Groundwater pH Research Articles

Morphological approach to understanding mineral alteration and nanoparticle formation under alkaline conditions using granitic rock thin sections

The cement components in deep geological disposal facilities (DGFs) for spent nuclear fuel can increase groundwater pH, potentially altering minerals within natural barriers. Mineral (biotite, quartz, plagioclase, chlorite, and K-feldspar) dissolution and secondary-phase precipitation were investigated to provide visually integrated understanding of multifaceted processes. This study was based on the morphological features of granitic rock thin sections exposed to alkaline aqueous solutions (initial pH: pHo 9 and 13) using atomic force microscopy (AFM), micro-X-ray fluorescence, and scanning electron microscopy/energy-dispersive X-ray spectroscopy. Batch kinetic-alteration tests were conducted from 4 h to 20 d. The minerals exhibited more pronounced changes in surface roughness and Si release at pHo 13 than at pHo 9. Furthermore, precipitates were more abundant on the mineral surfaces at pHo 9 than at pHo 13. Fe (oxy)hydroxides and Al (oxy)hydroxides prevailed as precipitates at pHo 9, whereas Ca (oxy)hydroxides dominated at pHo 13 (pH ≥ 12.8). These findings indicate that the aqueous solutions were significantly involved in the formation of the secondary-phase precipitates. Interestingly, secondary-phase precipitates formed not only on the surface of mineral (i.e., biotite) providing constituent ions but also on the surfaces of adjacent minerals (i.e., quartz and plagioclase). Moreover, the possibility of a multistep process involving Al precursors for nucleation of gibbsite precipitates on the surface of K-feldspar at pHo 9 and colloidal particle formation through surface modification, often overlooked in mineral research, were identified via AFM image analysis. This methodological approach using rock thin sections can provide new visual insights regarding the dissolution–precipitation processes, including nucleation reactions, under conditions closely resembling the expected environmental settings within DGFs.

Divergence of nutrients, salt accumulation, bacterial community structure and diversity in soil after 8 years of flood irrigation with surface water and groundwater

Irrigation with saline groundwater has become necessary to overcome freshwater scarcity in the agricultural industry in arid areas. However, the effects of long-term saline groundwater irrigation on soil salinity and bacterial diversity have rarely been examined. In this study, a Lycium ruthenicum field was divided into two parts and subjected to flooding irrigation with saline groundwater (pH 7.81, total salinity 0.95 g L−1) and surface water (pH 7.76, total salinity 0.36 g L−1) for 8 years. After 8 years of irrigation, the soil salinity and salt ion content (i.e., Na+, Mg2+, K+, Ca2+, Cl− and CO32−) in the groundwater irrigation group were significantly greater than those in the surface water irrigation group (p < 0.001), with notable accumulation in the topsoil (0–5 cm) (p < 0.01). The bacterial community structure differed between the surface water and groundwater irrigation groups. Salt-tolerant bacterial groups (e.g., Balneolaceae and Halomonadaceae) and species (e.g., the marine bacterium JK1007, the bacterium YC-LK-LKJ35, and Methylohalomonas lacus) dominated in the groundwater irrigation environment. Additionally, bacterial communities were associated primarily with soil salt ions (RV = 0.66, p < 0.001). The characteristic bacterial taxa in long-term groundwater irrigation soils were salt-tolerant species (e.g., the marine bacterium JK1007, the bacterium YC-LK-LKJ35, and Methylohalomonas lacus). These findings suggest that salinity is the key factor driving differences in bacterial community structure between long-term groundwater and surface water irrigation. The long-term use of surface water and groundwater for irrigation has different impacts on soil environments, with groundwater irrigation having a more pronounced negative effect. Highlights. The long-term effects of this practice on soil salt accumulation and bacterial diversity were examined. This study provides potential applications for sustainable land management in similar ecological contexts. Groundwater irrigation is characterized by saline-tolerant keystone species. Salinity filtering was used to determine the pattern of bacterial community construction.

Fulvic acid removal from landfill contaminated groundwater by a permeable reactive barrier: From laboratory to field-scale analyses

Permeable reactive barriers (PRBs) show great potential for remediating groundwater polluted by leachate from municipal solid waste landfills (MSWLs). In this study, we conducted a series of batch tests to investigate the effects of environmental factors (e.g., temperature, pollutant concentration, and pH in groundwater) and the composition of PRB materials (i.e., Fe and zeolite) on fulvic acid (FA) removal and also simulated PRB filled with different composition to investigate its effectiveness. The response surface method (RSM) was applied to optimize experimental conditions for single- and double-stage adsorption/desorption processes. Experimental findings demonstrated that an adsorbent mixture of 2.900 g Fe and 1.505 g zeolite achieved the highest adsorption efficiency of 67.22 % among four tested combinations. The double-stage adsorption process significantly enhances the FA removal efficiency compared to the single-stage process. Field-scale simulations indicated that the 1.0-m thick PRB developed in this study may achieve an FA adsorption efficiency of 67.31 %. Moreover, the implementation of PRB may lead to a significant reduction in downstream FA concentrations, with a decrease of 40.90 % compared to cases where only cut-off walls are employed. Therefore, the proposed Fe-Zeolite PRB system may serve as an alternative method to remedy polluted groundwater by landfill leachate.

Neutralisation of Acid Rock Drainage by Youngest Toba Tuff Leachate Revealed by Hydrogeochemistry

ABSTRACTThe Youngest Toba Tuff (YTT) supervolcanic eruption occurred 75000 years ago, and resulted in distinctive ash fall deposition in different locations encompassing marine, estuarine, lacustrine, and fluvial sedimentary basins. Of the different sedimentary basins, the YTT crypto‐tephra horizon preserved in the South Kerala Sedimentary Basin (SKSB) of the western coast of India is hosted by a paleo‐estuarine carbonaceous clay layer. Along the eastern margin of SKSB, confined aquifers hosting highly acidic groundwater is associated with this YTT ash and associated organic matter (OM)‐rich carbonaceous clay layer, creating worse acid rock drainage (ARD), which eventually gets neutralised during summer, signalled by the crystallisation of halotrichite. Hydrogeological investigation gave insights on some of the unique geochemical processes, which facilitated the neutralisation of ARD. The main aquifers in the area include laterite and clayey‐sand, which is separated by this impervious layer hosting YTT ash. Wells tapping the clayey‐sand aquifer, beneath this layer, is affected by the ARD condition due to the interaction with pyrite, manifested as low pH of groundwater (3.7). Simultaneously, leaching from YTT ash, which constitutes 11.91% of Al2O3, facilitates Al content to reach groundwater in high concentration (2879.97 ppb). During dry season, when the surface of YTT‐hosting OM‐rich carbonaceous clay layer is exposed, the leached Al interacts with the acid derived from the YTT‐hosting OM‐rich carbonaceous clay layer and results in the precipitation of halotrichite. The two processes, one resulting in ARD condition and the other as formation of halotrichite, occur in succession. Thus, the crystallisation of halotrichite signals the neutralisation of water as well as heralding the potability of water.

Long-term rainfall and water table influence on groundwater nutrient dynamics from an oil palm plantation

ABSTRACT Conservation of groundwater quality is of paramount importance for sustainable agricultural management. Hydrological factors such as rainfall patterns and water table (WT) management, including drainage practices, play a crucial role in groundwater recharge. This in turn has a significant impact on WT fluctuations, nutrient losses in the soil, and the leaching of fertilizers into groundwater which leads to groundwater pollution. Consequently, this study evaluates the long-term influence of seasonal rainfall and WT fluctuations on groundwater nutrient dynamics in tropical peatlands from an oil palm plantation (OPP). Linear regression analyses and Pearson correlation matrices were adopted to evaluate the relationships between seasonal rainfall, WT, and groundwater chemical parameters. The results showed that there was a significant increase in mean pH, NO3 −, Na+, Ca2+, and PO4 3- values during the wet season compared to the dry season which could be attributed to the leaching of nutrients into groundwater due to rainfall, nutrient runoff from drainage systems and increased nitrification rate. A significant positive correlation (p < 0.01) was found between groundwater pH and NO3 − during the wet season, suggesting that increased groundwater pH due to heavy rainfall directly affects the nitrification process. It was also observed that low WT promotes denitrification in shallow groundwater, with this effect being more significant (p < 0.05) during the dry season. This was reflected in the higher correlation values between the WT fluctuations and the NH4 + concentrations in the groundwater. This research represents the first study to explore the long-term impacts of rainfall and WT fluctuations on groundwater quality in tropical peatlands. The insights gained from this study offer valuable guidance for WT management strategies aimed at conserving groundwater quality in such environments, ultimately contributing to sustainable agricultural practices.

Spatial Distribution of Groundwater Fluctuation Mapping Using Arc-GIS in Hosur-1 Micro-watershed of Karnataka, India

Groundwater is a primary source of freshwater and used mainly for agriculture and irrigation purposes. Recharge to groundwater is the most important component in all the water balance studies. In the present study krigging technique was used for interpolate the groundwater level of the Hosur-1 micro watershed (Kanakvad sub watershed) in Gadag district of Karnataka state. In Hosur-1 micro- watershed 41 wells are there in the vicinity of major stream of the micro- watershed. The mean depth of ground water levels in the micro- watershed were monitored at a monthly frequency during January-2023 to March-2024. It was found that the maximum average depth of bore wells are about 9.55 mts and lowest average depth of borewell about 4.64 mts. The groundwater table between 2.48 to 14.70 mbgl during summer season period and 3.18 to 21.50 mbgl during the Rabi season. The pH of ground water varied between 7.0-9.0, maximum pH was recorded as 8.9 and minimum was recorded as 7.29 and maximum conductivity &gt;3.82 ds/m and minimum 0.87 ds/m was recorded at Hosur-1 micro-watershed. The average infiltration rate of clay soil 2.73 mm/hr and R2 value for the trend line reaches the value of 0.5876. In case of sandy clay loam average infiltration rate was 3.83 mm/hr and R2 value for the trend line reaches 0.6572. It necessitates continuous monitoring of groundwater for assessing the possible damage on salinity and alkalinity induced soil health.

Characterizing and tracing the heavy metals' spatial distribution in karst surface river affected by acid mine drainage

A series of pollution problems have been caused by the drainage of closed coal mines. This study focuses on the XZ River in Guizhou Province, employing a comprehensive approach involving hydrochemical analysis, mathematical statistics, and one-dimensional water quality modeling to investigate the spatial evolution and source apportionment of heavy metals in karst surface rivers affected by AMD. The average pH, EC, and Eh values of groundwater and surface water in the XZ river basin were 6.27, 331 μs/cm, 230 mV and 3.86, 1671.57 μs/cm, 412.71 mV, respectively, indicating severe pollution of surface water by AMD. The study reveals that groundwater in the XZ River Basin is predominantly of the HCO3-Ca-Mg type, shifting to HCO3-SO4-Ca-Mg type with the influx of acid mine wastewater. Utilizing statistical methods for source apportionment analysis indicated that downstream concentrations of Fe, Mn, Zn, Cu, As, and Sr most likely originate from tributaries. Further analysis through one-dimensional water quality simulation confirmed that downstream concentrations of Fe, Mn, Zn, Cu, As, and Sr are attributed to tributaries. This suggests that XZ River is affected by pollution from different coal mines, primarily from coal mine M4, followed by coal mine M1.

Comprehending Spatial Distribution and Controlling Mechanisms of Groundwater in Topical Coastal Aquifers of Southern China Based on Hydrochemical Evaluations

Groundwater quality and availability in coastal aquifers have become a serious concern in recent times due to increased abstraction for domestic, agricultural and industrial purposes. (1) Background: Zhuhai city is selected as a representative coastal aquifer in Southern China to comprehensively evaluate the hydrochemical characteristics, spatial distribution and controlling mechanisms of groundwater. (2) Methods: A detailed study utilizing statistical analyses, a Piper diagram, Gibbs plots, and ion ratios was conducted on 114 surface water samples and 211 groundwater samples. (3) Results: The findings indicate that the pH of most groundwater is from 6.06 to 6.52, indicating a weakly acidic environment. The pH of surface water ranges from 5.35 to 9.86, with most values being weakly alkaline. The acidity in the groundwater may be related to the acidic atmospheric precipitation, an acidic unsaturated zone, oxidation of sulphide minerals and tidal action. The groundwater chemical types are predominantly mixed, followed by Ca-Mg-HCO3 type. Surface water samples are predominantly Na-Cl-SO4 type. The NO3− concentration in groundwater is relatively high, with a mean value of 17.46 mg/L. The NO2− and NH4+ concentrations in groundwater are relatively low, with mean values of 0.46 mg/L and 7.58 mg/L. (4) Conclusions: The spatial distribution of the principal chemical constituents in the groundwater is related to the landform. The chemical characteristics of groundwater in the study area are mainly controlled by the weathering and dissolution of silicate and sulfate minerals, evaporation, seawater mixing and cation exchange. Nitrate in clastic fissure groundwater, granite fissure groundwater and unconfined pore groundwater primarily originates from atmospheric precipitation, agricultural activities of slope farmland and forest land. Nitrate in confined pore groundwater and karst groundwater primarily originates from domestic sewage and mariculture wastewater. Our findings elucidate the processes characterizing the hydrogeology and surface water interactions in Zhuhai City’s coastal system, which are relevant to other catchments with similar geological characteristics.

Human health risk and water quality assessment due to fluoride and nitrate around Cauvery River basin, southern India.

Good quality water for human consumption, irrigation, and industrial use is very important. Today, around the world, water is contaminated by natural processes and human activities. This study aimed to evaluate the suitability of groundwater for drinking and irrigation, identifythe source of fluoride and nitrate contamination, and assess thehuman health risks around the Cauvery River basin in southern India. A total of 30 groundwater samples were collected and analyzed for hydrochemical parameters, including EC, TDS, pH, Ca, Mg, Na, K, HCO3, Cl, SO4, NO3, and F-. The majority of groundwater samples in the study area are used for drinking and irrigation. The pH of groundwater in the study area was observed to be dominantly alkaline. The levels of TDS, Ca, Na, K, F, and TH exceeded the permissible limits recommended by BIS and WHO. Fluoride and nitrate levels in groundwater exceeded the permissible limits for drinking purposes in 43% and 50% of the samples, respectively. The excessive concentration of fluoride and nitrate in groundwater could pose serious human health problems. Fluoride and nitrate concentrations in groundwater vary between 0.1 and 2mg/l and 12 and 95mg/l, respectively. Based on the computation of the drinking water quality index, about 73% of groundwater samples were classified asexcellent to good. Health risk was assessed for infants, children, and adults using non-carcinogenic risk indices such as hazard quotients (HQ), hazard indexes (HI), total hazard indices (THI), and carcinogenic risk indices (CR). Infants, children, and adults have different total hazards indexes ranging from 1.508 to 5.733, 1.579 to 6.003, and 0.011 to 0.046, respectively. Health risk assessment results indicatedthat the hazard index and hazard quotient were above the recommended limit of > 1 in most of the samples for infants and children. Non-carcinogenic risk and carcinogenic risks were more likely to affect infants and children rather than adults through ingestion of contaminated water.

Unlocking the bioremediation potential of adapted Desulfovibrio desulfuricans in acidic low-temperature U-contaminated groundwater

Addressing the global challenge of uranium (U)-contaminated groundwater requires innovative bioremediation strategies. This study investigates Desulfovibrio desulfuricans, a neutrophilic and mesophilic sulfate-reducing bacteria (SRB) strain optimized for low-temperature (15 °C) and acidic (initial pH 4) conditions, to validate its bioaugmentation potential for uranium decontamination in groundwater. Our research aimed to assess its efficacy in treating U-contaminated groundwater and elucidate the optimal growth conditions for this strain in acidic and sulfate-enriched environments. We found that D. desulfuricans was phylogenetically distinct from the native microbial community in acidic U-contaminated groundwater, while it maintained appreciable activity in sulfate reduction under contaminated groundwater conditions after accumulation. Acid-tolerant D. desulfuricans removed 75.87 % of uranium and 30.64 % of sulfate from acidic U-contaminated groundwater (pH 4.0) at 15 °C within 14 days. Furthermore, we explored the optimal sulfate concentration for bacterial growth, which was found to be 2000 mg/L, and an elevated Fe2+ concentration from 100 to 1000 mg/L increasingly stimulated sulfate-reducing activity. These findings provide a novel insight into the application of neutrophilic and mesophilic SRB in bioremediation of acidic and low-temperature groundwater after accumulation and underscore the feasibility of bioremediation by using exogenously pure SRB.

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.

Phreatic Groundwater Quality Analysis Based on Physical and Chemical Parameters in Kuta Raja Sub-District

Phreatic groundwater, discovered easily around communities in the Kuta Raja Sub-district, is sourced from the subsurface and stored in saturated areas, where it flows naturally through seepage or jets. Therefore, this study aimed to analyze the quality of phreatic groundwater using physical and chemical parameters. Color, taste, smell, and temperature were the physical parameters analyzed, while chemical parameters tested included electrical conductivity value, acidity (pH), and hardness level. To conduct the experiment, a total of 50 samples were obtained using a random sampling method. Physical parameters were evaluated using the observational method. Test for groundwater hardness level was conducted at the Aceh Health Office's Health &amp; Medical Equipment Testing Laboratory. The pH was measured using a pH meter, while electrical conductivity value and phreatic groundwater temperature were tested using a water quality checker. The results showed that the physical quality of groundwater was in good condition. Approximately 64% of the samples had characteristics of yellow, tasteless, and odorless. The temperature value was in the medium category (30°C-35°C). Additionally, the electrical conductivity value of 84% was in the medium class (1,200–2,500) brackish groundwater category. It was important to acknowledge that a groundwater pH value of 6.5–8.5 based on field measurements was in the normal class. The hardness level (CaCO3) of phreatic groundwater was evaluated using the Titrimetric method based on SNI Number 06-6989.12-2004. The test was conducted on 6 groundwater samples in terms of water flow and variations in electrical conductivity values. Based on observations, 4 samples were categorized as "hard" samples, while 2 were classified as “very hard”.

Geochemistry of fluoride mobilization in the hard-rock aquifers of central India: Implication for fluoride-safe drinking water supply

Globally, groundwater contamination by fluoride (F−) is a threat to the safe drinking water supply. Nevertheless, our understanding of the geochemical processes of F− mobilization to the groundwater by linking groundwater and aquifer material chemistry is limited. We therefore characterized that in the hard-rock aquifers of Central India, an area that has not been investigated thoroughly despite the known severity of the problem. Exploratory drilling of boreholes (n = 45) and lithostratigraphic modeling identified weathered basalt, vesicular basalt, fractured basalt, sandstone of Lameta, and fractured granite as major aquifers in the study area. The groundwater contamination by F− (concentration >1.5 mg/L) mainly occurred at depths >35 m bgl (at elevations <500 m amsl) of the fractured basalt and fractured granite aquifers, while samples collected from the shallow basalt, sandstone of Lameta, and shallow granite were mostly safe. The F− contamination of groundwater was primarily governed by the chemical evolution of groundwater along the flow path. Solute mass balance in groundwater, in conjunction with the mineralogical characterization of the aquifer materials, suggests that weathering of silicate and carbonate minerals was the dominant form of mineral dissolution in aquifers, which consumed dissolved CO2 along the flow path and resulted in an alkaline pH (>8) in groundwater of the deeper aquifers. The mobilization of F− in the groundwater could primarily be attributed to the ion exchange between OH− in water and structural F− in fluorapatite and F-bearing mica/amphibole. By assessing water quality and aquifer properties, this study suggests that primarily, the sandstone of Lameta and weathered and vesicular basalts can be targeted for F-safe drinking water supply in the study area. Targeting shallow aquifers can be an option for F-safe drinking water supply in other affected areas with similar geological and environmental settings.

Prediction Model of Groundwater Sulphate Based on Combined Multi-source Spatio-temporal Data

The accurate prediction of spatial variation trends in groundwater SO42- is of great significance for improving groundwater quality and regional groundwater management level. The multi-source spatio-temporal data such as land cover data, soil parameter data, digital elevation data, and groundwater pH value in the plain area of the Yarkant River Basin in 2011, 2014, 2017, and 2020 were used as characteristic variables to analyze their correlation with groundwater SO42- concentration. To enhance the prediction accuracy, the Bayesian optimization algorithm (BOA) was used to optimize the random forest regression (RFR). Based on the BOA-RFR model, the importance of the characteristic variables was analyzed, the prediction accuracy of the model was evaluated, and the groundwater SO42- prediction map was generated. The results showed that pH value, ground elevation (GE), and percentage of bare land (BAR) in the contribution area were important parameters influencing groundwater hydrochemical composition, which were significantly negatively correlated with groundwater SO42- concentration, and the importance of impact factors for predicting groundwater SO42- concentration exceeded 25 %. The geostatistical interpolation method was used as an auxiliary tool for the predictive modeling of spatial distribution. After adding auxiliary samples, the R2 of groundwater SO42- concentration prediction of the BOA-RFR model was greater than 0.96, and the maximum values of RMSE and MAE were reduced by 4.7 % and 23.8 %, respectively, compared with the minimum values of the model with fewer samples. The SO42- concentration prediction map showed that high SO42- groundwater was enriched in the northeast of the plain area of the Yarkand River Basin, an area that was expanding.

Assessment of phytodiversity and phytoremediation potential of plants in the vicinity of a thermal power plant

A study was carried out to evaluate phytodiversity along with the metal accumulation potential of native plants growing in the vicinity of a thermal power plant (TPP). We documented 26 tree species, six shrubs, and 35 herbs. Importance value index (IVI), which measures the extent to which a species dominates in an area, was found highest for Senna siamea (95.7) followed by Tectona grandis (56.5), and Pithecellobium dulce (19.6). Soil was acidic (pH 5.4) in nature with higher concentrations of Al and Fe. The pH of ground water was found acidic while pH of nearby river was found slightly alkaline. Values of PM2.5 and PM10 were slightly higher than NAAQS standards for industrial areas. The concentration of metals was found higher in aquatic plants than in terrestrial plants. In general, herbs and shrubs showed more metal accumulation potential than trees. Our results suggest that Senna siamea could be used for revegetation purposes in FA landfills. Further, terrestrial and aquatic plants such as Ageratina adenophora and Stuckenia pectinata could be used for reclamation of Mn, Zn, Al, and Fe from contaminated soils. Hydrilla verticillata (Ni and Mn), Nelumbo nucifera, and Ipomoea aquatica (Cr) can be used for metal removal from contaminated water.

Groundwater in the coastal areas of Ghana: Quality and associated health risks

Self-supply water sources, particularly groundwater sources, play key roles in the water supply ecosystem of developing countries. Recent studies indicate that groundwater sources in coastal communities in Ghana are under threat from improper waste management practices, seawater intrusion and atmospheric aerosol deposition. In this study, Water Quality Index (WQI) and Nemerow's Pollution Index (NPI) were employed to assess groundwater quality in four coastal communities of Ghana. The health risks associated with metal pollution of groundwater were investigated using incremental life cancer risk and hazard quotient. pH of groundwater in all the studied communities were acidic during the rainy season. Electrical conductivity ranged from 0.44 to 2.61 mS/cm in the rainy season and from 0.43 to 2.45 mS/cm in the dry season for the four studied locations. Results also showed brackish conditions and mineralization of groundwater in Winneba, Accra, and Keta. Mean nitrate concentrations in Winneba and Accra were higher than the WHO standards for both the rainy and the dry season. Arsenic was higher than the acceptable level in Accra and Keta during the dry season, while iron was higher than the acceptable levels in Accra in both the rainy and dry seasons. Principal Component Analyses showed that Pb, As, and Fe had the highest loading in the first component in Essiama, while PO43-and Pb had the highest loading in the second component in Accra. WQI showed that the quality of groundwater in all the studied communities ranged from marginal to poor indicating that groundwater in the coastal communities often or usually departs from desirable quality. NPI revealed that NO3- , As, and Fe contribute to groundwater deterioration. Health risk assessment showed that As posed a high cancer risk in Accra and potential cancer risk in Essiama, Winneba, and Keta during the dry season. As also posed potential cancer risk in Accra during the rainy season. Non-cancer health risk was observed for As in Accra and Keta. The findings of this study suggest urgent regulations and monitoring strategies to improve groundwater quality in the coastal communities of Ghana.

Speciation simulation and sorption mechanism of 238Pu in radioactive waste repository lithosphere

Abstract The assessment of the migratory and environmental behavior of radioactive nuclides escaping from waste treatment facilities heavily relies on the use of numerical models capable of simulating and characterizing all significant processes of nuclides in complex geological environments. Adsorption models typically encompass the chemical properties of the nuclides themselves and their chemical reactions with the surrounding environment, as well as processes such as ion exchange or physical adsorption. These processes must be taken into consideration in the long-term safety assessment of radioactive waste repositories. The redox-sensitive nuclide 238Pu, a critical member among transuranic elements, exhibits a diverse range of aqueous forms, and concurrently, it possesses high toxicity. The chemical behavior of 238Pu shows strong spatial variability with changes in environmental conditions. In this study, we constructed a theoretical model for the migration of nuclides in soil and groundwater environments through indoor static batch experiments and hydrogeochemical simulations. Experimental methods were employed to dissect the micro-scale, irreversible adsorption reaction processes of nuclides and identify their primary existing forms. According to field measurements, the pH of groundwater was recorded as 7.48, with an Eh of 125.7 mV. Introducing a solid-to-liquid ratio of 1:10 g/mL in centrifuge tubes, we measured the radioactive nuclide concentration after achieving adsorption and desorption equilibrium, obtaining adsorption and desorption isotherms. The PHREEQC software was employed to investigate the changes in 238Pu forms under varying conditions of pH and redox potential. Field measurements provided groundwater pH and Eh values. The activity concentration of the nuclide was measured after reaching adsorption and desorption equilibrium. The results show that the adsorption isotherms of 238Pu differ from its desorption isotherms, indicating an irreversible adsorption-desorption process. Ion exchange and surface complexation were identified as the main modes of adsorption. PHREEQC simulations revealed that 238Pu primarily existed in forms such as tetravalent Pu(OH)4 and trivalent Pu(SO4)2 −, PuSO4 +. Pu(OH)4 accounted for the largest proportion (97%) in the groundwater solution system, while a minimal amount of pentavalent PuO2 + was present. Environmental factors, such as pH and the presence of ions like SO4 2− and HCO3 −, influenced the forms of 238Pu.

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.

Diethylenetriaminepentaacetic acid (DTPA)-reinforced fenton-like process for efficient abatement of sulfamethazine at circumneutral pH in simulated groundwater

The present study proposed a promising heterogeneous Fenton-like process that a chelating agent (diethylenetriaminepentaacetic acid, DTPA) was introduced into the nZVI/H2O2 system to improve its oxidation capacity for abatement of sulfamethazine (SMT) at circumneutral pH in the simulated groundwater. The nZVI/DTPA/H2O2 system possessed a high oxidation performance for the elimination of SMT under the selected experimental conditions within 45 min of reaction. OH was considered as the predominant radical special accountable for SMT degradation. The roles of DTPA in the reaction system mainly include complexing with Fe2+ to prevent the passivation of nZVI, and forming the Fe2+-DTPA complex to rapidly decompose H2O2 to produce OH and other free radicals. The degradation patterns of SMT in the nZVI/DTPA/H2O2 system were inferred on account of density functional theory (DFT) calculation and the detection of intermediates via LC-MS analysis. Besides, nZVI/DTPA/H2O2 process could effectively reduce biological toxicity of SMT by prediction based on QSAR analysis. The coexisting ions such as Cl−, SO42−, and humic acid (HA) had negligible influences for the oxidative abatement of SMT, while HCO3− had a concentration-dependent inhibitory effect. The oxidation capacity of nZVI/DTPA/H2O2 process in actual water matrix and different pollutants were also discussed.

Appraising groundwater quality and probabilistic human health risks from fluoride-enriched groundwater using the pollution index of groundwater (PIG) and GIS: a case study of adama town and its vicinities in the central main Ethiopian rift valley.

This research's main objective is to identify the level of contamination in drinking water in Adama town and its environs by employing PIG, GIS and HHRA. The physical-chemical parameters of groundwater were determined, and the results were compared to regional and global drinking water quality guidelines. The pH of groundwater is alkaline, and the contents of Ca2+, Na+, HCO3 -, and F- in the majority of samples surpassed the permissible drinking limit. The hydrochemical facies were identified in the following order: Ca-Mg-HCO3, Na-Ca-HCO3, and Na-HCO3. Cation exchange and Rock-water interaction are the major dominant natural mechanisms controlling groundwater chemistry. Using IDW interpolation methods with Arc GIS 10.8, spatial analysis of the physico-geochemical content of water divulged that TDS, pH, TH, EC, Mg2+, Ca2+, K+, Na+, Cl-, HCO3 -, F-, and SO4 2- all exhibit a positive trend in the direction of groundwater flow from the upland to the lowland (rift floor). As per PIG, the results show that 57%, 33%, 7% and 3% of the samples were found in the insignificant, low, moderate and high, correspondingly. The total hazard index (THI) is calculated from hazard quotients (HQIntake and HQDermal) results showing 83%, 73%, and 57% of the samples exceed the non-carcinogenic health threat of fluoride THI >1 in drinking water for children, women and men. Children are more susceptible to danger than either males or women, according to the THI data, based on body weights and consumption rates. Similarly, females are also more vulnerable to health risks than men.