Ground Water[JOURNAL]
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200 papers
Sampling in Long-Screened Wells: Issues, Misconceptions, and Solutions.
Day-Lewis FD, Mackley RD, Bence R
Ground Water · 2024 · PMID 39219098 · Publisher ↗
The issues associated with long-screened wells (LSWs) (and open boreholes) at contaminated sites are well documented in the groundwater literature but are still not fully appreciated in practice. As established in semina...
The issues associated with long-screened wells (LSWs) (and open boreholes) at contaminated sites are well documented in the groundwater literature but are still not fully appreciated in practice. As established in seminal and review papers going back over three decades, the interpretation of sampling results from LSWs is challenging in the presence of vertical hydraulic gradients and borehole flow; furthermore, LSWs allow for vertical redistribution of contamination between aquifer layers. Acknowledgment of these issues has led to the development of new technologies and well designs to enable discrete-zone monitoring (DZM), yet LSWs remain common for many reasons, for example, as multipurpose wells, for geophysical logging, and (or) as legacy installations. Despite the literature on LSWs and despite the adoption of DZM at many sites, the use of LSWs persists and the challenges of interpreting sampling results from LSWs remain. In this issue paper, we provide a conceptual overview of the problems posed by LSWs and review existing literature and past work to improve the interpretation of sampling in LSWs. We draw on experience from previous studies at the Hanford Site in eastern WA, USA, and use synthetic examples to illustrate key concepts and challenges for interpretation. A recently published analytical modeling framework is used to develop illustrative synthetic examples and demonstrate a workflow for building scientific intuition to understand issues around interpreting samples from LSWs, which is critical to effective characterization and groundwater remediation at sites with LSWs.
The Effective Vertical Anisotropy of Layered Aquifers.
Bakker M, Bot B
Ground Water · 2025 · PMID 39150282 · Full text
Many sedimentary aquifers consist of small layers of coarser and finer material. When groundwater flow in these aquifers is modeled, the hydraulic conductivity may be simulated as homogeneous but anisotropic throughout t...
Many sedimentary aquifers consist of small layers of coarser and finer material. When groundwater flow in these aquifers is modeled, the hydraulic conductivity may be simulated as homogeneous but anisotropic throughout the aquifer. In practice, the anisotropy factor, the ratio of the horizontal divided by the vertical hydraulic conductivity, is often set to 10. Here, numerical experiments are conducted to determine the effective anisotropy of an aquifer consisting of 400 horizontal layers of which the homogeneous and isotropic hydraulic conductivity varies over two orders of magnitude. Groundwater flow is simulated to a partially penetrating canal and a partially penetrating well. Numerical experiments are conducted for 1000 random realizations of the 400 layers, by varying the sequence of the layers, not their conductivity. It is demonstrated that the effective anisotropy of the homogeneous model is a model parameter that depends on the flow field. For example, the effective anisotropy for flow to a partially penetrating canal differs from the effective anisotropy for flow to a partially penetrating well in an aquifer consisting of the exact same 400 layers. The effective anisotropy also depends on the sequence of the layers. The effective anisotropy values of the 1000 realizations range from roughly 5 to 50 for the considered situations. A factor of 10 represents a median value (a reasonable value to start model calibration for the conductivity variations considered here). The median is similar to the equivalent anisotropy, defined as the arithmetic mean of the hydraulic conductivities divided by the harmonic mean.
MS Students Are the Missing Link in the Future of Hydrogeology - And How You Can Help!
Ferre T
Ground Water · 2024 · PMID 39150261 · Publisher ↗
Abstract loading — click title to view on PubMed.
Utility of an Instantaneous Salt Dilution Method for Measuring Streamflow in Headwater Streams.
Rogers KM, Fair JB, Hitt NP … +3 more , Kessler KG, Kelly ZA, Briggs M
Ground Water · 2025 · PMID 39136448 · Publisher ↗
Streamflow records are biased toward large streams and rivers, yet small headwater streams are often the focus of ecological research in response to climate change. Conventional flow measurement instruments such as acous...
Streamflow records are biased toward large streams and rivers, yet small headwater streams are often the focus of ecological research in response to climate change. Conventional flow measurement instruments such as acoustic Doppler velocimeters (ADVs) do not perform well during low-flow conditions in small streams, truncating the development of rating curves during critical baseflow conditions dominated by groundwater inflow. We revisited an instantaneous solute tracer injection method as an alternative to ADVs based on paired measurements to compare their precision, efficiency, and feasibility within headwater streams across a range of flow conditions. We show that the precision of discharge measurements using salt dilution by slug injection and ADV methods were comparable overall, but salt dilution was more precise during the lowest flows and required less time to implement. Often, headwater streams were at or below the depth threshold where ADV measurements could even be attempted and transects were complicated by coarse bed material and cobbles. We discuss the methodological benefits and limitations of salt dilution by slug injection and conclude that the method could facilitate a proliferation of streamflow observation across headwater stream networks that are highly undersampled compared to larger streams.
Septic Return Flow Pathlines, Endpoints, and Flows Based on the Urban Miami-Dade Groundwater Model.
Valencia ME, Sukop MC, Oldfield G … +8 more , Montoya A, Walsh V, Obeysekera J, Barquin S, Kelly E, Hagemann K, Karim A, Guzman OF
Ground Water · 2024 · PMID 39113498 · Publisher ↗
Miami-Dade County (MDC) has over 112,000 septic systems, some of which are at risk of compromise due to water table rise associated with sea level rise. MDC is surrounded by protected water bodies, including Biscayne Bay...
Miami-Dade County (MDC) has over 112,000 septic systems, some of which are at risk of compromise due to water table rise associated with sea level rise. MDC is surrounded by protected water bodies, including Biscayne Bay, with environmentally sensitive ecosystems and is underlain by highly transmissive karstic limestone. The main objective of the study is to provide first estimates of the locations and magnitudes of septic return flows to discharge endpoints. This is accomplished by leveraging MDC's county-scale surface-groundwater model using pathline analysis to estimate the transport and discharge fate of septic system flows under the complex time history of groundwater flow response to pumping, canal management, storms, and other environmental factors. The model covers an area of 4772 km in Southeast Florida. Outputs from the model were used to create a 30-year (2010 to 2040) simulation of the spatial-temporal pathlines from septic input locations to their termination points, allowing us to map flow paths and the spatial distribution of the septic flow discharge endpoints under the simulated conditions. Most septic return flows were discharged to surface water, primarily canals 52,830 m/d and Biscayne Bay (5696 m/d), and well fields (14,066 m/d). Results allow us to identify "hotspots" to guide water quality sampling efforts and to provide recommendations for septic-to-sewer conversion areas that should provide most benefit by reducing nutrient loading to water bodies.
Numerical Modeling of Recovery of Moisture from the Unsaturated Zone: A Feasibility Study.
Mukhopadhyay A, Akber A, Bhandary H
Ground Water · 2025 · PMID 39101766 · Publisher ↗
Numerical modeling of the recovery of moisture by injecting warm air in the unsaturated zone in a 100 m × 100 m plot of agricultural land in Kuwait, a country located in an arid environment, was conducted to provide "pro...
Numerical modeling of the recovery of moisture by injecting warm air in the unsaturated zone in a 100 m × 100 m plot of agricultural land in Kuwait, a country located in an arid environment, was conducted to provide "proof of concept" of the technique. If technically and economically feasible, it will be a potential additional source of water that could be exploited for farming activities and other uses. The COMSOL software was used to develop the model and, based on the results of the scenario runs, the effects of different hydraulic and operational parameters, including that of well spacing, on moisture recovery were assessed. In general, the results suggested that the recovery should increase with the increase in the hydraulic conductivity of the unsaturated zone, the amount of heat input, and the pressure differential between the unsaturated zone and the well head. Within the period examined (0 to 11 days), the recovery decreases with the increase in the soil moisture content, possibly due to the fall in relative permeability to moisture-rich air with the increased water contents in the pore spaces, although the effects may change over a longer period as water contents decrease with moisture recovery. The moisture recovery from the unsaturated zone through the injection of warm air appears to be a feasible proposition from this study that should be demonstrated through a pilot scale experiment in the field.
Enhanced Removal of Brine From Porous Structures by Supercritical CO.
Erramuspe IBV, Asafu-Adjaye O, Rojas-Márquez M … +3 more , Via B, Sastri B, Banerjee S
Ground Water · 2025 · PMID 39045759 · Publisher ↗
Supercritical CO (sCO) removes water from brine held in pumice stone at levels well above the solubility of water in sCO. The higher water removal results from a combination of passive emulsification of water in sCO and...
Supercritical CO (sCO) removes water from brine held in pumice stone at levels well above the solubility of water in sCO. The higher water removal results from a combination of passive emulsification of water in sCO and viscous fingering of sCO through the saturated pumice. This leads to higher levels of salt deposition than that expected from solubility considerations alone. These deposits could impact the injectivity of sCO as well as its movement in the subsurface. The finding that the water concentration in sCO is not necessarily capped at the solubility limit should influence the parametrization of injection models.
Parameter ESTimation With the Gauss-Levenberg-Marquardt Algorithm: An Intuitive Guide.
Fienen MN, White JT, Hayek M
Ground Water · 2025 · PMID 39041717 · Publisher ↗
In this paper, we review the derivation of the Gauss-Levenberg-Marquardt (GLM) algorithm and its extension to ensemble parameter estimation. We explore the use of graphical methods to provide insights into how the algori...
In this paper, we review the derivation of the Gauss-Levenberg-Marquardt (GLM) algorithm and its extension to ensemble parameter estimation. We explore the use of graphical methods to provide insights into how the algorithm works in practice and discuss the implications of both algorithm tuning parameters and objective function construction in performance. Some insights include understanding the control of both parameter trajectory and step size for GLM as a function of tuning parameters. Furthermore, for the iterative Ensemble Smoother (iES), we discuss the importance of noise on observations and show how iES can cope with non-unique outcomes based on objective function construction. These insights are valuable for modelers using PEST, PEST++, or similar parameter estimation tools.
Using Expert Participation to Evaluate the Accuracy of Hand-Drawn Water-Table Maps.
Marshall SK, Peeters LJM, Batelaan O … +2 more , Noorduijn S, Velterop T
Ground Water · 2025 · PMID 39023076 · Full text
Water-table maps are fundamental to hydrogeological studies and a manual, hand-drawn method is still commonly used to produce them. Despite this, the accuracy and variability of such maps have received little attention i...
Water-table maps are fundamental to hydrogeological studies and a manual, hand-drawn method is still commonly used to produce them. Despite this, the accuracy and variability of such maps have received little attention in international literature. In a unique experiment, 63 groundwater professionals drew water-table equipotential contours based on the same dataset of point measurements and were asked to infer flow directions and predict groundwater elevations at predefined locations. The root mean squared error (RMSE) for the average map calibration data was 10.5 m, which is accuracy comparable to numerical groundwater models. This study confirmed that to produce hand-drawn water-table maps, practitioners seek to not only fit the spatial data, but also to conform to their own cognitive model of hydrogeological concepts and processes. The calibration accuracy increased with experience; from a RMSE of 13.3 m for practitioners with 0-3 years of experience to a RMSE of 9.2 m for those with four or more years. Despite considerable variability in the style of the hand-drawn water-table maps, the maps were consistent in their representation of the dominant regional groundwater flow directions. There was less consensus, however, in predicting the direction of surface water-groundwater interaction for a stream reach. Hand-drawn water-table mapping remains useful and valid, especially as a starting point for hydrogeological conceptualization, yet further work is required to resolve issues around transparency, repeatability, and reproducibility.
Semi-Analytical Modeling of Transient Stream Drawdown and Depletion in Response to Aquifer Pumping.
Malama B, Lin YF, Kuhlman KL
Ground Water · 2024 · PMID 38961724 · Publisher ↗
Analytical and semi-analytical models for stream depletion with transient stream stage drawdown induced by groundwater pumping are developed to address a deficiency in existing models, namely, the use of a fixed stream s...
Analytical and semi-analytical models for stream depletion with transient stream stage drawdown induced by groundwater pumping are developed to address a deficiency in existing models, namely, the use of a fixed stream stage condition at the stream-aquifer interface. Field data are presented to demonstrate that stream stage drawdown does indeed occur in response to groundwater pumping near aquifer-connected streams. A model that predicts stream depletion with transient stream drawdown is developed based on stream channel mass conservation and finite stream channel storage. The resulting models are shown to reduce to existing fixed-stage models in the limit as stream channel storage becomes infinitely large, and to the confined aquifer flow with a no-flow boundary at the streambed in the limit as stream storage becomes vanishingly small. The model is applied to field measurements of aquifer and stream drawdown, giving estimates of aquifer hydraulic parameters, streambed conductance, and a measure of stream channel storage. The results of the modeling and data analysis presented herein have implications for sustainable groundwater management.
Conceptualizing Controlling Factors for PFAS Salting Out in Groundwater Discharge Zones Along Sandy Beaches.
Hort HM, Robinson CE, Sawyer AH … +6 more , Li Y, Cardoso R, Lee SA, Roff D, Adamson DT, Newell CJ
Ground Water · 2024 · PMID 38940354 · Publisher ↗
Understanding fate and transport processes for per- and poly-fluoroalkyl substances (PFAS) is critical for managing impacted sites. "PFAS Salting Out" in groundwater, defined herein, is an understudied process where PFAS...
Understanding fate and transport processes for per- and poly-fluoroalkyl substances (PFAS) is critical for managing impacted sites. "PFAS Salting Out" in groundwater, defined herein, is an understudied process where PFAS in fresh groundwater mixes with saline groundwater near marine shorelines, which increases sorption of PFAS to aquifer solids. While sorption reduces PFAS mass discharge to marine surface water, the fraction that sorbs to beach sediments may be mobilized under future salinity changes. The objective of this study was to conceptually explore the potential for PFAS Salting Out in sandy beach environments and to perform a preliminary broad-scale characterization of sandy shoreline areas in the continental U.S. While no site-specific PFAS data were collected, our conceptual approach involved developing a multivariate regression model that assessed how tidal amplitude and freshwater submarine groundwater discharge affect the mixing of fresh and saline groundwater in sandy coastal aquifers. We then applied this model to 143 U.S. shoreline areas with sandy beaches (21% of total beaches in the USA), indirectly mapping potential salinity increases in shallow freshwater PFAS plumes as low (<10 ppt), medium (10-20 ppt), or high (>20 ppt) along groundwater flow paths before reaching the ocean. Higher potential salinity increases were observed in West Coast bays and the North Atlantic coastline, due to the combination of moderate to large tides and large fresh groundwater discharge rates, while lower increases occurred along the Gulf of Mexico and the southern Florida Atlantic coast. The salinity increases were used to estimate potential perfluorooctane sulfonic acid (PFOS) sorption in groundwater due to salting out processes. Low-category shorelines may see a 1- to 2.5-fold increase in sorption of PFOS, medium-category a 2.0- to 6.4-fold increase, and high-category a 3.8- to 25-fold increase in PFOS sorption. The analysis presented provides a first critical step in developing a large-scale approach to classify the PFAS Salting Out potential along shorelines and the limitations of the approach adopted highlights important areas for further research.
An Imputation Method for Simulating 3D Well Screen Locations from Limited Regional Well Log Data.
Kourakos G, Pauloo R, Harter T
Ground Water · 2024 · PMID 38934581 · Publisher ↗
In groundwater modeling studies, accurate spatial and intensity identification of water sources and sinks is of critical importance. Precise construction data about wells (water sinks) are particularly difficult to obtai...
In groundwater modeling studies, accurate spatial and intensity identification of water sources and sinks is of critical importance. Precise construction data about wells (water sinks) are particularly difficult to obtain. The collection of well log data is expensive and laborious, and government records of historic well log data are often imprecise and incomplete with respect to the precise location or pumping rate. In many groundwater modeling studies, such as groundwater quality assessments, a precise representation of the horizontal and vertical distribution of well screens is required to accurately estimate contaminant breakthrough curves. The number of wells under consideration may be very large, for example, in the assessment of nonpoint source pollution. In this paper, we propose an imputation framework that allows for proper reconstruction of missing well data. Our approach exploits available information and tolerates data gaps and imprecisions. We demonstrate the value of this method for a subregion of the Central Valley aquifer (California, USA). We show that our framework imputes missing values that preserve statistical properties of available data and that remain consistent with the known spatial distribution of well screens and pumping rates in the three-dimensional aquifer system.
Estimation of Effective Fracture Aperture in Glacial Tills by Analysis of Dye Tracer Penetration.
Ouf M, Jørgensen PR, Mosthaf K … +1 more , Rolle M
Ground Water · 2025 · PMID 38924523 · Full text
This study advances a methodology to estimate effective apertures of fractures in glacial tills based on dye tracer infiltration tests and numerical simulations. The approach uses the visible penetration depth of the dye...
This study advances a methodology to estimate effective apertures of fractures in glacial tills based on dye tracer infiltration tests and numerical simulations. The approach uses the visible penetration depth of the dye tracer along fracture flow paths as primary information to calculate effective fracture apertures. Further data used in the calculation are the dye tracer input concentration and retardation, the duration of the tracer injection, and the hydraulic gradient applied to control the infiltrating water fluxes. The method does not require measurement of hydraulic conductivity for the fractured till and enables direct observation of flow and transport patterns within the fractures (e.g., uniform flow and dye tracer distribution, channeling due to aperture variability, and presence of biogenic macropores in fractures). The approach was successfully verified by using the estimated effective fracture aperture values in Large Undisturbed Columns (LUCs) to consistently simulate both the observed LUC effluent breakthrough of a conservative bromide tracer and the water fluxes with the hydraulic gradient applied in the experiments. Sensitivity analyses revealed that estimation of small effective fracture apertures (<10 μm) required accurate determination of the dye tracer retardation factor. By contrast, in the case of larger effective apertures (>20 μm), the sensitivity of the estimated effective fracture aperture to variations in the porous material and solute transport parameters was low compared to the dominant sensitivity to the water flow through the fractures (cubic relation between flow and aperture). The proposed approach may be extended beyond laboratory applications and assist in characterizing field-scale fracture networks.
Ghislain de Marsily: An Appreciation.
Simmons CT
Ground Water · 2024 · PMID 38922848 · Publisher ↗
Abstract loading — click title to view on PubMed.
Structural Uncertainty Due to Fault Timing: A Multimodel Case Study from the Perth Basin.
Bardot K, Lesueur M, Siade AJ … +2 more , Lang SC, McCallum JL
Ground Water · 2025 · PMID 38899427 · Full text
Faults can fundamentally change a groundwater flow regime and represent a major source of uncertainty in groundwater studies. Much research has been devoted to uncertainty around their location and their barrier-conduit...
Faults can fundamentally change a groundwater flow regime and represent a major source of uncertainty in groundwater studies. Much research has been devoted to uncertainty around their location and their barrier-conduit behavior. However, fault timing is one aspect of fault uncertainty that appears to be somewhat overlooked. Many faulted models feature consistent layer offsets, thereby presuming that block faulting has occurred recently and almost instantaneously. Additionally, barrier and/or conduit behavior is often shown to extend vertically through all layers when a fault may in fact terminate well below-ground surface. In this study, we create three plausible geological interpretations for a transect in the Perth Basin. Adjacent boreholes show stratigraphic offsets and thickening which indicate faulting; however, fault timing is unknown. Flow modeling demonstrates that the model with the most recent faulting shows profoundly different flow patterns due to aquifer juxtaposition. Additionally, multiple realizations with stochastically generated parameter sets for layer, fault core, and fault damage zone conductivity show that fault timing influences flow more than layer or fault zone conductivity. Finally, fault conduit behavior that penetrates aquitards has significant implications for transport, while fault barrier behavior has surprisingly little. This research advocates for adequate data collection where faults may cause breaches in aquitards due to layer offsets or conduit behavior in the damage zone. It also promotes the use of multiple geological models to address structural uncertainty, and highlights some of the hurdles in doing so such as computational expense and the availability of seamless geological-flow modeling workflows.
Seasonal Groundwater Level Dynamics in Unconfined Aquifers across the United States.
Stahl MO, Mar T, Jameel Y
Ground Water · 2024 · PMID 38855911 · Publisher ↗
Groundwater hydrographs contain a rich set of information on the dynamics of aquifer systems and the processes and properties that influence them. While the importance of seasonal cycles in hydrologic and environmental s...
Groundwater hydrographs contain a rich set of information on the dynamics of aquifer systems and the processes and properties that influence them. While the importance of seasonal cycles in hydrologic and environmental state variables is widely recognized there has yet to be a comprehensive analysis of the seasonal dynamics of groundwater across the United States. Here we use time series of groundwater level measurements from 997 wells from the National Groundwater Monitoring Network to identify and describe groundwater seasonal cycles in unconfined aquifers across the United States. We use functional data analysis to obtain a functional form fit for each site and apply an unsupervised clustering algorithm to identify a set of five distinct seasonal cycles regimes. Each seasonal cycle regime has a distinctive shape and distinct timing of its annual minimum and maximum water level. There are clear spatial patterns in the occurrence of each seasonal cycle regime, with the relative occurrence of each regime strongly influenced by the geologic setting (aquifer system), climate, and topography. Our findings provide a comprehensive characterization of groundwater seasonal cycles across much of the United States and present both a methodology and results useful for assessing and understanding unconfined groundwater systems.
The Hydraulic Evolution of Groundwater-Fed Pit Lakes After Mine Closure.
Moser B, Cook PG, Miller AD … +2 more , Dogramaci S, Wallis I
Ground Water · 2024 · PMID 38829279 · Publisher ↗
Open pit mining frequently requires regional water tables to be lowered to access ore deposits. When mines close, dewatering ceases allowing the water table to recover. In arid and semi-arid mining regions, the developin...
Open pit mining frequently requires regional water tables to be lowered to access ore deposits. When mines close, dewatering ceases allowing the water table to recover. In arid and semi-arid mining regions, the developing pit lakes are predominantly fed by groundwater during this recovery phase and pit lakes develop first into "terminal sinks" for the surrounding groundwater system. With time, the re-establishment of regional hydraulic gradients can cause pit lakes to develop into throughflow systems, in which pit lake water outflows into adjacent aquifers. In this study, we use numerical groundwater modeling to aid process understanding of how regional hydraulic gradients, aquifer properties, net evaporation rates, and pit geometry determine the hydraulic evolution of groundwater-fed pit lakes. We find that before the recovery of the regional water table to its new equilibrium, pit lakes frequently transition to throughflow systems. Throughflow from pit lakes to downstream aquifers can develop within two decades following cessation of dewatering even under low hydraulic gradients (e.g., 5 × 10) or high net evaporation rates (e.g., 2.5 m/year). Pit lakes remain terminal sinks only under suitable combinations of high evaporation rates, low hydraulic gradients, and low hydraulic conductivities. In addition, we develop an approximate analytical solution for a rapid assessment of the hydraulic status of pit lakes under steady-state conditions. Understanding whether pit lakes remain terminal sinks or transition into throughflow systems largely determines the long-term water quality of pit lakes and downstream aquifers. This knowledge is fundamental for mine closure and planning post-mining land use.
A Case Study for Determination of the Best Underground Dam Sites, Bursa Province, Turkey.
Aras E, Boz B, Vaheddoost B … +1 more , Yılmaz D
Ground Water · 2024 · PMID 38816964 · Publisher ↗
Water constitutes an indispensable resource vital for sustaining life. In this context, groundwater stands out as a paramount global water source. Throughout history, underground dams (UGDs) have been employed to augment...
Water constitutes an indispensable resource vital for sustaining life. In this context, groundwater stands out as a paramount global water source. Throughout history, underground dams (UGDs) have been employed to augment the storage capacity of local aquifers. This study employs a multistep elimination approach to identify optimal locations for constructing UGDs in the Bursa district, Turkey. Initially, the Digital Elevation Model (DEM) is utilized to pinpoint the potential construction sites at the watershed scale. Criteria such as suitable topographic slope range, proximity to the transport infrastructures, presence of natural or artificial reservoirs, distance to active or inactive faults, proximity to the urban and rural settlements, location of the irrigation zones, geological conditions, distance to the consumption hubs, thickness of alluvium layer, and the groundwater depth are used to establish the buffer zones for exclusion of potential sites. Then, storage volume in the proposed sites is determined, and formal requests from the local communities are taken into consideration for determining the best UGD sites. The study concludes that five UGDs for irrigation and one for drinking water purposes could be recommended for further implementation.
Groundwater Contamination in Arid Coastal Areas: Qatar as a Case Study.
Shomar B, Sankaran R
Ground Water · 2024 · PMID 38629132 · Publisher ↗
The Arab region is located in an arid environment and suffers from water scarcity and poor water quality which are expected to become more severe in coming years due to global warming. In this study, the groundwater qual...
The Arab region is located in an arid environment and suffers from water scarcity and poor water quality which are expected to become more severe in coming years due to global warming. In this study, the groundwater quality of 205 wells in Qatar was investigated. The physical parameters of pH, electrical conductivity (EC), total dissolved solids (TDS), salinity, inorganic carbon (IC), and organic carbon (OC) were determined. The study characterized the concentrations of major anions of Cl, F, Br, NO, PO, and SO, and major cations of Ca, K, Mg, and Na. Importantly, metals and metalloids including V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Ba, Pb, and U were determined. The results revealed that the groundwater of all wells is not drinkable due to high salinity (average TDS 4598 mg/L and salinity 0.4%, respectively). Additionally, average concentrations of major anions Cl, SO, and F were 1472, 1064, and 1.9 mg/L, respectively, and all exceed the World Health Organization (WHO) guidelines for drinking water. However, NO concentration in 11 out of 205 wells was above the WHO guidelines of 50 mg/L due to intensive agriculture and fertilizer applications. Major cations of Ca, K, Mg, and Na were higher than WHO guidelines with average concentrations of 345, 63, 127, and 923 mg/L, respectively. All trace metals were much lower than the WHO guidelines for drinking water; however, the vanadium (V) average concentration in groundwater of all wells was 31 μg/L, which is five times higher than the Dutch guidelines (whereas the WHO has no guidelines for V). The groundwater of Qatar is dominated by Ca and Mg sulfates in Sabkha environments and dominated by NaCl in the coastal zones from evaporate environments consisting of coastal salt flats, salt pans, estuaries, and lagoons supersaturated by salts and the influence of sea water intrusion.
Noble Gas Analyses to Distinguish Between Surface and Subsurface Brine Releases at a Legacy Oil Site.
Segal DC, Visser A, Bridge C
Ground Water · 2024 · PMID 38613255 · Publisher ↗
Attributing the sources of legacy contamination, including brines, is important to determine remediation options and to allocate responsibility. To make sound remediation decisions, it is necessary to distinguish subsurf...
Attributing the sources of legacy contamination, including brines, is important to determine remediation options and to allocate responsibility. To make sound remediation decisions, it is necessary to distinguish subsurface sources, such as leaking oil and gas ("O&G") wells or natural upward fluid migrations, from surface releases. While chemical signatures of surface and subsurface releases may be similar, they are expected to imprint specific dissolved noble gas signatures, caused by the accumulation of terrigenic noble gases in subsurface leaks or re-equilibration of noble gases following surface releases. We demonstrate that only a historic surface release influenced the dissolved noble gas signature of groundwater in monitoring wells contaminated with brine near an abandoned O&G well, rather than subsurface leakage from the well. Elevated brine concentrations were associated with lower terrigenic helium concentrations, indicating re-equilibration with atmospheric helium at the surface during the release. Geophysical surveying indicating elevated salinity in surficial soils upgradient of the wells further supported the interpretation of the noble gas data. Eliminating the possibility that subsurface leakage was the source of the plume was critical to selecting the proper remedial action at the site, which otherwise may have included an unnecessary and costly well re-abandonment. This study demonstrates the use of noble gas analysis to compare potential sources of brine contamination in groundwater and to exclude subsurface leakage as a potential source in an oilfield.
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