High Groundwater Research Articles

A Case Study of Using Numerical Analysis to Assess the Slope Stability of National Freeways in Northern Taiwan

Taiwan is located at a junction of tectonic plates, which results in frequent earthquakes. Its terrain is mostly hilly, and its rainfall ranks among the highest in the world. Each of these elements affects the stability of slopes in various regions of Taiwan. Several slopes along Taiwan’s Freeway 1 and 5 have experienced landslides and rockfalls. It is imperative that the slope stability of these national freeways be analyzed to avoid future slope collapses brought on by precipitation or other outside factors. Thus, three sites on Taiwan’s Freeway 1 and 5 were chosen for numerical slope stability analysis in this study. PLAXIS 2D CE (Version: 24.02.00.1144) finite element software was used in this study to simulate and analyze the safety of freeway slope protection projects. Displacements induced by normal and high groundwater levels were discussed. Moreover, a pseudo-static study of slope displacements under seismic conditions was performed. According to the results of the numerical study, the force operating on the slope was centered on the sliding surface when the groundwater level was normal, and it extended to the top when the groundwater level was high. By comparison, under seismic conditions, the force acting on the slope extended to the whole slope. Furthermore, the slope safety factor of Site 1 was greater than the design specification value in three different scenarios. This confirms that the slope protection project at Site 1 is effective.

Mapping the spatial transferability of knowledge-guided machine learning: Application to the prediction of drain flow fraction.

Machine learning (ML) methods continue to gain traction in hydrological sciences for predicting variables at large scales. Yet, the spatial transferability of these ML methods remains a critical yet underexamined aspect. We present a metamodel approach to obtain large-scale estimates of drain fraction at 10m spatial resolution, using a ML algorithm (Gradient Boost Decision Tree). Our variable of interest is drain, as artificial drainage of agricultural land is widespread in areas with high groundwater tables. Drainage has significant effects on the hydrological cycle, and impacts groundwater recharge, streamflow partitioning and nutrient transport. Drain flow is controlled by small-scale variations in topography, geology and groundwater depth, which presents challenges to its estimation at large scale. Drain fraction is the average ratio between drain flow and precipitation. The metamodel combines covariates based on topography, land use and geology with simulated drain fraction from 45 field-scalephysically-based hydrological models of Danish drain catchments. The 45 models were jointly calibrated against timeseries of drain flow observations. The metamodel was used to upscale predictions of drain fractions for the entirety of Danish agricultural land. This involved considerable extrapolation beyond the 45 drain catchments used for training, calling for an assessment of spatial transferability. To map transferability of the model, and distinguish areas where metamodel results are reliable or not, we used the concept of area of applicability (AOA). The AOA is determined from the similarity of covariate space covered by the training data compared to each prediction point, assuming a correlation between model performance and covariate similarity. AOA mapping showed 71% of Denmark's agricultural land falling within the AOA of the metamodel. The study presents a stepwise methodology to obtain national-scale results using a ML model trained on local-scale numeric models and an evaluation of its spatial transferability, highly relevant for decision-support purposes.

Active phytoextraction of toluene shifts the microbiome and enhances degradation capacity in hybrid poplar.

Hybrid poplars are widely recognized for their effectiveness in remediating subsurface aromatic hydrocarbon contaminants, including benzene, toluene, ethylbenzene, and xylene isomers (BTEX). While BTEX compounds are frequently found in the transpiration streams of poplars at contaminated sites, the microbial dynamics within these trees, particularly in response to hydrocarbon exposure, remain underexplored. This study utilized high-throughput amplicon sequencing to investigate the trunk microbiome in hybrid poplars at a field-scale toluene phytoremediation site. Across the plant growth season (spring to late summer), we observed a significant seasonal increase in bacterial diversity and richness, particularly in trees located in areas with the highest groundwater and in planta toluene concentrations. During late summer, the microbiomes of these trees were enriched with hydrocarbon-degrading taxa, including Acinetobacter, Pseudomonas, Burkholderia, Sandaracinobacter, and Allorhizobium-Rhizobium, and exhibited enhanced capacities for aerobic toluene degradation based on functional predictions. These findings reveal selective pressures exerted by hydrocarbons on endophytic microbial communities and underscore their role in mitigating volatile contaminant emissions. This study advances our understanding of microbial dynamics in phytoremediation systems and highlights the potential for leveraging endophytes to optimize contaminant degradation.

Study on Damage Characteristics and Failure Patterns of Sandstone Under Temperature–Water Interactions

In modern tunnel construction, complex environments with high geothermal gradients and abundant groundwater are frequently encountered. To investigate the damage and failure mechanisms of sandstone under the combined effects of temperature and water, uniaxial compression tests were conducted on sandstone at different temperatures (25 °C, 55 °C, 85 °C, and 95 °C) and soaking durations (0.5 h, 1 h, and 3 h). The acoustic emission (AE) signals and energy evolution during the damage and failure processes were analyzed, revealing the damage characteristics and failure mechanisms of sandstone. The results indicate the following: (1) As the temperature increases, under the 3 h condition, the water content of sandstone is highest at 55 °C, reaching 3.01%, and the thermal expansion effect of sandstone is not obvious. Under the conditions of 85 °C and 95 °C, the thermal expansion effect leads to a decrease in the water content, enhances the water absorption softening effect, increases the plastic deformation capacity of sandstone, and weakens its brittle failure capacity. (2) When soaked for 0.5 h and 1 h, the maximum acoustic emission ring count and maximum acoustic emission energy of sandstone increase initially, then decrease, and subsequently increase again as the temperature rises, while the cumulative acoustic emission ring count gradually increases with temperature. Under the 3 h soaking condition, the maximum ring count, maximum energy, and cumulative ring count of sandstone at all temperatures show a consistent increasing trend with temperature. (3) The increase in soaking time reduced the damage variable of sandstone, with the largest reduction of 54.17% under the 3 h condition. At different temperatures, the damage variable of sandstone was smallest at 55 °C, only 0.33. (4) Sandstone primarily experiences tensile failure under different temperatures and soaking times. The extension of soaking time promotes the development of shear cracks, while the increase in temperature can effectively promote the expansion of tensile cracks. The research results provide certain theoretical references for the damage and failure of surrounding rock in modern tunnel construction.

Modeling the impact of urbanization and climate change on groundwater flow pattern in Warri-Effurun area of the western Niger Delta

Warri-Effurun is one of the oil regions in the Niger Delta and has experienced industrial expansion with upsurge in population growth in the last five decades. The attendant effect of such growth is synonymous with more groundwater pumping needed to satisfy domestic, industrial and other purposes. The consequence is the subjection of aquifers to intensive abstraction of groundwater to meet the water needs of the inhabitants. The high demand for groundwater may be worsened by the climate change. The impact of climate change on groundwater is complex but can better be understood by modeling. The study used groundwater modeling software to understand groundwater flow pattern under high groundwater over-abstraction under climate change conditions. Model scenarios output revealed that pumping is sustainable when the aquifer was recharged with 2*10-4mm/year of precipitation and pumping rate of 6.1776m3/day, groundwater flow is towards the Warri River. However, flow direction was reversed when pumping rate was increased geometrically to 13,590.72m3/day with zero net recharge (drought conditions precipitated by climate change). The reversal in the flow direction is indicative of interaction between groundwater and river water. The implication is that contaminants may be transported from the river into the aquifer, consequently compromising groundwater quality and thus making it unsuitable for drinking. The study concludes that groundwater modeling is a better tool in understanding how stressed aquifer under the influence of climate change may respond to heavy groundwater over-pumping.

Modelling of shallow groundwater levels and interaction with drainage system and streams under the impact of climate change

ABSTRACT Under the impact of climate change, groundwater levels are anticipated to increase in temperate climatological zones with increased precipitation and sea level rise. Urban areas located at low elevations are especially at risk, and increased shallow groundwater levels can lead to flooding, water seepage into basements, capacity problems in water infrastructure, etc. Furthermore, old sewer systems can act as drains by allowing groundwater to seep into the sewer system. This process can artificially maintain the groundwater level low, and therefore if the sewer system is rehabilitated, the problems are even increased further if necessary solutions are not included in the planning process. In this article, we analyze an urban catchment in Aalborg, Denmark, which is currently facing problems with high groundwater levels. By simulating the groundwater interaction with sewer systems and watercourses, we show that the groundwater table can increase up to 1 m under the impact of sewer rehabilitation and climate change. This increase will lead to significant flood risk in the residential area. We propose multiple technical solution scenarios and evaluate their effectiveness, demonstrating how the impact of increasing groundwater levels can be mitigated through implementation of drains during sewer reconstruction, but not completely avoided.

Groundwater potential zones delineation in Oued Zdin basin using GIS, RS and hierarchical analysis process

Water scarcity poses a significant challenge, particularly in regions with limited rainfall such as Algeria, where groundwater plays a crucial role in supporting both daily life and economic activities. This research aims to evaluate the groundwater potential in the Oued Zdin basin in northern Algeria by utilizing advanced geomatics methods, particularly the Analytic Hierarchy Process (AHP). Through the integration of Remote Sensing (RS) and Geographic Information Systems (GIS), the study incorporates multiple datasets, including rainfall patterns, topography, geology, drainage networks, land use, and hydrological data to assess areas with high groundwater potential. By applying AHP, the study assigns relative importance to these factors, creating a groundwater potential map that classifies the region into very high, high, low, and poor potential zones. The results indicate that 7% of the basin has very high potential for groundwater recharge, 33% has high potential, while 56% is categorized as low potential, and 4% falls under poor potential. The accuracy of the results is validated through comparison with existing well data, which aligns with the identified high-potential zones. The research demonstrates that combining GIS, RS, and AHP is an effective approach for mapping groundwater potential, offering valuable insights for sustainable water resource management in areas experiencing water scarcity. This methodology presents a scalable model that can be applied to similar regions facing groundwater challenges.

Comparative study on genesis mechanism of high arsenic groundwater in typical alluvial plain of the Upper and lower Yellow River, China

Groundwater with naturally high‑arsenic (As) concentrations is a pervasive issue across several major plains (basins) traversed by the Yellow River in China. The genesis of this high-As groundwater and its interrelationships among different plains (basins) have consistently been focal and challenging topics for domestic and international experts. The study focuses on the Hetao Basin in the upper Yellow River and the North Henan Plain in its lower reaches. Selecting typical profiles within the study area, a comparative analysis is performed based on the hydrochemical and isotopic signatures of these profiles. This analysis elucidates the distribution patterns, formation environments, and hydrogeochemical evolution models of high-As groundwater under the influence of different sedimentary environments. The results demonstrate that the shallow groundwater in the upper Yellow River is progressively salinizing, and conversely, the lower reaches are exhibiting a gradual alkalization. Redox conditions, the degree of evaporative concentration, and the intensity of groundwater recharge can influence the distribution disparities of high-As groundwater in the upper and lower reaches of the Yellow River. High-As groundwater in the Hetao Basin of the upper Yellow River is predominantly affected by the strength of groundwater reduction. Conversely, in the North Henan Plain of the lower Yellow River, the chemical conditions of the groundwater are more intricate, with As enrichment being influenced by a confluence of factors such as redox conditions, evaporative concentration, and the intensity of groundwater replenishment.

Comparing Global Violations of Environmentally Critical Groundwater Discharge Thresholds

AbstractGroundwater is a crucial resource to support surface water bodies via groundwater discharge. In this study, we applied two methods of estimating global environmentally critical groundwater discharge, defined as the flux of groundwater to streamflow necessary to maintain a healthy environment, from 1960 to 2010: the Presumptive Standard stipulates that a standard proportion of groundwater discharge should be maintained at all timesteps, while the Q* is a low‐flow index that focuses on critical periods. We calculated these critical flow thresholds using simulated natural groundwater discharge, and estimated violations of the thresholds when human‐impacted groundwater discharge dropped too low. Our global assessment of the frequency and severity of violations over all timesteps in our study period showed that the Presumptive Standard estimated more frequent and severe violations than the Q*, but that the spatial patterns were similar for both methods. During low‐flow periods, when the relative importance of groundwater to support streamflow is greatest, both methods estimated similar magnitudes of violation frequency and severity. We further compared our results to a method of estimating environmentally critical streamflow, Variable Monthly Flow, which does not explicitly consider groundwater. From the differences in violation frequency between these groundwater‐centric and surface water‐centric methods, we evaluated the influence of including groundwater contributions to streamflow in environmental flow assessments. Our results show that including groundwater in such assessments is particularly important for regions with high groundwater demands in the drier climates of the world, while it is less important for regions with low groundwater demands and more humid climates.

Assessment of Aquifer Resistivity, Depth, and Thickness using Vertical Electrical Sounding (VES) in Parts of Bori Metropolis for Groundwater Exploration

Groundwater exploration is vital to guaranteeing a reliable water supply in both urban and rural locations. In Bori Metropolis, the growing demand for potable water necessitates a thorough examination of the aquifer system. Therefore, the purpose of this study is to determine the groundwater potential in Bori Metropolis by assessing aquifer resistivity, depth, and thickness using Vertical Electrical Sounding (VES). A total of 13 VES surveys were completed in the study region using the Schlumberger array. The apparent resistivity measurements were analyzed using 1D inversion techniques to determine aquifer depth and thickness. The results showed that aquifer resistivity values ranged from to at depths ranging from to . Aquifer thicknesses ranged from to , indicating a high groundwater potential in the area. The results indicate that the Bori Metropolis area comprises a well-defined aquifer system with a high potential for groundwater extraction. These findings give important information for future water resource management in the region.

Integrated geophysical investigations of groundwater for sustainable management in Faisalabad region of Pakistan

As global and local populations surge and climate change continue to disrupt surface and groundwater reservoirs, the urgent need arises to explore additional groundwater sources. Ensuring sustainable management necessitates the efficient identification of high-potential zones to meet escalating water demands. This study aims to delineate groundwater potential zones in Faisalabad District, Pakistan, utilizing a cost-effective geoelectrical resistivity survey method. Apparent resistivity data was collected using the Schlumberger electrode configuration and analyzed with the Interpex “IX1D v2 model” to determine true soil layer resistivities and thicknesses with average root mean square error of 5.12%. The results have revealed that the Aquifer thickness ranged from 13.35 to 165.59 m, and resistivity from 23.96 to 1125.0 Ωm. Hydraulic conductivity, transmissivity, and porosity of aquifers varied from 0.49 to 24.11 m/day (average 8.214 m/day), 35.67 to 1593.98 m2/day (average 567.771 m2/day), and 22.29 to 39.82% (average 37.465%), respectively. Integration of resistivity and geo-hydraulic properties data identified vertical electrical sounding (VES) points 1, 3, 4, and 6 as highly suitable for large-scale freshwater extraction due to having high groundwater potential repositories (coarse sand and gravel formations). Other points had varying suitability: VES points 7 and 8 for shallow wells only, VES points 5, 9, and 10 not recommended due to hard formations, and VES point 2 due to poor groundwater quality. This integrated approach has proven effective in assessing groundwater strata to support Sustainable Development Goal (SDG-3), making it applicable to other geographic locations and informing policy decisions for effective groundwater management.

Assessing inter-basin groundwater input to the Verlorenvlei estuarine lake using stable isotopes and hydrochemistry

Study region: Verlorenvlei Catchment (∼1 890 km2) is an agriculture-dominated area (∼43 % per km2) on South Africa’s west coast. This semi-arid region has variable rainfall and high evaporation rates, affecting the three major aquifers and Verlorenvlei – a RAMSAR-listed estuarine lake. Study focus: Natural processes (i.e., extended dry periods and evaporation) and anthropogenic activities (i.e., agricultural expansion and groundwater abstraction) have threatened Verlorenvlei’s ecological functions. Seasonal and spatial changes between the water sources (i.e., direct rainfall, surface water, and groundwater) supporting Verlorenvlei were determined using δ18O and δ2H isotopes and hydrochemical analyses. Inter-basin aquifer contribution was investigated to assist in explaining Verlorenvlei's slow recovery since the recent 2015 – 2018 Western Cape drought. New insights: A proportion of groundwater from outside the topographic and surface-water delineated catchment supports Verlorenvlei during the dry month of April (i.e., G30F Langvlei sub-catchment). Furthermore, Verlorenvlei experiences high evaporation (evaporation best fit line: δ2H = 12.49 x δ18O - 47.68, average δ2H value of 47.1 ‰ and average δ18O value of 7.64 ‰) compared to its feeding rivers. Two sandstone and shale-dominated sub-catchments exhibit overlapping groundwater δ18O and δ2H values and water types to the sub-catchment in the nearest vicinity of Verlorenvlei, suggesting a disproportionately high groundwater contribution from these sub-catchments to Verlorenvlei. Evaluation of Verlorenvlei’s water balance should consider both surface water and groundwater sources, particularly from inter-basin aquifer sources during prolonged droughts.

Identification and Validation of Groundwater Potential Zones in Al-Madinah Al-Munawarah, Western Saudi Arabia Using Remote Sensing and GIS Techniques

Groundwater is an essential water resource utilized for agricultural, industrial, and home applications. Evaluating the variability of groundwater is essential for the conservation and management of this resource, as well as for mitigating the reduction in groundwater levels resulting from excessive extraction. This study aimed to define the groundwater potential zones (GWPZ) in Al-Madinah Al-Munawarah, Western Saudi Arabia, utilizing remote sensing and geographic information system (GIS) techniques, alongside meteorological data. Seven thematic maps were produced based on the regulatory characteristics of geology, drainage density, height, slope, precipitation, soil, and normalized difference vegetation index (NDVI). The influence of each theme and subunit/class on groundwater recharge was evaluated by weighted overlay analysis, including previous research and field data. The groundwater potential map was created via the weighted index overlay approach within a GIS. The groundwater potentials were classified into three categories: very poor, moderate, and good zones. The low groundwater potential regions encompass 805.81 km2 (44.91%) of the research area, located in mountainous basement rocks, characterized by high drainage density and steep gradients. The moderate zones comprise 45.67% of the total area, covering 819.31 km2, and are situated in low-lying regions at the base of mountainous mountains. Conversely, the favorable zones, comprising 9.42% of the total area, span 169.06 km2 and are located within the alluvial deposits of the lowlands next to the Wadi Al-Hamd basin and agricultural farms. The results’ accuracy was confirmed by overlaying data from 26 wells onto the designated groundwater potential categories, revealing that all wells corresponded with regions of high groundwater potential. The generated map would contribute to the systematic and efficient management of groundwater resources in this area to meet the rising water demands of Al-Madinah. The groundwater potential map is one aspect of groundwater management. It is also very important to assess this potential further via groundwater temporal monitoring, groundwater balance, and modeling.

Real-time monitoring and numerical analysis of rainfall-induced slope instability

ABSTRACT The study of slope instability includes a detailed study of environmental conditions and soil’s geotechnical and hydrological parameters. In the present study, a thorough understanding of rainfall-induced slope instability is achieved by doing real-time monitoring on an unstable slope located in Shillong, Meghalaya, India. The area selected is prone to landslides due to heavy rainfall and because it is located in the wettest place on earth. The real-time monitoring involves observation of groundwater table variation, intensity of rainfall, soil suction, and their effects on the instability of an unsaturated slope. Boring data show that even if the area is in a hilly region, the groundwater table is very high. The effects of antecedent rain on the matric suction, which indirectly affected the stability of the unsaturated soil slope were noticed. The location of the irrometers helped us in assessing that the slope stability is affected by both the matric suction developed in the unsaturated shallow soil during rainfall and that developed due to the presence of high groundwater level. The displacements along the slope are independent of each other. The results of the numerical analysis show that the slope displacement is positively correlated with the principal strain and maximum shear stress, indicating that the infiltration of rainfall has a significant effect on the stress and strain associated with displacement.

Hydrochemical processes and fluoride enrichment patterns in high-fluoride geothermal water in the Weihe Basin, China

The enrichment of fluoride in the deep geothermal water of the Lantian – Bahe Formation in parts of the Weihe Basin in China is a potential health hazard for the millions of inhabitants of this region. We conducted hydrochemical and hydrogeological analyses of water samples from 31 geothermal wells in the Weihe Basin, with the aims of determining the distribution characteristics, enrichment patterns, hydrochemical processes, and the factors influencing the geochemistry of deep geothermal fluids. We also evaluated the potential health hazards of fluoride ions in these fluids. Our results show that geothermal fluids with high fluoride content are widely distributed in the deep aquifers of the Weihe Basin. The principal hydrochemical types are: HCO3–Na and SO4⋅HCO3⋅Cl–Na. We used hydrodynamic simulation and regression analysis to show that the high proportion of HCO3– in the geothermal water facilitates the precipitation of Ca2+ and the dissolution of fluorine-bearing minerals. The high temperature, alkaline environment, cation exchange reactions, and dissolution and precipitation processes lead to Ca2+ depletion, which facilitates the release of fluoride ions from the surrounding rocks into the geothermal fluids. A human health risk assessment shows that the hazard quotient (HQ) values of geothermal water for adult males, adult females, children, and infants are: 3.96 – 14.41 (median 6.55), 3.32 – 12.08 (median 4.50), 4.63 – 16.84 (median 5.50), and 7.48 – 27.22 (median 9.00), respectively. Infants are the most susceptible to the effects of high fluoride in groundwater due to their physiological characteristics. while the potential health risks of F− for children and adult women/men are relatively low. Therefore, in the process of developing deep geothermal water, it is necessary to prevent it from mixing into shallow drinking water as much as possible. If the fluoride ion content in the shallow water exceeds the standard, it may have an impact on the local environment and residents' health. These findings provide a scientific foundation for the effective management of high fluoride groundwater in the Weihe Basin and analogous regions elsewhere.

Snowmelt-mediated isotopic homogenization of shallow till soil

Abstract. The hydrological cycle of sub-arctic areas is dominated by the snowmelt event. An understanding of the mechanisms that control water fluxes during high-volume infiltration events in sub-arctic till soils is needed to assess how future changes in the timing and magnitude of snowmelt can affect soil water storage dynamics. We conducted a tracer experiment in which deuterated water was used to irrigate a plot on a forested hilltop in Lapland, tracked water fluxes of different mobility and monitored how the later snowmelt modifies the labelled soil water storage. We used lysimeters and destructive soil coring for soil water sampling and monitored and sampled the groundwater. Large spatiotemporal variability between the waters of different mobility was observed in the subsurface, while surface water flow during the tracer experiment was largely controlled by a fill-and-spill mechanism. Extensive soil saturation induced the flow of labelled water into the roots of nearby trees. We found that labelled water remained in deeper soil layers over the winter, but the snowmelt event gradually displaced all deuterated water and fully homogenized all water fluxes at the soil–vegetation interface. The conditions required for the full displacement of the old soil water occur only during a snowmelt with a persistently high groundwater table. We propose a conceptual model where infiltration into the soil and eventual soil water replenishment occur in three stages. First, unsaturated macropore flow is initiated via the surface microtopography and is directed towards the groundwater storage. The second stage is characterized by groundwater rise through the macropore network, subsequent pore water saturation and increased horizontal connectivity of macropores. Shallow subsurface lateral fluxes develop in more permeable shallow soil layers. In the third stage, which materializes during a long period with a high groundwater table and high hydrological connectivity within the soil, the soil water is replenished via enhanced matrix flow and pore water exchange with the macropore network.

Mobilization and enrichment of geogenic iodine in a floodplain groundwater system: New insights from sources and characterization of dissolved organic matter

High iodine groundwater occurs widely in the lower reaches of Yellow River floodplain, which has aroused public concern. The biogeochemical behavior of dissolved organic matter (DOM) plays a crucial role in the mobilizing iodine from aquifer media. In this study, the molecular composition of DOM in groundwater characterized by FT-ICR-MS, and the optical properties of organic matter obtained by combining three-dimensional fluorescence spectroscopy and parallel factor analysis (EEM ⁃ PARAFAC), were used to elucidate the effect of DOM on the migration and enrichment of iodine in groundwater in the eastern Henan Plain, which is located in the lower reaches of Yellow River floodplain, Northern China. The results show that，the total iodine concentration in groundwater in the study area is ranged from 4.68 to 1598 μg/L, and the average value was 216.4 μg/L. High iodine groundwater shows a distribution pattern along the Paleochannels of Yellow River, which is closely related to the richness of organic matter in the buried sediments of the Paleochannels of Yellow River. Organic matter in the sedimentary aquifers plays an important role in regulating the mobilization and enrichment of iodine, and its degradation process is conducive to the release of iodine. DOM components in high iodine groundwater are more homogeneous, more unsaturated, and has more aromatic molecules than those in low iodine groundwater. The activation of organic iodine in groundwater system may be accompanied by the degradation of N+ aliphatic compounds (CHON, CHONSP and CHON) and the formation of oxygen-poor highly unsaturated phenols (CHOSP, CHOP and CHOS) organic compounds. In addition to biodegradation, the adsorption of iron oxide rich in sedimentary aquifers can partially remove the high AI and O/C components of DOM in groundwater and enrich the remaining OPHUP components. The findings provide new insights into the coupling mechanism between iodine release and DOM in aquifers.

Controls on regional sulphate distribution in shallow groundwater in the western Canadian Interior Plains

Sulphate (SO4), predominantly derived from sulphur (S)-bearing glacial sediments distributed widely across the Canadian Interior Plains, contributes to high groundwater salinity and can be detrimental to riparian and dry-land ecosystems, agricultural production, and water use. While previous researchers investigated SO4 distribution and dynamics in shallow groundwater at local scales (<1500 km2), we examine SO4 occurrence in groundwater at larger scales, and to depths of ∼150 m, considering variations in geology, glacial history, climate, and geochemical and hydrogeological settings in the Canadian province of Alberta. Sulphate concentrations in groundwater vary considerably, with 15 % of 139,130 samples above the 500 mg/L Canadian drinking water aesthetic objective. Analysis of δ34SSO4 and δ18OSO4 from 179 wells throughout Alberta shows SO4 is dominantly derived from oxidation of S-bearing material. At this large scale, marine shale bedrock subcrops, glacial ice flow directions, and climate control SO4 distribution. Groundwater contains less SO4 (<200 mg/L) in western Alberta compared to the east due to a lack of S-bearing bedrock, higher groundwater recharge rates, thinner glacial sediments, and increased groundwater circulation. Focusing on a region in south-central Alberta (Red Deer area), hydrogeological characteristics relating to SO4 formation, recharge, permeability, hydraulic gradient, and travel time are included in a principal component analysis to identify six groundwater groups at varying stages of evolution and SO4 concentrations depending on their hydrogeological setting. Low SO4 concentrations are associated with areas of high recharge, where SO4 has been leached from the sediments, or with more evolved bedrock groundwater where SO4 has been reduced or was recharged in pre-glacial times. High SO4 concentrations are found in areas of lower recharge and permeability, where flushing occurs more slowly. Combining the Red Deer area and province-wide analyses, we identify seven regions across Alberta with characteristic distribution and controls on SO4 occurrence in shallow groundwater.

Monitoring groundwater vulnerability for sustainable water resource management: A DRASTIC-based comparative assessment in a newly township area of Bangladesh

Groundwater is a vital source of freshwater in our daily lives. Global and local groundwater quality are degrading due to rapid urbanization, human interference, and policy variations, which is prominent in developing nations like Bangladesh. The major purpose of this research is to analyze aquifer vulnerability in Bangladesh's north-central area (Mymensingh) using conventional and modified DRASTIC modeling. Seven influencing hydrogeological factors were employed to develop and integrate conventional DRASTIC modeling: soil media, net recharge, aquifer depth, aquifer media, topography, hydraulic conductivity, and influence of vadose zone, while land use and lineament density were used with them for modified DRASTIC modeling. The findings from four vulnerability analysis detected 29.56% (93.35 sq.km), 22.24% (83.12 sq. km), 28.52 (106.93 sq. km), and 37.6% (140.55 sq.km) of the study area as high to very high vulnerable zones for groundwater pollution. Lower groundwater depth, higher hydraulic conductivity, moderate to high groundwater recharge, dense lineaments, dense settlement, agricultural land, and inland waterbodies together might indicate a high vulnerability in the research area. The validation results based on EC and nitrate levels show that conventional (r = 0.884, p ≤ 0.01; r = 0.951, p ≤ 0.01) and modified DRASTIC models (r = 0.868, p ≤ 0.01; r = 0.840, p ≤ 0.01) have a stronger association with unconfined aquifers, than confined aquifers. Modification with both additional parameters showed more accuracy compared to the conventional one. Frequent monitoring of groundwater quality in high and moderately vulnerable zones is recommended for earlier detection and prevention of potential aquifer degradation.

Iodine Nutrition Status of Children Aged 3–13 Years in Areas with High Groundwater Iodine Content in China

BackgroundAdequate iodine status is crucial for children's health and normal development. However, there is a paucity of research on the iodine status of children from areas with high groundwater iodine content. ObjectivesThe objectives of this were to monitor the iodine status of children in Shandong, China (regions primarily characterized by high iodine concentrations in groundwater) and describe the factors influencing children's iodine status. MethodsA cross-sectional study was conducted from 2013 to 2023 on 3253 3- to 13-y-old children. We collected drinking water, spot urine, and 24-h urine samples from children to assess their iodine status [measuring drinking water iodine concentration (WIC), water iodine intake (WII), urine iodine concentration (UIC), 24-h urine iodine excretion (24-h UIE), daily iodine intake (DII), etc.], and analyzed influencing factors. ResultsThe median WIC for children was 183 (IQR: 70.2, 362) μg/L, and the median spot UIC was 428 (IQR: 194, 737) μg/L, surpassing the WHO cutoff (300 μg/L). Children at risk of iodine excess numbered 1750 (61.8%). Approximately 61% of iodine intake came from drinking water. Boys had significantly higher iodine intake than girls (P < 0.001). Children's age showed positive correlations with spot UIC, 24-h UIC, and 24-h UIE. There were no significant differences in 24-h UIC and 24-h UIE among children with different BMIs. The logistic regression model revealed that the risk of iodine excess was increased by boy gender, increment in age (OR: 1.05; 95% CI: 1.02, 1.08), and every 10 μg (OR: 1.04; 95% CI: 1.03, 1.04) or 50 μg (OR: 1.19; 95% CI: 1.16, 1.22) increment in WII. ConclusionsChildren in areas with high groundwater iodine content are at a risk of iodine excess. As age increases, the risk of iodine excess in children rises, with boys at a higher risk than girls.