Groundwater Salt Research Articles

Simulating the emergence of institutions that reverse freshwater salinization: An agent-based modeling approach

Salt concentration in global freshwater supplies has increased steadily, leading to the Freshwater Salinization Syndrome (FSS). To curb the FSS, stakeholders can self-organize to develop institutions, or a set of rules that limit salt emissions. This research develops an agent-based modeling framework to explore how institutions reverse the FSS. Property owners are represented as agents that apply rules of behavior to apply salt to deice pavement in response to winter weather, vote on institutions, and comply with or defect from institutions. Salt enters the soil-groundwater system through infiltration, which is modeled using a transit time distribution approach. Results demonstrate that stable institutions lead to positive economic outcomes for stakeholders, based on their ability to apply salt during winter events and access high-quality drinking water. Simulations are analyzed to explore institutions, or limits to the application of salt, that emerge based on the interactions of stakeholders as they agree on salt application limits, the intensity of monitoring for defectors, and sanctions. Institutions that emerge effectively limit the concentration of salt in drinking water. The emergence of stable institutions low rates of innovation among stakeholders, and the concentration of salt in groundwater exceeds standards due to high rates of defection among stakeholders. This research demonstrates how self-organized institutions can lead to sustainable application strategies that reverse the FSS.

Unraveling the hydrogeochemical characteristics and pollution sources of groundwater in an intensive industrial area, East China.

It is challenging to interpret hydrogeochemical datasets with complex natural and anthropogenic genesis in intensive industrial areas. This paper elucidates the hydrogeochemical characteristics and pollution sources of groundwater in an industrial park, East China, combining the self-organizing map (SOM), hydrochemical graphs, and correlation analysis. The results show that the total dissolved solids of groundwater range from 73.45 to 997.92mg/L and can be regarded as freshwater. The pH varies greatly from 6.44 to 9.90, most of samples belonging to weakly acidic-weakly alkaline. The groundwater can be classified into five clusters by SOM, representing the non- or least-polluted groundwater (cluster D), high salt groundwater (cluster A), high NH4+-N and HCO3- groundwater (cluster B), high Fe and Mn groundwater (cluster C), and high pH groundwater (cluster E), which were contaminated by industrial salts, historical agriculture activity, industrial reducing substances, and industrial alkali, respectively. The natural evolution of groundwater (cluster D) in the study area is mainly controlled by mineral weathering/dissolution. The contributions of calcite, dolomite, gypsum, halite, and silicate mineral to groundwater solute are 55.8-66.3%, 15.1-18.0%, 9.0-10.7%, 2.5-10.1%, and 2.3-9.4%, respectively, based on the mass conservation. The contaminated groundwaters (all other clusters except for cluster D) have different hydrochemical characteristics associated with the pollution sources. In addition, the relatively reductive environment in quaternary flu-lacustrine sediments favored the formation of high level of Fe, Mn, and NH4+-N in groundwater. This study provides a new insight into the characteristic contaminants and their distributions in groundwater and the associated pollution sources based on the large datasets in an intensive industrial area. The data evaluation methods and results of this study could be useful to the groundwater usage management and pollution control in this area and other industrial areas.

Assessment of groundwater quality and the effects of chromium residues in the vicinity of shutdown tanneries

Tanneries, among India’s earliest industries, historically used chromium (Cr) in leather and vegetable tanning, leading to unsuitable effluent discharge on land and in nearby water bodies. This research investigates chromium dispersion and accumulation in environmental and biological samples from the vicinity of closed tanneries in the Sembattu region, Tiruchirappalli district, South India. The study reveals chromium in sediment and biological samples but not in water samples. Sediment from S3 showed higher Cr concentration (132.65 ± 7.48 µg/g), with paddy straw 1 (18.72 ± 1.17 µg/g) and neem tree bark 3 (15.03 ± 1.04 µg/g) exhibiting higher plant concentrations. Among animals, cow dung 1 (143.93 ± 1.32 µg/g) and cow dung 5 (37.74 ± 1.28 µg/g) recorded higher concentrations. Geoaccumulation index (Igeo) values suggest “Uncontaminated-to-moderately contaminated” levels. The investigation reports permissible chromium concentrations in the Sembattu tannery area, yet groundwater salt levels exceed drinking water standards. The study highlights tanneries’ historical impact, stressing the need for increased awareness, strategic water management, and prudent land use planning. Future priorities include continuous monitoring, targeted remediation, community engagement, innovative research, and robust policy enforcement for sustainable environmental protection and resource management.

Feasibility of sustainability separation of drinking water network by groundwater desalination Bajestan urban catchment, Iran

Fresh water supply in arid land is facing many challenges that require proper management of water resources, especially in drinking water. Management of water projects depends on the conditions of each country or region. Bajestan is located in Razavi Khorasan province, Iran. The certain resource of drinking water supply is desalinated of high salinity groundwater from Playa. Government has implemented the project “Separation of Drinking and sanitary water networks by groundwater desalination” since of 2014, by creating “Government Drinking Water Withdrawal Smart Stations (GDWWSS)" in this city. This study evaluates the feasibility of different methods of separation drinking water from sanitary water by considering sustainability dimensions these methods. These methods including of Home Water Desalination Machines, Mobile Packaged Water, GDWWSS (with new design), Private Drinking Water Withdrawal Stations (PDWWS) and Dual Drinking Water Distribution Network (DDWDN). Findings showed, that if just the economic dimension is considered in the drinking water separation project, PDWWS would be the best method but since the social dimension is an integral part of a sustainable project, the most compatible method is DDWDN. The environmental evaluation showed that production of salt water and salt (NaCl) is the most common adverse effect of all the proposed methods, but the DDWDN will produce more salt wastewater. On the other hand, Mobile packaged water method will produce 17,000 tons of PET annually, which will cause biological problems if it is not recycled. Therefore, the best way is to use the water resources of the plain and not use the desalination of salt groundwater resources. Also, to increase people's satisfaction and reduce water consumption with good quality water, DDWDN is suggested.

Water, Salt, and Ion Transport and Its Response to Water-Saving Irrigation in the Hetao Irrigation District Based on the SWAT-Salt Model

Soil salinization is one of the main hazards affecting the sustainable development of agriculture in the Hetao Irrigation District (HID) of Inner Mongolia. To grasp the water and salt transport patterns and spatial–temporal distribution characteristics of the HID at the regional scale, the improved Soil and Water Assessment Tool with a salinity module (SWAT-Salt) model was used to establish the distributed water and salt transport model for the watershed in this study. The results demonstrated that the modified model could more accurately represent the process of water and salt changes in the HID. The coefficient of determination (R2) in the simulation of streamflow and discharge salt loading was 0.83 and 0.86, respectively, and the Nash–Sutcliffe efficiency (NSE) was 0.80 and 0.74, respectively. Based on this, different hydrological processes (surface runoff, lateral flow, groundwater, soil seepage) as well as spatial–temporal distribution characteristics of water salinity in groundwater and soil were analyzed in the HID. Differences in groundwater and soil salinity in different land uses and soil types were also compared. Of these, surface runoff and lateral flow salt discharge loading are concentrated in the southwestern portion of the basin, while groundwater salt discharge loading is concentrated in the eastern as well as southwestern portions of the basin. The salt discharge loading from groundwater accounts for about 98.7% of the total salt discharge loading from all hydrological pathways and is the major contributing part of salt discharge from the irrigation area. Soil salinity increases gradually from west to east. Groundwater salinity (2946 mg/L) and soil water electrical conductivity (0.309 dS/m) were minimized in the cropland. Meanwhile, rational allocation of irrigation water can appropriately increase the amount of salt discharge loading. In conclusion, the model could provide a reference for the investigation of soil salinization and water–salt management measures in irrigation areas.

Study on inverse geochemical modeling of hydrochemical characteristics and genesis of groundwater system in coal mine area - a case study of Longwanggou Coal Mine in Ordos Basin.

The exploitation of coal resources has disturbed the equilibrium of the original groundwater system, resulting in a perturbation of the deep groundwater dynamic conditions and hydrochemical properties. Exploring the formation of mine water chemistry under the conditions of deep coal seam mining in the Ordos Basin provides a theoretical basis for the identification of sources of mine water intrusion and the development and utilization of water resources. This paper takes Longwanggou Coal Mine as the research area, collects a total of 106 groups of water samples from the main water-filled aquifers, comprehensively uses Piper trilinear diagram, Gibbs diagram, ion correlation, ion ratio coefficient and mineral saturation index analysis, and carries out inverse geochemical modeling with PHREEQC software, so as to analyze the hydrochemical characteristics and causes of the main water-filled aquifers in deep-buried coal seams in the research area. The results show that the main hydrochemical processes in the study area are leaching and cation exchange, and the groundwater is affected by carbonate (calcite, dolomite), silicate (gypsum) and evaporite. Calculations of mineral saturation indices and PHREEQC simulations have led to the conclusion that the dissolution of rock salt and gypsum in groundwater accounts for most of the ionic action. Na+, Cl- and SO42- are mainly derived from the dissolution of rock salt and gypsum minerals, while Ca2+ and Mg2+ are mostly derived from the dissolution of dolomite and calcite. The results of the inverse geochemical modeling are consistent with the theoretical analysis.

Quantifying climate change impacts on future water resources and salinity transport in a high semi-arid watershed

High salinity mobilization and movement from salt-laden deposits in semi-arid landscapes impair soils and water resources worldwide. Semi-arid regions worldwide are expected to experience rising temperatures and lower precipitation, impacting water supply and spatio-temporal patterns of salinity loads and affecting downstream water quality. This study quantifies the impact of future climate on hydrologic fluxes and salt loads in the Gunnison River Watershed (GRW) (14,608 km2), Colorado, using the APEX-MODFLOW-Salt hydro-chemical watershed model and three different CMIP5 climate models projection downscaled by Multivariate Adaptive Constructed Analogs (MACA) for the period 2020–2099. The APEX-MODFLOW-Salt model accounts for the reactive transport of major salt ions (SO42−, Cl−, CO32−, HCO3−, Ca2+, Na+, Mg2+, and K+) to streams via surface runoff, rainfall erosional runoff, soil lateral flow, quick return flow and groundwater-stream exchange. Model results are analyzed for spatial and temporal trends in water yield and salt loading pathways. Although streamflow is primarily derived from surface runoff (65%), the predominant source of salt loads is the aquifer (73%) due to elevated concentrations of groundwater salt. Annual salt loading from the watershed is 582 Mkg, approximately 10% of the salt load in the Colorado River measured at Lee's Ferry, AZ. For future climate scenarios, annual salt loads from the watershed increased between 4.1% and 9.6% from the historical period due to increased salt loading from groundwater and quick return flow. From the results, applying the APEX-MODFLOW-Salt model with downscaled future climate forcings can be a helpful modeling framework for investigating hydrology and salt mobilization, transport, and export in historical and predictive settings for salt-affected watersheds.

Experiment and Simulation of Groundwater Salt Transport Based on Different Contact Relations in Heterogeneous Soil Layers

With the expansion of reserve cultivated land resources in coastal saline–alkali areas, the problem of soil salinization is becoming more and more prominent. In order to reveal the influence of different soil media and contact modes on soil water movement, a two-domain Hydrus-3D model was established to verify its performance in heterogeneous soil layers, and the characteristics of water, salt, and wet peak transport of surface soil and sandy soil under horizontal contact and inclined contact conditions were analyzed through experiments and simulations. The measured data show that in horizontal contact mode, probe 3 and probe 2 are close to the interface of the two layers of soil, and their maximum values are measured in about 60 min. The time difference between probe 1 and probe 2 is about 15 min. In the inclined contact mode, probe 4 in the topsoil reached 45% in 10 min and remained stable; the peak lag time of probes 3 and 2 was 10 min, and the peak lag time of probes 2 and 1 was 15 min; the water in the surface soil gradually increases and then stabilizes; and the water in the sand soil is similar to the normal curve. The salt characteristics in the surface soil are similar to the normal curve, while the salt characteristics in the sandy soil gradually increase and then stabilize. The simulation results show that the water content in the topsoil is more than 40%, and the maximum water content in the center of the sand is only 36.9%, which is roughly the same as the experimental results. The results showed that the Hydrus-3D model had a good simulation effect on the groundwater salt transport of heterogeneous soil under two contact methods. The RMSE value and E value are close to 0 and 1, respectively, indicating that the simulation has good feasibility and can be applied to the simulation of water and salt transport processes under different contact modes of soil media.

Characterization of subsurface pathways contributing to freshwater salinization of urban streams using electrical and electromagnetic imaging techniques

Salinization of inland fresh surface waters in temperate climates is a growing concern due to increasing salt inputs from sources including chloride (Cl)-containing road salt de-icers, industrial waste, and landfill leachate. Groundwater pathways play an important role in the year-round delivery of Cl to streams, but quantifying this pathway, including spatiotemporal variability and amount of Cl mass stored in the subsurface, is challenging. The objective of this study was to demonstrate, evaluate, and compare the potential applications of the geoelectrical techniques – electromagnetics (EM) and direct current (DC) resistivity – for mapping salt contamination in shallow urban groundwater and characterizing the groundwater pathways delivering Cl to urban streams. EM and DC surveys were conducted (3D mapping and 2D time-lapse) across a 20 m salt-impacted stream section and surrounding riparian zone that is located near an arterial road and parking lot. Groundwater samples and soil cores were also collected to validate the geoelectrical results. Both the EM and DC surveys detected high salt concentrations in the shallow subsurface (up to 3 m depth) near the road, parking lot, and stream; however, DC more accurately represented groundwater Cl concentrations. DC results were used to calculate the total Cl mass in the subsurface, with the spatial mass distribution used to infer the temporal variability in the subsurface salt plume. Finally, time-lapse DC showed that the highest groundwater salt concentrations existed near the stream between June and October – this is expected to contribute to the elevated salt concentrations in the stream during summer months. This study has shown that EM and DC can be useful for identifying groundwater salt concentration, storage, and transport in a non-intrusive and efficient manner, making them valuable field tools for characterizing and quantifying groundwater salt pathways to urban streams.

The sources, leaching, remediation, and environmental concerns associated with groundwater salinity.

Water resources management and sustainable development depend on the quality of groundwater as a major source of fresh water. As a result of rising water demand in emerging nations and overexploitation, groundwater quality has declined globally in many aquifers. One of the most significant elements that lower the quality of the groundwater is salinization. This review is to provide an overview of various materials that are used in the design and development of innovative chitosan-based nanocomposite polymeric membranes for desalination. Biodegradable, non-toxic, affordable, and easily available, with film-forming ability and poly-functionality, chitosan is an ideal material for a sustainable future. Membrane preparation for desalination using chitosan helps to provide antibacterial and antioxidant activities, great chelating capabilities, and strong adsorption capacity. In this research, we discuss a variety of concepts concerning the different sources of elevated salinity and available desalination methods. A comprehensive framework was also developed to understand the leaching and percolation of salt in groundwater, an essential component of managing risks and ensuring safety. Additionally, we explain the various remediation strategies for reducing groundwater's salt concentration and explore the best method for desalination specifically focused on chitosan.

Current hydrogeochemical profile of groundwater in the Middle Jurassic hydrogeological complex of the Lyaminsky oil and gas field

The aim of the study is to identify the influence of some parameters of the geological environment on the formation of the current hydrogeochemical profile in the Middle Jurassic hydrogeological complex (layers YU2-4) of the Lyaminsky oil and gas field in Western Siberia.The factors controlling the changes in the chemical composition of the groundwater (geotemperatures, influence of neotectonics, etc.) after the process of sedimentation and water accumulation were analysed on the basis of the lithogenetic theory of the transformation of the composition of groundwater during geological evolution. In the course of the research, correlation coefficients were obtained for the value of groundwater mineralisation in the complex with the modern and paleotemperatures of the Tyumen suite, the porosity coefficient and the depth of the foundation. The obtained results allowed assuming that the current hydrogeochemical profile of the Middle Jurassic hydrogeological complex is the result of the consistent action of the whole complex of factors. The results of the analysis showed that the influence of neotectonic processes on the current hydrogeochemical profile is quite probable. The reasons for the heterogeneity of mineralisation, apart from neotectonic processes, may be different, but in any case, the identification of relationships such as "Mineralisation - a parameter of the state of the geological environment" indicates a change in the concentration of salts in groundwater after their accumulation together with sediment.

Biogeochemical State of Salinized Irrigated Soils of Central Fergana (Uzbekistan, Central Asia)

The Central Fergana region is one of the overpopulated regions of Central Asia, which includes parts of Uzbekistan, Kyrgyzstan, and Tajikistan. Here, in the dry subtropical climate are the most ancient, irrigated oases used for agriculture. Fergana valley is the key to the food security of the region as a whole. The article provides information on diversity and chemical composition of newly developed, new and old-irrigated Calcisols soils formed on alluvial and alluvial–prolluvial sediments. Soils are poor with organic matter (0.37–0.81% of organic carbon), with high nitrogen content (C/N ratio is 4.92–5.79), and with neutral (7.01–7.30) pH values. Data on the content and the ratio of the key components of soil salinity (Na2CO3, Ca(HCO3)2, CaSO4, MgSO4, Na2SO4, NaCl) and the bulk content of salts in soils under different irrigation regimes are presented. It was shown that Na2CO3 concentration is minimal in all the soils, and this salt presents only in ground waters (0.100–0.135 g L−1). Newly irrigated soils are characterized by higher content of salts than old irrigated soils. All the soils investigated are characterized by increasing salinity rate within the soil depth with the highest content of all salts in ground waters. This chloride–sulfate type of salinization is most pronounced in all the soils studied. Gypsum content in agricultural soils results in limited water and nutrient retention and the potential for dissolution, primarily in response to irrigation. The soils of the Fergana Valley are also subjected to polychemical pollution, so the content of trace elements in them was studied. Irrigated meadow-takyr and meadow-saz soils show low levels of environmental hazard, but irrigation results in accumulation of such trace elements as nickel (30 mg kg−1), arsenic (11.75 mg kg−1), bromine (5.00 mg kg−1), antimony (1.48 mg kg−1), cesium (5.00 mg kg−1), and hafnium (2.97 mg kg−1). Irrigation also affects the soil texture and thus increases fine particle percentages in the superficial soil horizons. Thus, the complex chemical characteristics of salinized soils are presented for numerous irrigated landscapes of the region.

Impact of limestone caves and seawater intrusion on coastal aquifer of middle Andaman

Seawater intrusion has become a common problem in coastal and island aquifers with the rise in climate change that greatly affects the majority of developing countries. The island hydrology is very complex and associated with a unique set of environmental characteristics with the dynamic interaction of groundwater, surface water, and seawater. Further, Sea level rise, erratic rainfall, and over-extraction of groundwater triggered salt-water intrusion. A study on seawater intrusion and the effect of limestone caves on groundwater was carried out in middle Andaman using a combination of ionic ratios of major ions. A total of 24 samples and a reference sample from the sea were collected and analysed using ICP, spectrophotometer, and flame photometer. A combination of 10 ionic ratios Cl/HCO3, Ca/(HCO3 + SO4), (Ca + Mg)/Cl, Ca/Mg, Ca/Na, Cl/(SO4 + HCO3), Ca/SO4, K/Cl, Mg/Cl, and SO4/Cl was used to assess the dissolution of limestone minerals and the level of saltwater intrusion into groundwater. The geospatial method was used to extract and combine all the hydrogeochemical parameters and ionic ratios in the GIS platform. Durov plot was used for the interpretation of groundwater chemistry and the identification of natural processes controlling the hydrogeochemistry of the area. The dominance of Ca-HCO3 and Na-HCO3 was confirmed in 48% and 24% of the sample respectively. The equiline graph of chloride with other major ions showed the enrichment of alkali and alkaline earth metal salt in groundwater. Schoeller's diagram depicted the dominance of Cl, Ca, and the sum of CO3 and HCO3 in seawater near Mayabunder. The lower concentration of Na with respect to Cl (64%) and Ca (100%) showed the presence of a reverse ion exchange process. Further, the correlation matrix showed a strong relationship between Cl, K, Ca, and Na. The analysis of X-ray diffraction of the rock samples confirmed the presence of limestones such as Aragonite, Calcite, Chlorite, Chromite, Dolomite, Magnetite, and Pyrite in the study area. The integration of ionic ratios showed moderately affected and slightly affected saline regions in 44% and 54% of the region respectively. Finally, the role of tectonic activities and active lineaments connected to the sea was found to play a major role in the intrusion of seawater where interconnected faults created an opening for surface water to recharge groundwater leading to the deep aquifer.

Spatio-Temporal Evolution of the Ecological Environment in a Typical Semi-Arid Region of Northeast China

Increasing trends of groundwater and soil salinization, as well as desertification, is characteristic of many arid and semi-arid regions under climatic and anthropogenic influences. This has led to the implementation of management strategies to protect the ecological environment. Changling County in Northeast China is a typical semi-arid area that has experienced these changes. Thus, management strategies such as the “Three North Shelterbelt Project” which involves planting trees to reduce wind speed and halt desertification, and the Changling local alkaline land restoration project, from the year 2000, involving fencing of grasslands have been implemented in the area. Premised on the dynamic nature of the ecological environmental problems, this study was undertaken to assess the spatio-temporal evolution of the ecological environment using hydro-geochemical, spatial, remote sensing, and statistical techniques from the year 2001 to 2019. It was found that groundwater salinity was stable within the period due to groundwater exploitation that declined depth to groundwater table (DWT) thus reducing the impact of evaporation concentration of salts in groundwater. Salinized land area increased by about 6706 ha at a rate of 0.06%/year as a result of the reduction in the size of water bodies and swampland as the declining water table exposed shallow water to more evaporation. The effect of the conversion of water bodies and swamplands to salinized land is believed to overshadow the climatic influence of decreased evaporation-precipitation ratio that normally decreases soil salinization. Most of the study area was stable in terms of desertification (98.22%, 56,3497 ha) as significantly degraded lands covered only 0.03% (148 ha) of the area while 1.67% (9556 ha) had significantly increased vegetation, respectively. Precipitation had an insignificant relationship with desertification with irrigation believed to be the main driver of significant vegetation improvement. Water-saving irrigation practices and the growing of salt-tolerant or semi-tolerant crop species are recommended to maximize food production while stemming the environmental degradation trend due to declining DWT.

Comprehensive simulation of salinity transport in irrigated watersheds using an updated version of SWAT-MODFLOW

Salinity can have major detrimental impacts on soil health, crop yield, and environmental ecosystem services. In this paper we introduce SWAT-MODFLOW-Salt, a version of SWAT-MODFLOW that simulates the fate and transport of major salt ions (SO42−, Cl−, CO32−, HCO3−, Ca2+, Na+, Mg2+, K+) in watershed systems, and focus on its development and application to irrigated stream-aquifer systems. The modeling code accounts for water and salt mass storage in soils, aquifer, and streams, and the movement of water and salt mass in surface runoff, soil lateral flow, percolation and recharge, groundwater flow, and groundwater-surface water exchange. The model is applied to a highly managed, irrigated 700 km2 region of the saline Lower Arkansas River Valley in Colorado, USA. The model is tested against groundwater salt concentrations and in-stream salt mass loadings, and then used to quantify the impact of soil salinity on crop yield.

Investigation on the chloride ion erosion mechanism of cement mortar in coastal areas: From experiments to molecular dynamics simulation

• The influences of chloride ions on the phsysical and mechanical properties of cement mortar were analyzed. • The mechanism of bound and free chloride ions on the cement mortars properties were investigated in long-term erosion. • The effect of chloride ions in pores on C S H adsorption was investigated by molecular dynamics simulation. Chloride salts in groundwater are a serious threat to the durability of underground reinforced concrete structures in coastal areas. In order to effectively improve the durability performance of underground structural concrete in coastal areas, physical and mechanical properties such as compressive strength, water absorption rate and chloride ion permeability of cement mortar were studied. The influence laws of mineral additives such as fly ash, ground granulated blast-furnace slag and chloride ions on the relevant properties of cement mortar were analyzed. The effect of chloride ions on these physical and mechanical properties was investigated. The main hydration product categories of cement mortar were derived using microscopic analysis (XRD). The internal microstructure and the surface morphology of cement mortar were obtained by scanning electron microscopy (SEM). The effect of chloride ions in pores on C S H adsorption was studied by using molecular dynamics simulations. The results showed that chloride ion erosion increased the compressive strength of cement mortars doped with FA and GGBS at 28, 100, and 180 days by 2.76 %, 14.32 %, and 7.83 %, respectively. Chloride ion erosion moderately increased the compressive strength of cement mortar doped with FA and GGBS at all curing period. After chloride ion erosion, the electric fluxes of the four groups of specimens at 180 days decreased by 30.37 %, 31.64 %, 23.22 % and 17.41 %, respectively. After the addition of mineral additive, the bound chloride ions changed the influence law of water absorption rate of cement mortar, and reduced the electric flux of cement mortar. The molecular dynamics simulations revealed that the chloride ions in the pores weakened the physical adsorption of external chloride ions by C S H, resulting in the easier passage of external chloride ions through the pores. Microscopic analysis showed that the Friedel's salt generated by chloride ions attacking the cement-based materials filled communicating pores, which may be one of the reasons for the reduced electric flux of the cement mortar.

Impacts of Geological Formations on Quality of Groundwater

Sedimentary environment and impacts of geological formations on quality of groundwater in Navizak, Taleghan was studied. To examine sedimentary environment, we sampled formations and examined the samples at both microscopic and macroscopic scales. For hydrogeochemical analysis of water we used Piper, Stiff, Shuler, Wilcox, star, and composite diagrams. Saturation indices were analyzed using PHREEQC codes. The results indicate that hydrogeochemistry of groundwater at confined aquifers and aquitards is affected by geological formations of the region. At the north and northeast areas, aquitards are predominantly calcium bicarbonate layers. This layer is fed by Karaj formation and the quality observed in this zone is because the layer is located above the upper red formation (URF). The central and southern zones have waters of calcium-sulfate type with acceptable quality for drinking. This is the result of significantly thick layers of clay and marl which reduce hydraulic conductivity, improve water retention, and therefore, increase the amount of salts in groundwater. Although alluvial confined aquifers with layers of salt and gypsum lower the quality of groundwater, however, their undesirable effects can be neglected due to the narrow range of their presence.

Boron and lithium isotopic constraints on their origin, evolution, and enrichment processes in a river–groundwater–salt lake system in the Qaidam Basin, northeastern Tibetan Plateau

The Nalenggele River Catchment (NRC) is the largest river sourced from the northern slope of the Eastern Kunlun Mountains (EKM). The NRC terminates in the Qaidam Basin and feeds tail salt lakes. The river–groundwater system (freshwater) and the terminal salt lakes display high concentrations of B and Li, ranking the Qaidam Basin as a world–class mineral system. However, the source, pathway, and enrichment mechanism of these elements remain unclear. In this study, the B and Li isotopes from rivers and groundwater from mountain to basin were used to trace their origin and evolution processes. B and Li are found in high concentrations even in river and groundwater with low total dissolved solids (TDS), with average concentrations tens to hundreds times higher than those of natural freshwater systems. The observed B and Li isotopic footprints are significantly depleted in heavy isotopes in the NRC if compared to other geological systems dominated by natural weathering processes. Following the confluence of one of the main tributaries of the Hongshui River (HSR) sourced from the EKM, the B and Li concentrations increase sharply, while the δ11B and δ7Li values gradually decrease. This study indicates that the mechanism accounting for the B and Li endowment of the river–groundwater–salt lake system is mainly related to the Li–B fertility of the sources (deep fluids and country rocks), favorable tectonic conduits for water circulation, and high evaporation rates. Specifically, the deep fluids upwelling is responsible for the sourcing of B and Li. These fluids are then discharged to the river and groundwater through geothermal springs developing along deep faults or within volcanic craters. In this frame, the river and groundwaters act as carriers, and input B and Li into the lake basin. Ultimately, B and Li undergo an evaporation–mediated fractionation ending with the formation of brines and eventually accounting for the formation of the world–class Li–B salt lake deposits.

Road salting and natural brine migration revealed as major sources of groundwater contamination across regions of northern Appalachia with and without unconventional oil and gas development

High methane and salt levels in groundwater have been the most widely cited unconventional oil and gas development (UOGD) related water impairments. The attribution of these contaminants to UOGD is usually complex, especially in regions with mixed land uses. Here, we compiled a large hydrogeochemistry dataset containing 13 geochemical analytes for 17,794 groundwater samples from rural northern Appalachia, i.e., 19 counties located on the boundary between Pennsylvania (PA; UOGD is permitted) and New York (NY; UOGD is banned). With this dataset, we explored if statistical and geospatial tools can help shed light on the sources of inorganic solutes and methane in groundwater in regions with mixed land uses. The traditional Principal Component Analysis (PCA) indicates salts in NY and PA groundwater are mainly from the Appalachian Basin Brine (ABB). In contrast, the machine learning tool – Non-negative Matrix Factorization (NMF) highlights that road salts (in addition to ABB) account for 36%–48% of total chloride in NY and PA groundwaters. The PCA fails to identify road salts as one water/salt source, likely due to its geochemical similarity with ABB. Neither PCA nor NMF detects a regional impact of UOGD on groundwater quality. Our geospatial analyses further corroborate (1) road salting is the major salt source in groundwater, and its impact is enhanced in proximity to highways; (2) UOGD-related groundwater quality deterioration is only limited to a few localities in PA.

In Situ Pumping–Injection Remediation of Strong Acid–High Salt Groundwater: Displacement–Neutralization Mechanism and Influence of Pore Blocking

Acid-polluted groundwater may cause many environmental problems due to its corrosivity. Pumping and injection technology is a commonly used remediation technology, and its main principles are displacement and neutralization. However, due to the high salinity in groundwater, blockage easily occurs and reduces the efficiency. The mechanism of pumping and remediation of strong acid–high salinity groundwater is unclear, and the mechanism and effect of pore blocking are unknown. In this paper, based on an actual polluted site, a field pumping test was carried out. Through groundwater monitoring and drilling core sampling, the process and mechanism of acid groundwater pumping–injection remediation were clarified, and the principle and impact of pore blockage are revealed. The results showed that increasing the injection pressure can effectively improve the repairing efficiency. When the pressure increased from 0.2 MPa to 0.3 MPa, the water injection efficiency per unit time was increased by more than 20%. The principle of pumping–injection remediation of acidic groundwater was mainly displacement, accounting for more than 93%, while neutralization only contributed less than 0.1%. Although the neutralization contribution was small, the neutralization interface of injected alkaline water and acidic groundwater was the main place for precipitation. The precipitation was mainly formed around the injection well, the amount of which decreases greatly with the increase in displacement distance. This was because the formation of precipitation required both an appropriate concentration of Fe and high pH (5.63). Affected by neutralization and dispersion, the pH of the acid–base water interface decreased and the necessary conditions for the formation of precipitation were not met. Therefore, in the actual pumping–injection restoration project, optimization can be carried out from two perspectives of appropriately increasing the injected water pressure and reducing the injected water pH. This study has important reference value for the control and remediation of such acid-polluted groundwater.