, is a significant environmental carcinogen when consumed via 222Rn-enriched groundwater and acts as a valuable geochemical tracer of the interaction between groundwater and surface water. Identifying the spatial patterns and influential factors of 222Rn in groundwater is therefore critical. However, there is a scarcity of specific studies on alluvial-lacustrine plains. In this study, 170 groundwater samples were collected to analyze the spatial patterns and controlling factors of 222Rn in the central Yangtze River plain, a typical alluvial-lacustrine plain. Through correlation and principal component analyses, as well as a random forest model (RF), it was determined that the groundwater 222Rn concentration was affected by several factors, including the hydrogeochemical environment, its associated water-rock interactions, the provenance of aquifer sediments, their mineral composition, and spatial distances from bedrock. Specifically, a thinner layer of Quaternary strata closer to the bedrock, combined with a less reducing hydrogeochemical setting and shorter-term water-rock interactions, along with a higher presence of silicate minerals in the aquifer sediments, promoted the accumulation of 222Rn in groundwater. An RF model was employed to predict the spatial distribution of the 222Rn concentration in the alluvial-lacustrine aquifer, revealing elevated groundwater 222Rn concentrations around local uplifts within the plain, at its edges, and near shallow-buried faults. The insights gained from this study can be applied to similar alluvial-lacustrine plains globally. [Display omitted] • Groundwater 222Rn dynamics is assessed by statistical and random forest models. • Higher 222Rn in groundwater was around basin edge, uplift and shallow-buried faults. • 222Rn enrichment was related to more silicate minerals in aquifer sediments. • A less reducing setting with shorter-term water-rock interaction favors 222Rn accumulation. [ABSTRACT FROM AUTHOR]

This study investigates the potential of bioturbated strata within the Jubaila Formation in Saudi Arabia to serve as water aquifers with exceptional storage and flow capacities. Additionally, it explores scenarios related to remediating oil as a possible contaminant in these aquifers. The study employs multipoint statistics modeling to model the burrow attributes of the dominant burrow, Thalassinoides , aiming to understand how the burrow network impacts the flow capacity of the water aquifer in these strata. The modeling results demonstrate that Thalassinoides can generate a connected burrow network responsible for permeability that may exceeds 3.5 Darcey, indicating potential for super permeable aquifers. The study also modeled a hypothetical aquifer for the bioturbated strata in the Jubaila Formation and conducted fluid flow simulation to understand the behavior of oil as a contaminant in such highly permeable strata. The simulation results suggest challenges in extracting oil from aquifers with such permeability, as more than 50% of the oil remains in the aquifer despite the simulation being run for ten times the duration it took for a water breakthrough occurred. This study provides valuable insights into the potential for bioturbated strata in carbonate succession to form water aquifers with exceptional storage and flow capacities. The study also highlighted the challenges associated with remediating oil contamination in such environments. [Display omitted] • Study of Jubaila aquifer and explores oil contamination remediation scenarios. • Insight into the bioturbated aquifers during oil production as contaminants. • The study applied Multipoint stats modeling using burrow to develop 3D-models. • Simulation shows high-permeability, exceptional storage and flow capacities. • Simulation shows that reducing oil flow rate causes delay in water breakthrough. [ABSTRACT FROM AUTHOR]

Anthropogenic activities, including wastewater discharges and fertilizer use, were identified as the primary factors influencing nitrate concentrations in the lower Soummam Valley in the North-East of Algeria. This study aimed to investigate nitrogen pollution and simulate nitrate mass transport coupled with a numerical flow model. Hydrogeochemical findings revealed significant seasonal variations between the high-water period (May 2019 and 2021) and the low-water period (September 2019 to November 2020 and 2021). During the low-water period, both temperature and electrical conductivity increased. However, pH, dissolved oxygen, and nitrate levels decreased in the high-water period. Nitrites and ammonium exhibited irregular fluctuations. The numerical flow model was developed using PMWIN and coupled with a solute transport model simulated with the Model Transport 3 Dimensions (MT3D). Calibration was conducted under steady-state conditions from 2011 to 2021 and was validated by comparing piezometric heads and nitrate concentrations measured in May 2021. Three scenarios were devised to simulate transient conditions from 2011 to 2050, considering variations in both groundwater levels and nitrate concentrations. The simulation revealed that river and dependent head boundaries are the primary sources of groundwater recharge. These boundaries contributed to approximately 87% of the total inflow. The model also depicted the water exchange between the aquifer and the river. However, the constant head boundary represented the main outflow, accounting for 85.7% of the total. The nitrate model illustrated an increase in nitrate concentrations, reaching 3.8 mg/L in 27 out of the 29 simulated wells. Both the river and groundwater head boundaries were identified as the key factors governing the hydrodynamic aquifer system and nitrate transport in the alluvial aquifer of the lower Soummam Valley. • Anthropogenic activities wastewater discharges and fertilizer use were the main factors controlling nitrate concentration in the lower Soummam valley in the North-East of Algeria. • A hydrogeological model was performed using PMWIN and coupled with a solute transport model simulated on the Model Transport 3 Dimensions (MT3D). Calibration was achieved under steady-state conditions from 2011 to 2021, it was validated through the comparison with piezometric levels and nitrate concentrations measured in May 2021. • The results from the nitrates analysis (may 2021) were used to implement the nitrate transport modeling. Firstly, calibration processes were achieved in steady states conditions, then the validation based on the optimization of differences between the simulated and calculated nitrate concentrations, and finally simulation scenarios were accomplished between 2021 and 2050 in order to provide predictions on the spatial-temporal evolution of nitrate concentration in the aquifer. • The river and groundwater head boundaries are the main factors controlling the hydrodynamic aquifer system and nitrate transport in the alluvial aquifer of the lower Soummam valley. • The modeling issues aim to enhance the scientific community's hydrogeological and hydrogeochemical knowledge, provide reliable water resource management options, and help overcome Algeria's current water crisis. [ABSTRACT FROM AUTHOR]

High fluoride (F−) groundwater (F−>1.5 mg/L) widely occurred in the North Henan Plain, located in the arid and semi-arid region of the lower reaches of the Yellow River, which poses a threat to the health of local residents. Seventy-six groundwater samples were collected from the quaternary aquifers in 2022 to explore the spatial pattern of F−, hydrogeochemical evolution processes, and driving factors of F− release using hydrochemical and isotopic analysis, and hydrogeochemical simulation. The health risk was evaluated to determine the hazards of excessive intake of F− for people with different ages using Monte Carlo simulation. Results showed that 54 % of groundwater and 57 % of surface water samples exceeded the WHO recommended limit (1.5 mg/L). The hydrogeological settings have a significant impact on the spatial variability of groundwater F−. In the low-lying area in the front of alluvial fan, groundwater with elevated F− concentration prevail duo to shallow burial depth of groundwater table and strong evaporation. Dissolution of fluorite and removal of Ca2+ resulted from calcite precipitation are the dominant controlling factors responsible for elevated F− content in groundwater from the Yellow River crevasse fan, where the groundwater is characterized by low TDS and high F− due to the lateral recharge from Yellow River. In the Yellow River floodplain, groundwater F− increases with groundwater flow direction. Prolonged water-rock interaction and evaporation promote the formation of sodic groundwater, facilitating the enrichment of F− in groundwater in the northeast part of study area. Compared to adults, the intake of high F− groundwater was more harmful to infants and children. These findings have important implications for F− mobilization driven by climate, sedimentary setting and anthropogenic factors, and health risk prevention. • High-F- groundwater occurred widely in sedimental aquifers with 20–80 depth. • Sedimentary landform significantly dominated groundwater F− levels. • Sluggish flow and Na–HCO 3 hydrochemical type facilitated the enrichment of F− in plain. • Residents are severely affected by intaking high-F- groundwater, especially infants. [ABSTRACT FROM AUTHOR]

Due to scarcity of precipitation in Egypt, the groundwater is the basic source of fresh water in the regions located far from the River Nile. This contribution represents an integration between geophysical and hydrogeochemical studies to determine the distribution of groundwater and assess the water quality of the fractured limestone aquifer in the western end of Al Kurimat-Al Zafrana Road, (The east of Al Kurimat area), Eastern Desert, Egypt. To determine the thickness and depth of the water-saturated zone and infer the quality of the groundwater, vertical electrical probing or sounding (VES) and electromagnetic probing in time domain (TDEM) measurements were performed in sites selected based on prepared digital elevation map. The results of the geophysical measurements were confirmed by calibrating the calculated electrical resistance values with design reports and log records of 18 wells have been drilled beside the geophysical sounding sites. VES and TEM data revealed the occurrence of one groundwater layers divides into two parts, which differ in thickness and water quality. The upper part of the aquifer has variable thickness (89–250 m) and resistivity values ranging from 27 to 76 Ωm, reflecting saturation with fresh water, whereas the lower part is thinner (6–20 m) and contain brackish water as indicated by lower resistivity values (8 and 23 Ωm). The geochemical results of eighteen samples of groundwater taken from wells dug in the aquifer of fractured limestone are used to verify the groundwater's hydrogeochemical characteristics and its suitability for different uses, and to assess the processes controlled its chemistry. The domination of common ions was following the order of Na+ > Ca2+ > Mg2+ > K+ for cations and Cl− > HCO3− > SO42− > NO3− for anions. Na–Cl is the most prevalent water type, whereas Ca-HCO3 type is subordinate. Saturation indices of anhydrite, halite and gypsum are observed as undersaturated, while 61% of samples reveal oversaturated respecting to calcite and dolomite minerals. According to the understanding of groundwater geochemical characteristics, ion exchange, silicate and carbonate mineral dissolution, and the evaporation process each have a great influence on aquifer chemistry. The total dissolved solids (TDS) and total hardness (TH) values signify that the most of groundwater samples (88%) are very hard brackish. Various hydrogeochemical indices (PI, RSC, SAR and Na%) indicate that the groundwater of the fractured limestone aquifer is permissible to excellent for poultry farming and irrigational purposes; nevertheless, the high salinity needs cultivation of crops and plants that support such high salinity and arid nature of the region. Additional studies are needed to assess the extent of groundwater pollution using other methods such as Induce Polarization measurements, contaminant transport modelling and isotopic analysis, as well as to successfully manage groundwater in this aquifer. [ABSTRACT FROM AUTHOR]

The interpretation of aquifer responses to pumping tests is an important tool for assessing aquifer geometry and properties, which are critical in the assessment of water resources or in environmental remediation. However, the responses of aquifers, measured by time-drawdown relationships in monitoring wells, are nonunique solutions that are affected by many factors. Jacob's Zoo is a collection of graphical interpretations that allows students and practitioners to develop an intuitive feel for how natural hydrogeological systems work, and develop a set of skills that provide a better understanding of aquifer properties far beyond interpretation of pumping tests. Jacob's Zoo, based on the work of Jacob (1950), fosters a deeper understanding, although few practitioners realize the full utility of the method. Jacob CE (1950) Flow of groundwater, In: Rouse H (ed) Engineering Hydraulics, Wiley, New York. P 321–386. [ABSTRACT FROM AUTHOR]

Natural aquifers usually exhibit complex physical and chemical heterogeneities, which are key factors complicating kinetic processes, such as contaminant transport and transformation, posing a great challenge in the remediation of contaminated groundwater. Aquifer heterogeneity usually leads to a distinct feature, the so-called "anomalous transport" in groundwater, which deviates from the phenomenon described by the classical advection-dispersion equation (ADE) based on Fick's Law. Anomalous transport, also known as non-Fickian dispersion or "anomalous dispersion" in a broad sense, can explain the hydrogeological mechanism that leads to the temporally continuous deterioration of water quality and rapid spatial expansion of pollutant plumes. Contaminants enter and then are retained in the low-permeability matrix from the high-permeability zone via molecular diffusion, chemical adsorption, and other mass exchange effects. This process can be reversed when the concentration of pollutants in high-permeability zones is relatively low. The contaminants slowly return to the high-permeability zones through reverse molecular diffusion, resulting in sub-dispersive anomalous transport leading to the chronic gradual deterioration of water quality. Meanwhile, some contaminants are rapidly transported along the interconnected preferential flow paths, resulting in super-dispersive anomalous transport, which leads to the rapid spread of contaminants. Aquifer heterogeneity is also an important factor that constrains the efficacy of groundwater remediation, while the development, application, and evaluation of groundwater remediation technologies are usually based on the Fickian dispersion process predicted by the ADE equation. Comprehensive studies of the impacts of non-Fickian dispersion on contaminant transport and remediation are still needed. This article reviews the non-Fickian dispersion phenomenon caused by the heterogeneity of geological media, summarizes the processes and current understanding of contaminant migration and transformation in highly heterogeneous aquifers, and evaluates mathematical methods describing the main non-Fickian dispersion features. This critical review also discusses the limitations of existing research and outlines potential future research areas to advance the understanding of mechanisms and modeling of non-Fickian dispersion in heterogeneous media. [ABSTRACT FROM AUTHOR]

Geological deformations like anticlines have a prominent role in aquifer system functioning. Structural deformations control erosion patterns, areas of nondeposition, lateral facies variations and thickness variations. The nature and geometry of geological bodies have a major impact on the aquifers and interconnections between them. To characterize these features and to quantify their influence on overall hydrogeological functioning, a multidisciplinary approach is proposed at a local scale. In southwestern France, the Aquitaine Basin contains a regional multilayered aquifer system affected by numerous anticlines. The Villagrains-Landiras anticline is a major anticline of the Aquitaine Basin, and near its axis is the subcropping Cenomanian aquifer; thus, the Cenomanian aquifer has potential for drinking water supply. An extensive research program was developed, including reconnaissance drilling, water level measurements, geochemical analyses, and petrophysical tests, and the results were combined with existing data. This integrated work precisely defined the complex architecture of the aquifer and confining units linked with the uplift and the polyphase erosion of the anticline. It resulted in the characterisation of the deposits' geometries, lithology, and aquifer properties. The areas of aquifer interconnection have been defined and recharge flows have been estimated. A new groundwater circulation pattern constrained by isotopic water residence times was developed. A new geological model was built, which enables a rethink of the local functioning of the aquifer targeted for drinkable-water supply, but also it allows an understanding of the importance of anticline structure on the recharge conditions of the aquifers of this regional multilayered aquifer system. [ABSTRACT FROM AUTHOR]

The behavior of As in aqueous media in the complex crystalline aquifers like that of the present study area is not yet understood properly. To that end, groundwater and river water samples from two different seasons are analyzed for As and physicochemical parameters. The groundwater in the area is evolved by simple dissolution or mixing of two or more different facies (Ca2+–Mg2+–Na+–SO42–). However, the majority of samples with the base-exchange indices (85%) and meteoric genesis indices (77%) value less than unitary (<1) divulges that Na+– SO42– type water and deeper meteoric percolation. The estimation of As in groundwater (<0.1–202 ppb) shows the spatial and temporal inconsistency with 17.31% (pre-monsoon) and 11.67% (post-monsoon) of the samples surpassed the permissible limit of 10 ppb. Furthermore, health risk associated with As in terms of hazard quotient (HQ) values > 1 (pre-monsoon: 21.15% and post-monsoon: 20%) for children and carcinogenic risk values >1.00 × 10−6 for different seasons (44.25% and 33.33% of samples) represents a serious health risk. Furthermore, the different stages of Keratosis and Melanosis diseases reported in the study area establish the severity of As toxicity on the local populace. The study concludes geogenic arsenic contamination in the study area is primarily associated with Rhyolite and its comagmatically formed Dongargarh granite batholith emplacements. [ABSTRACT FROM AUTHOR]

The microbiome of an aquifer contaminated by landfill leachate and undergoing intrinsic remediation was characterised using 16S rRNA metabarcoding. The archaeal/bacterial V3–V4 hypervariable region of the 16S rRNA gene was sequenced using Illumina MiSeq, and multivariate statistics were applied to make inferences. Results indicate that the aquifer recharge and aquifer sediment samples harbour different microbial communities compared to the groundwater samples. While Proteobacteria dominated both the recharge and groundwater samples, Acidobacteria dominated the aquifer sediment. The most abundant genera detected from the contaminated aquifer were Polynucleobacter, Rhodoferax, Pedobacter, Brevundimonas, Pseudomonas, Undibacterium, Sulfurifustis, Janthinobacterium, Rhodanobacter, Methylobacter and Aquabacterium. The result also shows that the microbial communities of the groundwater varied spatially, seasonally and interannually, although the interannual variation was significant for only one of the wells. Variation partitioning analysis indicates that water chemistry and well distance are intercorrelated and they jointly accounted for most of the variation in microbial composition. This implies that the species composition and water chemistry characteristics have a similar spatial structuring, presumably caused by the landfill leachate plume. The study improves our understanding of the dynamics in subsurface microbial communities in space and time. [ABSTRACT FROM AUTHOR]

The main goal of this study is to investigate the effect of soil properties such as permeability on the dispersion and movement of a water dissolved contaminant in three types of soil in saturated and 2D conditions. The experimental modeling was conducted using a constructed sand box. In order to evaluate the effect of soils particle size on the distribution and self‐remediation of the contaminant, three types of soil, as coarse, medium, and fine‐grained sand were used. Results of experiments showed that, at the first 25% of the test time, the contaminated area reduction rate in all three specimens varies significantly, so that for the medium and coarse sand, it is 2.2 and 3 times that of fine sand, respectively. The contaminant width reduction at the first 25% of the test time was 5%, 6%, and 35% for the fine, medium, and coarse sand, respectively, while the contaminant length reduction was 13%, 18%, and 37% for the fine, medium, and coarse sand, respectively. In addition, by comparing the contaminant movement in the saturated and semi‐saturated areas, it was observed that the longitudinal and transverse movement of the contaminant under the water level are almost 2.5 times of the semi‐saturated area. Practitioner points: Reduction rate of solution area in fine, medium and coarse‐grained sample are nearly convex, linear and concave‐shaped, respectively.The remediation process in saturated zones is implemented in both directions with higher intensity in a shorter time than unsaturated zones.In the strip formed plumes, the volume of the self‐remediation is proportional to the time intervals during the test.In the elliptic masses the self‐purification amount is lower at the beginning, due to the small cross‐section ending of the contamination mass. [ABSTRACT FROM AUTHOR]

This study explores the groundwater vulnerability of the chalk aquifer (northern part of France) using a well-known overlay and index DRASTIC method for intrinsic scenario and using land use (LU) parameter as additional factor. Different sources have allowed to compile data necessary to map the vulnerability of the aquifer under study, which used to generate the seven parameters of DRASTIC, namely: groundwater Depth, groundwater Recharge, lithology, Soil media, Topography, Impact of the vadose zone and hydraulic Conductivity. Applying the model in ArcGIS 10.2 platform leads to identify three classes of vulnerability: low, medium and high vulnerability. The highest DRASTIC indexes appear in areas where the groundwater depth is low and in more permeable unsaturated zones. The LU has a little effect on the distribution of vulnerability classes: this distribution is marked by the low vulnerability 44% against 6.5 of high vulnerability. [ABSTRACT FROM AUTHOR]

In this paper, a parallel heuristic search strategy based on Bayesian approach was first proposed for recognizing groundwater DNAPL contaminant source and aquifer parameters (unknown variables). Frequent calls to numerical simulation model effectuated large computational burden during likelihood calculation. Single surrogate system was established to reduce the burden, but it had unavoidable limitations. Thus, we first presented the particle swarm optimization-tabu search hybrid algorithm to construct an optimal combined surrogate system for the simulation model, which assembled Gaussian process, kernel extreme learning machine, support vector regression, and also improved the accuracy of the surrogate system to simulation model. Thereafter, a parallel heuristic search iterative process was first implemented for simultaneous recognition of unknown variables. Each round of iteration involved determination of candidate points and state transitions. The Monte Carlo approach was used widely for selecting candidate point, but it did not readily converge to posterior distribution when the probability density functions were complex. And the search ergodicity was weak. In order to improve the search ergodicity, a DE algorithm with variable mutation rate based on rand-to-best, 1, and bin strategy was first proposed in this paper to determine multiple candidate points. The recognition results were obtained when the iteration process terminated. The accuracy and efficiency of our approaches were demonstrated through a hypothetical case in DNAPLs-contaminated aquifer, and the recognizing accuracy was high. More importantly, the new simulation model based on the recognition results is helpful in calculating future contaminant plume in the aquifer, which can provide credible basis for groundwater contaminant remediation plan design and risk assessment. [ABSTRACT FROM AUTHOR]

Estimation of hydraulic parameters is important for the prediction of the future availability of groundwater reserves. Conventionally, pumping tests are conducted on boreholes to measure these parameters. However, such tests are costly and time consuming, and can only provide limited spatial information. An integrated approach of geophysical method and pumping tests is cost-effective and efficient alternative for the estimation of aquifer parameters. A geophysical method of vertical electrical sounding (VES) was carried out in Huizhou ADS site of China for the delineation of aquifer potential zones to assess the groundwater resources contained within the weathered rock. Initially, the pumping test data were used to determine the hydraulic parameters namely hydraulic conductivity (Kw) and transmissivity (Tw) for available production wells. Afterwards, one empirical relation between pumped hydraulic conductivity (Kw) and aquifer resistivity (ρa), and another between pumped transmissivity (Tw) and transverse resistance (Tr) were obtained to estimate hydraulic conductivity (K) and transmissivity (T) for all VES stations where pumping tests were not conducted. In this way, the entire study area was investigated to delineate the aquifer potential zones i.e., high potential aquifer zone with ρa < 100 Ωm, T > 150 m2/day and K > 4 m/day, medium potential aquifer zone with ρa ranging from 100 to 150 Ωm, T from 100 to 150 m2/day and K from 3 to 4 m/day, poor potential aquifer zone with ρa from 150 to 300 Ωm, T from 50 to 100 m2/day and K from 2 to 3 m/day, and negligible potential aquifer zone with ρa > 300 Ωm, T < 50 m2/day and K < 2 m/day. This investigation also deciphers functional analogous relation of Ωa with K and Tr with T in Huizhou, China. Therefore, similar integrated approach can be used in any geological similar area where the aquifer properties are required for the management of groundwater reserves. [ABSTRACT FROM AUTHOR]

Arsenic (As) contamination of groundwater aquifers is a global environmental problem, especially in South and Southeast Asian regions, and poses a risk to human health. Arsenite-oxidizing bacteria that transform As(III) to less toxic As(V) can be potentially used as a groundwater As remediation strategy. This study aimed to examine the community and abundance of arsenite-oxidizing bacteria in groundwater with various As concentrations from Rayong Province, Thailand using PCR-cloning-sequencing and quantitative PCR (qPCR) of catalytic subunit of arsenite oxidase gene (aioA). Key factors influencing their community and abundance were also identified. The results demonstrated that arsenite-oxidizing bacteria retrieved from groundwater were phylogenetically related to Betaproteobacteria and Alphaproteobacteria. The aioA gene abundances ranged from 8.6 × 101 to 1.1 × 104 copies per ng of genomic DNA, accounting for 0.16–1.37% of the total 16S rRNA bacterial gene copies. Although the abundance of arsenite-oxidizing bacteria in groundwater was low, groundwater with As(III) dominance likely promoted their abundance which possibly played an important role in chemolithoautotrophic oxidation of As(III) to As(V). Fe and As(III) were the major environmental factors influencing the community and abundance of arsenite-oxidizing bacteria. The knowledge gained from this study can be used to further contribute to the development of bioremediation strategies for As removal from groundwater resources. [ABSTRACT FROM AUTHOR]

This review focuses on investigations of groundwater flow and solute transport in karst aquifers through laboratory scale models (LSMs). In particular, LSMs have been used to generate new data under different hydraulic and contaminant transport conditions, testing of new approaches for site characterization, and providing new insights into flow and transport processes through complex karst aquifers. Due to the increasing need for LSMs to investigate a wide range of issues, associated with flow and solute migration karst aquifers this review attempts to classify, and introduce a framework for constructing a karst aquifer physical model that is more representative of field conditions. The LSMs are categorized into four groups: sand box, rock block, pipe/fracture network, and pipe‐matrix coupling. These groups are compared and their advantages and disadvantages highlighted. The capabilities of such models have been extensively improved by new developments in experimental methods and measurement devices. Newer technologies such as 3D printing, computed tomography scanning, X‐rays, nuclear magnetic resonance, novel geophysical techniques, and use of nanomaterials allow for greater flexibilities in conducting experiments. In order for LSMs to be representative of karst aquifers, a few requirements are introduced: (1) the ability to simulate heterogeneous distributions of karst hydraulic parameters, (2) establish Darcian and non‐Darcian flow regimes and exchange between the matrix and conduits, (3) placement of adequate sampling points and intervals, and (4) achieving some degree of geometric, kinematic, and dynamic similitude to represent field conditions. [ABSTRACT FROM AUTHOR]