Groundwater Flow Research Articles

Interaction regimes of surface water and groundwater in a hyper-arid endorheic watershed on Tibetan Plateau: Insights from multi-proxy data

The interaction between surface water and groundwater is crucial for the management of water resources and the preservation of ecosystems within arid basins, but knowledge on their interaction regimes at the watershed scale remains relatively limited. The present research synthesizes a range of multi-proxy data, including satellite thermal infrared remote sensing, water piezometric level, hydrochemical analyses, and isotopic signatures (2H, 18O and 222Rn), to elucidate the interaction dynamics and patterns between surface water and groundwater within a representative hyper-arid closed basin on Tibetan Plateau. The findings indicate that the water in the basin originates primarily from the glacier/snow melt water and precipitation in the mountainous regions, and would experience multiple but spatially heterogeneous interactions between river and aquifers from the mountain pass to the tail salt lakes after entering the basin. Water interaction in the piedmont alluvial plain is dominated by the pattern of river seepage into aquifers with a water flux of 25.82 m3/s, which drives the development of hierarchical groundwater flow systems in the basin. The interaction pattern converts to groundwater discharge of the local groundwater flow system at the front of alluvial fan plain, which forms the principal spring-fed rivers and the predominant overflow zone in the basin with the groundwater discharge flux of 3.22 m3/s. Most of these discharged groundwaters would infiltrate back into the aquifers in the middle-upper part of the loess plain with the river water leakage flux of 2.89 m3/s. River water and phreatic groundwater present a gradual enrichment of hydrochemcial components and water stable isotopes (2H and 18O) along the flow path due to the intense evaporation in the loess plain. The multiple water interactions between surface water and groundwater lead to the anomalous distribution of fresh water in the middle-lower stream area, which is related to the intermediate groundwater flow system and the local variable groundwater flow system. Water interaction in the lowest salt-marsh plain is in the pattern of regional groundwater flow system discharge into the tail salt lakes under natural condition, but evolves to only discharge into the artificial brine extraction canals rather than the tail salt lakes after decades of brine exploitation. Our findings provide a conceptual and preliminarily quantificational understanding of the interaction regimes between surface water and groundwater in large arid closed basins at the watershed scale.

Comparison of methods measuring electrical conductivity in coastal aquifers

Coastal aquifers, the transition zone between freshwater and saltwater, show large salinity contrasts in the subsurface. Salinity is a key parameter to understand coastal groundwater flow dynamics and consequently also geochemical and microbial processes. For mapping porewater salinity, a variety of methods exists, mainly using electrical conductivity as a proxy. We investigate methods including hydrological/geochemical (well sampling, fluid logger) as well as geophysical method (direct push, geoelectrics) utilising measurements near the high-water line of a high-energy beach at the North Sea island of Spiekeroog. We compare the methods, discuss their benefits and limitations and assess their spatial and temporal resolution. One key to enable a comparison is the estimation of formation factors transforming bulk conductivity measured by geophysical tools in to fluid conductivities obtained from direct measurements. We derive depth-dependent formation factors derived from time-series measurements of fluid loggers and a vertical electrode installation. Using these formation factors, the vertical electrode chain proves to provide reliable salinities at high spatial and temporal dimension. Direct-push profiling data provide the highest vertical resolution. However, a careful calibration is needed to allow for salinity quantification. On the other hand, electrical resistivity tomography (ERT) exhibits the lowest spatial resolution, but can image two-dimensional salinity distributions. We found ERT to fit very well to all other methods, but the data analysis should be aimed at salinities instead of bulk conductivities, i.e. including formation factors and temperature models into the inversion process.

Effectiveness and impact factors of passive convergence-permeable reactive barrier (PC-PRB): Insights from tracer simulation study

Passive convergence-permeable reactive barrier (PC-PRB) represents a green and sustainable technology for in-situ remediation of contaminated groundwater. A laboratory-scale PC-PRB tracer simulation system was established to quantify its contaminant plume capture performance using image analysis method. Results indicate that PC-PRB captures the plume 65% wider than C-PRB, which means that fewer PRB sizes and materials volume would be necessary to treat an equivalent contaminated plume. This improvement is due to a significant drawdown within the PC-PRB's passive well, known as the passive hydraulic decompression-convergent flow effect. We further evaluated the effects of water pipe length, hydraulic gradient, and media particle size on PC-PRB's plume capture performance. Results indicate that an increased water pipe length enhances the PC-PRB's plume capture capacity due to greater well drawdown. PC-PRB not only captures the plume but also acts as a hydraulic barrier. The retardation effect of PC-PRB on plume migration increases with water pipe length. Conversely, both hydraulic gradient and media particle size impact the plume capture capacity of PC-PRB by modifying groundwater flow velocity and pollutant dispersion. An increase in either hydraulic gradient or media particle size decreases the plume capture performance of PC-PRB. Therefore, PC-PRB technology may be more effective in contaminated sites characterized by low hydraulic gradients and permeability. Overall, PC-PRB demonstrates significant effectiveness in enhancing plume capture performance, which can notably reduce remediation costs and environmental footprint, broadening its application scope.

Ground Behavior of Parallel Tunnels in Response to Variations in Groundwater Flow

With the steady expansion of urban development, the importance of tunnel design and construction has increased, particularly with respect to changes in the groundwater level. Excavation without considering groundwater variations can destabilize tunnels; and this problem has been exacerbated by recent climate change-induced groundwater level fluctuations. This study evaluates the impact of various factors, such as filler width, lateral earth pressure coefficient, and groundwater flow, on tunnels by analyzing the ground behavior around parallel tunnels in Korea. The findings reveal that an increase in filler width reduces settlement and displacement, while the coefficient of lateral earth pressure affects convergence displacement to a higher degree than other settlements. Moreover, steady flow conditions are observed to wield a more pronounced impact on ground behavior than unsteady ones. These findings emphasize the importance of thoroughly evaluating groundwater flow characteristics during tunnel excavation and provide essential data for the future design and construction of parallel tunnels.

Geoelectrical resistivity mapping for sustainable groundwater management in Umuahia South: Insights from vertical electrical sounding

The study of geoelectrical resistivity provides critical insights into subsurface characteristics and aquifer dynamics, particularly in regions with varying geological formations. This research investigates the geoelectrical properties of the aquifer system in Umuahia South, highlighting its significance for sustainable groundwater management. The primary aim of this study is to characterize the geoelectrical layers, assess aquifer thickness and resistivity, and evaluate the implications for groundwater resource management. Vertical Electrical Sounding (VES) was conducted across ten locations to measure the resistivity and thickness of subsurface layers. The data collected were analyzed to identify distinct geoelectrical layers, their respective resistivity values, and thicknesses. The study reveals significant variations in aquifer properties across the region, with VES 1 showcasing the largest thickness of 69.2 m and VES 9 the smallest at 5.2 m. Aquifer thickness decreases from the Benin Formation toward the Ameki and Ogwashi-Asaba Formations. Hydraulic conductivity ranges from 0.207 to 0.954 m/day, indicating varying groundwater flow potential, while transmissivity values vary from 4.965 to 30.441 m²/day, with 60% of aquifers classified as intermediate. Groundwater Potential Index (GWPI) highlights approximately 70% of the area as high potential, underscoring the need for targeted management strategies to optimize water resource extraction and sustainability. The variability in resistivity and thickness across the study area suggests significant subsurface heterogeneity. High resistivity values indicate favorable conditions for groundwater flow, particularly in areas like VES 6. Conversely, lower resistivity in locations such as VES 9 indicates potential challenges for groundwater storage. This study provides vital information on the aquifer system in Umuahia South, emphasizing the need for targeted groundwater management strategies based on the geoelectrical characteristics identified. The research contributes to a deeper understanding of the aquifer dynamics in the region and offers a framework for sustainable groundwater resource management, highlighting the importance of geoelectrical assessments.

The John Mitchell Lecture 2022: thinking conceptually about groundwater problems

Many excavations and tunnels experience problems and instability caused by uncontrolled groundwater inflows or groundwater pressures that influence stability and soil behaviour. A range of groundwater control measures can be used to overcome these problems and create stable and workably dry conditions below groundwater level. A key challenge for designers is that the performance of the various different techniques is strongly influenced by the hydrogeological conditions at a site. Furthermore, the available ground investigation data may have data gaps or considerable uncertainty regarding key parameters such as hydraulic conductivity or hydraulic boundary conditions. This means that, when working with real-world data sets, there are some groundwater problems where analysis involves so many assumptions and uncertainties that the design outcomes are of little practical value. This paper will discuss how thinking conceptually about groundwater problems can be of great benefit when developing of groundwater control schemes, and that a robust conceptual model helps reduce the risk of designs being developed using inappropriate techniques. Historic examples from the 19 th Century and early 20 th century (before sophisticated methods of groundwater analysis were available) are described, where developing a conceptual understanding of groundwater conditions was vital in developing practical engineering solutions.

Combining WetSpass and MODFLOW to assess the groundwater recharge in the agricultural highlands of Ethiopia

Estimating the temporal and spatial patterns of recharge is crucial in Jedeb Watershed, which has shallow aquifers, a proliferation of wells, and limited observations. This paper uses the WetSpass-MODFLOW coupling to evaluate the groundwater recharge in the Jedeb watershed. The ArcGIS tool is used to build grid maps that contain the input data for the WetSpass-M model. These findings are then used to simulate the hydraulic head distribution in the groundwater flow simulation program MODFLOW. WetSpass-M calculated that long-term spatial and temporal average annual precipitation of 1394 mm is distributed as 99 mm (7.1%) groundwater recharge and 722 mm (51.79%) surface runoff, while 574 mm (41.11%) is lost through evapotranspiration. In such seasonal variations, the groundwater level due to the annual stress period varied from 2164.2 to 2213.1 m. The findings contribution could serve as a benchmark for future research by researchers, policymakers, and specialists in regional water resources.

Analytical investigation of porous medium effects on the flow of two micropolar fluids in a rotating annulus

Fluids with microstructures and microinertia play a vital role in microfluidics and nanfluidics system. One of such significant fluid is micropolar fluid. The characteristic behavior of micropolar fluid flow in conduit/pipe, etc. filled with porous medium helps us understand the flow behavior of biological fluids in porous media, groundwater flow in aquifiers, rotatory machines or viscometer. To understand such real-world problems, it is necessary to get into the mathematical model of such flow models. One such model with wide number of application is presented in this paper. This work investigated the flow of two micropolar fluids between the region formed by two concentric cylinders. Authors have considered inner cylinder to be at rest and outer cylinder rotating at a constant angular velocity. The region between two concentric cylinder is filled with an isotropic porous material. A slip condition at the outer wall and continuity conditions at interface of two fluids has been utilized to obtain an analytical solution for the proposed model. The numerical solution of the obtained solution for present problem is used to graphically analyze the motion of immisicble micropolar fluids rotating in an annulus filled with the porous medium. It is found that an outer cylinder has a notable influence on the flow behavior of immiscible micropolar fluids, contrary to the effect observed within the inner region. An analytical approach of this work not only helps us obtain precise results and analysis of the flow, but it also serves as a useful validation for future approximations within the scope of this work.

Longitudinal Investigation of Groundwater and Surface Water Interaction of Two Gravel Pit Lakes in Central Texas: Chemical and Flow Implications

Two gravel pit lakes in central Texas were examined over the course of two years with upgradient and downgradient piezometer installations. Groundwater and lake water were sampled bimonthly for nutrients, water levels, and groundwater chemistry, and in addition, rain and lake gauges and mini-piezometers were installed, depth surveys were conducted, and a simple 2D flow model was constructed. The project goal was evaluating and examining flow dynamics and chemical effects as groundwater flows to surface water and back to groundwater with the intent to understand the effects that gravel pit lake systems have on connected shallow groundwater. Both lake systems were shown to be flow-through systems that influence the water quality by decreasing the dissolved nutrients in the groundwater in their vicinity while oxygenating the water and altering the pH. However, the lakes are also prone to high levels of evaporation, meaning that minor improvements to water quality come at the cost of decreasing the quantity of water in storage within the aquifer. Similar groundwater and mine lake systems may show comparable tendencies, providing new information for water managers, regulators, and stake-holders about the potential roles that non-remediated gravel pit lakes may play in local ecosystems and aquifer dynamics.

Intensification of submesoscale frontogenesis and forward energy cascade driven by upper-ocean convergent flows

Upper-ocean fronts are an important component of the global climate system, regulating both the oceanic energy cycle and material transports. In the common paradigm, upper-ocean fronts are generated by frontogenesis at the mesoscale (20–300 km), driven predominantly by confluent horizontal flows initiated by a background straining field. However, the mechanisms by which this frontogenesis extends down to and influences the submesoscale (0.2–20 km), which dominates vertical transports in the ocean, are still understudied. Here, we provide direct observational evidence that submesoscale frontogenesis, defined as the rate at which submesoscale buoyancy gradients intensify, is closely linked to convergent flows. Analysis of year-long measurements by a mooring array in the North Atlantic indicates that both the upper-ocean frontogenetic rate and the horizontal convergence exhibit strong seasonality and scale dependence, with larger magnitudes in winter and at smaller horizontal scales (down to at least 2 km). The frontogenetic rate is found to correlate more strongly with horizontal convergence as the scale decreases, suggesting that convergent flows are the main driver of submesoscale frontogenesis. Crucially, a rapid forward cascade of kinetic energy and enhanced vertical velocities preferentially occur during periods of submesoscale frontogenesis. Our findings highlight a mechanism underpinning the key role of submesoscale fronts in the oceanic kinetic energy cascade and as a focus of vertical transports, and call for a parameterization of such effects in climate-scale ocean models.

A Systematic Review of the Current State of Numerical Groundwater Modeling in American Countries: Challenges and Future Research

In arid and semi-arid regions, groundwater is often the only available water source. However, overexploitation and pollution have led to a decrease in groundwater quantity and quality. Therefore, the proper management of groundwater resources is essential to promote sustainable development. Numerical simulation models (NSMs) have emerged as a valuable tool to address these challenges due to their ability to accurately and efficiently model groundwater systems. This study provides a comprehensive systematic review to evaluate the current knowledge on using numerical groundwater flow models for planning and water resource management in countries in the American region. A total of 166 research articles were published between the years 2000 and 2024. We analyzed and summarized details such as the study regions, numerical simulation methods and applied software, performance metrics, modeling units, modeling limitations, and prediction scenarios. In addition, we discuss alternatives to address the constraints and difficulties and suggest recommendations for future research. The continued research, improvement, and development of numerical groundwater models are essential to ensure the sustainability of groundwater resources.

Spatial thinking skills used by hydrogeology practitioners and students while completing a hydrogeology task

AbstractA typical classroom exercise in hydrogeology is to develop a conceptual model of a contaminated site, identify groundwater flow direction(s), and predict the location and mass of a contaminant plume. This requires knowledge of key hydrogeological concepts and is highly visuospatial in nature. Among multiple discrete spatial thinking skills identified by cognitive science, the combination of visual penetrative ability and working in multiple frames of reference were identified to significantly predict performance on a hydrogeology task and showed that together with hydrogeology knowledge, these spatial thinking skills account for 49% of the variability on task performance. Seventy-two hydrogeology practitioners and students with varying levels of expertise were administered multiple spatial thinking tests and an assessment of hydrogeology knowledge before completing a hydrogeology task that was developed for the study. Using spatial thinking and knowledge test scores as predictor variables, a hierarchical regression analysis was conducted with performance on the hydrogeology task as the outcome variable. The resulting model predicts that at low levels of hydrogeology knowledge, the identified spatial thinking skills account for more than a 25% difference on the hydrogeology task. This study provides empirical evidence that visual penetrative ability and working in multiple frames of reference are important skills in hydrogeology; thus, instructors are encouraged to recognize that underdeveloped spatial thinking skills could present hurdles for students and that targeted spatial thinking training may yield positive results for both weak and strong spatial thinkers.

Insight into performance and lifetime of ecofriendly pollution barriers in landfill for emergency: A thermogravimetric analysis for novel polymer materials

The novel polymer barrier wall is an in-situ remediation technology designed to effectively control the migration of pollution and prevent the diffusion of pollutants by blocking, sealing, or altering the direction of groundwater flow. With its advantages of rapid chemical reaction (achieving 95 % strength within 15 min) and portable equipment suitable for narrow and rugged emergency sites, this innovative polymer barrier demonstrates promising prospects for practical application. Hence, ensuring the long-term durability of new materials under corrosive and high-temperature leachate conditions is crucial. In this study, a comprehensive investigation was conducted on the corrosion and thermal aging performance of novel polymer materials. Firstly, the mechanical tensile properties of the polymer materials were examined after immersion in leachates, aiming to elucidate the degradation mechanism underlying these properties. Subsequently, thermogravimetric (TG) analysis was performed on the polymer materials immersed in various leachates. And the thermal stability and oxidation stability of novel materials were investigated using a thermogravimetric analyzer coupled with a Fourier transform infrared spectrometer (TG-FTIR). Based on the results obtained from thermal analysis, the service life of polymer materials under different pollutants was ultimately predicted utilizing the Arrhenius model. The findings indicate that the novel polymer materials exhibit commendable durability and pose little risk of causing secondary pollution.

Recent Advances (2018–2023) and Research Opportunities in the Study of Groundwater in Cold Regions

ABSTRACTIncreasing greenhouse gas levels drive extensive changes in Arctic and cold‐dominated environments, leading to a warmer, more humid, and variable climate. Associated permafrost thaw creates new groundwater flow paths in cold regions that are causing unprecedented environmental changes. This review of recent advances in groundwater research in cold environments has revealed that a new paradigm is emerging where groundwater is at the center of these changes. Groundwater flow and associated heat and solute transport are now used as a basis to understand hydrological changes, permafrost dynamics, water quality, integrity of infrastructure along with ecological impacts. Although major advances have been achieved in cold regions' cryohydrogeological research, the remaining knowledge gaps are numerous. For example, groundwater as a drinking water source is poorly documented despite its social importance. Lateral transport processes for carbon and contaminants are still inadequately understood. Numerical models are improving, but the highly complex physical‐ecological changes occurring in the arctic involve coupled thermal, hydrological, hydrogeological, mechanical, and geochemical processes that are difficult to represent and hamper quantitative analysis and limit predictive capacity. Systematic long‐term observatories where measurements involving groundwater are considered central are needed to help resolve these research gaps. Innovative transdisciplinary research will be critical to comprehend and predict these complex transformations.

Initiation of prefrontal convection within a Northeast China cold vortex: The roles of elevated front and dry air intrusion

AbstractConvective initiation ahead of a surface cold front within the Northeast China cold vortex of June 1, 2021, is investigated using observations and a convection‐permitting simulation. The initiation of the convection is elevated without identifiable surface mesoscale forcing. Air feeding the initial convective cells originates from at least 1 km above the ground where parcel‐based convective available potential energy is sufficiently large. An elevated front with large equivalent potential temperature gradient and flow convergence across is primarily responsible for the initiation of elevated convection and later organization into a deep convective line. The elevated front is similar to the upper cold front within extratropic cyclones studied elsewhere, but its altitude is lower in this case. Backward‐trajectory analysis of air parcels on the cold side of the elevated front shows that dry air intrusion reinforces the elevated front by increasing the equivalent potential temperature gradient and moment convergence across the front. The convergence forcing combined with access to convective unstable air at the leading edge of the westerly flows east of the elevated front causes the initiation of convection. The development and spreading of a surface cold pool help push the convective line eastward away from the surface cold front located to the west. Orographic gravity waves provide additional forcing so that convection cells are initiated first at the upward branches of the gravity waves, but the overall organization of initial cells into a solid convective line is controlled mainly by mesoscale structures associated with the elevated front.

Projection of land use and land cover changes based on land change modeler and integrating both land use land cover and climate change on the hydrological response of Big Creek Lake Watershed, South Alabama

Changing land use/land cover (LULC) and climate substantially affect the hydrological components of a watershed. This study explored the future impact of the hydrological responses due to the changing LULC and climate on the Big Creek Lake watershed in Alabama, USA, from 2021 to 2050 using the Soil and Water Assessment Tool (SWAT). Five climate model datasets were used under the moderate scenario (Representative Concentrative Pathways 4.5) and the extreme scenario (Representative Concentrative Pathways 8.5), and the datasets were downscaled and bias-corrected. In addition, changing the LULC of five categories was predicted by Cellular Automata Markov (CA- Markov). With these data combined with the elevation (Digital Elevation Model), soils, and weather data, the SWAT model was calibrated and validated for the studied watershed to quantify how climate change will affect streamflow, nitrogen, and phosphorus. Our results indicate streamflow will increase due to the 50-acre increase in urban LULC. As streamflow increases, the percolation, surface runoff, lateral flow, groundwater flow, and water yield will also increase because the streamflow impacts these hydrological components. Moreover, the increase rate in streamflow is the same for all the components for January, February, and March. Therefore, there is a strong correlation between these months. On the contrary, evaporation will be high in May, June, and July because of the increasing temperature and streamflow. However, the changes in the water hydrological parameters and total nitrogen and phosphorus will be more intense in RCP8.5 than in RCP4.5.

Groundwater-surface water exchanges in an alluvial plain in southern France subjected to pumping: A coupled multitracer and modeling approach

Study regionThe study was conducted in an alluvial plain between the Rhône and the Ouvèze Rivers (in the southeast of France) extensively exploited for drinking water. The research area is characterized by significant groundwater-surface interactions influenced by groundwater pumping activities. Study focusThe aim of this study is to enhance the understanding of interactions between rivers and alluvial aquifers by combined multi-tracer and numerical modeling approaches. Over an 18-month period, groundwater temperature, piezometric levels, and river surface water levels were continuously monitored. Field campaigns focused on conductivity, stable isotopes of water, and radon-222 activity concentration in both groundwater and surface water. Radon-222 was used to quantify water exchanges between the river and the aquifer. A MODFLOW model, calibrated using piezometric data and PEST, was employed to simulate groundwater flow and reactive transport of radon-222 using MT3DMS. New hydrological insights for the regionThe study reveals that river water recharges the aquifer, with radon-222 data delineating this recharge zone. The methodology extended the interpretation of periodic groundwater temperature signals to isotopic signals, allowing the identification of dispersivity and Darcy's velocity. The Ouvèze River was found to contribute approximately 55 % of the pumping water supply, alongside the Rhône. These findings provide valuable insights for sustainable water resource management, demonstrating the relevance of using natural tracers in scenarios where artificial tracers are impractical.

Electrical Resistivity Tomography and Boreholes Data to Investigate the Near-Surface Structure under the Campus Area of Çanakkale Onsekiz Mart University, Çanakkale, Turkey (Türkiye)

We study the soil foundation underneath the Çanakkale Onsekiz Mart University (ÇOMU) campus, Çanakkale, Türkiye by employing the electrical resistivity tomography – ERT supported by 27 boreholes data. The studied area taking place in southwest Marmara region was historically affected by large earthquakes () created by the North Anatolian Fault system. The boreholes data show that the near surface structure beneath the ÇOMU campus is made of mostly silty sands and marls. A high sensitivity resistivity instrument is used to collect the field data in which nine ERT profiles reaching lengths as long as 315 m are utilized. The current geoelectrical measurements are simulated by using two numerical models to estimate the inversion depth sensitivity from which it is found satisfactory in the depth range 0-30 m and then somewhat decreasing. The observed electrical resistivity values are in the range 2-160 W m. The geoelectrical structure corresponding to the silty sands are represented by low resistivities (<20 W m) while the high resistivity (>40 W m) depth sections are associated with the marl units. The resistivity structure beneath the ÇOMU campus is complex where both low and high resistivity depth sections reside side by side. The groundwater and clay mineralogy contribute to the broad changes in the subsurface resistivities. The groundwater flow below the steep terrain of the ÇOMU campus causes low resistivities (<10 W m) deeper than 10-m depth. The boreholes data superimposed on the two-dimensional (2-D) ERT profiles show consistency with the resistivity-depth distributions at corresponding depths.

Groundwater flow-controlled migration of dissolved microbial gas in the Eastern Hungarian Pannonian Basin

The formation of commercial microbial gas accumulations requires specific migration and accumulation conditions which can be effectively provided by groundwater flow systems. Namely, if microbial methane can be gathered and transported in aqueous solution over large lateral distances, great amounts of free gas can be exsolved where flows turn upward, causing a decrease in solubility. Based on this concept and the flow pattern of regional scale topography-driven groundwater flow systems, the present study built a simplistic 2D model in MS Excel including a methane solubility database with 32 000 data points. The model can calculate the required flow pathway length to saturate groundwater with methane, the amount of free gas that can be released in a potential accumulation zone and the necessary time interval for the whole process. Application of the model was demonstrated based on the geological and hydrogeological conditions of a study area in the Central Pannonian Basin (Hungary), focusing on the Hajdúszoboszló gas field. In light of the upscaled results of the 2D model, the known microbial gas accumulations of the study area could be charged according to the model. In addition, parameter sensitivity analysis also provided valuable insights into the complex mechanisms of microbial gas migration.

Groundwater Contamination by Heavy Metals in Malaysia: Sources, Transport, and Remediation Strategies

Groundwater contamination by heavy metals is a pressing environmental concern, particularly in regions highly dependent on groundwater as a freshwater source. While Malaysia primarily relies on river water, certain states and islands depend on groundwater for their supply. Research on heavy metal contamination in Malaysia’s groundwater remains limited, making it crucial to study the distribution and mobility of contaminants to develop appropriate remediation strategies. In addition to natural sources, anthropogenic activities such as landfills, mining, and the use of fertilizers contribute significantly to heavy metal pollution in groundwater. Factors like rainfall, fluctuating groundwater levels, and low soil pH can exacerbate heavy metal leaching into aquifers. Various models and techniques, including 2D resistivity imaging and MODFLOW, are used to assess groundwater flow and contaminant transport. These models suggest that contaminant concentrations decrease with increased depth and radial distance from pollution sources such as landfills and mining areas. The health risks associated with heavy metal exposure through groundwater consumption are significant, necessitating effective remediation strategies. Phytoremediation is an economical solution for groundwater containing low concentrations of heavy metals, while permeable reactive barriers may be suitable for more complex cases, pending detailed site investigation. This review aims to examine the current state of knowledge on heavy metal contamination in Malaysia’s groundwater, focusing on sources, distribution patterns, and movement of pollutants. It also seeks to evaluate existing remediation methods, including phytoremediation and permeable reactive barriers, while identifying gaps in research, particularly concerning risk assessments and heavy metal speciation.