Groundwater Types Research Articles

Distribution and Co-Enrichment Factors of Arsenic and Fluoride in the Groundwater of the Plain Area of the Aksu River Basin, Xinjiang, PR China

The Aksu River Basin is located in the western region of the middle part of the southern foothills of the Tianshan Mountains and the northwestern edge of the Tarim Basin in Xinjiang, China. High-arsenic (As)/high-fluoride (F) groundwater is widely distributed in this area and is harmful to the life of local residents and to agricultural production. It is of great importance to understand the distribution and causes of As-F co-enrichment in the groundwater in this area. Based on the test results of 138 groundwater samples in the plain area of the Aksu River Basin, the hydrochemical characteristics of groundwater and the spatial distribution of As-F co-enrichment groundwater were analyzed under the following conditions: a single-structure phreatic aquifer (SSPA), a phreatic aquifer in a confined groundwater area (PACGA), a shallow confined aquifer (SCA), and a deep confined aquifer (DCA), all in a recharge area, transition area, and an evaporation area. The hydrogeochemical processes affecting the source, migration, and enrichment of As-F in the groundwater were revealed. The results showed that the chemical types of groundwater in the study area were mainly HCO3·SO4-Ca·Mg and SO4·Cl-Na·Mg. Horizontally, high-As-F groundwater was mainly distributed in the transition area and evaporation area in the middle and lower reaches of the Aksu River Basin. The area is close to the edge of the desert, where the groundwater runoff is sluggish and in an alkaline-reducing groundwater environment. Vertically, high-As groundwater was mainly distributed in the PACGA at a depth of 10–20 m and in the SCA at a depth of 80–100 m. High-F groundwater was mainly concentrated in the PACGA at a depth of 10–30 m and in the SCA at a depth of 80–100 m, and As-F co-enrichment groundwater was mainly concentrated in the PACGA at a depth of 10–20 m and in the SCA at a depth of 80–100 m. The hydrochemical characteristics of the groundwater in the Aksu River Basin were closely related to geological conditions, hydrogeological conditions, and the hydrochemical environment of the groundwater. As-F co-enriched groundwater was mainly affected by the combination of a small topographic gradient, a shallow groundwater burial depth, a weak reducing alkaline groundwater environment, strong evaporation and concentration, the weathering and dissolution of evaporated salt rock, and the alternating adsorption of cations.

Hydrogeochemical Characteristics and Formation Mechanisms of High-Arsenic Groundwater in the North China Plain: Insights from Hydrogeochemical Analysis and Unsupervised Machine Learning

Hydrochemical data were utilized in this study to elucidate the hydrogeochemical characteristics and genesis of high-arsenic groundwater in the North China Plain, employing both traditional hydrogeochemical analysis and unsupervised machine learning techniques. The findings indicate that the predominant hydrochemical types of groundwater in the study area are HCO3-Ca·Na and SO4·Cl-Na·Ca. The primary mechanism influencing groundwater chemistry has been identified as rock weathering. The unsupervised machine learning framework incorporates various methods, such as principal component analysis (PCA), non-negative matrix factorization (NMF), machine learning models (gradient boosting trees and random forests), and cluster analysis to explore the characteristics and genesis of groundwater hydrochemical types within the study area. This study demonstrated that the formation mechanism of high-arsenic groundwater results from multiple interacting factors.

Geological and hydrological controls on the pressure regime of coalbed methane reservoir in the Yanchuannan field: Implications for deep coalbed methane exploitation in the eastern Ordos Basin, China

The pressure regimes of the No. 2 coalbed methane (CBM) reservoir in the Yanchuannan field located in the southeastern Ordos Basin are highly variable and divided into overpressured (pressure gradient >9.80 kPa/m), slightly underpressured (pressure gradient of 8–9.80 kPa/m), and moderately underpressured (pressure gradient of 5–8 kPa/m). The controlling factors for the variable pressure regimes were investigated through the analysis of geological and hydrological characteristics. The pressure regimes are controlled by different mechanisms in different hydrodynamic environments. In the closed hydrodynamic environment characterized by TDS > 10,000 mg/L and NaCl type of groundwater, the pressure regime is dominated by overpressured to slightly underpressured and is controlled by CBM migration. Overpressure was developed by thermogenic CBM generation during the coalification process and is maintained by thermogenic CBM migration from the extended northwestward and deeply buried CBM reservoir during tectonic uplift. The transition from overpressure to slight underpressure and then to moderate underpressure towards the southeast is the result of the progressively weakened migrated thermogenic CBM with increasing migration distance. In the open hydrodynamic environment characterized by TDS < 10,000 mg/L and NaHCO3 type of groundwater, the pressure regime is dominated by slightly to moderately underpressured and is governed by hydrodynamics. Groundwater is fed by meteoric recharge along the structurally upturned basin margin and creates the hydrodynamic framework during tectonic uplift. The transition from moderate to slight underpressure towards the southwest is associated with the minor decrease range in ground elevation from basin margin to basin interior and the gradually weakened runoff intensity of groundwater with increasing distance to meteoric recharge. The idealized models for the pressure regimes are established, which can provide guidance to deep CBM sweet spot identification in CBM fields in the eastern Ordos Basin and elsewhere.

Geographical analysis of groundwater type distribution in Khabat district, using geographical information system (GIS)

Geographical analysis of groundwater type distribution in Khabat district, using geographical information system (GIS)

Occurrence and distribution of atrazine in groundwater from agricultural areas in China

There has been heavy application of chemical pesticides to farmland worldwide. As a state with a heavy emphasis on farming, China has extensively applied chemical pesticides to farmlands. Atrazine (ATZ), one of the most widely used herbicide in the world, has been used in large quantities in weed control in many crops, which poses a relatively large threat to groundwater utilization and agricultural safety. A nationwide sampling and analysis of ATZ in 8146 groundwater monitoring wells from 10 main grain producing areas were conducted during 2019. The results showed that the detection rate of ATZ in groundwater was 40.79 %, with detected concentrations up to 2.86 μg/L. ATZ detection rate was significantly higher in phreatic aquifers than confined aquifer. The concentration of ATZ decreased significantly with the depth increasing, the detected depth of ATZ in groundwater was varied from 5 to 1100 m, and 70.27 % of the detected ATZ was distributed in the depth of 0–51.8 m. The detection rate of ATZ in most north regions lower than south regions in China, and ATZ with high concentration was mainly occurred in southern regions. ATZ is more likely to migrate into the groundwater in the water resource rich areas. The concentration of ATZ decreased with TDS increasing, 74.39 % of the ATZ was detected in groundwater with TDS concentration <1 g/L. The hydrochemical type of groundwater in ATZ-enrichment environment were mainly Ca-HCO3 and Mixed type. According to classification and regression tree analysis, the high ATZ detection rate were closely related with groundwater depth (<51.8 m) and high organic matter content.

Integrated study of hydrochemistry, quality and risk to human health of groundwater in the upper reaches of the Wulong River Basin.

Groundwater, a vital source of water supply, is currently experiencing a pollution crisis that poses a significant risk to human health. To understand the hydrochemical formation mechanisms, quality and risk to human health of groundwater in the upper reaches of the Wulong River basin, 63 sets of groundwater samples were collected and analyzed. A combination of mathematical statistics, correlation analysis, Gibbs diagram, ion ratio, and cation exchange were comprehensively employed for hydrochemical analysis, and further water quality index (WQI) and human health risk assessment were conducted. The results indicate that groundwater is generally neutral to weakly alkaline. The dominant cations in the groundwater are Ca2+ and Mg2+, while the main anions are HCO3- and SO42-. The hydrochemical types of groundwater mainly include HCO3·SO4-Ca, HCO3-Ca and HCO3-Na. The diverse hydrochemical types are mainly due to the fractured and discontinuous nature of the aquifers. The hydrochemical characteristics are influenced by the dissolution of silicate and carbonate minerals, cation exchange processes, and anthropogenic pollution. The presence of NO3- in groundwater is primarily attributed to agricultural activities. The groundwater is mainly categorized as "Good" (36.6%) and "Poor" (60.8%). "Very poor" and "Excellent" categories are rare, accounting for only 1.2% and 1.4%, respectively, and no samples are classified as "Non-drinkable". The Ewi for NO3- is the highest, indicating severe contamination by anthropogenic NO3- pollution. Human health risk assessment reveals that water samples posing exposure risks account for 82.54% for children and 79.37% for adults. This study highlighted that anthropogenic nitrate pollution has deteriorated groundwater quality, posing risks to human health. It also suggests an urgent need to enhance research and protective measures for groundwater in similar regions, such as the Shandong Peninsula.

Groundwater dynamics clustering and prediction based on grey relational analysis and LSTM model: A case study in Beijing Plain, China

Study regionBeijing Plain, China Study focusThe traditional zoning of groundwater systems relies on lithological characteristics and hydraulic connections. However, the influence of climate change and human activities has led to the emergence of diverse dynamic patterns within these systems. Additionally, the differences in groundwater dynamic characteristics are often ignored when modeling with machine learning methods. In this study, a new clustering method named GRA-CLU was proposed to classify dynamic types of groundwater. Then, regional models are built using LSTM based on the dynamic zoning, aiming to incorporate hydrogeological significance into the pure data-driven model.New hydrological insights for the region: The GRA-CLU method classified the study area into six groundwater dynamic types. Compared with the traditional hydrogeological units, the new zoning result identified two dynamic types that have never been considered: urban influence zone and mountain-plain junction zone where surface water interacts with groundwater. Through analysis, the significant rise of groundwater levels in 2021 was more influenced by heavy rainfall events rather than human activities. This study further explored the performance of LSTM regional models based on the six dynamic zones. The results indicated that the NSE of models increased by 5.7–50.0 %, the improvement was more obvious in zones with irregular fluctuations. The RMSE decreased by 31.5–59.8 %, particularly noticeable in zones with regular annual fluctuations and large samples.

Appraisal of contamination, hydrogeochemistry, and Monte Carlo simulation of health risks of groundwater in a lithium-rich ore area.

This study incorporated hydrogeochemical facies, the entropy-weighted water quality index (EWQI), multivariate statistics, and probabilistic human exposure assessment to investigate hydrogeochemistry, analyze groundwater quality, and estimate potential risks to human health in a lithium-rich ore area (Jadar River basin, Serbia). The findings designated the Ca·Mg-HCO3 hydrogeochemical type as the predominant type of groundwater, in which rock weathering and evaporation control the major ion chemistry. Due to the weathering of a lithium-rich mineral (Jadarite), the lithium content in the groundwater was very high, up to 567mg/L, with a median value of 4.3mg/L. According to the calculated EWQI, 86.4% of the samples belong to poor and extremely poor quality water for drinking. Geospatial mapping of the studied area uncovered several hotspots of severely contaminated groundwater. The risk assessment results show that groundwater contaminants pose significant non-carcinogenic and carcinogenic human health risks to residents, with most samples exceeding the allowable limits for the hazard index (HI) and the incremental lifetime cancer risk (ILCR). The ingestion exposure pathway has been identified as a critical contaminant route. Monte Carlo risk simulation made apparent that the likelihood of developing cancerous diseases is very high for both age groups. Sensitivity analysis highlighted ingestion rate and human body weight as the two most influential exposure factors on the variability of health risk assessment outcomes.

Chemical Spatiotemporal Characteristics and Environmental Driving Factors of Groundwater in Hetao Irrigation Area

To explore the chemical characteristics and environmental factors of groundwater in the Hetao Irrigation Area of Inner Mongolia, five irrigation fields, including UulanBuh, Jiefangzha, Yongji, Yichang, and Wulat, were selected as the research area. From 72 groundwater observation wells, a total of 216 groundwater samples were collected throughout three typical periods： the end of freeze-thaw （March）, the middle of irrigation （July）, and the end of autumn watering （November）. Comprehensive methods were utilized, such as statistical analysis, Piper three-line diagram, Gibbs diagram, ion ratio, and principal component analysis, to explore the changes in the groundwater chemical environment and the environmental driving factors of groundwater component formation. The groundwater drinking suitability was evaluated using the water quality index （WQI）, and the irrigation suitability was analyzed using the USSL and Wilcox plots. The results indicated that the groundwater in the research areas was generally saline, and the total anion and cation concentrations in each period in ascending order were as follows： late freeze-thaw stage, late autumn irrigation stage, and mid-irrigation stage, with Na+ and Cl- being the major contributing ions. The chemical type of groundwater was dominated by Cl-Na, followed by Cl·SO4-Ca·Mg and a coexistence with SO4-Ca·Mg, HCO3·Cl-Na, HCO3-Na, and HCO3-Ca·Mg. Based on WQI values, the shallow groundwater in Hetao Irrigation District was mainly classified as Class IV and Class V, and the quality was poor in general. According to the USSL diagram and Wilcox diagram, the comprehensive evaluation results showed that the salinity and sodium concentration of shallow groundwater in the irrigation area were generally high. A total of 80.6% of the water samples during the late freeze-thaw period, 76.1% during the mid-irrigation period, and 77.6% during the late autumn irrigation period lacked irrigation suitability. Two major controlling factors of groundwater chemical characteristics were present in the study area, namely, evaporation and rock weathering, and Na+ and Cl- mainly came from the dissolution and cation exchange of salt rocks. Agricultural irrigation and drought were the chief driving factors of groundwater chemical evolution in the Hetao Irrigation Area. The study provides technical support for optimizing agricultural management measures and a theoretical reference for rational utilization of groundwater resources in the Yellow River irrigation area of Inner Mongolia.

Ion sources and seasonal recharge characteristics of groundwater around Dali Lake in semi-arid region of Inner Mongolia Plateau, China

The interaction between groundwater and surface water around an inland lake in semi-arid regions creates a unique ecological pattern and is a key link in the regional ecohydrological cycle. In this paper, the major ions and hydrogen and oxygen isotope characteristics of groundwater, lake water, river water, and rain water were analyzed, which were sampled in Dali Lake and its surrounding areas in the dry and wet seasons. The ion ratio method and the end-member mixing analysis (EMMA) based on principal component analysis (PCA) were applied. The causes of the major ions in groundwater during the dry and wet seasons were analyzed. The temporal and spatial recharge sources and characteristics of groundwater were identified and quantified. The hydraulic relation between groundwater and surface water was clarified. The main hydrochemical type of groundwater was Ca-HCO3 with changed to Ca-Mg-Cl type in some areas in the wet seasons. Rock weathering was the main genetic mechanism of groundwater hydrochemistry which mainly from the dissolution of silicate. River water and precipitation were the main sources of groundwater recharge. However, there was a large difference in spatio-temporal distribution and recharge contribution. Gongar River water and precipitation were the main recharge sources of groundwater during the dry season with a contribution rate of 49 % and 48 % respectively. Haolai River water and Liangzi River water together became the main recharge sources of groundwater during the wet season with a contribution rate of between 83 % and 92 %. Rain water covered from 7 % to 13 % of groundwater recharge during the wet season. Overall, compared with river water and precipitation, the contribution of lake water to groundwater recharge was almost negligible, ranging from 0 % to 6 %.

An urbanized phantom tributary subsidizes river–riparian communities of a mainstem gravel‐bed river

Abstract Urbanization transforms natural river channels, and surface water of some rivers disappeared over time. How and whether the subsurface domains of the original waterways and aquifers connecting them (a phantom of historical landscape) are functional is not known. This study examined the effects of tributary groundwater inflow on the response of river–riparian organisms in an alluvial mainstem river in northern Japan, where the tributary disappeared over the course of urban landscape transformation. A 2.8‐km lowland segment of the mainstem gravel‐bed river was examined for water properties and the river–riparian food web. In addition, watershed‐wide water sampling was conducted to isotopically distinguish several types of groundwater that contributed to the hyporheic water in the study segment. Altitude had a clear effect on the hydrogen/oxygen stable isotope ratios in the river water collected across the watershed. Groundwater unique both in chemical and isotopic signatures occurred in several spots within the study segment, and its properties resembled and its upwelling locations matched groundwater from a tributary river whose surface channel disappeared 60 years ago. Positive numerical increases in abundance and/or a sign of nitrogen transfer in river–riparian communities (algae, invertebrates and riparian trees) originating from groundwater high in nitrate with elevated nitrogen stable isotope ratios were found. We demonstrated that tributary groundwater with unique chemical properties manifested by an urban watershed river network continued to have trophic effects on biota across the river–riparian boundary in the mainstem river, even after urbanization transformed the tributary into a phantom river. We highlighted the legacy effects of landscape transformation in the subsurface domain and the significance of scrutinizing the past landscape and hydrological connectivity at the watershed scale in urban environments.

Carbonate Nanoparticles Formed by Water–Rock Reactions in Groundwater: Implication of Carbonate Rock Weathering in Carbonate Aquifers

Carbonate rocks are highly reactive and exhibit higher ratios of chemical weathering compared to most other rock types. A chemo-mechanical mechanism, which is particularly effective in groundwater due to higher ion concentrations, is common in fine-grained carbonates at the nanoscale. As a result, the weathering of carbonate aquifers produces a substantial number of carbonate nanoparticles (CNPs). In this study, we utilized high-resolution transmission electron microscopy (HRTEM) to analyze CNPs formed by water–rock reactions in two types of groundwater from Shandong Province, China. Our findings reveal a significant presence of naturally occurring CNPs in groundwater. The HRTEM results show that CNPs display spherical, cubic, hexagonal, and irregular shapes, with some forming aggregates. Energy-dispersive spectrometry indicates that most nanoparticles contain O, C, Ca, and Fe, with some also containing Si, Mg, S, Sr, and Cl. Selected area electron diffraction (SAED) patterns show that CNPs are mainly amorphous, with some crystalline forms. The diverse shapes and complex compositions of these CNPs suggest that they are not man-made but formed through the weathering of carbonate minerals via chemo-mechanical mechanisms. This discovery provides new insights into carbonate mineral evolution and mineralization during weathering. Given their widespread presence, CNPs in groundwater could represent the transportation of elements in the form of particles.

Hydrochemical insights, water quality, and human health risk assessment of groundwater in a coastal area of southeastern China.

Groundwater is a vital water supply worldwide, but its quality has gradually deteriorated with the development of society. In this study, a total of 40 groundwater samples were collected during the pre- and post-monsoon to analyze the hydrochemical process and assess the groundwater quality and human health risks in a coastal area of southeastern China. The results showed that the concentrations of major ions were in the order of Ca2+> Mg2+ > Na+ > K+ and HCO3- > SO42- > Cl- > NO3- > F- during the pre- and post-monsoon periods. A slight increase was observed during the post-monsoon period. The Piper diagram suggested that the hydrochemical type of groundwater was predominantly HCO3-Ca. Principal component analysis (PCA), ionic ratios, and saturation index (SI) determined that the water-rock interactions involving silicate and carbonate minerals played a significant role in the hydrochemical process. The results of the entropy-weighted water quality index (EWQI) and irrigation water quality index (IWQI) evaluations revealed that the general qualities of groundwater were suitable for both drinking and irrigation purposes. However, the excesses of NO3- and SO42- were observed locally. Human health risk assessment concluded that groundwater posed a low risk to human health, and infants faced higher risk compared with adults. The study would provide valuable information for groundwater environmental protection.

Application of major ions and Sr isotopes to indicate the evolution of river water and shallow groundwater chemistry in a typical endorheic watershed, northwestern China

Studying the hydrochemical evolution of river water and groundwater is vital for comprehending complex regional hydrological cycles and managing water resources. An investigation of hydrochemical evolution mechanism of river water and groundwater was executed in an arid and semi-arid endorheic watershed located in the eastern edge of Qaidam Basin, northwest China, by analyzing major ions and strontium isotopic compositions with the combination of hydrogeochemical methods, PMF model and Pearson correlation analysis. From upstream to downstream, the major ions, 87Sr/86Sr values and hydrochemical types of river water and groundwater show spatial variations. Major ions and 87Sr/86Sr analysis reveal that the hydrochmical compositions of river water and groundwater are primarily attributed to silicate weathering, carbonate weathering, evaporite weathering, and agricultural activity. The contribution of four factors affecting the hydrochemical evolution show obvious spatial variations along the flow path. The hydrochemical compositions of river water from the upstream to downstream are mainly contributed by carbonate and silicate weathering as well as weak evaporite weathering (<25%), which are affected by agricultural activity with a great contribution (>25%) in the middle and lower reaches. The contribution to the hydrochemical compositions of groundwater is relatively small (<25%) for carbonate, silicate and evaporite weathering, but great (>25%) for agricultural activity. This study provides implications for understanding the formation and evolution of water and better watershed water management in that typical endorheic watershed basin and even at larger scales.

Perfluorooctanoic acid transport and fate difference driven by iron-sulfide minerals transformation interacting with different types of groundwater

Perfluorooctanoic acid (PFOA) is an emerging persistent organic pollutant that threatens human health and ecosystems. However, the intricate mechanism of the change in PFOA transport behavior that interacts with FexSy minerals under groundwater-type differences is not clear. To address this knowledge gap, multi-scale experiments and multi-process reaction models were constructed to investigate the underlying mechanisms. The results showed that different groundwater (NO3-, Cl--Na+, SO42-, and HCO3- types) had significant effects on PFOA transport. NO3-, Cl--Na+, SO42-, and HCO3- decreased the retardation effect of PFOA in the FexSy media. Compared to other groundwater types, the adsorption sites of FexSy were the least occupied in the NO3- groundwater. This observation was supported by the least inhabition of λ in FexSy-NO3- interaction system, which demonstrated that more PFOA was in a high reaction zone and electrostatic repulsion was weakest. The surface tension of different ion types in groundwater provided evidence explaining the lowest inhibition in the FexSy-NO3- system. The 2D spatiotemporal evolution results showed that in FexSy with NO3- system, the pollutant flux (6.00 ×10−5 mg·(m2·s)−1) was minimal. The pollutant flux in the SO42- groundwater system was 9.95-fold that in FexSy with the NO3- groundwater. These findings provide theoretical support for understanding the transport and fate of PFOA in FexSy transformations that interact with different types of groundwater.

Hydrochemical appraisal and suitability for irrigation and portable purposes in eastern Himalayan syntaxis of Tibet Plateau

The formation mechanism and quality evaluation of surface water and groundwater have provided valuable information on water management of alpine catchment, such as Tibet Plateau. However, scarce knowledge of surface water and groundwater has been achieved from Eastern Himalayan syntaxis in eastern Tibet due to harsh and complicated natural and geological conditions. This study collected 60 water samples from the Layue alpine catchment within Eastern Himalayan syntaxis, including 35 samples of groundwater and 25 of surface water. A combination of multivariate statistical analysis, ion ratio analysis, geochemical modeling, hydrogen and oxygen isotope analysis, and water quality index (WQI) analysis was employed to explore hydrochemical processes and irrigation and portable suitability. Results indicate that the groundwater types identified include bicarbonate-calcium, sulfate·chlorine-sodium, and mixed bicarbonate-calcium·sodium, while surface water are sulfate·chlorine-sodium, mixed bicarbonate-calcium·sodium, and mixed chlorine-calcium·magnesium types. Groundwater recharge primarily originates from meteoric precipitation, with recharge elevations ranging from 2216 to 3698 m, while surface water receives both precipitation and groundwater recharge in a proportion of 50.51%–87.96%. Silicate weathering and carbonate dissolution predominantly control the hydrochemical compositions. Sodium adsorption ratios (0.75–88.55) and electrical conductivity (85.20–1686.12 μs/cm) indicate water resource are mostly suitable for irrigation. The entropy-weighted water quality index (97% in total <100) denotes the suitability for portable use. These achievements would provide substantial support for the sustainable water management in alpine areas, especially for Tibet Plateau.

Identification of Groundwater Potential Zone Existence in GAR Housing Using Electrical Resistivity Method

The GAR (Grand Aceh Residence) housing estate is located in Baet Village, Aceh Besar District and was constructed on the land of a pond that has been filled in and is close to the coast. The majority of residents use clean water sources from PDAM because of the difficulty of obtaining clean water. The purpose of the research was to identify potential groundwater zones and determine the conditions. The research method used was electrical resistivity method, SuperSting R8/IP with Wenner-Schlumberger configuration. The research was conducted in 3 lines with 6 m spacing. RES2DINV software based on the least square inversion approach was used for data processing. The results obtained show resistivity values varying from 0.1 - 100 Ohm.m with a depth penetration of up to 28.8m. There are 3 lithological layers obtained, namely clay (0.1 - 1.5 Ohm.m), clayey sand (1.5 - 17.7 Ohm.m), and sand (17.7 - 100 Ohm.m). The groundwater presence zone is assumed to be in the sand layer. There are 2 types of groundwater obtained, which are shallow groundwater (phreatic) located from the center to the north of the lines to a depth of ± 13 m and deep groundwater, located varies in the middle of the lines from a depth of ± 15 m to the end with groundwater conditions may still be brackish due to the influence of seawater intrusion with a resistivity value of 0.1 Ohm.m identified to a depth of ± 25 m

Perfluorooctanoic acid efficient chain reaction degradation in multifunctional iron-sulfur mineral augmentation geobiochemical remediation system

Serious contamination of perfluorooctanoic acid (PFOA) has aroused global concern. General biotransformation or iron-based materials did not meet efficient PFOA elimination. Here, specific green and low-carbon microorganism-biochar pellets, multi-component and multifunctional iron-sulfur (FexSy) mineral pellets, and a microbe-FexSy interaction device were developed to solve this problem. The multi-scale (molecular, interface, and column scales) research method combined with the multi-process reaction model was constructed to explore PFOA removal mechanism. Results revealed that microbe-FexSy interaction achieved excellent PFOA degradation performance and retention effect, with degradation rate λ (0.213 h−1) increased by 113 % than FexSy (0.100 h−1) device. The distribution coefficient Kd and kinetic adsorption α increased by 18.54 % and 22.61 %; the fraction of kinetic sorption increased by 63.83 % in microbe-FexSy device (77 %) than alone FexSy (47 %) device. Delftia and Pseudomonas combined with Fe2+ drove an efficient cycle chain reaction for PFOA. Quantitative structure–activity relationship (QSAR) model prediction results indicated that intermediates exhibited lower biotoxicity than PFOA. Furthermore, NO3– further increased the retention effect of microbe-FexSy device for PFOA with little reaction rate fluctuation, making it promising for eliminating PFOA contamination, especially in NO3– type of groundwater. It provided an efficient technology and device based on microbe-mineral interaction in remediating PFOA-contaminated groundwater.

Identifying seawater interaction with coastal aquifers using hydrochemical and GIS for Nagapattinam district, southeast coast of India

Groundwater chemistry of the two different seasons collected between 2020–2021 from the coastal areas of Nagapattinam, Mayiladuthurai and Karaikal in Tamil Nadu state of southeast India were evaluated for seawater intrusion into coastal aquifers. Groundwater types, its classification was evaluated to know the extension of seawater intrusions into coastal aquifers using the Groundwater Quality Indices (GQI) such as GQIPiper(mix), GQIPiper(dom), fsea, GQIfsea and GQISWI. Piper diagram grouped most samples (GQIPiper(mix) and GQIPiper(dom)) in domain-II, representing Na-Cl water type, followed by domain-IV, indicating mixed Ca-Mg-Cl water for both the seasons. As measured by the saltwater Intrusion as Groundwater Quality Index (GQISWI), about 62.5 % and 37.5 % of the pre-monsoon samples showed low saltwater intrusion and moderate seawater intrusion, respectively. In the post-monsoon samples, the low saltwater intrusion increased to around 82.5 % and the moderate seawater intrusion decreased to 17.5 % of the groundwater samples. The GIS framework was used to display the geographical distribution of groundwater types as well as the delineation of vulnerable zones from seawater intrusion.

2D and 3D Modeling of Resistivity and Chargeability to Identify the Type of Saturated Groundwater for Complex Sedimentary Facies

Determining the type and properties of saturated groundwater for complex sedimentary facies, as well as the various properties of these sedimentary facies, requires extensive geological, hydrogeological, and geophysical studies. Therefore, identifying the different types of subsurface deposits and their physical properties as well as their geological, hydrogeological, and structural settings are the interesting features in this study which play an important role in achieving its objectives. To achieve these objectives, the Direct Current (DC) resistivity method and the Direct Current Time-Domain Induced Polarization (DC-TDIP) method were used. These two methods were applied because they are complementary methods, one of which is more accurate in sediments saturated with fresh water (the DC resistivity method) and the other in sediments saturated with salt water (DC-TDIP method). Also, the DC-TDIP method was applied to avoid ambiguity in the resistivity results, as well as their results were compared with the available geological and hydrogeological field data. Accordingly, 2D and 3D resistivity values were designed to describe the hydro-lithological environment of the recorded sediments, and their hydrogeoelectric properties and groundwater zones were also identified and divided. Also, 2D and 3D chargeability values were designed to distinguish between sediments, their depositional facies, and their saturated water properties. These values also succeeded in separating clay from non-clay layers, and clay layers from layers containing salt water. Therefore, it was found that the integration between the two methods helped in identifying and visualizing the characteristics of the sediments and determining their facies and their water content, which helped in understanding the complex sedimentary facies recorded in the study area as well as identifying the types and characteristics of groundwater contained in these facies. Therefore, it can be recommended to apply the previous methodology and include the two geophysical methods and their results to study complex facies deposits and determine their water content and type, especially in similar depositional environments that are located next to a source of salt water mixed with other types of water.