Groundwater Types Research Articles

Iron (hydr)oxide dynamic transformation-induced perfluorooctanoic acid transport and attenuation effect: Impacts of initial goethite and associated minerals content and groundwater type

Perfluorooctanoic acid (PFOA) has been widely utilized, leading to serious contamination. Iron (hydr)oxide transformation was varied in media. Whereas, dynamic transformation effect was extensively unclear. Here, iron (hydr)oxide dynamic transformation-induced PFOA transport and attenuation was investigated by emphasizing initial goethite (α-FeOOH) and associated minerals content and groundwater type based on the multi-process attenuation model. Results revealed that groundwater type did not affect the PFOA attenuation pathway. However, it controlled the iron (hydr)oxide dynamic transformation differences. PFOA transport behavior (retardation factor R from 2.61 to 1.91) was significantly affected by iron (hydr)oxide dynamic transformation. Iron (hydr)oxide transformation induced the greatest PFOA transport risk (R = 1.91, attenuation rate λ = 0.0001 min−1) in SO42− environment, where complex α-FeOOH, Fe3O4, and β-Fe2O3·H2O transformed to simplex β-FeOOH, leading to instantaneous (Kd) and kinetic (α) two-site sorption fraction change. Furthermore, the associated mineral Fe3O4 of goethite was crucial in PFOA attenuation (λ from 0.0001 to 0.0002 min−1). Fe3O4 released Fe2+ and the oxidation of Fe2+ to Fe3+ provided electrons, facilitating the formation of F–(CF2)7–COO· radicals, which played a key role in the following cycle attenuation process. This study provides a theoretical basis for understanding the interaction mechanism of PFOA and iron (hydr)oxide dynamic transformation under groundwater differences.

Pathogen survival in groundwater: Influence of redox and organic matter

Microbial pathogen survival within the environment can be variable and can depend on many criteria, including environmental conditions e.g. oxygen concentration, temperature, pH, sunlight, etc. (e.g., Horswell et al. (2010)). Groundwater has been shown to enable the prolonged survival of pathogenic organisms due to the absence of sunlight and relatively stable temperatures (Cook and Bolster 2007). In other studies, however, survival has been lower in groundwater when compared with a sterile environment (e.g. sterilised groundwater or artificial groundwater) due to the presence of competing organisms and adverse conditions of pH and redox. To elucidate these discrepancies two experiments were designed: The first, hypothesised that, due to Campylobacters' low tolerance to high oxygen levels, survival in oxic (dissolved oxygen (DO) levels over 5 mg per L) would be less than in anoxic groundwater (DO levels below 2 mg per L). The second hypothesised that the survival of the pathogen Salmonella typhimurium, in groundwater, will be enhanced by organic carbon. METHODS Campylobacter experiment: Campylobacter jejuni isolated from the Havelock North drinking water source was used (designated HN16) (Gilpin et al. 2020). To compare the survival of the outbreak strain with type strain Campylobacter, NCTC 11351 was used. Salmonella experiment: For this experiment, environmental isolates were used rather than laboratory strains. Salmonella, isolated from a stream in Wellington, New Zealand, was identified as Salmonella enterica serovar Typhimurium. The Escherichia coli used was a phylogroup A, isolated from stream sediment in Whangarei Falls, New Zealand. Mesocosm experiments were established containing groundwater (oxic and anoxic for Campylobacter experiment and ultrafiltered, groundwater, groundwater amended with 1% or 10% dissolved organic carbon (DOC). pH, dissolved oxygen (DO), and temperature were monitored over the experimental period. The temperature was maintained at 12-14°C during both experiments. Samples (5 mL) of the groundwater from each jar were taken aseptically at set time points over the experimental period. Samples were then serially diluted in sterile peptone water to give a dilution series from 10-1 to 10-4. Samples were analysed by plating onto selective media. RESULTS Campylobacter experiment: The results presented demonstrated differences in the survival of the two Campylobacter strains tested and differences in survival of Campylobacter HN16 depending on groundwater type. Fig. 1 shows the average concentration of Campylobacter strains in groundwater types over time. The results presented are average of three replicates. Over the whole experimental period survival of Campylobacter HN16 was greatest in anoxic groundwater, and only a 1 log reduction was observed (Fig. 1), equating to a 79.6% survival after 16 days. The die-off rate of Campylobacter HN16 in anoxic groundwater was calculated to be 0.0873 days and T90 6.85 days. Salmonella experiment: Die-of rates for Salmonella were similar over the course of the experiment when no or low levels of DOC were present (Fig. 2a). At high levels of DOC, however, Salmonella showed similar survival to the control. After 84 days only a 1 Log decrease was observed. In comparison, E. coli died off at a faster rate than Salmonella in all mesocosms (Fig. 2). It is interesting to note that in the high DOC mesocosms after day 56 counts of E. coli remained at 103 per mL until the end of the experiment. Conclusions and significance Both experiments demonstrated the survival of pathogenic microorganisms in varying groundwater conditions. The variation in the outbreak strain Campylobacter compared to the type strain indicated variation within species that may lead to enhanced survival in the environment. The Salmonella experiment indicated the presence of additional organic carbon can enhance the survival of pathogens in groundwater. In addition, the variation between the microbial indicator E. coli and Salmonella provides evidence of differences in the survival of microbes in the environment and indicates caution is needed when considering the survival of pathogens in groundwater if reliance is made on microbial indicator organisms.

Influence of the concentration and nature of total dissolved solids in brackish groundwater on water intake, nutrient utilization, energy metabolism, ruminal fermentation, and blood constituents in different breeds of mature goats and sheep

Brackish water is being progressively utilized in livestock farming across the globe where freshwater is scarce, potentially leading to detrimental consequences for animal health and performance. This study was conducted to determine effects of different brackish groundwater types on water and feed intake, nutrient utilization, ruminal fluid characteristics, and blood constituent concentrations in different breeds of goats and sheep in a 6 (animal types; AT) × 6 (water treatments; WT) Latin square design. Six AT (Boer, Spanish, and Tennessee Stiff-Leg does and Dorper, Katahdin, and St. Croix ewes) consumed drinking water differing in total dissolved solids (TDS) and mineral composition. Six WT were fresh water (FRW; 287 mg TDS/kg), a natural brackish water (BR) alone (100-BR; 5734 mg TDS/kg), BR with concentrations of all minerals increased by about 100 % (200-BR; 10,603 mg TDS/kg), FRW added with NaCl having similar TDS level (6654 mg/kg) as 100-BR (100-SL), FRW added with NaCl having similar TDS (12,197 mg/kg) as 200-BR (200-SL), and water with similar TDS (10,643 mg/kg) level as 200-BR by adding NaCl to 100-BR (200-BR/SL). Water treatment only affected (P < 0.05) water intake, total volatile fatty acids in ruminal fluid, blood phosphorus, blood aldosterone, and plasma osmolality. Water intake was greater (P < 0.05), but total ruminal volatile fatty acid concentrations were lower (P < 0.05) for 200-SL than other WT. Plasma osmolality and aldosterone concentrations were lower (P < 0.05) for 200-SL and 200-BR/SL than FRW. There were no significant interactions between WT and AT for any variable. Water and feed intake, digestibilities, ruminal ammonia concentration, and methane emission were similar among AT (P > 0.05). There were differences (P < 0.05) among AT for many ruminal fermentation and blood characteristics. Although there were some differences among WT, no AT seemed adversely affected by water with a TDS level near or slightly above 10,000 mg/kg regardless of mineral sources.

Survival Strategies of High GC-Content Microorganisms in Oligotrophic Deep Groundwater

Deep groundwaters are among the most energy and nutrient-limited ecosystems on the planet. The limited resources are mainly due to the absence of photosynthesis-driven primary production (Kadnikov et al. 2020). These ecosystems do however host phylogenetically diverse and metabolically active microorganisms from all domains of life plus viruses (Holmfeldt et al. 2021, Mehrshad et al. 2021). In this study, we used a large metagenomic dataset generated over the last eight years from the Äspö Hard Rock Laboratory (Äspö HRL) in Sweden and drill holes in Olkiluoto Island, Finland. This dataset, termed the “Fennoscandian Shield Genomic Dataset” (FSGD), contains metagenome-assembled genomes (MAGs) and single-cell amplified genomes (SAGs). Previous studies on this dataset have shown that reciprocal symbiotic partnerships and efficiency of energy metabolism define the core microbiome of these deep groundwaters (Mehrshad et al. 2021). Studies on different marine and freshwater ecosystems show that oligotrophic environments host streamlined genomes with lower GC content. However, it is not known how the low carbon and energy availability in deep groundwaters affect the microbial community regarding their genome size and GC content. To address this, we used the FSDG to study the distribution of genome size and GC content among bacterial and archaeal genomes in Fennoscandian Shield deep groundwaters. We further disentangled the prevalent metabolic strategies in these genomes that is being used to support their carbon and nitrogen demands for replication and survival. A total of 1990 MAGs/SAGs with a completeness of ≥50% and &amp;lt;5% contamination were recovered from 43 metagenomic datasets. The taxonomy of the MAGs/SAGs was assigned using the GTDB-tk (Chaumeil et al. 2022) and the GC content and genome size of MAGs/SAGs were calculated. MAGs/SAGs were also functionally annotated to investigate the genome-encoded functional potential. To survey the preference for different metabolic pathways and metabolic cross-feeding, the C-fixation pathways were subdivided into 82 routes that lead to the production of intermediate compounds (e.g., formate, pyruvate, oxaloacetate, etc.). A similar analysis for nitrogen acquisition pathways and CO2-capturing enzymes was performed and the presence/absence of these metabolic modules was investigated in representative MAGs/SAGs from various deep groundwater types to explore the microbial community’s metabolic interaction. The GC content and estimated genome size (EGS) of the recovered MAGs/SAGs were linearly correlated, suggesting that higher genome-level GC content is associated with larger genome size. The most common taxa among high GC (≥50%) content MAGs/SAGs were affiliated with the phyla Proteobacteria, Desulfobacterota, Actinobacteriota, Chloroflexota, and Patescibacteria. Analysis of metabolic modules in the environmental context revealed that high GC content MAGs constituted the main primary producers in all investigated groundwaters. Among the seven investigated C-fixation pathways, routes leading to the production of intermediates of reductive tricarboxylic acid (rTCA) were significantly enriched in high GC-content genomes. Both carboxylation/reduction first CO2-capturing enzymes were significantly enriched in MAGs with high GC contents. Of the various carbon fixation strategies, rGly and rTCA are the most energy-efficient and consume one and three ATP molecules, respectively (Bar-Even et al. 2011), matching the high prevalence of rTCA in oligotrophic deep groundwater. High GC content genomes featured metabolic pathways to generate key precursors for synthesizing purine/pyrimidine and amino acids. As GC base-pairs require one more nitrogen than AT base-pairs, prokaryotes with a higher GC content need proportionally more nitrogen for genome replication. In agreement with this, high GC content MAGs/SAGs from the FSGD feature additional nitrogen uptake systems including ammonium permease and N-fixation genes. High GC content MAGs/SAGs appear to be metabolically versatile and capable of acquiring nutrients via different carbon and nitrogen fixation pathways along with various C-scavenging strategies for substrate uptake to acquire energy and survive in oligotrophic conditions. Although their larger genome size and higher GC content entail higher expenses for replication and maintenance, their presence within the community of deep groundwater is supported by the “Black Queen Theory”. According to this theory, a cell containing an expensive metabolic pathway is maintained within the community as it provides a service that other members cannot.

The assessment of groundwater quality through the water quality and nitrate pollution indexes in northern Türkiye.

Groundwater is contaminated by anthropogenic factors such as industry, domestic waste, and excessive fertilizers. Groundwater samples, which were obtained from 50 different wells in July 2020, were used in this study. Thirteen hydrochemical properties, including electrical conductivity (EC), pH, total dissolved solids (TDS), total hardness (TH), nitrate NO3-, anions, and cations were analyzed. Also, types of groundwater were investigated via the Piper diagram. The groundwater was also evaluated for irrigation suitability using the sodium percentage (Na%), sodium adsorption ratio (SAR), Kelly's index (KI), residual sodium carbonate (RSC), potential salinity, magnesium hazard (MR), and permeability index (PI). The samples were assessed for drinking the suitability using the water quality index (WQI) and the nitrate pollution index (NPI). Geographic information systems (GIS) were used to create spatial distribution maps of irrigation water quality indices, WQI, and NPI values. The results of major cations varied sodium 28.69-211.80mg/L, calcium 78.74-258.89 magnesium 27.78-161.30mg/L, and potasium 0.10-3.57mg/L. The results from the study area showed that 62.70 of EC, 32.40% of PI, 20.09% of RSC, 51.55% of PS, and 49.36% of MR were inappropriate for irrigation purposes. The NPI data ranged from - 0.75 to 9.65, and 21.06% of the study areas were heavily polluted. The WQI showed that almost 62.90% of the experimental area was categorized as poor, very poor, and inappropriate for drinking water purposes, whereas 37.10% of the areas were categorized as good and excellent.

Utilizing geographic information system and indexing to evaluate irrigation suitability of groundwater in Kalihati Upazila, Bangladesh

The aim of this research was to evaluate groundwater quality for irrigation in Kalihati Upazila, Bangladesh, a region that is significantly reliant on groundwater for crop development, especially during dry periods. By combining hydrochemical analysis and Geographic Information System (GIS), the research examined the physicochemical attributes and their spatial distribution. Fifteen groundwater samples from various locations were analyzed to measure parameters such as sodium adsorption ratio (SAR), soluble sodium percentage (SSP), residual sodium carbonate (RSC), magnesium adsorption ratio (MAR), electrical conductivity (EC), total dissolved solids (TDS), total hardness (TH), Kelly's ratio (KR), permeability index (PI), and potential salinity (PS). The pH of the groundwater ranged between 5.51 and 7.53, indicating slightly acidic to moderately alkaline conditions suited for irrigation. The EC ranged between 115.7 and 458 μS/cm, mostly falling into the "excellent" or "good" categories. Groundwater displayed irrigation suitability with TDS below 182 ppm and low SAR values, but variable RSC and MAR values indicated localized water quality issues. Based on the irrigation water quality index, all samples were within the "permissible" range. However, GIS-generated maps showed disparities in groundwater quality across the study area. Correlation matrices revealed significant links between various factors. Both the Piper and Gibbs diagrams displayed a prevalent Ca-HCO3 groundwater type influenced by geological formations. Overall, the study confirmed groundwater's appropriateness for irrigation while recommending periodic evaluations due to a few uncertainties. In conclusion, the study found that hydrochemical analysis, GIS mapping, and correlation matrices reveal groundwater quality and spatial trends, allowing for sustainable water resource management and agricultural advancement.

Replenishment Impacts on Hydrogeochemistry and Water Quality in the Hutuo River Plain

To investigate the influence of the Hutuo River (North China) ecological water replenishment project on the hydrogeochemical processes of groundwater, 64 groundwater samples collected at different time intervals after four replenishment events, and four samples from the Middle Route of the South-to-North Water Diversion Project water, were analyzed for water chemistry. Hydrogeochemical methods such as the Piper diagram, chloride-alkalinity index, and ion correlation were employed to analyze the characteristics of groundwater chemical evolution through replenishment. The results demonstrated that the hydrochemical types of groundwater in the study area underwent significant changes during continuous replenishment in the Hutuo River region. During the initial replenishment period (October 2019), the dominant hydrochemical type of groundwater in the study area was Mg-Na-HCO3-SO4, whereas the dominant type in the Middle Route of the South-to-North Water Diversion Project water was Ca-Na-SO4-HCO3. As the replenishment continued, the hydrochemical types of groundwater in the study area evolved into Ca-Na-Mg-HCO3-SO4, Na-Ca-Mg-HCO3-SO4, and Ca-Na-Mg-SO4-HCO3. The groundwater experienced a dissolution of calcite, gypsum, nitratine, carbonate rocks, and gypsum, accompanied by dilution effects, resulting in reduced ion exchange as replenishment progressed. The input of the high quality Middle Route of South-to-North Water Diversion Project water effectively promoted groundwater quality improvement, leading to an overall decrease or stabilization of components other than Ca2+ in the groundwater. Water quality was assessed using the entropy water quality index, with indicators including Na+, SO42−, Cl−, pH, total dissolved solids, NO3−-N, NO2−-N, F−, Al, As, and Zn. The evaluation results showed that, except for one medium-quality water sample, the water quality of the other samples was suitable for drinking and domestic purposes during the early replenishment period. The Middle Route of the South-to-North Water Diversion Project exhibited excellent quality (Rank 1), and as replenishment progressed, all water samples demonstrated good quality by October 2020, with a gradual improvement.

Hydrochemical Characteristics and Formation Causes of Ground Karst Water Systems in Gudui Spring Catchment

As one of the famous karst springs in Shanxi Province, the Gudui spring is the only medium-low temperature hot spring, with a long history of development and a rich cultural accumulation. The karst groundwater in the Gudui spring catchment was taken as the research object. Through systematic sample collection and isotope analysis, hydrochemistry (Durov map, ion ratio, Gibbs map, and hydrogen and oxygen isotope) methods were comprehensively used to analyze groundwater hydrochemistry and groundwater system runoff characteristics. The87Sr/86Sr value of karst groundwater in the Gudui spring catchment was 0.709 to 0.717, and the Mg/(Mg+Ca) value was 0.27 to 0.74. By analyzing the Sr isotope composition and Mg/(Mg+Ca) and 1/Sr variation characteristics, it was concluded that the karst groundwater in the Gudui spring catchment was a mixture of deep hot water and shallow cold water. The karst water subsystem of Nanliang spring presented the characteristics of carbonate stratum runoff. The karst water subsystem of Fuling Mountain Gaoxian Haitou spring and the deep circulation subsystem of Houma Basin exhibited the runoff characteristics of carbonate rock and igneous rock strata. The karst water subsystem of Taiershan Jiuyuanshan Gudui spring presented the runoff characteristics of carbonate rock and ancient silicoaluminate strata. The δ18O value in karst groundwater of Guodui spring area ranged from -11.46‰ to -7.81‰, and the average value was -10.08‰. The range of the δD value was -83.7‰ to -60.8‰, and the average value was -73.6‰. This showed that karst groundwater in the spring area was the result of mixing of various types of water. Through comparative analysis of hydrogen and oxygen isotopes of 2014 and 2021 sampling points at the same location, it was concluded that the change in water samples at the Guduiquan resulted from the gradual accumulation of water supplied by Sanquan Reservoir. The change in Sanquan Reservoir was due to the influence of Yellow River diversion. The karst groundwater in the spring area were characterized by large calcium ion, magnesium ion, and sodium ion values; a small potassium ion value; a large sulfate value; and a small chloride value. The hydrochemical types of karst groundwater in Gudui spring catchment could be divided into SO4-Na, SO4-Ca, HCO3-Na, HCO3-Mg, HCO3-Ca, and Cl-Na. The hydrochemical types of karst groundwater showed evident hydrochemical composition zoning from HCO3-Ca·Mg→HCO3·SO4-Ca·Mg→SO4·HCO3-Na·Ca→SO4·Cl-Na·Ca. According to the comprehensive analysis of hydrochemical isotope and hydrogeological conditions, the karst water subsystem of Nanliang spring was primarily recharged by rainfall infiltration in the exposed limestone area and river infiltration, and its karst groundwater was recharged by runoff from south to north to the karst water subsystem of Fuling Mountain Gaoxian Haitou spring and the deep circulation subsystem of Houma Basin. The karst water subsystem of Taier Jiuyuan Mountain Gudui spring received rainfall infiltration supplement and upstream runoff supplement from the exposed limestone area. Its karst groundwater flowed from north to south and received the supply of Sanquan Reservoir from Yellow River water in the natural discharge area of Gudui spring.

Study on the Law of the Electric Folding Water Coefficient in Chayuo Middle Banner

In this paper, based on the investigation and research of groundwater types, topography and geomorphology, geological structure, stratigraphic lithology, groundwater richness and agricultural irrigation wells in the area of Chayou Middle Banner Inner Mongolia, a test area is selected and typical wells are determined. The estimating water consumption of typical wells was measured. Based on the calculation results, the distribution map of the Electricity-to-water conversion factor was drawn, and the influence of groundwater type on the Electricity-to-water conversion factor was analyzed. The results show that the type of groundwater has a significant impact on the number of electric water conversion factors, and the electric water conversion coefficients of fracture pore pressure water and groundwater in Neoproterozoic clastic rocks are relatively large; The electric water conversion coefficient of pore and fissure water pressure and groundwater in Neoproterozoic basalt ranks second; Quaternary loose rock pore water average; The bedrock fissure water is the smallest. At the same time, the influence of topography, atmospheric precipitation, and agricultural production on the Electricity-to-water conversion factor under the same type of groundwater was preliminarily investigated.

Identifying Karst Aquifer Recharge Area Using Environmental Stable Isotopes and Hydrochemical Data: A Case Study in Nusa Penida Island

Identifying the recharge area of karst aquifers is scientifically challenging due to the complexity of karst groundwater flow characteristics. It is essential to identify the recharge zones to conserve the groundwater resources contained within these aquifers. This paper proposes a combined methods for identifying recharge area of karst aquifers on Nusa Penida Island using stable isotopes (18O and 2H) and a hydrogeochemical approach. Based on the analysis of δ18O and δ2H values and their spatial distribution, it is possible to retrace karst aquifer recharge areas using average isotope elevations. In the meantime, groundwater facies will be determined in the karst region of Nusa Penida using the hydrogeochemical approach with the Piper diagram. According to the calculation of water stable isotope results, the average elevation of the groundwater recharge area at the study site is between 62 - 450 meters. If applied to the location of the study, the recharge area is almost entirely distributed across Nusa Penida. In addition, based on the hydrogeochemical analysis, the groundwater type at the study site can be divided into three categories: Na-Cl, mixed, and Mg-HCO3. The water types indicate that the groundwater in Nusa Penida comes from a combination of old water stored from its internal geological formations and mix with modern rainwater.&#x0D;

Hydro-chemometrics of the Nubian Aquifer in Sudan: an integration of groundwater quality index, multivariate statistics, and human health risk assessment

This research employed the groundwater quality index (GWQI), multivariate statistical methods, and human health risk assessment model to investigate the suitability of groundwater for domestic uses in northern Khartoum state, Sudan. The groundwater samples were analyzed for eleven physiochemical parameters, including pH, EC, TDS, TH, Cl−, SO42−, NO3−, Ca2+, Mg2+, Na+, HCO3− and the primary investigation indicated the deviation of these parameters from World Health Organization (WHO) standards. The hydrochemical analysis revealed different groundwater facies with the dominance of Ca–Mg–HCO3 water type. Consequently, the groundwater samples were classified, based on GWQI, into three categories as 76.4% of the samples fall in the excellent water class, 17.6% are projected in the good water class, and 5.9% of groundwater samples are considered unsuitable for human consumption. The multivariate statistical methods were applied, including Pearson’s correlation analysis, principal component analyses (PCA), and hierarchical cluster analysis (HCA). Three principal components (PCs) explaining 86.07% of total variances are extracted. These PCs indicated that rock-water interactions and agricultural practices influence groundwater quality in the study area. Additionally, HCA is used to categorize groundwater samples based on the concentration of the physiochemical parameters. Consequently, three types of groundwater were identified as low, medium, and highly mineralized. In the final stage, the non-carcinogenic human health risk was assessed based on the concentration of NO3− using the United States Environmental Protection Agency (USEPA) models. The obtained hazard quotient for children indicated that 64.7% of groundwater samples are beyond the permissible limit (1 <), and the use of these samples may result in health consequences. Therefore, remedial measures are suggested for the sustainable use of groundwater.

Sources and hydrogeochemical processes of groundwater under multiple water source recharge condition

Ecological water replenishment (EWR) is an essential approach for improving the quantity and quality of regional water. The Chaobai River is a major river in Beijing that is replenished with water from multiple sources, including reclaimed water (RW), the South-North Water Transfer Project (SNTP), reservoir discharge (RD). The effects of multiple water source recharge (MWSR) on groundwater quality remain unclear. In this study, hydrochemical ions, isotopes (δ2H-H2O, δ18O-H2O, δ15N-NO3−, and δ18O-NO3−), mixing stable isotope analysis in R (MixSIAR), and hydrogeochemical modeling were used to quantify the contributions and impacts of different water sources on groundwater and to propose a conceptual model. The results showed that during the period before reservoir discharge, RW and SNTP accounted for 38 %–41 % and 54 % of the groundwater in their corresponding recharge areas, respectively. The groundwater in the RW recharge area contained high levels of Na+ and Cl− leading to the precipitation of halite, and was the main factor for the spatial variation in groundwater hydrochemical components. The surface water changed from Na·K – Cl·SO4 type to Ca·Mg – HCO3 type which was similar to groundwater after reservoir discharge. RD accounted for 30 % of the groundwater; however, it did not change the hydrochemical type of groundwater. Dual nitrate stable isotopes and MixSIAR demonstrated that RW was the primary source of NO3− in groundwater, contributing up to 76–89 %, and reservoir discharge effectively reduced the contribution of RW. δ15N-NO3− or δ18O-NO3− in relation to NO3-N suggests that denitrification is the main biogeochemical process of nitrogen in groundwater, whereas water recharge from the SNTP and RD reduces denitrification and dilutes NO3−. This study provides insights into the impact of anthropogenically controlled ecological water replenishment from different water sources on groundwater and guides the reasonable allocation of water resources.

Regional characterization of the vulnerability of the unconfined groundwaters in Bulgaria

Groundwater vulnerability to contaminant infiltration from the surface, and to state deterioration, is related to the spatial distribution of rocks with diverse porosities, flow characteristics and unsaturated zone thickness. For the present regional assessment of groundwater vulnerability, it is considered most appropriate to adopt a method based on spatial differences in the geological and tectonic, and related hydrogeological, conditions in Bulgaria. The objective of the present study is to compile a vulnerability map of the unconfined groundwater in the country. This groundwater type is very important for drinking water supply, and it is at the highest risk of contamination. The groundwater on the territory of the Republic of Bulgaria has been divided into seven vulnerability classes, based on the corresponding hydrogeological units. The map is based on the geological map of Bulgaria in scale 1:100 000. It shows that groundwater is of low vulnerability over a large part of the country’s area (57%). Medium to medium-high groundwater vulnerability is defined for approximately 31% of the total area, while high and very high vulnerability are defined for 7% and 5%, correspondingly.

Combining hydrochemistry and 13C analysis to reveal the sources and contributions of dissolved inorganic carbon in the groundwater of coal mining areas, in East China.

East China is a highly aggregated coal-grain composite area where coal mining and agricultural production activities are both flourishing. At present, the geochemical characteristics of dissolved inorganic carbon (DIC) in groundwater in coal mining areas are still unclear. This study combined hydrochemical and carbon isotope methods to explore the sources and factors influencing DIC in the groundwater of different active areas in coal mining areas. Moreover, the 13C isotope method was used to calculate the contribution rates of various sources to DIC in groundwater. The results showed that the hydrochemical types of groundwater were HCO3-Ca·Na and HCO3-Na. The main water‒rock interactions were silicate and carbonate rock weathering. Agricultural areas were mainly affected by the participation of HNO3 produced by chemical fertilizer in the weathering of carbonate rocks. Soil CO2 and carbonate rock weathering were the major sources of DIC in the groundwater. Groundwater in residential areas was primarily affected by CO2 from the degradation of organic matter from anthropogenic inputs. Sulfate produced by gypsum dissolution, coal gangue accumulation leaching and mine drainage participated in carbonate weathering under acidic conditions, which was an important factor controlling the DIC and isotopic composition of groundwater in coal production areas. The contribution rates of groundwater carbonate weathering to groundwater DIC in agricultural areas and coal production areas ranged from 57.46 to 66.18% and from 54.29 to 62.16%, respectively. In residential areas, the contribution rates of soil CO2 to groundwater DIC ranged from 51.48 to 61.84%. The results will help clarify the sources and circulation of DIC in groundwater under the influence of anthropogenic activities and provide a theoretical reference for water resource management.

Potential Ecological Risk Assessment and Source Analysis of Heavy Metals in Soil-crop System in Xiong'an New District

In order to evaluate the distribution characteristics of fluorine geochemistry in the surface soil and human health risk in Xiong'an New District, GIS spatial analysis and correlation analysis were used to analyze the depleted and enriched features and influencing factors of soil fluoride and to carry out the soil fluoride health risk assessment. The uncertainty of the health risk assessment results was studied based on the Monte Carlo stochastic simulation. The results showed that the average content of fluorine was 641 mg·kg-1, which was 1.34 times the background value of the national A-layer soil. The excess fluorine and high-grade samples accounted for more than 85%, and the overall soil fluorine content was relatively high. The average content of fluoride of the irrigation water samples was 0.85 mg·L-1, the spatial distribution characteristics of which were affected by the hydrochemical type and flow direction of shallow groundwater. The vertical spatial variation of soil fluoride, mainly affected by the vertical distribution of soil physicochemical properties such as soil organic carbon and texture, was not obvious. The depletion and enrichment of topsoil fluorine was mainly controlled by the geological background, and its spatial distribution was affected by external inputs, such as human factors (agricultural irrigation water, fertilization, and atmospheric dry and wet deposition). The soil fluoride content was significantly correlated with the iconic indicators of the geomorphological environment, including the content of Al2O3, Fe2O3, MgO, K2O, soil organic carbon (Corg.), cation exchange capacity (CEC), clay, and silt (P<0.01). The results of human health risk assessment showed that oral intake was the main exposure risk route of soil fluoride. The non-carcinogenic health risk index HQ of adults was less than 1, and the harm could be ignored. The probability of non-carcinogenic health risk exceeding the threshold for adults and children was 34.3% and 27.6%, respectively, and daily soil intake was the most sensitive parameter.

Groundwater Hydrochemistry and Aquifer Identification at Wana Area, Northwest of Mosul, Iraq

The suitability of groundwater for various uses is primarily determined by its major ions content, which is determined by its hydrochemical properties, including geogenic and anthropogenic factors. To gain a deeper understanding of groundwater management and sustainability in Wana, one of the most important agricultural areas northwest of Mosul, 18 wells were chosen and groundwater samples were taken from them over two seasons (October 2020 and April 2021) and their physicochemical properties were analyzed. The Piper diagram revealed that the most common type of groundwater in the study area is Ca-SO4. The mineral saturation index, cation exchange values, and Gibbs diagram results revealed that rock dissolution and weathering processes, including both gypsum and carbonate rocks, dominated the chemistry of groundwater in the region, with clastic rocks and ion exchange processes having a limited effect. This is also confirmed by the findings of the Principal Component Analysis, which further revealed that there is an effect of an anthropogenic factor caused by agricultural activities on the concentration of NO3-. The Cluster Analysis results revealed three groups of wells based on the water-bearing layers: those that draw water from the Quaternary deposits aquifer, those that draw water from the Fatha Formation aquifer, and those that draw water from both aquifers. The findings of this study can contribute to the preservation and sustainability of groundwater, as well as the optimal management of this crucial resource in the studied region.

Physicochemical effect on soil in sliding zone of reservoir landslides

The fate of reservoir landslides is mainly dictated by the mechanical behavior of soil in the sliding zone. This soil may be altered under changing environmental conditions of both physical and chemical nature. In this paper, we present a laboratory study on the changing soil properties under complex physicochemical interactions. The soil specimens are subjected to 1, 2, 3, 5, 7, and 10 wetting-drying cycles. The soil strength is determined by triaxial tests. These tests are performed with three types of pore water, namely, acidic groundwater (AGW), normal groundwater (NGW), and distilled water (DW). The deterioration of soil strength, the change in soil microstructure and mineral composition are observed and correlated. Interesting findings for reservoir landslides are drawn: acidic underground water considerably damages the soil microstructure and deteriorates the shear strength compared to normal underground water, while distilled water causes minimal disaggregation. A three-stage micromechanism associated with four physicochemical interactions is revealed, providing insights into microstructure damage and mineral transformation.

A multiple isotope (S, H, O and C) approach to estimate sulfate increasing mechanism of groundwater in coal mine area

Groundwater in North China type coal mine area is an important source of domestic, industrial and agricultural water. To explore the sulfate increasing mechanism of groundwater in mining area and identify key influencing factors. In this paper, hydrochemistry and multi-isotope tracer techniques such as δ34SSO4, δ18OSO4, δ2HH2O, δ18OH2O and δ13CDIC were used to study the groundwater circulation law and the migration and transformation mechanism of sulfate and carbonate in coal mine area. The results show that: the hydrochemical types of groundwater in the coal mine area are mainly HCO3− and SO42− anions, while the cations are mainly Ca2+ and Mg2+. The sulfate content is significantly increased, and the pH shows weak alkalinity; the relationship between δ18OH2O and δ18HH2O shows that the dynamic field of groundwater changes significantly after coal mining or closure, and limestone water mainly comes from surface water recharge through ‘skylight’ infiltration. The relationships between δ18OSO4 and δ18OH2O, δ34SSO4 and δ18OSO4 show that the sulfate in groundwater of coal mine area is mainly derived from sulfide oxidation. The ∆δ18OSO4-H2O value of groundwater in coal mine area is greater than 8 ‰, and the oxygen content in sulfate is 25 %–75 % from oxygen in water, indicating that coal mining has disturbed the groundwater in the study area from reducing environment to oxidizing environment, promoted sulfide oxidation, and accelerated the dissolution of carbonate minerals. The δ13CDIC value and δ34SSO4 value in the coal mine area are inversely proportional. The δ13CDIC of groundwater in the coal mine area is affected by the δ34SSO4 value to a certain extent. Sulfuric acid participates in the dissolution of carbonate minerals, making the pH value weak and alkaline as a whole. This paper expounds the migration and transformation law of sulfate in groundwater in coal mine area, which has practical significance for groundwater quality management. The research results can provide theoretical support for the rational development and utilization of groundwater resources in coal mine areas.

Analysis of Hydrochemical Characteristics and its Influences on Jiaodong Water Diversion Project

The water chemistry characteristics along the Jiaodong water transfer line and its impact analysis play an important role in supporting water quality safety and operation management. In this paper, the water chemistry characteristics along the Jiaodong water transfer project were studied, and the water chemistry characteristics and their influencing factors in the study area were analyzed by using Piper's trilinear diagram, Gibbs diagram and SPSS26 statistical analysis software for correlation. The results show that the surface water and groundwater along the Jiaodong water transfer project are both weakly alkaline, and the chemical type of groundwater in the traversing area is Na Ca-HCO-3 water, while the chemical type of surface water is Na Ca- HCO-3 water. The groundwater in the crossing area of Jiu Dong water transfer project is mainly controlled by rock weathering and evaporation concentration, and the water chemistry type of groundwater in different areas shows certain differences; the correlation between the channel water and groundwater and surface water along the route is weak in water quality, and surface water and groundwater basically have no influence on the water quality of channel water transfer during the normal water transfer period; the groundwater quality along the route basically has no corrosive influence on concrete, and the groundwater quality has no corrosive influence on Groundwater quality has no corrosive effect on concrete, but groundwater quality has some influence on reinforcement and steel structure in concrete.

Assessment of Hydrochemical Facies on Groundwater Quality in Daenaa Village and its Surroundings, West Limboto District

The study is required to evaluate the groundwater condition, such as finding the relationship with the lithology, determining the facies of groundwater, and providing an overview of the present groundwater conditions, genetics, and groundwater quality. This study aims to explain the relationship between lithology and groundwater chemistry, groundwater quality, and the determination of the chemical facies of groundwater to determine the genetic type of groundwater. This study uses field survey methods and random sampling techniques, measurements of groundwater physical properties, trilinear piper diagrams, and laboratory analysis in the form of rock geochemical analysis (XRF) at the PSDMBP Laboratory and chemical analysis of groundwater at the PT Global Quality Analytical Laboratory. The results show that the lithology in the study area consists of clastic limestone, sandstone, breccia, and dacite. Lithology in the study area primarily plays an essential role in chemical ion enrichment in groundwater. Determination of groundwater quality is based on Permenkes, Permen ESDM, and ISDW, which obtained eleven well points in the good quality category, five well points in the poor quality category, and four other well points categorized as poor quality. Based on the analysis results in the trilinear piper diagram, there is one type of groundwater chemical facies (not varied), namely the Ca-Cl type facies. The presence of the Ca-Cl facies type is interpreted as a seawater intrusion phase.