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Iodate reduction by dissimilatory iodate-reducing microorganisms (DIRMs) plays a crucial role in the biogeochemical cycling of iodine on Earth. However, the occurrence and distribution of DIRMs in iodine-rich groundwater remain unclear. In this study, we isolated the dissimilatory iodate-reducing bacterium Azonexus hydrophilus strain NCP973 from a geogenic high-iodine groundwater of China for the first time. The analysis of genome, transcriptome, and heterologous expression revealed that strain NCP973 uses the dissimilatory iodate-reducing enzyme IdrABP1P2 to reduce dissolved or in situ sediment-bound iodate to iodide. The location of IdrABP1P2 in the conjugative plasmid of strain NCP973 implies that IdrABP1P2 could be spread by horizontal gene transfer and allow the recipient microorganisms to participate in the enrichment of iodide in aquifers. Based on the global iodine-rich groundwater metagenomes and genomes, the identification of idrA showed that phylogenetically diverse DIRMs are widely distributed not only in geogenic high-iodine groundwater of China but also in radionuclide-contaminated groundwater of USA as well as in subsurface cavern waters in Germany and Italy. Moreover, the abundance of idrA was found to be higher in groundwater with a relatively high iodine content. Collectively, these results suggest that terrestrial iodine-affected groundwater systems are another important habitat for DIRMs in addition to marine environments, and their activity in aquifers triggers the mobilization and enrichment of iodine in groundwater worldwide.

This study aimed to utilise cheap and abundantly available date palm fibre (DPF) wastes for the remediation of methylene blue (MLB) dye-contaminated groundwater. The DPF adsorbents were first prepared, followed by various characterisation analyses, including surface morphology, functional groups, and material structure. Subsequently, the DPF adsorbents were applied in the batch and continuous adsorption studies to assess the MLB dye removal from aqueous environments. The batch adsorption study achieved 98% maximum removal efficiency with a contact time, adsorbents dosage, initial pH, temperature, particle size, initial dye concentration, and agitation speed of 105 min, 3 g/L, 7.0, 45 °C, 0.075 mm, 50 mg/L, and 150 rpm, respectively. Langmuir was the best-fitted isotherm model depending on a higher correlation coefficient (R 2  = 0.985), with a maximum monolayer dye adsorption capacity (q max ) of 54.204 mg/g. Additionally, the second order was the best-fitted kinetic model (R 2  = 0.990), indicating that MLB dye was removed through chemisorption. Besides, the positive enthalpy change (ΔH°) and negative Gibb's free energy (ΔG°) values verified the endothermic process and spontaneous adsorption. According to the impact analysis of initial dye concentrations and flow rates on the permeable reactive barrier (PRB) performance in the continuous adsorption study using the Thomas, Belter, and Yan models, the experimental results and predicted breakthrough curves reflected an excellent agreement (R 2  ≥ 0.8767) and a sum of squared errors (SSE) ≤ 0.4834. In short, the results demonstrated DPF as an effective adsorbent material in PRB technology., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

There has been heavy application of chemical pesticides to farmland worldwide. As a state with a heavy emphasis on farming, China has extensively applied chemical pesticides to farmlands. Atrazine (ATZ), one of the most widely used herbicide in the world, has been used in large quantities in weed control in many crops, which poses a relatively large threat to groundwater utilization and agricultural safety. A nationwide sampling and analysis of ATZ in 8146 groundwater monitoring wells from 10 main grain producing areas were conducted during 2019. The results showed that the detection rate of ATZ in groundwater was 40.79 %, with detected concentrations up to 2.86 μg/L. ATZ detection rate was significantly higher in phreatic aquifers than confined aquifer. The concentration of ATZ decreased significantly with the depth increasing, the detected depth of ATZ in groundwater was varied from 5 to 1100 m, and 70.27 % of the detected ATZ was distributed in the depth of 0-51.8 m. The detection rate of ATZ in most north regions lower than south regions in China, and ATZ with high concentration was mainly occurred in southern regions. ATZ is more likely to migrate into the groundwater in the water resource rich areas. The concentration of ATZ decreased with TDS increasing, 74.39 % of the ATZ was detected in groundwater with TDS concentration <1 g/L. The hydrochemical type of groundwater in ATZ-enrichment environment were mainly Ca-HCO3 and Mixed type. According to classification and regression tree analysis, the high ATZ detection rate were closely related with groundwater depth (<51.8 m) and high organic matter content., (Copyright © 2024. Published by Elsevier B.V.)

Structural differences among non-aqueous phase liquids (NAPLs) result in varying oxidation rates, limiting mass transfer between NAPLs and oxidants and seriously impairing the effectiveness of remediation via traditional in-situ chemical oxidation. To tackle this challenge, a novel approach is proposed for remediating multi-NAPL-polluted groundwater that leverages phase transfer catalysis (PTC) to enhance heterogeneous mass transfer by transferring oxidants from groundwater to NAPLs. Meanwhile, "oxidation-in-situ activation" is achieved through bifunctional oxidation using permanganate and peroxymonosulfate (PP). The proposed approach is referred to PTC-PP in this study. Herein, trichloroethene (TCE) and benzene serve as a representative multi-NAPL system. Experimental results indicated that PP significantly improved degradation efficiency of benzene in multi-NAPL system by at least 60.8 % compared to single-oxidant systems, and further enhancement (17.6 %) was achieved when PP was combined with PTC compared to PP alone. Dissolved Mn(II) and MnO 2 generated by MnO 4 - reduction effectively activated peroxymonosulfate in PTC-PP system, with colloidal MnO 2 being the most effective activator. Consequently, SO 4 •- , O 2 •- and 1 O 2 addition. These findings lay the theoretical groundwork for PTC-PP application in groundwater remediation.• OH was formed in aqueous phase, playing a crucial role in benzene oxidation. In phase transfer process of PTC-PP, the proportion of MnO 4 - transferred to benzene exceeded that to TCE. This finding illustrated that nondirectional phase transfer of oxidants posed a challenge for simultaneous promotion of TCE and benzene degradation. However, TCE and benzene removal efficiencies were both >75.7 % by applying peroxymonosulfate after KMnO 4 addition. These findings lay the theoretical groundwork for PTC-PP application in groundwater remediation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

With the growing global prevalence of open-pit mining activities, there is an increasing necessity for sustainable mine life cycle plans with an early outlook towards mine closure. A major consideration in mine closure planning is the potential formation of lakes in the mine void and how these "pit lakes" can be managed to minimise risks and, if possible, create benefits. Understanding the long-term interactions between pit lakes, groundwater, and surface water systems is essential for that purpose. While numerous site-specific studies have been undertaken, there have been no studies that aim to provide a general, broadly applicable understanding of how pit lake hydrology relates to geographical context, and no efforts to hydrologically classify pit lakes using geographical criteria. This research employs an integrated generic pit lake water balance model to examine mine pit lake interactions with the surrounding surface water and groundwater. Simulating 243 scenarios, the influence of five input factors (climate, hydraulic conductivity, regional groundwater level, catchment area and pit slope) on pit lake behaviour up to 6000 years beyond the closure of the mine was considered. The assessment focused on four pit lake hydrological attributes once the system reached equilibrium: water level, time to equilibrium, the fraction of days where the pit recharges groundwater, and the fraction of days where there is surface overflow from the lake. All scenarios were assigned to one of five hydrological classes based on the interactions between the pit lake and the surrounding surface water and groundwater. Our findings show that, in many contexts, general data on climate type and subsurface hydraulic conductivity can yield reliable predictions of a pit lake's long-term hydrological classification without having to develop a detailed, site-specific pit lake model. The classification needs improvements in non-arid climates where inter-annual variation in rainfall is pronounced. The pit lake classification is particularly valuable for first-pass risk assessments to determine whether site-specific modelling is required., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Benedictor Mang'era Kemanga reports financial support was provided by CRC TiME. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Per-and polyfluoroalkyl substances (PFAS) are synthetic chemicals that are increasingly being detected in groundwater. The negative health consequences associated with human exposure to PFAS make it essential to quantify the distribution of PFAS in groundwater systems. Mapping PFAS distributions is particularly challenging because a national patchwork of testing and reporting requirements has resulted in sparse and spatially biased data. In this analysis, an inhomogeneous Poisson process (IPP) modeling approach is adopted from ecological statistics to continuously map PFAS distributions in groundwater across the contiguous United States. The model is trained on a unique data set of 8910 PFAS groundwater measurements, using combined concentrations of two PFAS analytes. The IPP model predictions are compared with results from random forest models to highlight the robustness of this statistical modeling approach on sparse data sets. This analysis provides a new approach to not only map PFAS contamination in groundwater but also prioritize future sampling efforts.

Systematically studying the hydrochemical evolution of bedrock groundwater in mining areas during mining process is crucial for effective groundwater resource management and coal mine production. The spatiotemporal characteristics and hydrochemical evolution patterns of the Permian fractured sandstone aquifer (PA) and the Carboniferous Taiyuan Formation limestone aquifer (CTA), both of which are directly associated with coal mining in the northern Linhuan mining area, China, were investigated using multivariate statistical analyses, hydrochemical graphical methods, ion ratio analysis, and a conceptual model. 72 groundwater samples, collected before and after mining, were classified into four groups by hierarchical cluster analysis (HCA). Principal component analysis (PCA) and ion ratio analysis indicated that water-rock interactions involve mineral dissolution (carbonates, gypsum, dolomite, silicates), cation exchange, and common ion effects. Hydrochemical evolution is influenced by bedrock paleotopography, aquifer hydraulic conductivity, and mining drainage. Paletopographic differences significantly influence water-rock interactions and spatial variability in hydrochemistry, with ion concentrations in groundwater increasing as paleotopographic elevation decreases. The pattern of hydraulic conductivity reflects the control exerted by variations in aquifer characteristics on mineral dissolution, leading to minor changes in hydrochemical characteristics. Mining activities disrupt the aquifer's reducing environment, resulting in a significant increase in groundwater SO 4 concentration. These findings provide insights and a solid theoretical foundation for studying the hydrochemical variations patterns of groundwater and these control mechanisms in the hidden coal fields of North China.2- concentration. These findings provide insights and a solid theoretical foundation for studying the hydrochemical variations patterns of groundwater and these control mechanisms in the hidden coal fields of North China., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Groundwater is consumed by over 2 billion people globally, though it can be impacted by microbial and chemical contamination in both rural and (peri-)urban areas. This issue is particularly pertinent in regions like East Africa, where rapid urbanisation has strained local infrastructure, including water and sanitation systems. We use selected tracers of human and animal waste to assess the quality of community drinking sources with regards to surface-derived groundwater inputs and to compare urban versus rural water quality, under the rapidly developing urban area of Gulu, Northern Uganda. Specifically, we examine bulk and fluorescent dissolved organic matter (DOM), microorganisms (total coliforms, E.coli) and inorganic tracers of anthropogenic waste (NO 3 - , SO 4 2- were elevated in groundwater sources in the Gulu city urban area and the Cl/Br ratio was elevated in springs, compared to concentrations in the more rural Aswa and Omoro County area (p < 0.05). Interestingly, human and animal waste indicators E.coli and Tryp:FA (the ratio of tryptophan-like to fulvic-like fluorescence) displayed no significant difference between rural and urban settings (p > 0.05), though total coliforms were significantly higher in rural boreholes (p < 0.05). The presence of a pollution source, pollution carrier and a breakdown of a sanitary barrier at the borehole, as spot-checked by a visual sanitary risk assessment, was significantly associated with groundwater E.coli abundances. Evidence suggests monitoring and mitigation should be improved for all water types in Gulu District to meet WHO and Uganda Standard guidelines for potable water. This study offers valuable insights for water management planning and risk assessment of community water sources particularly in the context of East Africa and similar settings.3 - and SO 4 2- were elevated in groundwater sources in the Gulu city urban area and the Cl/Br ratio was elevated in springs, compared to concentrations in the more rural Aswa and Omoro County area (p < 0.05). Interestingly, human and animal waste indicators E.coli and Tryp:FA (the ratio of tryptophan-like to fulvic-like fluorescence) displayed no significant difference between rural and urban settings (p > 0.05), though total coliforms were significantly higher in rural boreholes (p < 0.05). The presence of a pollution source, pollution carrier and a breakdown of a sanitary barrier at the borehole, as spot-checked by a visual sanitary risk assessment, was significantly associated with groundwater E.coli abundances. Evidence suggests monitoring and mitigation should be improved for all water types in Gulu District to meet WHO and Uganda Standard guidelines for potable water. This study offers valuable insights for water management planning and risk assessment of community water sources particularly in the context of East Africa and similar settings., (Copyright © 2024. Published by Elsevier B.V.)

Tims Branch riparian wetland located in South Carolina, USA has immobilized 94 % of the U released >50 years ago from a nuclear fuel fabrication facility. Sediment organic matter (OM) has been shown to play an important role in immobilizing U. Yet, uranium-OM-mineral interactions at the molecular scale have never been investigated at ambient concentrations. The objectives of this study were to extract, purify, and concentrate U-bound sediment OM along the stream water pathway and perform molecular characterization using Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS). Out of 9614 identified formulas, 715 contained U. These U-containing formulas were enriched with Fe, N, and/or S compared to the total OM. Lignin-like and protein-like molecules accounted for 40 % and 19 % of the U-containing formulas, respectively. Phosphorus-containing formulas were found to exert an insignificant influence on complexing U. U-containing formulas in the 'mobile' (groundwater extractable) OM fraction had lower (reduced) nominal oxidation states of carbon (NOSC); and less aromatic moieties than OM recovered from the 'immobile' (sodium pyrophosphate extractable) OM fraction. U-containing formulas in the redox interfacial zones (stream banks) compared to those in nearby up-slope zones tended to have smaller molecular weights; lower NOSC; higher contents of COO and/or CONO functional groups; and higher abundance of Fe-containing formulas. Fe was present in 38 % of the U-containing formulas but only 20 % of the total OM formulas. It is postulated that Fe played an important role in stabilizing the structure of sedimentary OM, especially U-containing compounds. The identification for the first time of hundreds of Fe-U-OM formulas demonstrates the complexity of such system is much greater than commonly believed and numerically predicting U binding behavior in OM-rich systems may require greater use of statistical or artificial intelligence approaches rather than deterministic approaches limited to measuring metal complexation with well-defined individual analogue organic ligands., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

This study investigated the presence of rubber additives and relevant oxidation products (RAROPs) in groundwater in central China's aboveground river region. Seven RAROPs were detected, and their levels in shallow groundwater showed a mild decreasing trend from the area near the Yellow River (Avg: 8.49 ng L -1 ) to the area on the far bank of the Yellow River (Avg: 5.01 ng L -1 ). In contrast, deep groundwater's RAROPs contents showed a dramatic decrease to only 0.26 ng L -1 . The dominant contaminant was found to be N-(1, 3-dimethylbutyl) -N'-phenyl -p-phenylenediamine (6PPD). The vicinity of the garages and car parks was often characterized as contamination hotspots. Correlation analyses further indicated that aquaculture was likely to be a potential pathway for shallow groundwater contaminant inputs. The amount of RAROPs intake by humans through groundwater is nearly 30 times different due to the imbalanced development between urban and rural areas. Children were the most vulnerable to RAROPs. Therefore, human activities (transportation, waste tire storage, water resource allocation and utilization patterns, diversion of Yellow River water to aquaculture ponds) may exacerbate RAROPs pollution in groundwater by leaching contaminants through the surface soil. These results are important for developing appropriate utilization and protection strategies for groundwater resources in developing countries., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The elevated levels of geogenic (natural) ammonium in groundwater have been frequently documented in recent years. Although improving insights have been achieved in understanding the genesis of ammonium in the subsurface environment, the vertical variability of the geogenic ammonium in groundwater remains poorly understood. Here, we selected typical multi-layered aquifer systems in the central Yangtze River plain and characterized the vertical heterogeneity of geogenic ammonium through the hydrogeochemical analysis. Subsequently, the controlling factors were identified by examining the molecular composition of dissolved organic matter (DOM) and aquifer sediment features. The results indicated that the ammonium concentration in groundwater increased from the deep to shallow aquifers (2.13 to 9.88 mg/L as N), accompanied by a transition in organic matter (OM) degradation towards the methanogenic stage (δ 13 C-DIC: -23.07 to -0.34‰). Compared to the deeper aquifers, the DOM in the shallow aquifer was characterized by a higher abundance of the N-containing OM (15.1% > 13.13% > 12.76%) with a lower molecular lability index, corresponding to more thorough degradation extent. The characteristics of the soluble OM in depth-matched sediments were similar to those of the DOM in groundwater, suggesting the persistent water-rock interactions. Besides, the pumping tests revealed that the hydraulic conductivity decreased from deep to shallow aquifers (2.28 to 0.62 m/d), which further facilitated the more retention of geogenic ammonium in the shallow aquifer. That is, the combined effects of the abundant N-containing OM in sediments, strong degradation of the bioactive DOM, and long retention governed by hydrodynamics contributed to the increased ammonium enrichment in the shallow aquifer, thereby generating the vertical variability. The findings underscore the significance of the complex coupled factors in controlling the vertical distribution of geogenic ammonium in multi-layered aquifer systems, which was crucial for understanding the spatial heterogeneity of geogenic contaminated groundwater., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The excessive presence of geogenic ammonium (NH 4 ) in groundwater poses a global environmental concern, commonly linked to the degradation of nitrogen-containing dissolved organic matter (DOM). However, there is a gap in systematic studies on the combination of soluble organic matter (SOM) in sediments and DOM in groundwater, with few indoor incubation experiments to validate their degradation pathways. This study utilized ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry to analyze the molecular characteristics of DOM and SOM in aquifer systems affected by geogenic NH + ) in groundwater poses a global environmental concern, commonly linked to the degradation of nitrogen-containing dissolved organic matter (DOM). However, there is a gap in systematic studies on the combination of soluble organic matter (SOM) in sediments and DOM in groundwater, with few indoor incubation experiments to validate their degradation pathways. This study utilized ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry to analyze the molecular characteristics of DOM and SOM in aquifer systems affected by geogenic NH 4 + in groundwater than that produced through the mineralization of DOM. This study is the first to analyze DOM and SOM together in aquifer systems and validate their degradation pathways through incubation experiments, thereby providing novel insights into the enrichment of geogenic NH 4 in groundwater.+ produced through the direct mineralization of SOM may contribute more to the enrichment of NH 4 + in groundwater than that produced through the mineralization of DOM. This study is the first to analyze DOM and SOM together in aquifer systems and validate their degradation pathways through incubation experiments, thereby providing novel insights into the enrichment of geogenic NH 4 + in groundwater., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Redox conditions play a crucial role in determining the fate of many contaminants in groundwater, impacting ecosystem services vital for both the aquatic environment and human water supply. Geospatial machine learning has previously successfully modelled large-scale redox conditions. This study is the first to consolidate the complementary information provided by sediment color and water chemistry to enhance our understanding of redox conditions in Denmark. In the first step, the depth to the first redox interface is modelled using sediment color from 27,042 boreholes. In the second step, the depth of the first redox interface is compared against water chemistry data at 22,198 wells to classify redox complexity. The absence of nitrate containing water below the first redox interface is referred to as continuous redox conditions. In contrast, discontinuous redox conditions are identified by the presence of nitrate below the first redox interface. Both models are built using 20 covariate maps, encompassing diverse hydrologically relevant information. The first redox interface is modelled with a mean error of 0.0 m and a root-mean-squared error of 8.0 m. The redox complexity model attains an accuracy of 69.8 %. Results indicate a mean depth to the first redox interface of 8.6 m and a standard deviation of 6.5 m. 60 % of Denmark is classified as discontinuous, indicating complex redox conditions, predominantly collocated in clay rich glacial landscapes. Both maps, i.e., first redox interface and redox complexity are largely driven by the water table and hydrogeology. The developed maps contribute to our understanding of subsurface redox processes, supporting national-scale land-use and water management., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Big data have become increasingly important for policymakers and scientists but have yet to be employed for the development of spatially specific groundwater contamination indices or protecting human and environmental health. The current study sought to develop a series of indices via analyses of three variables: Non-E. coli coliform (NEC) concentration, E. coli concentration, and the calculated NEC:E. coli concentration ratio. A large microbial water quality dataset comprising 1,104,094 samples collected from 292,638 Ontarian wells between 2010 and 2021 was used. Getis-Ord Gi* (Gi*), Local Moran's I (LMI), and space-time scanning were employed for index development based on identified cluster recurrence. Gi* and LMI identify hot and cold spots, i.e., spatially proximal subregions with similarly high or low contamination magnitudes. Indices were statistically compared with mapped well density and age-adjusted enteric infection rates (i.e., campylobacteriosis, cryptosporidiosis, giardiasis, verotoxigenic E. coli (VTEC) enteritis) at a subregional (N = 298) resolution for evaluation and final index selection. Findings suggest that index development via Gi* represented the most efficacious approach. Developed Gi* indices exhibited no correlation with well density, implying that indices are not biased by rural population density. Gi* indices exhibited positive correlations with mapped infection rates, and were particularly associated with higher bacterial (Campylobacter, VTEC) infection rates among younger sub-populations (p < 0.05). Conversely, no association was found between developed indices and giardiasis rates, an infection not typically associated with private groundwater contamination. Findings suggest that a notable proportion of bacterial infections are associated with groundwater and that the developed Gi* index represents an appropriate spatiotemporal reflection of long-term groundwater quality. Bacterial infection correlations with the NEC:E. coli ratio index (p < 0.001) were markedly different compared to correlations with the E. coli index, implying that the ratio may supplement E. coli monitoring as a groundwater assessment metric capable of elucidating contamination mechanisms. This study may serve as a methodological blueprint for the development of big data-based groundwater contamination indices across the globe., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

In recent years, it has become evident that human activities have significantly disrupted the nitrogen cycle surpassing acceptable environmental thresholds. In this study, chemical and isotopic tracers were combined with a mathematical mass balance model (EMMA), PHREEQC inverse mixing model, and statistical analyses to evaluate groundwater quality, across an area experiencing substantial human activities, with a specific focus on tracing the origin of nitrate (NO 3 ) with potential water mixing processes. This multi-technique approach was applied to an unconfined aquifer underlying an agricultural area setting in an inter-mountain depression (i.e., the "Pampa de Pocho Plain" in Argentina). Here, the primary identified geochemical processes occurring in the investigated groundwater system include the dissolution of carbonate salts, cation exchange, and hydrolysis of alumino-silicates along with incorporating ions from precipitation. It was observed that the chemistry of groundwater, predominantly of sodium bicarbonate with sulfate water types, is controlled by the area's geology, recharge from precipitation, and stream water infiltration originating from the surrounding hills. Chemical results reveal that 60% of groundwater samples have NO - concentrations exceeding the regional natural background level, confirming the impact of human activities on groundwater quality. The dual plot of δ 3 - concentrations exceeding the regional natural background level, confirming the impact of human activities on groundwater quality. The dual plot of δ 15 N NO3 values indicates that groundwater is affected by NO 18 sources overlapping manure/sewage with organic-rich soil. The mathematical EMMA model and PHREEQC inverse modeling, suggest organic-rich soil as an important source of nitrogen in the aquifer. Here, 64 % of samples exhibit a main mixture of organic-rich soil with manure, whereas 36 % of samples are affected mainly by a mixture of manure and fertilizer. This study demonstrates the utility of combining isotope tracers with mathematical modeling and statistical analyses for a better understanding of groundwater quality deterioration in situations where isotopic signatures of contamination sources overlap.NO3 values indicates that groundwater is affected by NO 3 - sources overlapping manure/sewage with organic-rich soil. The mathematical EMMA model and PHREEQC inverse modeling, suggest organic-rich soil as an important source of nitrogen in the aquifer. Here, 64 % of samples exhibit a main mixture of organic-rich soil with manure, whereas 36 % of samples are affected mainly by a mixture of manure and fertilizer. This study demonstrates the utility of combining isotope tracers with mathematical modeling and statistical analyses for a better understanding of groundwater quality deterioration in situations where isotopic signatures of contamination sources overlap., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Tritium (³H) is a vital tracer in isotope hydrology and environmental studies, necessitating accurate and precise low-level detection methods. This study evaluated the performance of the new Hidex ULLA Liquid Scintillation Counter for ultra-low-level tritium assays in environmental water samples. The optimization of instrumental parameters enabled accurate and reproducible 3 H measurements. Test samples (10-132 TU) were analyzed in triplicate, including 3 H-free water and NIST traceable standards. The results demonstrated excellent accuracy and reproducibility, as evidenced by Zeta scores and linearity across these tritium concentrations. The system's stability over extended measurement time periods ensured reliable performance for routine ultra-low level 3 H analysis. The optimization of key parameters such as coincidence time and region of interest (ROI) achieved the highest figure of merit (FoM) by using a 25 ns coincidence time and the DigPb open mode for optimal spectral fittings. Detection limits (DL) based on ISO11929 recommendations were significantly improved but highlighted the need for sample enrichment for most low-level environmental applications, with LSC counting times preferably exceeding 1000 min. Overall, the Hidex ULLA Liquid Scintillation Counter proved to be a robust and reliable instrument suitable for ultra-low-level tritium detection in environmental water samples., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Risto Juvonen and Timo Oikari reports a relationship with HIDEX that includes: employment. This study was funded by the International Atomic Energy Agency with technical support from Hidex Oy. All sample preparation and 3H measurements were conducted independently at the IAEA. Blind raw data was supplied to Hidex for advanced processing using spectral fittings algorithms. RJ and TO conducted Hidex data processing and are employed by Hidex Oy. Lorenzo Copia and Leonard I Wassenaar declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Groundwater is an essential resource for drinking water, food production, and industrial applications worldwide. Over-exploitation and pollution pose significant risks to groundwater sustainability. Groundwater models can be powerful tools for optimizing use, managing risks, and aiding decision-making. For this purpose, models should assimilate pertinent data and quantify uncertainties in outcomes. We examine applied modelling for characterization and decision support in Sweden from 2010 to 2023. We also review syllabi of water-related courses in Swedish higher education to assess the inclusion and extent of groundwater modelling education. We find that important academic advances in groundwater modelling over the past two decades have not translated into practical application within Sweden's industry, that uncertainty quantification is rarely undertaken, and that groundwater modelling remains a low priority in higher education. Based on these findings, we offer recommendations that, while informed by the Swedish context, hold relevance for educational institutions, industry, and decision-makers internationally., (© 2024. The Author(s).)

The effects of climate change in the forms of rising sea levels and increased frequency of storms and storm surges are being noticed across many coastal communities around the United States. These increases are impacting the timing and frequency of tidal and rainfall influenced compound groundwater flooding events. These types of events can be exemplified by the recent and ongoing occurrence of groundwater flooding within building basements at the historic Strawbery Banke Museum (SBM) living history campus in Portsmouth, New Hampshire. Fresh water and saline groundwater intrusion within basements of historic structures can be destructive to foundations, mortar, joists, fasteners, and the overlaying wood structure. Although this is the case, there appears to be a dearth of research that examines the use of wireless streaming sensor networks to monitor and assess groundwater inundation within historic buildings in near-real time. Within the current study, we designed and deployed a three-sensor latitudinal network at the SBM. This network includes the deployment and remote monitoring of water level sensors in the basements of two historic structures 120 and 240 m from the river, as well as one sensor within the river itself. Groundwater salinity levels were also monitored within the basements of the two historic buildings. Assessments and model results from the recorded sensor data provided evidence of both terrestrial rainfall and tidal influences on the flooding at SBM. Understanding the sources of compound flooding within historic buildings can allow site managers to mitigate better and adapt to the effects of current and future flooding events. Data and results of this work are available via the project's interactive webpage and through a public touchscreen kiosk interface developed for and deployed within the SBM Rowland Gallery's "Water Has a Memory" exhibit.

The primary goal of this study is to predict the current and future water quality index for irrigation (WQII) of the western Mitidja alluvial aquifer in northern Algeria. The modified WQII was used to evaluate groundwater suitability for irrigation through geographic information system (GIS) techniques. Additionally, a long short-term memory (LSTM) model was employed to calculate the WQII and map future groundwater quality, considering factors like overexploitation, anthropogenic pollution, and climate change. Two scenarios were analyzed for the year 2030. Results from applying the modified WQII model to 2020 data showed that about 83% of the study area has medium to high groundwater suitability for irrigation. The LSTM model exhibited strong predictive accuracy with determination coefficients (R 2 ) of 0.992 and 0.987, and root mean square error (RMSE) values of 0.061 and 0.084 for the training and testing phases, respectively. For the first 2030 scenario, the area with low and medium groundwater suitability is expected to increase by 4% and 7% compared to the 2020 map. Conversely, under the second scenario, groundwater quality is predicted to improve, with a decrease of 14% and 11% in the low and medium suitability areas. The combination of the modified WQII and LSTM model proves to be an effective tool for estimating and predicting water quality indices in similar regions globally, offering valuable insights for water resource management and decision-making processes., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Artificial objects, particularly tunnels used for water transport under pressure, impact the geological and hydrogeological environment to a greater or lesser extent, and it is vital to assess their contributions to groundwater quality. Although tunnels are typically lined with concrete, their interaction with the hydrogeological environment intensifies over time. In this study, the detailed spatiotemporal monitoring of all hydrogeological features within the potential influence zone of the hydraulic tunnel of the Pirot Hydropower Plant has been conducted in order to determine the degree of interaction between the artificial object and the natural environment in real time, and to assess the correlation between monitored parameters. Natural conditions of the environment were defined, as well as potential changes through the observing groundwater regimes. The monitoring network included observations of groundwater regimes at seven springs located in close proximity to the hydraulic tunnel, within the tunnel, at three piezometers, and along the river, while methods employed were hydrological monitoring, physicochemical monitoring, and groundwater piezometer sensing. Cross-correlation analysis has been applied for assessing the impact of precipitation dynamics on the spring discharge regime. The results indicate a direct influence of the tunnel on the hydrogeological environment, proving the consistency and high correlation between the monitored parameters.

Onsite wastewater treatment systems (OWTS) are a major source of excess nutrients and co-pollutants in watersheds across the United States. In Barnstable County (Cape Cod), Massachusetts, effluent from septic systems and cesspools contributes approximately 80% of the controllable reactive nitrogen (N) load to numerous impaired estuaries and degrades water quality in the region's sole source aquifer, streams and ponds. In unsewered areas, wastewater N loads could be reduced substantially by Innovative/Alternative (I/A) septic systems designed for enhanced removal. Use, however, has been partly limited by the availability of high performing, cost effective options, while conventional septic systems continue to be installed in watersheds with well documented N impairments. This paper describes the strategic replacement of residential OWTS with two I/A models that incorporate woodchip bioreactors to enhance N removal. Systems were installed at 14 neighboring homes in Barnstable, MA, and monitored for field performance. Influent and effluent were sampled monthly and analyzed for N and phosphorus (P), among other water quality indicators. Flow to each system was continuously metered to estimate nutrient loads. Results from the first 25 months of monitoring for 13 systems with at least a full year of data are presented in terms of 1) reductions in nutrient concentrations and mass loads and 2) reliability of the systems for meeting a performance goal of total N (TN) < 10 mg/L. Discussion supports consideration of where and how these technologies may be successfully used to manage excess N in sensitive watersheds., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Published by Elsevier Ltd.)

During the Mining-Agriculture Complex Areas, the mining and agriculture activities could lead to an excessive presence of sulfate content in the regional groundwater. Sulfate exhibits the potential to influence the positive accumulation of RGs, although its mechanisms remain inadequately explored. To address this gap, this study analyzed the RGs buildup mechanisms in the groundwater of the mining-agriculture complex area. Results showed a widespread presence of antibiotic resistance genes (ARGs) and metal resistance genes (MRGs), especially in coal-seams crevice groundwater. And iron and sulfur are primary environmental factors conducive to RGs accumulation through a synergistic interaction. Microbial annotation of gene sets sourced from coal-seams crevice groundwater samples unveiled part of sulfur-metabolizing microorganisms that were hosts of both ARGs and MRGs. Mechanistic insights revealed that iron may stimulates reactive oxygen species (ROS) generation, facilitating RGs accumulation, while adjusting sulfur metabolism and the synthesis of iron-sulfur clusters, thereby augmenting microbial growth which as predominant hosts of RGs, thereby intensifying the buildup of RGs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

Submarine groundwater discharge is a pivotal factor in modifying the structure of phytoplankton communities in coastal waters. The objective of the study was to investigate how variations in nutrient concentrations and ratios influence the composition of phytoplankton communities along the coastal waters of Bay of Bengal. The experiment involved mixing groundwater with coastal water at 5 % and 10 % proportions. Phytoplankton growth was more pronounced in 10 % groundwater than those with 5 % and control samples. In control samples, Chl-a and other pigments, experienced decrease from 20 % to 80 %, except in Odisha-Paradeep and Visakhapatnam-Andhra Pradesh, where peridinin concentrations increased by 60 % to 65 % owing to low Si:N ratios below 0.2. A shift was observed from diatoms to dinoflagellates due to low Si: N ratios. The results reaffirm the hypothesis that variations in nutrient concentrations and ratios play a substantial role in shaping the composition of phytoplankton in the adjacent coastal waters., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the research reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Biodiversity, the source of origin, and ecological roles of fungi in groundwater are to this day a largely neglected field in fungal and freshwater ecology. We used DNA-based Illumina high-throughput sequence analysis of both fungal gene markers 5.8S and internal transcribed spacers region 2 (ITS2), improving taxonomic classification. This study focused on the groundwater and river mycobiome along an altitudinal and longitudinal transect of a pre-alpine valley in Austria in two seasons. Using Bayesian network modeling approaches, we identified patterns in fungal community assemblages that were mostly shaped by differences in landscape (climatic, topological, geological), and environmental conditions. While river fungi were comparatively more diverse, unique fungal assemblages could be recovered from groundwater, including typical aquatic lineages such as Rozellomycota and Olpidiomycota. The most specious assemblages in groundwater were not linked to the input of organic material from the surface, and as such, seems to be sustained by characteristic groundwater conditions. Based on what is known from closely related fungi, our results suggest that the present fungal communities potentially contribute to mineral weathering, carbon cycling and denitrification in groundwater. Furthermore, we were able to observe the effects of varying land cover due to agricultural practices on fungal biodiversity in groundwater ecosystems. This study contributes to improving our understanding of fungi in the subsurface aquatic biogeosphere., (© The Author(s) 2024. Published by Oxford University Press on behalf of FEMS.)

Background: Arsenic is a well-known, highly poisonous metalloid that affects human health and ecosystems and is widely distributed in the environment. Nevertheless, data on the spatiotemporal distribution of arsenic in groundwater sources in Ethiopia are scarce., Objective: The principal aim of this study was to assess the extent of arsenic in groundwater sources and analyze the spatiotemporal variations in the central rift valley of Ethiopia., Methods: The study employed a serial cross-sectional study design and census sampling methods. The concentrations of arsenic in the groundwater samples were determined using inductively coupled plasma mass spectrometry (ICP-MS) at the Ethiopian Food and Drug Authority laboratory. Descriptive statistical analyses were performed using IBM SPSS version 29 software. Additionally, ArcGIS software was utilized to map the spatiotemporal distribution of arsenic. Furthermore, Minitab statistical software version 21.4 was employed to assess the correlation between spatiotemporal variations of arsenic concentrations in groundwater sources., Results: The mean values of arsenic in the groundwater samples were 11.2 µg/L during the dry season and 10.7 µg/L during the rainy season. The study results showed that 18 wells (42.2%) and 22 wells (48.8%) had higher arsenic concentrations (>10 µg/L) during the dry and rainy seasons, respectively. Thus, arsenic levels in 42.2% and 48.8% of the samples exceeded the maximum threshold limit set by WHO, USEPA, and Ethiopian standards (10 µg/L), respectively, during the dry and rainy seasons. Furthermore, our analysis revealed a significant positive correlation between arsenic in groundwater and well depth ( r  = .75, P  < .001), indicating a strong association between higher arsenic concentrations and deeper wells. Similarly, we observed a substantial positive correlation between arsenic concentration in groundwater and season ( r  = .9, P  < .001), suggesting notable variations in arsenic levels between dry and rainy seasons., Conclusions: The majority of the groundwater sources in the studied area are unfit for human consumption because they contain high amounts of arsenic, which poses a significant risk to human health. Moreover, the arsenic concentration varied spatially and temporally. Therefore, special attention is needed to reduce arsenic exposure and associated health risks., Competing Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2024.)

Algal physiological ecology on submarine groundwater discharge (SGD) influenced reefs is likely shaped by intermittent, tidally-driven estuarine conditions that occur with SGD fluxes of fresh-to-brackish groundwater from the subterranean estuary to reef ecosystems. SGD is a common inconspicuous feature worldwide on reefs of basaltic high islands and continental margins. Yet, SGD-driven dynamics of algal physiology are not well understood. To understand how invasive species have physiologically outcompeted native species on many SGD-influenced reefs, physiology in tissue water potential (TWP) regulation, photosynthesis, nitrogen storage, and cellular anatomy were measured across a gradient of SGD-influence, for four Rhodophyte species. Compared with non-SGD conditions, SGD was associated with higher TWP, larger medulla cells with thinner walls, and thinner cortical cell walls for two invasives, Gracilaria salicornia and Acanthophora spicifera, higher photosynthetic rates in G. salicornia, greater nitrogen concentration for A. spicifera and G. salicornia, and increased δ 15 N ratios for A. spicifera, G. salicornia, and native Laurencia dendroidea. Distinct physiological strategies were measured for the two invasive species across the gradient of SGD-influence, and for L. dendroidea and Gracilaria perplexa offshore. This study illuminates species-specific physiological response, and how introduced opportunistic species may outcompete native species under conditions of SGD., (© 2024. The Author(s).)

Per- and polyfluoroalkyl substances (PFAS) are known to be highly persistent in groundwater, making it vital to develop new approaches to important practical questions such as the time scale for future persistence of PFAS in contaminated groundwater. In the approach presented here, groundwater from beneath streambeds was analyzed for PFAS and age-dated using SF 6 and 3 H/ 3 He. The results were coupled with groundwater flux measurements in a convolution approach to estimate past and future PFAS concentrations in groundwater discharge to the streams. At our test site near the Cape Fear River (CFR) of North Carolina, PFAS were detected in groundwater up to 43 years old, suggesting that some PFAS entered groundwater immediately or shortly after fluorochemical production began at the nearby Fayetteville Works. Results are consistent with little to no retardation in groundwater for perfluoroethers such as hexafluoropropylene oxide-dimer acid (HFPO-DA) and perfluoro-2-methoxypropanoic acid (PMPA), the two most abundant PFAS, with mean concentrations of 229 and 498 ng/L, respectively. Future PFAS concentrations in groundwater discharge to streams were estimated to remain above current MCL or health advisory levels through at least 2050 or 2060 (using 3 H/ 3 He and SF 6 , respectively). Recent atmospheric deposition data suggest lower but non-negligible amounts of PFAS may continue to enter groundwater, likely further extending PFAS persistence in groundwater and the adjacent CFR. This approach shows promise for giving an overall perspective on persistence of PFAS in groundwater discharge from a broad contaminated area.

While unconventional oil and gas (UOG) development is changing the world economy, processes that are used during UOG development such as high-volume hydraulic fracturing ("fracking") have been linked with water contamination. Water quality risks include leaks of gas and salty fluids (brines) that are coproduced at wellpads. Identifying the cause of contamination is difficult, however, because UOG wells are often colocated with other contaminant sources. We investigated the world's largest shale gas play with publicly accessible groundwater data (Marcellus Shale in Pennsylvania, U.S.A. with ∼29,000 analyses) and discovered that concentrations of brine-associated barium ([Ba]) and strontium ([Sr]) show small regional increases within 1 km of UOG development. Higher concentrations in groundwaters are associated with greater proximity to and density of UOG wells. Concentration increases are even larger when considering associations with the locations of (i) spill-related violations and (ii) some wastewater impoundments. These statistically significant relationships persist even after correcting for other natural and anthropogenic sources of salts. The most likely explanation is that UOG development slightly increases salt concentrations in regional groundwaters not because of fracking but because of the ubiquity of wastewater management issues. These results emphasize the need for stringent wastewater management practices across oil and gas operations.

Green stormwater infrastructure (GSI) practices like bioretention are considered a sink for microplastics washed in from urbanized land uses-land covers, and thereby regulating the environmental dispersion of microplastics. However, the capacity of GSI in microplastic sequestration remain unclear. This work investigated the spatial distributions of microplastics within bioretention cells and their soils, concentration in the GSI groundwater monitoring well, and the overall potential of GSI as a sink for microplastics. The average microplastic concentration in GSI soils (2718 - 3833 MPs/kg dry soil) is 7-10 times higher than background soils (262 - 520 MPs/kg dry soil). The most abundant microplastics observed were polypropylene (57 %), polyethylene (17 %), and rubber/bituminous (16 %), indicating the major sources of microplastics derived from post-consumer plastics and tire wear. Soils closest to the GSI stormwater inlet sequestered the most particles, and the microplastic concentration decreased with soil depth. Our hydrologic modeling, based on measured soil and hydraulic parameters, suggested that runoff overtopping the freeboard of the bioretention cell - and potentially dispersing microplastics into the surrounding environment - was unlikely. Microplastics in the GSI groundwater monitoring well was minimal at 11 MPs/L. These results suggest that GSI can capture and sequester microplastics to mitigate microplastic pollution in the environment., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

In Ontario, monitoring, maintenance, and treatment of private drinking systems (e.g. wells) are the responsibility of the well owner. Fecal contamination of drinking water threatens public health, particularly in rural communities which are often fully reliant on unregulated private groundwater as a primary drinking water source. Private well users face a higher risk of acute gastrointestinal illness compared to those served by municipally operated systems (Murphy et al., 2016). Accordingly, the current study sought to characterize the fecal indicator, E. coli, isolated from southeastern Ontario private groundwater wells, including phylogroups and host source. Results were examined in the context of antecedent climate and local hydrogeological setting to elucidate likely contaminant sources and pathways. A total of 737 E. coli isolates from 260 private wells were assigned to phylogroups using the Clermont PCR phylotyping method, with likely host source determined using host-specific Bacteroidales 16S rRNA RT qPCR assays. Multivariate models were developed for the main E. coli phylogroups (A, B1, B2, and D) and all microbial source tracking markers. Models were coupled for interpretation where possible, based on associations between phylogroups and MST markers. Preferential subsurface flow, and to a lesser degree, overland flow, were likely mechanisms of contamination across all models. Distinct temporal associations were found based on the fecal source. Multiple models were developed and will be discussed, in an attempt to elucidate source-specific contamination mechanisms, in support of risk assessment and appropriate protective actions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: Bacteria of the candidate phyla radiation (CPR), constituting about 25% of the bacterial biodiversity, are characterized by small cell size and patchy genomes without complete key metabolic pathways, suggesting a symbiotic lifestyle. Gracilibacteria (BD1-5), which are part of the CPR branch, possess alternate coded genomes and have not yet been cultivated. The lifestyle of Gracilibacteria, their temporal dynamics, and activity in natural ecosystems, particularly in groundwater, has remained largely unexplored. Here, we aimed to investigate Gracilibacteria activity in situ and to discern their lifestyle based on expressed genes, using the metaproteogenome of Gracilibacteria as a function of time in the cold-water geyser Wallender Born in the Volcanic Eifel region in Germany., Results: We coupled genome-resolved metagenomics and metaproteomics to investigate a cold-water geyser microbial community enriched in Gracilibacteria across a 12-day time-series. Groundwater was collected and sequentially filtered to fraction CPR and other bacteria. Based on 725 Gbps of metagenomic data, 1129 different ribosomal protein S3 marker genes, and 751 high-quality genomes (123 population genomes after dereplication), we identified dominant bacteria belonging to Gallionellales and Gracilibacteria along with keystone microbes, which were low in genomic abundance but substantially contributing to proteomic abundance. Seven high-quality Gracilibacteria genomes showed typical limitations, such as limited amino acid or nucleotide synthesis, in their central metabolism but no co-occurrence with potential hosts. The genomes of these Gracilibacteria were encoded for a high number of proteins involved in cell to cell interaction, supporting the previously surmised host-dependent lifestyle, e.g., type IV and type II secretion system subunits, transporters, and features related to cell motility, which were also detected on protein level., Conclusions: We here identified microbial keystone taxa in a high-CO 2 aquifer, and revealed microbial dynamics of Gracilibacteria. Although Gracilibacteria in this ecosystem did not appear to target specific organisms in this ecosystem due to lack of co-occurrence despite enrichment on 0.2-µm filter fraction, we provide proteomic evidence for the complex machinery behind the host-dependent lifestyle of groundwater Gracilibacteria. Video Abstract., (© 2024. The Author(s).)

Dwindling groundwater supplies threaten food security and livelihoods. Output subsidies for farmers are a ubiquitous agricultural policy tool, yet their contribution to growing groundwater stress remains poorly quantified. We show how output subsidies guaranteeing the purchase of crops at higher than market prices may have contributed substantially to declining water tables in India. Our analysis suggests that these policies may have led to a 30% over-production of water intensive crops. In the northwestern state of Punjab, rice procurement can potentially account for at least 50% of the groundwater table decline over 34 years. In the central state of Madhya Pradesh, wheat procurement adopted in the late 2000s appears to have driven a 5.3 percentage point increase in dry wells and a consequent 3.4 percentage point increase in deep tubewells. These results suggest that well-intentioned but poorly designed subsidies can impose harmful externalities on the environment and undermine long-term sustainable development., (© 2024. The Author(s).)

Fluoride (F¯) contamination in groundwater in India has gained global attention due to human health hazards. India's hydrogeological heterogeneity, spatio-temporal variability of F¯, and health hazards due to geogenic and geo-environmental control pose unique challenges. Addressing these with only a single region-specific study is not possible. Therefore, this study provides an in-depth, holistic analysis of pan India F¯ contamination, controlling factors, and health hazards using a coupled advanced geostatistical and geospatial approach. Alarming F¯ contaminations are identified in Rajasthan, Telangana, Western Andhra Pradesh, Eastern Karnataka, Parts of Haryana, Gujarat, Madhya Pradesh, Tamil Nadu, Uttar Pradesh, Jharkhand, Bihar, and Chhattisgarh. Probabilistic health-risk evaluation using hot-spot, showed similar spatio-temporal distribution of F¯ contamination. The hazard quotient (HQ) for high F¯ shows more adversity to children than adults. Nationally, 8.65 % and 7.10 % of pre- and post-monsoon sites exceed the recommended safe limit of 1.50 mg/L. The highest average F¯ concentration is in Rajasthan. Very high-risk skeletal fluorosis is possible at around ≤ 2 %, whereas dental caries due to deficiency in F¯ concentration is approximately 40 %. A decisive hierarchy of lithology, geomorphology, soils, and lineaments control are identified on F¯ contamination. Climatic conditions are pivotal in governing all these controlling variables. Thus, in arid/semi-arid dry western regions, F¯ contamination is much higher than in the humid areas. Integration of strengths, weaknesses, opportunities, and threats (SWOT) analysis with the results can aid policymakers and government authorities in achieving sustainable remedial measures for future adaptability., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Groundwater pollution caused by fluoride is a significant concern for the global population owing to its toxicity, which has negative health consequences. Industrial discharges, agricultural practices, and improper waste disposal are primary concerns in evaluating the degree of fluoride contamination in the selected districts of Eastern India. In a targeted area sampling approach, exactly 196 samples were collected during pre- and post-monsoon, and precise fluoride detection was performed using Ion-Selective Electrodes. Fluoride levels in pre-monsoon water were observed within a range of 0.02 to 2.7 mg/L, with an average abundance of 0.4 ± 0.50. In post-monsoon, the concentration ranged from 0.02 to 4.7 mg/L (mean 0.53 ± 0.60). The study found that 97 % of groundwater samples had acceptable fluoride levels within the 1.5 mg/L limit during pre and post-monsoon. Moreover, approximately 87 % of the samples exhibit fluoride content below the 1 mg/L limit. The hazard quotient was observed to be 0.17 to 0.58 in adults, 0.23 to 0.79 in children and 0.36 to 1.26 in infants during pre-monsoon, whereas 0.05 to 0.55 in adults, 0.12 to 0.74 in children and 0.11to 1.19 in infants during post monsoon. The above data indicates that infants had the highest risk of fluoride exposure, with a significant negative correlation between fluoride and calcium ions. Fluoride had minimal to no link with other ions, a modest positive correlation with sulfate, and a weak negative relationship with overall hardness and alkalinity across both seasons. The present study contributes towards the identification of fluoride levels in various areas, making society aware of water contamination and its health impacts., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Groundwater is particularly vulnerable to pollution in places with a high population density and extensive human usage of the land, especially in southern parts of Tirupati, India. To assess this, 60 bore-well samples were obtained and assessed for physical specifications, ion chemistry, and heavy metals during the pre- and post-monsoon seasons 2022. The current investigation employed a modified integrated water quality index (IWQI), conventional graphical and human health risk assessment (HHRA) of nitrates and heavy metals to know the groundwater chemistry and its detrimental health effects on humans. The major ions were analyzed using American public health association (APHA) standards, whereas heavy metals were analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES). Additionally, pH Redox Equilibrium and C (PHREEQC), a geochemical model written in C programming language was employed to determine the saturation indices of mineral facies and ArcGIS 10.3.1 was used for spatial distribution patterns of IWQI. Then, the HHRA of nitrates and heavy metals was performed using United States environmental protection agency (US EPA) guidelines. The noteworthy outcomes include elevated levels of Ca 2+ , Mg 2+ , Cl - , NO 3 , Cu, Fe, Mn, and Pb, demonstrating rock-water interaction, silicate weathering, Ca-Mg-HCO3 followed by mixed water facies, dissolution/precipitation, reverse exchange, and anthropogenic contamination are the major controlling processes in groundwater of southern Tirupati, India. The modified IWQI reveals that most groundwater samples (38%) fall under the bad quality class, with (47%) in the poor quality class and only (15%) classified as medium quality class in pre- and post-monsoon seasons. Elevated IWQI were observed in all directions except in the east, which is suitable for drinking. Moreover, the major hazard quotient (HQ) and hazard index (HI) for nitrates (NO - ) and heavy metals like copper (Cu), iron (Fe), manganese (Mn), lead (Pb) and zinc (Zn) are above the critical value of 1, revealing potential risk to humans, especially infants, followed by children and adults, entailing the instantaneous implementation of proper remedial measures and stringent policies to reduce the risk associated with groundwater pollution in the southern parts of Tirupati.3 - ) and heavy metals like copper (Cu), iron (Fe), manganese (Mn), lead (Pb) and zinc (Zn) are above the critical value of 1, revealing potential risk to humans, especially infants, followed by children and adults, entailing the instantaneous implementation of proper remedial measures and stringent policies to reduce the risk associated with groundwater pollution in the southern parts of Tirupati., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Unintended releases of CO 2 from carbon capture and storage operations presents the risk of atmospheric emissions and groundwater or surface water quality impacts. Given the potential impacts, it is valuable to have tools capable of predicting groundwater concentrations and likely pathways of CO 2 migration in the subsurface. Traditional multiphase flow models struggle to simulate the discontinuous flow expected at leakage sites. This work applied a coupled continuum-discrete model, ET-MIP, to simulate a bench-scale injection of CO 2 . Results demonstrate the capability of ET-MIP to accurately capture gas fingering behaviour, and the complexity of multicomponent mass transfer observed in the experiment. Simulations were computationally efficient, allowing for the use of multiple displacement pressure realizations. CO 2 migration in the subsurface was shown to be sensitive to mass transfer, as i) increased groundwater velocity can dissolve leaked CO 2 prior to reaching the surface and ii) background dissolved gases in the subsurface can impact the rate of upwards gas movement, gas distribution, and the composition and persistence of the gas phase. The sensitivity to mass transfer suggests it may be preferable to monitor for low-solubility gases in the source mixture rather than CO 2 . These findings are applicable to other gases in the subsurface, such as hydrogen or methane migrating from geoenergy wells., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

The current study investigates removing tetracycline from water using batch, column, and tank experiments with statistical modelling using ANN for continuous tests. An artificial neural network (ANN) using the Levenberg-Marquardt back-propagation (LMA) training algorithm is constructed to compare the effectiveness of Tetracycline removal from aqueous solution using the sorption technique with prepared adsorbent. Several characterization analyses XRD, FT-IR, and SEM are employed for prepared Brownmillerite (Ca 2 Fe 2 O 5 )-Na alginate beads. The operating conditions of batch tests involved, contact time (0.1-3 h), initial of tetracycline (C o ) of (100-250 mg/L), pH (3-12), agitation speed (50-250) rpm and dosage of adsorbent (0.2-1.2 g/50 mL). The outcomes of experiments have demonstrated that the optimum conditions for the batch test to achieve the maximum adsorbent capacity (q max =7.845 mg/g) are achieved at pH 7, contact time 1.5 h, adsorbent dose 1.2 g/50 mL, agitation speed of 200 rpm, and initial concentration of TC 100 mg/L. Minimum mean square error (MSE) values of 7.09E-04 for 30 hidden neurons and 0.0029 for 59 hidden neurons in the 1D and 2D systems are accomplished, respectively. The artificial neural network model has exhibited excellent performance with correlation coefficients exceeding 0.980 for the operating variables, demonstrating its accuracy and effectiveness in predicting the experimental outcomes. According to sensitivity analysis, the influential parameter in the column test (1D) is the flow rate (mL/min), with a relative importance of 32.769%. However, in the tank test (2D), time (day) is signified as an influential parameter with a relative importance of 31.207%., (© 2024. The Author(s).)

Alternative water sources are necessary in developing nations because surface water is not always accessible, and groundwater is depleted. In such situations, rainwater harvesting is considered a promising sustainable water resource management solution. Numerous studies have been conducted to determine suitable locations for rainwater harvesting (RWH) using bottom-up approaches applied to large watersheds. The bottom-up methods begin with various geographic criteria and end with regions suitable for RWH intervention, even considering the distance from settlements to be one of the criteria, excluding urban areas from RWH site identification. This study developed a top-down methodology that began with the distributed pinpoint locations of potential RWH sites, as determined by distributed flow accumulation values produced from a digital elevation model (DEM), and then filtered out the sites based on various criteria in the context of urban areas. The flow accumulation values were apportioned according to the flow-contributing area of each RWH site. Five flow-contributing areal scenarios corresponding to 1 km 2 , 2.5 km 2 , 5 km 2 , 7.5 km 2 , and 10 km 2 were considered in this study, as it is challenging to choose a suitable location for RWH sites in urban zones for efficient water storage owing to a variety of land uses. Based on this technique, a case study was conducted in Jaipur, Rajasthan, India, where it was found that the volumetric potential of rainwater storage is maximum (403,679,424.9 cu. m) for 1 km 2 and minimum (169,951,322 cu. m) for 10 km 2 flow contributing areal distribution per RWH site., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

This paper presents a new approach to the spatiotemporal design of groundwater quality monitoring networks for coastal aquifers. A fusion model combines the outputs of several developed simulation models to make estimates more accurate. A modified GALDIT method is used to incorporate the aquifer vulnerability to saltwater intrusion. The value of information (VOI) theory is applied to determine sufficient monitoring wells. The groundwater quality monitoring network is designed by employing a robust decision-making (RDM) approach under different management strategies and economic considerations. This approach incorporates the deep uncertainties of some critical variables, including water level and total dissolved solids (TDS) concentration at the coastline and pumping flow rates of agricultural wells. The new methodology is implemented in the coastal Qom-Kahak aquifer, Iran. The results illustrate that the combination model has significantly improved evaluation criteria compared to individual prediction models. The fusion model results indicate that thirty monitoring wells would be ideal. The RDM-based analyses in the Qom-Kahak aquifer showed that an optimal network with 30 monitoring wells outperforms the current network regarding various criteria, such as VOI and variance of estimation error. The new well configuration also demonstrates a suitable spatial distribution. Given that the current sampling frequencies are unsuitable for areas with varying vulnerabilities, we recommend sampling every 3 months in areas with moderate vulnerabilities and once every three seasons in areas with low vulnerabilities, based on the information transfer index. Finally, a management strategy in which the pumping rate should be less than 60% of the current rate is suggested to prevent saltwater intrusion into the aquifer., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Wildfires induce changes in soil and vegetation composition, significantly impacting the hydrological cycle and altering future runoff and infiltration patterns. Ash residue on the ground can infiltrate the subsoil along with water, leading to modifications in groundwater hydrochemistry. Climate change and summer heatwaves can create favourable conditions for severe wildfires, such as the one that occurred in Zamora, Spain, in 2022. Fourteen simultaneous points of origin across various locations in Zamora triggered the worst environmental disaster in this province, as well as the largest fire recorded in the history of Spain. Following the severe wildfires in Sierra de la Culebra, Zamora, groundwater samples were obtained to compare the hydrochemistry with pre-fire background data spanning several years. A general decline in pH across all sampling points was observed, most notably at Z1, likely due to its very high permeability and leaching of organic acids from burned vegetation. Increases in major ions such as SO 4 2- and NO 3 levels decreased, indicating possible oxidation of soil organic matter and the introduction of wildfire-derived organic acids into the groundwater system. Elevated concentrations of Na - were detected at Z1-2, while HCO 3 - levels decreased, indicating possible oxidation of soil organic matter and the introduction of wildfire-derived organic acids into the groundwater system. Elevated concentrations of Na + were observed at Z3, suggesting possible ash residue infiltration. Despite the severity of the wildfires, the results indicate that there were no significant long-lasting impacts on groundwater quality overall. This finding suggests that the groundwater systems in the study area are resilient to such environmental catastrophes.+ , Mg 2+ , and Ca 2+ were observed at Z3, suggesting possible ash residue infiltration. Despite the severity of the wildfires, the results indicate that there were no significant long-lasting impacts on groundwater quality overall. This finding suggests that the groundwater systems in the study area are resilient to such environmental catastrophes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Groundwater is an essential source of drinking water and agricultural irrigation water, and its protection has become a global goal for public health. However, knowledge about heavy metal(loid) resistance genes (MRGs) in groundwater and the potential co-selection of antibiotic resistance genes (ARGs) have seldom been developed. Here, during the wet and dry seasons, we collected 66 groundwater samples (total dissolved solids = 93.9-9530 mg/L) adjacent to Baiyangdian Lake in Northern China, which presented the few metal(loid) and antibiotic contamination. We identified 160 MRGs whose composition exhibited significant seasonal variation, and dissolved metal(loid)s (particularly Ba) played a determinative role in promoting the MRGs proliferation though with relatively low concentrations, suggesting the relatively vulnerable groundwater ecosystems. Moreover, 27.4% of MRG-carrying metagenome-assembled genomes (MAGs) simultaneously carried ARGs, with the most frequently detected MRG types of Cu, Hg, and As, and ARG types of multidrug and bacitracin. Physicochemical variables, variables related to total dissolved solids, metal(loid)s, and antibiotics synthetically shaped the variation of MRG-ARG hosts in groundwater. We found that the increase of MRG-ARG hosts was critically responsible for the spread of MRGs and ARGs in groundwater. Our findings revealed the widespread co-occurrence of MRGs and ARGs in few-contaminated groundwater and highlighted the crucial roles of salinity in their propagation and transmission., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Subsurface substance migration in the fractured rock aquifer is mainly controlled by fractures, and immiscible fluid-fluid displacement in fractures is important to many geophysical processes and engineering activities. Using a fracture-visualization system, we present the qualitative and quantitative assessment of fracture geometry associated with fluid movement and distribution in the rough fracture. Based on fracture geometry and statistical analysis, we first conducted a quantitative study of fracture surface roughness and aperture distribution. Then, fractal dimensions of displacement front and residual oil distribution were determined by image processing procedures. Influenced by wettability and micro-scale roughness, at the end of the displacement, residual oil saturation of molded sample is lower (6.45%-25.74%), and displacement pattern is more uniform, indicating that displacement effect is better. Due to smaller differences in residual oil saturation (9.08%) under different injection directions, the impact of wettability on the displacement process is greater than that of anisotropic roughness. Additionally, the fractal dimension of the displacement front increased under low injection rates initially but decreased when the rate was increased later. Overall, visualized temporal monitoring of experimental images enabled us to provide a preliminary assessment of the impact of anisotropic roughness and the material constituting the fracture wall on invading fluid saturation and the fractal dimension of the displacement front under various injection rates., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Climate change in California is expected to alter future water availability, impacting water supplies needed to support future housing growth and agriculture demand. In groundwater-dependent regions like California's Central Coast, new land-use related water demand and decreasing recharge is already stressing depleted groundwater basins. We developed a spatially explicit state-and-transition simulation model that integrates climate, land-use change, water demand, and groundwater gain-loss to examine the impact of future climate and land use change on groundwater balance and water demand in five counties along the Central Coast from 2010 to 2060. The model incorporated downscaled groundwater recharge projections based on a Warm/Wet and a Hot/Dry climate future from a spatially explicit hydrological process-based model. Two urbanization projections from a parcel-based, regional urban growth model representing 1) recent historical and 2) state-mandated housing growth projections were used as alternative spatial targets for future urban growth. Agricultural projections were based on recent historical trends from remote sensing data. Annual projected changes in groundwater balance were calculated as the difference between land-use related water demand, based on historical estimates, and climate-driven recharge plus agriculture return flows. Results indicate that future changes in climate-driven groundwater recharge, coupled with cumulative increases in agricultural water demand, result in overall declines in future groundwater balance, with a Hot/Dry future resulting in cumulative groundwater decline in all but Santa Cruz County. Cumulative declines by 2060 are especially prominent in San Luis Obispo (-2.9 to -5.1 Bm 3 ) and Monterey counties (-6.5 to -8.7 Bm 3 ), despite limited changes in agricultural water demand over the model period. These two counties show declining groundwater reserves in a Warm/Wet future as well, while San Benito and Santa Barbara County barely reach equilibrium. These results suggest future groundwater supplies may not be able to keep pace with regional demand and declining climate-driven recharge, resulting in a potential reduction in water security in the region. However, our county-scale projections showed new housing and associated water demand does not conflict with California's groundwater sustainability goals. Rather, future climate coupled with increasing agricultural groundwater demand may reduce water security in some counties, potentially limiting available groundwater supplies for new housing., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Tamara Wilson reports financial support was provided by California Strategic Growth Council. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Published by Elsevier Ltd.)

Compound pollution at industrial sites impedes urban development, especially when there is a lack of understanding about the spatial variations of internal pollution in industrial areas producing light-weight materials. In this study, spatial distribution and ecological risks of potentially toxic elements (PTEs), volatile organic compounds (VOCs), and petroleum hydrocarbons (C10-40) in the soil and groundwater of an Al/Cu (aluminum/copper) industrial site have been analyzed comprehensively. Results revealed the progressive clustering of pollutants in different soil layers, which indicated varying levels of penetration and migration of pollutants from the surface downward. Furthermore, severity of pollution varied according to pollutant type, with Cu (5-10,228 mg kg -1 ) often exceeding the background levels significantly (>40). Cd (0.03-2.60 mg kg -1 ) and Hg (0.01-3.73 mg kg -1 ) were found at elevated concentrations in deeper soil layers, suggesting distinct variations of PTEs across different soil depths. Among the more hazardous VOCS, polychlorinated biphenyls (1.80-234 μg kg -1 ) were particularly prevalent in the deeper layers of soil. Petroleum hydrocarbons (C10-40) were widely detected (6-582 mg kg -1 ), showing significant migration potential from surface to deep soil. These findings suggest that prolonged industrial activities lead to deep-seated accumulation of pollutants, which also impacts the groundwater, contributing to long-term dispersion of contaminants. Furthermore, multivariate statistical analysis indicated certain positive correlations among the distribution of Cu, Pb and petroleum hydrocarbons, indicating possible coupling of these pollutants. Severe Cu pollution caused an ecological risk in the surface soil layer (covering >20 % area of high pollution site, contributing >40 % ecological risk). While the Hg and Cd posed significant risks in the deeper soil layers, showing higher risk coefficients and mobility. The study provides crucial insights into the transformation of urban areas with a history of industrial uses into community spaces and highlights the risks posed by the remaining pollutants., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

To counteract the ongoing salinization of coastal aquifers, which poses a significant environmental and socioeconomic challenge to local communities, it is necessary to first understand the origin and mechanisms of this phenomenon. This study investigates the origins of salinity in the Volturno River lowland in Southern Italy and reveals that the primary source in the area is paleo-seawater entrapped within sediments that were subject to evapoconcentration processes. By systematically collecting sediment samples at variable depths and locations and extracting porewaters, a comprehensive understanding of the interplay between freshwater and saline water was gained, including complex patterns of vertical stratification of groundwater salinity. The study highlights the limitations of traditional methods that rely on salinity monitoring via integral depth sampling, particularly in capturing the vertical redox and salinity gradients characteristics of layered aquifer/aquitard systems. On the contrary, environmental tracers, like chloride and bromide, provide valuable insights into the sources of groundwater salinity, distinguishing between current seawater intrusion and other causes, such as paleo-seawater and return flow from drained agricultural land. Results suggest that the majority of salinity does not originate from modern seawater intrusion or recent evaporation. Instead, it can be attributed to paleo-seawater affected by evapoconcentration processes. This study has broader implications for the sustainable management of coastal aquifers and the safeguarding of freshwater resources. While our findings are specific to the Volturno River coastal area, the methodologies and insights here presented can be reproduced in every coastal region facing similar salinity challenges., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Nitrate pollution in groundwater is a serious problem worldwide, as its concentration in many areas exceeds the WHO-defined drinking water standard (50 mg/L). Hydrogen-oxidizing bacteria (HOB) are a group of microorganisms capable of producing single-cell protein (SCP) using hydrogen and oxygen. Furthermore, HOB can utilize various nitrogen sources, including nitrate. This study developed a novel hybrid biological-inorganic (HBI) system that coupled a new submersible water electrolysis system driven by renewable electricity with HOB fermentation for in-situ nitrate recovery from polluted groundwater and simultaneously upcycling it together with CO 2 into single-cell protein. The performance of the novel HBI system was first evaluated in terms of bacterial growth and nitrate removal efficiency. With 5 V voltage applied and the initial nitrate concentration of 100 mg/L, the nitrate removal efficiency of 85.52 % and raw of 47.71 % (with a broad amino acid spectrum) were obtained. Besides, the HBI system was affected by the applied voltages and initial nitrogen concentrations. The water electrolysis with 3 and 4 V cannot provide sufficient H 2 for HOB and the removal of nitrate was 57.12 % and 59.22 % at 180 h, while it reached 65.14 % and 65.42 % at 5 and 6 V, respectively. The nitrate removal efficiency reached 58.40 % and 50.72 % within 180 h with 200 and 300 mg/L initial nitrate concentrations, respectively. Moreover, a larger anion exchange membrane area promoted nitrate removal. The monitored of the determination of different forms of nitrogen indicated that around 60 % of the recovered nitrate was assimilated into cells, and 40 % was bio-converted to N 2 . The results demonstrate a potentially sustainable method for remediating nitrate contaminant in groundwater, upcycling waste nitrogen, CO 2 sequestration and valorization of renewable electricity into food or feed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Understanding the role of hydrologic variation in structuring aquatic communities is crucial for successful conservation and sustainable management of native freshwater biodiversity. Partitioning beta diversity into the additive components of spatial turnover and nestedness can provide insight into the forces driving variability in fish assemblages across stream flow regimes. We examined stream fish beta diversity across hydrologic and anthropogenic disturbance gradients using long-term (1916-2016) site occurrence records (n = 17,375) encompassing 252 species. We assessed total beta diversity (Sørensen dissimilarity), spatial turnover, and nestedness of fish assemblages in contrasting stream flow regimes across a gradient of decreasing flow stability: groundwater stable (n = 77), groundwater (n = 67), groundwater flashy (n = 175), perennial runoff (n = 141), runoff flashy (n = 255), and intermittent (n = 63) streams. Differences in total beta diversity among the stream flow regimes were driven predominantly (>86 %) by spatial turnover (i.e. species replacement) as opposed to nestedness (i.e. species loss or gain). Total fish beta diversity and spatial turnover were highest in streams with intermediate flow stability (groundwater flashy), while more flow-stable streams (groundwater stable and groundwater) had lower turnover and higher nestedness. Species turnover was also strongly associated with seasonal variation in hydrology across all flow regimes, but these relationships were most evident for assemblages in intermittent streams. Distance-based statistical comparisons showed significant correlations between beta diversity and anthropogenic disturbance variables, including dam density, dam storage volume and water withdrawals in catchments of groundwater stable streams, while hydrologic variables were more strongly correlated with beta diversity in streams with runoff-dominated and flashy flow regimes. The high spatial turnover of species implies that fish conservation actions would benefit from watershed-focused approaches targeting multiple streams with wide spatial distribution, as opposed to simply focusing on preserving sites with the greatest number of species., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Freshwater scarcity poses challenges to aquaculture worldwide, including countries like Egypt. In this study, we investigate the feasibility of integrating underground saline water (USW) with varying salinities into a Biofloc (BFT) system for desert mariculture of Florida red tilapia (FRT) and its impacts on water quality, fish performance and health. Four BFT treatments (C/N ratio = 15) were examined in triplicate using four salinity levels 0 ppt, 12 ppt, 24 ppt and 36 ppt, expressed as S0, S12, S24 and S36, respectively. For 75 days, a total of 12 fiberglass tanks (each 250 L -1 water) were used to store FRT fry (average weight of 1.73 ± 0.01 g/fish). The fish were fed an experimental diet (protein/fat = 30/5) and an additional carbon source of rice bran. The results revealed that group S12 showed better growth indicators, higher survival rate, lower FCR, and lower ammonia levels, while group S0 exhibited lower growth indicators (final weight, weight gain, and specific growth rate) than all groups. The serum kidney, liver, and antioxidant indices performed better in the S12 group. At 12 ppt, the immune-related parameter (IgM) increased by 22.5%, while the stress parameter (cortisol) decreased by 40.8% compared to the S0 group. The liver and intestinal histopathological results revealed that the S12 and S24 groups performed better. Pathogenic bacterial load counts favored the S24 group, which had the lowest number among the groups studied. The recommended salinity for FRT cultivation in USW and BFT is 19.94-20 ppt, determined by polynomial regression of FW and FCR., (© 2024. The Author(s).)

Electrochemical oxidation has emerged as an effective and straightforward technology for groundwater remediation. While recent studies have investigated parameters such as current, electrolyte composition, and electrode materials, most have been conducted using small-scale batch or flow reactors, limiting their applicability to real-world conditions. In this study, a pilot-scale sandbox reactor was employed to simulate realistic groundwater conditions and assess the removal of sulfanilamide, a model organic contaminant. Various electrode configurations were systematically evaluated to identify the key operational parameters influencing pollutant removal efficiency, providing insights for practical applications in groundwater treatment. This study proposes three configurations, including a single well with the anode and cathode, a double well with the separated anode and cathode, and an e-barrier with electrodes separately mounted inside a permeable barrier. Single well had the lowest removal efficiency (60%) because cathodic reaction inhibited the anodic oxidation. A double well with a separate anode and cathode can achieve 80% removal efficiency. However, effluent pH can reach up to 13.2, which can adversely impact groundwater. Meanwhile, the e-barrier not only achieved complete removal, but also maintained a neutral pH of 7.0 over 30 days. The e-barriers proved to be the most effective configuration based on their removal efficiency (100%) while yielding an effluent with neutral pH. The energy consumption of the e-barrier was most effective at 1.54 kWh/m 3 , while the other configurations were 5.40 and 22.18 kWh/m 3 . E-barriers are deemed a very reasonable configuration, both in terms of removal efficiency and practical application in groundwater., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Improving the living condition of residents of Palladan and Basawa community requires access to drinking water. The main objectives of this paper are to identify suitable groundwater zones for productive drilling and to assess groundwater mineralization in the coastal aquifers of the study area. Geographic Information Systems (GIS) and Analytical Hierarchy Process (AHP) were used in the methodology to generate the groundwater potential map. Slope, landcover/land use, lineament density, rainfall, soil cover and drainage density were taken into account to characterize the groundwater potential zones. Weights were assigned to the various parameters and their characteristics according to their impact on groundwater recharge. The groundwater potential map was classified into five zones namely: poor, fair, moderate, good, excellent. Based on the lineament density map, the distribution of these lineaments reveals the degree of porosity or permeability in each area and, consequently, its groundwater potential. Aeromagnetic data filtering permits the construction of a structural map that illustrates various geophysical lineaments that are known to be fault systems in the research area. These faults are the main routes via which groundwater seeps into the subsurface and granitoid-type magnetic rocks intrude into the basement. The research region is badly fractured/failed and made up of four lithologic units, including the aquifer layer (clayey sands in the cracked basement) with thicknesses varying from 12-55 m, according to the vertical electrical sounding (VES) applications. According to geoelectric cross-sections, the subsurface structures are made of granitic rocks that are surrounded by normal faults that trend both NW and NE. It is believed that groundwater flows into the hard rock aquifers in the studied locations through these notable geological features, such as faults and fractures. Two phenomena are responsible for the mineralization of water: a process of interaction between water and rock; and a process of salinization resulting from natural phenomena or anthropic activities. The present study could guide hydrogeological investigations and groundwater resource management planning in the study area., (© 2024. The Author(s).)