Alkaline Groundwater Research Articles

Hydrochemical Characteristics and Variation in Karst Groundwater in the Baiquan Spring Area of Xingtai Over the Last 30 Years

To elucidate the variation patterns in the hydrochemical characteristics of karst groundwater in the Baiquan Spring area of Xingtai over the past 30 years, an integrated approach utilizing mathematical statistics, Piper trilinear diagrams, Gibbs diagrams, and ion ratio analyses was employed. Comparative analysis was conducted on 62 sets of karst water samples collected during the dry seasons of 1991 and 2020. The findings indicated that the groundwater in the spring area was generally weakly alkaline with a low salinization degree, predominantly characterized by Ca2+ and HCO3- as the dominant ions. Compared to that in 1991, the alkalinity of groundwater in 2020 had intensified, with a general increase in the concentration of various indicators. The hydrochemical types had shifted from the relatively concentrated HCO3-Ca and HCO3-Ca·Mg types to a broader spectrum of types, gradually exhibiting a salinization trend. The distribution characteristics of exceeding components such as TDS, Na++K+, SO42-, and F- showed significant spatial differences. Rock weathering played a pivotal role in the changes observed in the hydrochemical components of groundwater, with enhanced cation exchange and evaporation processes further influencing the hydrochemical characteristics and their spatial distribution.

Causes and Effects of Scale Deposition in Water Supply Pipelines in Surakarta City, Indonesia

Globally, scale deposition in water supply pipelines is one of the major problems faced by water utilities. This research aimed to determine the causes and effects of scale deposition in the water supply pipelines in Surakarta City, Indonesia. The total dissolved solids (TDS), hardness, manganese, and alkalinity in groundwater were higher than those in the surface water and spring water; thus, the supply areas from groundwater were identified using TDS at the taps. The three scaling indicators, i.e., the Langelier saturation index (LSI), the Ryznar stability index (RSI), and the Puckorius scaling index (PSI), indicated moderate calcium carbonate scaling. However, elemental analysis of eight scale samples using X-ray fluorescence (XRF) revealed that the major components of scale were either manganese (50.1–80.8%) or iron (45.6–63.8%), whereas calcium (3.0–7.8%) was a minor component. Because only five of twenty groundwater sources were chlorinated before distribution, it is estimated that dissolved manganese is oxidized by manganese-oxidizing bacteria. The manganese deposition rate in the networks was estimated to be 1660 kg/year using the manganese concentration at groundwater sources and in customers’ taps. These results suggest the importance of the elemental analysis of scale and avoidance of overreliance on scale indicators.

Hydroclimatic non-stationarity drives stream hydrochemistry dynamics through controls on catchment connectivity and water ages

We used data from 17 years of routine stream flow sampling to characterise hydrochemical dynamics in the Girnock Burn, an internationally important long-term catchment monitoring site. We combined hydrochemical time series analysis with hydrological modelling to understand short- and long-term dynamics in relation to dominant runoff processes. Isotopic tracer data employed within the model enabled flux tracking of water as it transited the catchment, facilitating water age estimates. The stream drains an upland 31 km2 catchment with complex topography and variable geology, which influences soil distributions; peaty soils dominate valley bottoms which receive drainage from more permeable podzolic soils on steeper slopes. Short-term hydrochemical dynamics largely reflect the relative dominance of hydrological sources: summer low flows are dominated by alkaline groundwater high in weathering products (Ca2+, Mg2+, SiO2) whilst high flows generated by overland flow from peaty soils are more acidic, DOC enriched, and dominated by atmospheric solutes (Na+, Cl-, SO42-). Baseflows are dominated by older groundwater (>∼3years) in contrast to storm runoff dominated by younger (<∼0.5 years), near-surface, waters. Usual seasonal distributions of stream flows, with high flows in winter and summer low flows, result in strong seasonality in most solutes. However, coupled effects of hydroclimatic variability and catchment heterogeneity dictates marked scatter in flow-concentration relationships for most determinands. A long-term decreasing trend was evident for SO42-concentrations, reflecting continuing effects of reductions in atmospheric deposition of pollutants from coal burning. Reductions in large storm event frequency post-2016 and protracted periods of low flows in the droughts of 2018 and 2022 have resulted in the catchment becoming dominated by low flows, derived from older groundwater with more alkaline chemistry for longer periods. Changing climatic conditions and stream flow responses seem likely to continue to cause changes in stream water quality and associated ecosystem services of the Girnock Burn and similar upland catchments.

Factors influencing the increased 90Sr radioisotope migration in highly alkaline groundwater at Chornobyl NPP site

This paper analyses the formation of high Sr2+ concentration in strong alkaline (pH = 9.5–12.5) groundwater using data of the 27 years of observations around the destroyed Chernobyl NPP Unit 4. It appears that the formation of strong alkaline groundwater in different monitoring wells is consistent with the distribution of 90Sr, pH and main ions.The reason for the increase in 90Sr concentrations is the process of its migration from the sources of contamination - leaks of highly active water localized in certain premises inside the «Shelter » object.These computational experiments showed that for the groundwater in pH range 9.5–12.4, the concentration of strontium in the form of SrOH + increases and in the form of Sr2+ - decreases. In addition, the fraction of 90Sr in the form of a soluble neutral complex compound SrCO30, which is not sorbed, reaches 14–35%. Increased fractions of 90Sr in forms of SrOH+ and SrCO3 are factors which reduce the isotope ability to be sorbed by soils and therefore increase its migration ability. In strongly alkaline groundwater a sharp increase in 90Sr volumetric activity may also be caused by ionic strength (IS) increase above 5 mmol/L. Thus, the factors that influence the increase in 90Sr volumetric activity in strongly alkaline groundwater are the formation of its complex compounds and an increase in ionic strength (IS), which reduces the thickness of the double electric layer and, as a result, reduces the sorption capacity of soils.

Study on enhancing groundwater quality in a coastal area of Saudi Arabia using a curved glass solar still

Due to the complex geological factors and their causes, it is essential to realize the saltiness and pollution of the groundwater in the arid shoreline aquifer. The intrusion of seawater into coastline aquifers is an increasingly significant issue due to urbanization, the exploitation of groundwater, and the global rise in temperature. The increasing salt concentration of groundwater in shoreline aquifers has emerged as a significant social and economic problem in Saudi Arabia. Consequently, groundwater alkalinity levels must be accurately determined to ensure the effective protection and preservation of water resources. A compilation of eight water samples was collected along the south-western coast of Saudi Arabia, and a comprehensive evaluation of the groundwater quality was conducted using a combination of indicators. The findings indicated that the intrusion of saltwater caused a significant increase in the salt concentration and damage to the groundwater quality near the coastline. In this work, a curved glass solar still (CGSS) has been deployed to process the groundwater, and the performance of the CGSS in improving the groundwater quality was assessed under clear sky conditions. The findings indicate that the desalination process executed using the CGSS resulted in a more substantial improvement in groundwater quality, with an average daily yield of 3513 ml/day achieved with the CGSS.

Paleovegetation and environment during deposition of the Late Oligocene sub-bituminous coal in the Bobov Dol Basin (SW Bulgaria) as deduced from petrographic and geochemical characteristics

Coal and carbonaceous shale samples were taken from the Late Oligocene Bobov Dol Basin, SW Bulgaria. Seams Ia, I, IIa+b, III, IV and V from the coal-bearing Bobov Dol Fm. were sampled to provide insights into the peat forming vegetation and depositional environment based on detailed organic petrological and geochemical study.The petrographic composition indicates that both coals and carbonaceous shales contain predominantly terrestrial organic matter with abundant huminite macerals and locally enriched liptinite macerals. Inertinite is rare or absent. Good tissue preservation in seams I, IV and V indicates deposition under wet sedimentary environment, whereas predominance of detrohuminite and lower Tissue Preservation Index (TPI) in seams Ia, IIa+b and III are linked to enhanced humification of the plant remains due to changes in the hydrological regime. The low percent of inertinite and the overall high Gelification Index (GI), however, argue for peat formation under wetter climatic settings, whereas low to moderate ash yields of coal samples indicate organic matter deposition in oligo- to mesotrophic topogenous mires. Reconstructed evolution of the environmental settings during peat formation denotes differences which might be caused by changes in the hydrological regime and tectonic activity.The biomarker composition shows prevalence of gymnosperm-derived sesqui- and diterpenoids, followed by lower concentration of n-alkanes (apart from the carbonaceous shale samples from seam Ia), whereas angiosperm-derived non-hopanoid triterpenoids, acyclic isoprenoids, steroids and hopanoids, are generally present in minor amounts. Diterpenoid composition indicates dominant contribution from Cupressaceae and Pinaceae conifers. Minor amounts of predominantly lupane-type non-hopanoid triterpenoids denote limited development of angiosperm vegetation, presumably mostly related to Betulaceae family. Relative abundance of mid-chain (n-C21–25) n-alkanes, associated with elevated proxy ratio (Paq) furthermore, suggest possible contribution from aquatic macrophytes to peat formation. Very low hopane concentrations and low/moderate ββ/(ββ + αβ) hopane ratios imply minor aerobic bacterial activity under mild acidic conditions. The presence of inorganic carbon suggests that environmental acidity might be controlled by the occasional input of neutral to slightly alkaline ground waters. Moderate sulfur contents and the occurrence of hopenes denote anaerobic bacterial activity after organic matter burial.Low maturity of the organic matter and limited hydrocarbon generation potential is indicated by the low huminite reflectance, hopane (C31 22S/(22S + 22R)) and sterane (αααC29 20S/(20S + 20R)) isomerization ratios, as well as Rock-Eval parameters, Tmax and Production Index (PI).

Enhancing the Fenton-like degradation of organic contaminants with silicate-iron in aquifer media by ascorbic acid

In this study, silicate-iron (FeSi-ox, FeAlSi-ox) in aquifer media was utilized as an original iron source in groundwater to systematically investigate the effects of ascorbic acid on the degradation of p-nitrophenol (PNP) in the in-situ Fenton-like reaction. Silicate-iron in the aquifer media increased the PNP removal rate by activing H2O2 following the addition of ascorbic acid. The optimal removal rate of PNP was nearly 89% within 40 h, which was 6.8 times higher than that without ascorbic acid. In addition to PNP, some other common pollutants, such as nitrobenzene, trichloromethane, and trichloroethylene, can also be effectively degraded and mineralized. The suitable pH range for the silicate-iron Fenton-like system with ascorbic acid was 5–9, indicating that it is feasible in near-neutral or alkaline groundwater environments. The main functional free radicals were hydroxyl free radicals (•OH), which were produced slowly but continuously. In this novel Fenton-like system, dissolved Fe played a major role in H2O2 decomposition and pollutant degradation. The main mechanism underlying the increased strength of the degradation was the ability of ascorbic acid to facilitate the dissolution of surface Fe from aquifer media and accelerate the cycling of Fe(Ⅲ)/Fe(Ⅱ) in the liquid phase.

Rare earth element behaviors of groundwater in overlying aquifers under the influence of coal mining in northern Ordos Basin, China.

Rare earth elements (REEs) have been used as tracers to reveal the hydrochemical sources and processes in groundwater systems that are usually modified by anthropogenic inputs. However, the REE behaviors in groundwater affected by mining activities have yet to be fully understood. In combination of REE geochemistry with general hydrochemical and isotopic (δ2H and δ18O) methods, this study investigated the concentration and fractionation of REEs in alkaline groundwater from two coal mines with similar aquifer lithology but different mining histories in the Northern Ordos Basin. One of the coal mines started mining in March 2009 (Ningtiaota coal mine, NTT), while the other started mining in December 2018 (Caojiatan coal mine, CJT). Results show that the primary hydrochemical type is HCO3-Ca in NTT groundwater with pH value ranging between 7.68 and 8.60, while CJT groundwater was dominated by the HCO3-Na type with higher pH of 9.09-10.00. The average values of ΣREEs were lower, and the NASC-normalized pattern reflected more intense fractionation in NTT groundwater than those in CJT groundwater. The evident differences are caused by the distinctions in water-rock interaction, complexation of inorganic species, and adsorption of REEs in NTT and CJT groundwater. Furthermore, these processes were closely related to the pH of groundwater that was different in two coal mines, which is likely linked to the different durations of coal mining activities that led to differences in development of rock fractures and pyrite oxidation. It is expected that REEs, combined with other indicators such as pH, can be used to trace and help better understand the hydrochemical changes in groundwater caused by mining.

Polyurethane-Degrading Potential of Alkaline Groundwater Bacteria.

Plastic waste is a global environmental burden and long-lasting plastic polymers, including ubiquitous and toxic polyurethanes (PUs), rapidly accumulate in the water environments. In this study, samples were collected from the three alkaline groundwater occurrences in the geotectonic regions of the Pannonian basin of northern Serbia (Torda and Slankamen Banja) and Inner Dinarides of western Serbia (Mokra Gora) with aim to isolate and identify bacteria with plastic- and lignocellulose-degrading potential, that could be applied to reduce the burden of environmental plastic pollution. The investigated occurrences belong to cold, mildly alkaline (pH: 7.6-7.9) brackish and hyperalkaline (pH: 11.5) fresh groundwaters of the SO4 - Na + K, Cl - Na + K and OH, Cl - Ca, Na + K genetic type. Full-length 16S rDNA sequencing, using Oxford Nanopore sequencing device, was performed with DNA extracted from colonies obtained by cultivation of all groundwater samples, as well as with DNA extracted directly from one groundwater sample. The most abundant genera belong to Pseudomonas, Acidovorax, Kocuria and Methylotenera. All screened isolates (100%) had the ability to grow on at least 3 of the tested plastic and lignocellulosic substrates, with 53.9% isolates degrading plastic substrate Impranil® DLN-SD (SD), a model compound for PUs degradation. Isolates degrading SD that were identified by partial 16S rDNA sequencing belong to the Stenotrophomonas, Pseudomonas, Paraburkholderia, Aeromonas, Vibrio and Acidovorax genera. Taking into account that plastics, including commonly produced PUs, are widespread in groundwater, identification of PUs-degrading bacteria may have potential applications in bioremediation of groundwater polluted with this polymer.

Natural and anthropogenic factors regulating fluoride enrichment in groundwater of the Nansi Lake Basin, Northern China

Excess fluoride (F−) in groundwater can be hazardous to human health of local residents who rely upon it. Beside natural sources, anthropogenic input may be an additional source to be considered. Twenty surface water and 396 groundwater samples were collected from the Nansi Lake Basin, with hydrogeochemical and isotope techniques employed to clarify the spatial variability, source, and the natural and anthropogenic factors regulating the occurrence of high F− groundwater. The factors responsible for elevated F− levels in surface water and deep confined aquifers are discussed based on their hydraulic relationship. Also a conceptual model of F− enrichment with different aquifer systems is put forward based on the geomorphic units of the basin. The results show that F− concentration is between 0.1 and 6.9 mg/L in the west of Lake, while ranged from 0.03 to 1.74 mg/L in the east of Lake. The hydrogeological setting and lithology are the primary factor determining the provenance of high-fluoride groundwater in the basin. Fluoride mainly originated from the dissolution of fluorine-bearing minerals, and is affected by the alkaline groundwater environment, cation exchange, adsorption, and evaporation. The landforms on the east side of Nansi Lake are low hills and piedmont sedimentary plains, where the aquifers consist of karst fissure water and overlying porewater. High F− groundwater is not observed in this area due to its rapid flow and Ca2+-enriched hydrochemical characteristics. The anthropogenic input (such as fertilizer application on farms and illegal industrial pollutant discharge), contribute F− to groundwater in varying degrees, especially in the shallow aquifers east of the lake and in some parts west of the lake. This work is a clear example of how natural processes together with human activities can affect the chemical quality of groundwater, which is essential to safeguard the sustainable management of water resources in semi-arid areas.

Groundwater pollution and risk assessment using indexed-based models: a case study of Igbo-Etiti area, eastern Nigeria.

Water is one of the most abundant resources on earth not evenly distributed. Due to the high shortage of water sources in Igbo-Etiti and intensive agricultural practices in the area, assessment of groundwater pollution and its potential risk to contamination is imperative, as its remediation when contaminated is extremely challenging. Vertical electrical sounding (VES) and physicochemical analysis were carried out in twenty (20) locations and five groundwater samples, respectively, with the aim to evaluate the groundwater pollution indices and the ecological and human health risk associated with its pollution. The VES results delineated five geologic layers and ten characteristic curve types. The fourth layer with the aid of the VES results constrained by the borehole lithologic information on the water bearing geologic unit was delineated as the major exploitable aquifer layer. Results of groundwater vulnerability to pollution classified the area into low (15%), moderate (60%), and high (20%) vulnerability. Physicochemical analysis results on the studied groundwater revealed acidic (pH 4.6) to alkaline (pH 7.2) groundwater conditions. Pollution index of groundwater results delineated a moderate to very high pollution index, with cadmium and arsenic consistently identified as the heavy metals contaminating the groundwater. Ecological risk assessment revealed a moderate to very high integrated potential ecological risk, while human health risk results delineated a target hazard index greater than one in all the studied groundwater samples. This study will serve as a guide to the residents and society in sustainable development decision-making that will preserve the quality of the study area groundwater.

Detection of Groundwater Quality Changes in Minia Governorate, West Nile River

The need for freshwater supplies is increasingly rising according to the increase in the inhabitants’ expansion and economic growth. Available water resources are reduced by pollution and overpumping. This research’s prime objective is to study changes in the water quality of the Pleistocene aquifer in Minia Governorate. Historical hydro-chemical data of the groundwater in two years 2009 and 2019 were used to study the changes in the groundwater quality of the Pleistocene aquifer under the impact of the recharge and discharge processes. The Nile River, and the Al-Ibrahimia and Bahr Youssef Canals are considered the main sources of aquifer recharge. Collected data from 53 groundwater wells in the Pleistocene aquifer were used to calculate the sodium adsorption ratio (SAR), sodium percentage (Na%), Kelly index (KI), Soluble Sodium Percentage (SSP), magnesium ratio (MR%), permeability index (PI) and chloro-alkaline index (CAI). These data were used to evaluate and detect the quality and changes in groundwater through the years 2009 and 2019 using spatial mapping in the geographic information system (GIS). The values of SAR, KI and Na% varied between 0.06–1.22, 0.02–0.57 meq/L and 3.7–37.63%, respectively, in the year 2009, but these values changed to 0.4–0.75, 0.16–0.28 meq/L and 15.07–23.44% in the year 2019. The calculated MR and PI values indicate that 100% of the groundwater samples were in the “suitable” category. The calculated SSP reflects no changes in groundwater alkalinity between the years 2009 and 2019. The hydro-chemical analysis of the studied groundwater (G.W.) samples shows high pollution levels caused by Pb and Fe in some parts of the study area. Pb was found to be &gt;40 µg/L in the middle parts, whereas Fe was found with high levels in 27% of the studied groundwater samples. The localities of these samples were affected by pollution from the industrial wastewater from the sugar factory of Abou-Qarqas city (e.g., El-Moheet drain), the fertilizer leaching process and pesticides seeping into groundwater from soils and agricultural wastewater.

Effect of super-absorbent polymer on swelling pressure of compacted bentonite infiltrated by alkaline solutions

The application of bentonite in geological disposal of radioactive waste is still under evaluation, especially concerning the decreased swelling pressure of pure bentonite exposed to alkaline groundwater. In this paper, in order to improve the chemical resistance of bentonite to alkaline solutions, super-absorbent polymer (SAP), a hydrophilic polymer with much higher swelling ability than that of bentonite, was dry-blended with Gaomiaozi (GMZ) bentonite and compacted into blocks of different dry densities. Swelling pressure of the bentonite-SAP composites infiltrated with deionized water, NaOH and KOH alkaline solutions were tested, accompanied with scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and X-ray diffractometer (XRD) tests conducted on the selected specimens. Results showed that, for the specimens hydrated by deionized water, the swelling pressure increased with increasing SAP content, dry density and concentration of NaOH solutions. With increasing concentration of KOH solutions, however, the swelling pressure decreased obviously and tended to undergo a slow long-term degradation. Results of SEM, MIP and XRD indicate that the SAP hydrogels swell extensively to clog the inter-aggregate pores and coat the aggregates (for high density specimens) or montmorillonite stacks (for low density specimens), while do not insert into the interlayer spaces. The swelling pressure was therefore mainly contributed by the crystalline swelling of montmorillonite and the osmotic swelling of SAP. The SAP chains could be associated with the montmorillonite crystallites, protecting them from chemical attack and thus improving the chemical resistance of bentonite to alkaline solutions.

Delineation of safe groundwater aquifers in a Fluoride contaminated region: Walwa Taluka, Maharashtra

Groundwater aquifer contamination has leads health problems in village areas of Maharashtra, India. In this study, groundwater analysis was carried out for different groundwater parameters along with fluoride to delineate the high and low contaminated fluoride region in the Walwa taluka, Maharashtra. A distinct contaminated regions for high and low F‒ contaminated regions were identified in the collected post monsoon groundwater samples (n = 144). In total 98% samples are unsuitable for consumption. Hydro-geochemistry of the region showed highest anion concentration for bicarbonate (1880 mg/L), whereas highest cation concentration for calcium was measured as 118 mg/L. It is main cause for alkaline groundwater condition in this region. The 2D ordinary kriging results are well corborated with the obtained hydrogeochemistry results. The low F‒ concentration region was found near the Krishna River, whereas high concentration regions were found near the agricultural and high land region. The primary hydrogeochemistry of the region suggests that the geogenic source of F‒ minerals in the region. The practice of fertiliser, herbicides and pesticides on agricultural field suggests that these are the secondary source for groundwater F‒ contamination. The applied numerical groundwater modelling software, provided technically viable and effective decision making-tool for identification of safe region in the study area.

Вплив іонної сили розчину на формування підвищеної міграції 90Sr в підземних водах промислового майданчика Чорнобильської АЕС

Thermodynamic modeling of 90Sr migration was performed based on data from monitoring studies on well 4-G, which, before its liquidation in 2008, was located on the industrial site of the Chornobyl nuclear power plant. The study of the 90Sr migration forms was carried out using a set of software tools “Geochemist’s Workbench Community Edition”. In order to confirm and understand the migration processes, modeling of the spread of various complex 90Sr compounds such as SrCO3, SrHCO3, SrSO4, SrOH+ and SrNO3 + with groundwater was carried out. With the help of SpecE8, the calculation of various forms of 90Sr was performed, and the ionic strength of the groundwater solution (ISS) was also calculated. In the range of pH 9.5–12.4, there is an increase in the Sr2+ concentration in groundwater by 200–500 times to 550 Bq/l. In the same pH interval, according to thermodynamic modeling, an increase in the concentration of strontium in the form of SrOH+ and a decrease in the form of Sr2+ is observed in groundwater. At the same time, the dominance of strontium concentrations in the form of SrOH+ over Sr2+ does not occur. The reason for the sharp increase in the volume activities of 90Sr in strongly alkaline groundwater was the increase in the ISS &gt; 5 mmol/l. An increase in the ISS of strongly alkaline groundwater leads to a decrease in the sorption properties of soils, and to the remobilization of adsorbed 90Sr back to groundwater through cation exchange. Probably, in the pH range of 9.5–12.4 and the ISS &gt; 5 mmol/l, there is a change in the surface charge of soil particles, usually from negative to positive, in which cations cannot be sorbed, but, on the contrary, must to remobilize from the soil surface to groundwater. At the same time, pH = 9.5 is probably the point of zero charge (pzc). To assess the possibility of a relationship between the concentrations of 90Sr and ISS, a correlation analysis using the geochemical statistics method was carried out. At the same time, the correlation coefficient K = 0.87, which proves the existence of a close relationship.

Hydrogeological feasibility of mine water deep geological storage in Baotashan coarse sandstone: A case study in Ordos Basin

AbstractFor the sake of mine water drainage and sustainable groundwater protection, the new approach of mine water deep geological storage (MWDGS) is highly necessary to save water resources in the semi‐arid region of China. However, up to now, little academic research has been done on mine water geological storage. Given this situation, the hydrogeological feasibility of MWDGS was explored in Baotashan coarse sandstone (BCS) of Jurassic measure in Ordos Basin. The results show that the white‐gray BCS with a fragile skeleton of quartz (41.4%), feldspar (21.1%), and clay minerals (16.4%) provides the potential variable‐void for mine water; and its hydro‐chemical type of BCS aquifer is CO3‐Na and Cl‐Na. As the burial depth increases, the strong alkaline groundwater is in stagnant and poor recharge‐runoff‐discharge condition. The lab test shows that the pores whose diameter is over 10 μm could be treated as the main storage of mine water; and the effective porosity varies from 1.36% to 3.46%. When mine water is injected, the strong hydrodynamics of mine water storage would change the permeability significantly and about 0.201% soluble solids would be dissolved. Partial clay minerals obstruct the pores and induce the saturated phase of high permeability to evolve into steady phase of lower permeability. Under the condition of nonhydraulic fracturing during continuous storage, the heterogeneous anisotropic medium obtained by Transition PRObability GeoStatistics (TPROGS) shows that the capacity of BCS aquifer is 0.455 to 1.226 Mm3 for 1 km2 in the study area. The simulation shows that the groundwater mound in well‐scale and mine‐scale would be formed. The groundwater quality characteristics of “Three Zone” would occur around and gradually drop to approximate the original brine within 10 years. The hydrogeological feasibility reveals that this approach is useful for the well design and groundwater environment management during the mine water deep geological storage project in the Ordos basin.

Natural and Anthropogenic Processes Affecting Domestic Groundwater Quality within the Northwestern Appalachian Basin.

Domestic wells serve as the primary drinking-water source for rural residents in the northern Appalachian Basin (NAB), despite a limited understanding of contaminant distributions in groundwater sources. We employ a newly collected dataset of 216 water samples from domestic wells in Ohio and West Virginia and an integrated contaminant-source attribution method to describe water quality in the western NAB and characterize key agents influencing contaminant distributions. Our results reveal arsenic and nitrate concentrations above federal maximum contaminant levels (MCLs) in 6.8 and 1.3% of samples and manganese concentrations above health advisory in 7.3% of samples. Recently recharged groundwaters beneath upland regions appear vulnerable to surface-related impacts, including nitrate pollution from agricultural activities and salinization from road salting and domestic sewage sources. Valley regions serve as terminal discharge points for long-residence-time groundwaters, where mixing with basin brines is possible. Arsenic impairments occurred in alkaline groundwaters with major-ion compositions altered by ion exchange and in low-oxygen metal-rich groundwaters. Mixing with as much as 4-10% of mine discharge-like waters was observed near coal mining operations. Our study provides new insights into key agents of groundwater impairment in an understudied region of the NAB and presents an integrated approach for contaminant-source attribution applicable to other regions of intensive resource extraction.

Assessment of the Hydrochemical Characteristics and Formation Mechanisms of Groundwater in A Typical Alluvial-Proluvial Plain in China: An Example from Western Yongqing County

The geographic location of Yongqing County is optimal, covering the center of the Beijing, Tianjin, and Baoding triangle. However, the economic and social development of Yongqing County in recent years has resulted in negative impacts on groundwater. Therefore, investigating the current status of groundwater chemistry in Yongqing County is of great significance to provide a useful basis for future studies on groundwater quality assessment. The aim of this study is to assess the hydrochemical characteristics and formation mechanisms of the unconfined aquifers of Yongqing County using descriptive statistical and multivariate statistical methods. In addition, ionic ratios, Piper diagram, Gibbs diagrams, and PHREEQC software were used in this study to determine the main factors influencing the hydrochemical characteristics of the unconfined aquifers. The results suggested slightly alkaline groundwater of the unconfined aquifers in the western part of Yongqing County, belonging to the fresh-brackish groundwater type. In addition, the hydrochemistry facies types in the study area are complex, consisting of four facies types, namely HCO3−−Mg·Ca, HCO3−−Na, HCO3−-Na·Ca, and HCO3−-Na·Mg. On the other hand, the main factors influencing the hydrochemical characteristics of groundwater are mineral dissolution followed by some anthropogenic pollution. Rock dominance was the main influencing factor, demonstrated by thedissolution of silicate and carbonate rock minerals. In addition, the alternating adsorption of cations occurring in the aquifer plays a non-negligible effect on the hydrochemical characteristics of the unconfined aquifers in the study area. In fact, the validation results using PHREEQC inverse hydrogeochemical simulations demonstrated consistent conclusions with those mentioned above. According to the findings obtained, the dissolution of carbonate and silicate minerals as well as Na+, K+, and Ca2+ ion exchange in the aquifer are the main factors influencing the hydrochemical characteristics of the unconfined aquifers of Yongqing County. The recommendations suggest put forward in this research are helpful to understand the formation mechanism of hydrochemistry in typical alluvial proluvial plain and provide insights for decision makers to protect the groundwater resources.

Study on the preparation of manganese oxide filter media for catalytic oxidation removal of ammonium and manganese in high alkalinity groundwater: The effect of copper and cobalt doping

Owing to the low efficiency of catalytic oxidation of ammonium and manganese in high alkalinity groundwater by manganese oxide filter column, the effect of doping copper (Cu) and cobalt (Co) on catalytic activity was investigated. A pilot-scale filter column system was used in this experiment. The catalytic oxidation activities of manganese oxide filter media prepared at different Cu and Co concentrations (0, 0.1, 1.0 mg/L) in raw water were compared. The results showed that the removal efficiency of ammonium by the filter column increased from 65% to 100% due to low Cu doping, while the removal efficiency of manganese decreased from 95% to 60% due to high Cu doping. Low Co doping was beneficial to the start-up period of the filter column and the effluent ammonium concentration reached the standard on the 8th day. In addition, X-ray diffraction (XRD) and Scanning electron microscopy coupled energy dispersive spectroscopy (SEM-EDS) results showed that the high alkalinity of water led to the formation of a large amount of calcium carbonate on the surface of the filter media. Combined with X-ray photoelectron spectroscopy (XPS) analysis, it was found that the conversion of different valence manganese species caused by Cu and Co doping and the Cu and Co elements with different valence were the key factors determining the catalytic activity of manganese oxide filter media. Cu2+/Cu+ and Co3+/Co2+ electron cycles also participated in the electron transfer process of catalytic reaction. This study provides a research idea for solving the pollution problem of ammonium and manganese in high alkalinity water.

Efficient Fluoride Removal by a Fixed-Bed Column of Self-Assembled Zr(IV)-, Fe(III)-, Cu(II)-Complexed Polyvinyl Alcohol Hydrogel Beads.

Fixed-bed column adsorption studies are performed with metal-complexed polyvinyl alcohol (PVA) hydrogel beads to remove fluoride from groundwater. The fixed-bed column (bed height = 8 ± 0.2 cm) of copper–zirconium–PVA (PCZH), zirconium–PVA (PZH), and iron–zirconium–PVA (PFZH) hydrogel beads have equilibrium fluoride removal capacities of 17.26 ± 0.05, 31.67 ± 0.05, and 11.84 ± 0.05 mg g–1 from a 10 ± 0.20 mg L–1 fluoride solution of pH 6.5 maintained at a flow rate of 1 ± 0.01 mL min–1. The breakthrough curves for fluoride adsorption are analyzed by non-linear empirical models of Thomas, Bohart–Adams, Yoon–Nelson, and semi-empirical bed depth service time models. The maximum fluoride adsorption capacities obtained from the Thomas model are 25.66 ± 0.05, 38.17 ± 0.05, and 13.75 ± 0.05 mg g–1 for PCZH, PZH, and PFZH. Moreover, the column of PZH (bed height = 4 ± 0.2 cm) removes about 1.67 ± 0.05 mg g–1 of fluoride from the alkaline groundwater sample with high total dissolved solids containing 2.84 ± 0.20 mg L–1 fluoride maintained at a flow rate of 0.5 ± 0.01 mL min–1. The fluoride removal efficiency decreases marginally (<1 ± 0.02%) in the presence of interfering ions such as chlorides, sulfates, phosphates, bicarbonates, and nitrates. Furthermore, the fixed-bed column (bed height = 4 ± 0.2 cm) of PCZH, PZH, and PFZH remove 7.40 ± 0.05, 14.85 ± 0.05, and 6.53 ± 0.05 mg g–1 fluoride, respectively, even after the third regeneration cycle. Additionally, the hydrogel beads are effective in the removal of arsenate (≤90 ± 0.02%) and chromate ions (≤96 ± 0.02%) from 100 ± 0.20 mg L–1 solution in batch adsorption studies. Therefore, the hydrogel beads could be used as potent filters for the removal of fluoride, chromate, and arsenate ions from water.