Chemical Characteristics Of Groundwater Research Articles

Groundwater chemical evolution characteristics and human health risk assessment in Shicheng County, Jiangxi Province.

Groundwater plays a pivotal role in the water resources of Shicheng County; however, the issue of excessive fluoride content in groundwater and its associated health risks often goes unnoticed. Groundwater assumes a crucial role in the hydrological dynamics of Shicheng County; nevertheless, the matter concerning elevated levels of fluoride within groundwater and its accompanying health hazards frequently evades attention. The hydrogeochemical analysis, obscure comprehensive water quality assessment based on cloud model, and probabilistic human health risk assessment using Monte Carlo simulation were conducted on 34 collected water samples. The findings indicate that the predominant groundwater hydrochemical types are SO4·Cl-Na and HCO3-Na. The processes of rock weathering and cation exchange play crucial roles in influencing water chemistry. Groundwater samples generally exhibit elevated concentrations of F-, surpassing the drinking water standard, primarily attributed to mineral dissolution. The concentrations of F- in more than 52.94% and 23.53% of the groundwater samples exceeded the acceptable non-carcinogenic risk limits for children and adults, respectively. Considering the inherent uncertainty in model parameters, it is anticipated that both children and adults will have a probability exceeding 49.36% and 30.50%, respectively, of being exposed to elevated levels of F ions in groundwater. The utilization of stochastic simulations, in contrast to deterministic methods, enables a more precise depiction of health risks. The outcomes derived from this investigation possess the potential to assist policymakers in formulating strategies aimed at ensuring the provision of secure domestic water supplies.

Groundwater hydrochemistry, source identification and health assessment based on self-organizing map in an intensive mining area in Shanxi, China

The Changzhi Basin in Shanxi is renowned for its extensive mining activities. It's crucial to comprehend the spatial distribution and geochemical factors influencing its water quality to uphold water security and safeguard the ecosystem. However, the complexity inherent in hydrogeochemical data presents challenges for linear data analysis methods. This study utilizes a combined approach of self-organizing maps (SOM) and K-means clustering to investigate the hydrogeochemical sources of shallow groundwater in the Changzhi Basin and the associated human health risks. The results showed that the groundwater chemical characteristics were categorized into 48 neurons grouped into six clusters (C1–C6) representing different groundwater types with different contamination characteristics. C1, C3, and C5 represent uncontaminated or minimally contaminated groundwater (Ca–HCO3 type), while C2 signifies mixed-contaminated groundwater (HCO3–Ca type, Mixed Cl–Mg–Ca type, and CaSO4 type). C4 samples exhibit impacts from agricultural activities (Mixed Cl–Mg–Ca), and C6 reflects high Ca and NO3− groundwater. Anthropogenic activities, especially agriculture, have resulted in elevated NO3− levels in shallow groundwater. Notably, heightened non-carcinogenic risks linked to NO3−, Pb, F−, and Mn exposure through drinking water, particularly impacting children, warrant significant attention. This research contributes valuable insights into sustainable groundwater resource development, pollution mitigation strategies, and effective ecosystem protection within intensive mining regions like the Changzhi Basin. It serves as a vital reference for similar areas worldwide, offering guidance for groundwater management, pollution prevention, and control.

Study on Hydrochemical Characteristics and Interactions between Groundwater and Surface Water in the Dongting Lake Plain

The Dongting Lake Plain is a major ecological reserve for river and lake wetlands in the Yangtze River Basin, with complex river and lake relationships and frequent water flow exchange. Studies on the hydrochemical characteristics and the mechanism of interaction between groundwater and surface water will actively promote the scientific management, utilization of water resources, and protection of the ecological environment in the Dongting Lake Plain. Based on hydrogeochemical statistics, Gibbs diagrams, ion ratios, rock weathering end-element diagrams, hydrogen–oxygen isotope relationship diagrams, and other technical methods, the chemical characteristics, ion sources, and the distribution of hydrogen–oxygen isotopes of groundwater and surface water in “the Three Inlets” and “the Four Rivers” water system areas as well as the Dongting Lake water were analyzed. Additionally, the interactions between groundwater and surface water and the proportions of these contributions were discussed. The results show that both groundwater and surface water in the Dongting Lake Plain are weakly acidic or alkaline, and the anions are mainly HCO3−, the cations are mainly Ca2+and Mg2+, with the hydrochemical types being mainly HCO3−Ca−Mg and HCO3−Ca. The chemical characteristics of groundwater and surface water are mainly affected by the interaction between water and rock; the ions in surface water mainly come from the weathered dissolution of carbonate and silicate rocks, while the ions in groundwater mainly come from the weathered dissolution of carbonate and silicate rocks, with the dissolution of evaporite rocks locally. Groundwater and surface water are mainly distributed near the local meteoric water line (LMWL), and the slope of the local evaporation line is less than that of the LMWL, which indicates that atmospheric rainfall is an important recharge source for groundwater and surface water and that at the same time, it is affected by evaporation to a certain extent. Part of the groundwater in the Dongting Lake Plain is discharged into the surface rivers in “the Three Inlets” and “the Four Rivers” water system areas, and the other part is directly discharged into Dongting Lake. According to the mass balance relationship of isotopes, the proportions of surface water in “the Three Inlets” and “the Four Rivers” water system areas contributing to Dongting Lake’s water are 18.48% and 60.38%, respectively, and the proportion of groundwater in the lake plain contributing to Dongting Lake water is 21.14%.

Hydrochemical Characteristics and Genesis Mechanism of Groundwater in the Dry Period in the Zhangjiakou Area

In order to better support the construction of the capital water conservation functional area and ecological environment support area， research on the chemical characteristics of groundwater and its formation mechanism in the dry period in the Zhangjiakou area can provide a great reference for the rational development and utilization of groundwater resources. A total of 41 groups of groundwater samples were collected， and the hydrochemical types， composition characteristics， and control factors of groundwater in the study area were analyzed by using the combined method of descriptive statistical analysis， Piper triplot， correlation analysis， Gibbs plot， and ion ratio. The results showed that the groundwater in the study area was weakly alkaline， with the total hardness and ρ（TDS） ranging from 105.00 mg·L-1 to 1 433.00 mg·L-1 and 137.00 mg·L-1 to 2 286.00 mg·L-1， respectively. The total hardness and TDS mass concentrations of groundwater in the Bashang area were higher than those in the Baxia area. HCO3- and Na+ were the main dominant anions and cations in the groundwater in the study area. The highest overstandard rate of the main components in groundwater was that of total hardness （36.59%）. The overstandard rate and maximum excess multiple of each component in groundwater in the Bashang area were greater than those in the Baxia area. HCO3-Ca·Mg·Na was the main type of groundwater hydrochemistry in the study area， and there was little difference between the Bashang area and the Baxia area. SO42-， Cl-， HCO3-， Na+， and Mg2+ contributed the most to TDS. The chemical characteristics of groundwater were affected by weathering and filtration of rock minerals such as salt rock， albite， and dolomite； cation exchange； and human activities. Evaporative crystallization and atmospheric precipitation contributed to a small part of the main ion source of groundwater in the area. The effect of human activities on groundwater in the Bashang area was greater than that in the Baxia area， and NO3- mainly originated from agricultural activities.

Hydrochemical Characteristics and Quality Evaluation of Groundwater in Jinta Basin, Northwest China

The ecological environment of the northwest inland basin is fragile. The groundwater environment is a crucial influencing factor for the harmonious and sustainable development of the local social economy and the ecological environment. It is significant to investigate the groundwater chemical characteristics, water quality, and the factors that influence groundwater chemistry for groundwater resources development and construction of the ecological environment. In this study, the Jinta Basin (JB), Gansu Province, was the selected study area. Three hundred and fifty groups of shallow groundwater samples in the JB were collected and analyzed, and the characteristics and controlling factors of groundwater were determined by using Piper diagram, Gibbs plot, ion ratio relationship, and factor analysis. Single index evaluation method, comprehensive evaluation method, and entropy-weighted water quality index method were used to evaluate the water quality of the groundwater. The results indicated that the shallow pore water in the JB was alkaline as a whole; the ranges of total dissolved solids (TDS) in the Beidahe River impact area (BIA), the transition area (TA) and the Heihe River impact area (HIA) were 328.4–12,400 mg·L−1, 372.70–3774.0 mg·L−1, and 366.30–75,200.0 mg·L−1, respectively; the major anions and cations of the shallow pore water were SO42−/Cl− and Mg2+/Na+, respectively. The Piper diagram illustrated that the hydrochemical type of groundwater in the JB were mainly HCO3·SO4-Mg type, SO4·HCO3-Mg type, SO4-Mg·Na type, SO4·Cl-Na·Mg type, and Cl-Na type. The overall water quality of the shallow groundwater in the JB was relatively poor, mainly falling into Class IV-V water quality. Sulfate, total hardness (TH), TDS, chloride and sodium were the main influencing factors of water quality. The chemical characteristics of groundwater in the JB were controlled by a variety of natural factors, including rock weathering, evaporative concentration, and cation exchange, among which the main controlling factors of shallow pore water were leaching, evaporative concentration and anthropogenic activities (contribution rate of 73.94%), and sulfate rock and carbonate rock dissolution (contribution rate of 14.91%).

Identification of groundwater hydrogeochemistry and the hydraulic connections of aquifers in a complex coal mine

It is important to understand the changes in the chemical composition and connectivity of each aquifer in the arid-semi-arid riverine mines under the driving force of coal mining and to establish a rapid identification of water sources in the riverine mines, which is important for the protection of groundwater resources and safe production in the study area. By analyzing the numerical characteristics of conventional elements, cluster analysis and the deuterium–oxygen and tritium isotopes of different aquifers, the groundwater chemical characteristics and hydraulic connections of each aquifer were determined. Three identification charts (Piper and Durov identification charts of conventional hydrochemical components and deuterium–tritium isotope identification charts) were established to enable the rapid identification of each aquifer water source. The results showed that the main recharge source of groundwater in the study area was atmospheric precipitation. There was a significant indigenous connection between the Quaternary aquifer and the Zhiluo Formation aquifer but a limited indigenous connection between the Zhiluo Formation aquifer and the Yan'an Formation aquifer, creating local groundwater systems that altered the local groundwater circulation patterns, driven by coal mining. Three identification charts were established to determine the water inrush sources and propose targeted solutions for water inrush from different aquifers in the Shendong mining area based on the differences in hydrochemical ion characteristics as well as deuterium–oxygen and tritium isotopes.

Pollution Source Identification and Suitability Assessment of Groundwater Quality for Drinking Purposes in Semi-Arid Regions of the Southern Part of India

The quality of groundwater plays an important role in human health, and it majorly influences the agricultural process in the southern part of India. The present study mainly focused on evaluating the quality of groundwater used for domestic purpose in semi-arid regions of the southern part of India. The samples were collected in 36 locations, covering the entire investigation zone. The collected samples were analyzed for various physical and chemical characteristics of groundwater and compared with the world health organization standards. The entropy-weighted water quality index (EWQI) of the groundwater revealed that 16.67% of the samples required primary-level treatment before they could be used for drinking purposes. About 72.23% of the samples were in the good-to-medium category for drinking purposes, as was identified through weighted overlay analysis. The ionic relationship plot was used to identify the source of contamination and it revealed that carbonate weathering and anthropogenic activities are the primary sources of groundwater contamination. The present results show the contaminated zones and offer more helpful solutions to strengthen the water management policy in the study region.

Chemical Characteristics-Based Evolution of Groundwater in Tailan River Basin, Xinjiang, China

Groundwater plays an important role in ecological environment protection in arid and semi-arid areas. Therefore, understanding the characteristics of hydrochemical evolution is of great significance for the sustainable use of groundwater in the area of the Tailan River Basin. The Tailan River Basin is located in an arid, ecologically sensitive area in western China. In this study, we collected 42 groups of representative water samples from the Tailan River Basin and analyzed the chemical distribution in the groundwater using mathematical statistics, Piper and Gibbs diagrams, ion ratio analysis, and hydrogeochemical simulation methods. We also discussed the water–rock interactions in the groundwater hydrochemical evolutionary process. The results were as follows: (1) The chemical types of groundwater changed from HCO3·SO4-Ca·Na to SO4·Cl-Na·Ca, Cl·SO4-Na, and Cl-Na, and the total dissolved solids content increased from less than 1 g/L to more than 40 g/L from the gravel plain to the fine soil plain. (2) The Gibbs diagram, the ion ratio analysis, and the saturation index showed that the groundwater chemical characteristics in the study area were mainly controlled by water–rock interactions, as well as evaporation and concentration. Along the runoff of groundwater, halite and gypsum were dissolved. Nevertheless, dolomite and calcite precipitated. The relationship between the chlor-alkali index and [(Na+ + K+)-Cl−] and [(Ca2+ + Mg2+)-(HCO3− + SO42−)] indicated that cation exchange also affects the chemical composition of groundwater in the area. (3) Through reverse hydrogeochemical simulation, the main water–rock effect of the groundwater runoff process revealed by qualitative analysis was quantitatively verified.

Hydrochemical Characteristics and Formation Mechanism of Quaternary Groundwater in Baoshan Basin, Western Yunnan, China

The shallow groundwater of the quaternary system in the Baoshan basin, Yunnan Province is seriously polluted, threatening human health and restricting local socio-economic development; therefore, it is necessary to investigate the hydrochemical characteristics and formation mechanisms of the shallow groundwater of the quaternary system in the Baoshan basin. This study used EVS 2022 to establish a 3D visual geological model of the quaternary system in the basin and divided the shallow groundwater aquifers of the quaternary system into three groundwater systems, sampling 22, 9, and 4 groups in each groundwater system, respectively. Mathematical statistics, Piper’s trilinear diagram, Gibbs plots, the Gaillardet model, the ion ratio method, groundwater saturation, and the PCA-APCS-MLR model were used to analyze the groundwater hydrochemical characteristics and genesis of the study area. The results show the following: (1) The types of groundwater chemicals are mainly HCO3-Ca-Mg type and HCO3-Ca, the causes of the water chemical characteristics are mainly influenced by water–rock interaction and alternate cation adsorption, and the rock types with which the groundwater exchanges substances are carbonate rocks and silicate rocks. (2) The Fe2+, Mn2+, and NH3-N contents in groundwater systems I and II exceed the standard, which is the human activity area, and groundwater pollution is mainly affected by human activities. (3) Four main categories of factors were obtained according to the PCA-APCS-MLR model, namely dissolution filtration, migration and enrichment factors, geological and human activity factors, and environmental factors and pollution factors; the cumulative contribution of variance was 77.84%, and the groundwater chemical characteristics were jointly influenced by hydrogeological conditions and human activities. The results of this study provide a basis for groundwater protection and management in the Baoshan basin, where groundwater system I is the key area for pollution and should be strengthened for control.

Assessment of the Impact of Abandoned Mine Water on Groundwater Environment

The assessment of the impact of abandoned mine water on the underwater environment is critical for protecting and restoring the groundwater environment. Taking the abandoned coal mining area in the west of Zhangqiu District as the engineering background and comprehensively considering the regional groundwater chemical characteristics data during the wet and dry seasons, the main characteristics of the ions, hydrochemical types, and ion correlations of the abandoned mine water with the regional groundwater components were analyzed using mathematical statistics, correlation analysis, and Piper diagrams. An impact assessment was conducted on the water quality index values of the groundwater monitoring point. Furthermore, this research establishes an evaluation method of abandoned mine water in a regional groundwater environment based on the improved Nemero index method and matter element theory. Overall, the groundwater pH is weakly alkaline in Zhangqiu District. The groundwater Ca2+ is the dominant cation, while HCO3− and SO42− are the dominant anions. The main ion concentration during the dry season is slightly greater than during the wet season. The main hydrochemical type of groundwater during the wet and dry seasons is HCO3-Ca. In addition, there is a correlation between NO3− and F−, which may be caused by human activities. The groundwater environment is classified as level IV and severely polluted.

Groundwater quality for agricultural use in Zacoalco de Torres and Autlan de Navarro, Mexico

In Mexico, one of the main sources for agricultural irrigation is groundwater, which irrigates approximately 2 million hectares, accounting for 75% of the country's rural and urban water volume. These water resources are affected by industrial waste and residual pollutants, as well as the leaching of chemical substances from agricultural soils. In order to evaluate the physical and chemical characteristics of groundwater, this study was conducted in Zacoalco de Torres and Autl á n de Navarro. Sampling was conducted during the dry and rainy seasons in 2017. The sampling locations were deep wells and water wheels. A total of 48 samples were obtained from two sites. In each sample, pH value, anion and cation, electrical conductivity (EC), residual sodium carbonate (CSR), sodium adsorption ratio (SAR) and hydrogeochemical classification were analyzed. The underground water of Zacoalco is mostly chlorinated-magnesic and in Autlán it is bicarbonate-magnesic with medium and low concentrations, so it is recommended for irrigation. With respect to salinity, Zacoalco has 40% high salinity water in dry conditions and 66% medium salinity water in rains; Autlan has 75% high salinity water in dry and 75% medium salinity water in rainfall, so its use shows moderate restrictions.

Hydrochemical characteristics of groundwater in a plain river network region: Establishing linkages between source and water quality variables

The chemical characteristics of groundwater can indicate water quality condition and provide useful information for pollution source identification. This study aimed to understand the effects of dissolved organic matter (DOM) on ionic composition of groundwater and identify the main ions and sources of pollution. The Lake Taihu is a typical eutrophic lake in China. In this study, the hydrochemical composition of groundwater in the surrounding aquifer of Lake Taihu Basin was analyzed. The results showed that the values of water quality index (WQI) range from 13.29 to 56.26 (good water quality). The dominant hydrochemical type of groundwater was Ca–Mg–HCO3 type, and the rock dominance was the major mechanism controlling the groundwater chemistry. With an increasing concentration in dissolved organic carbon (DOC), the Na+, Mg2+, and HCO3– concentrations all showed a sharp increase followed by a slow increase, while the NO3– concentration showed an opposite trend, indicating the DOM can affect the ions composition. In addition, K+ was positively correlated with NO3–, As, and Cd. Hence, DOM input may directly or indirectly change the hydrochemistry of groundwater. Besides, the NO3– concentration in groundwater was much higher than that in Lake Taihu, indicating that the NO3– in groundwater mainly came from surface soil leaching. The anthropogenic sources are probably the main sources of different ions, including K+, NO3–, As, and Cd. This study can help to better understand the effects of lake eutrophication on groundwater and its pathways.

Hydrochemical Characteristics and Formation Mechanism of Groundwater in Qingdao City, Shandong Province, China

The coastal area is a major area of socio-economic development and the most active zone for human activities. With the rapid development of the economy and the strengthening of urban construction, the groundwater environmental problems in coastal areas are increasingly prominent. It is significant to investigate the groundwater chemical characteristics, hydrochemical types, and the factors that influence groundwater chemistry for water resources protection and groundwater resources development. In this paper, 48 groundwater samples and 5 surface water samples from the study area were analyzed with statistical analysis, Piper diagram, Gibbs diagram, mineral saturation index method, and the ionic scale factor, and explored the factors that influence groundwater chemistry. The modified Nemerow index method was also applied to evaluate the groundwater. The results show that the groundwater in the study area is neutral to weakly alkaline (average pH = 7.0~8.0). The groundwater chemical types are mainly Cl·SO4-Na and SO4·Cl-Ca·Mg. Hydrochemistry is mainly influenced by rock weathering and evaporative concentration. TDS was strongly correlated with TDS, Na+, Mg2+, K+, Ca2+, Cl−, SO42−, and the saturation index showed a gradual increase along the groundwater drainage flow path, it indicates that the main groundwater ions originate from the dissolution of halite, sulfate, and carbonate. Combining GIS technology and the kriging spatial interpolation method, we obtained the current situation map of groundwater quality in Laoshan District. The groundwater quality is mainly III water, and the overall water quality is good; IV and V water is mainly distributed in the middle and lower reaches of rivers, distributed in a belt pattern along the coastline. It is mainly influenced by both the human factor and seawater intrusion. It is significant for the utilization of groundwater resources and the management of seawater intrusion in the Laoshan District. In addition, the proposed research ideas and methods provide a reference for the study of groundwater genesis in other coastal areas in the world.

Identifying the factors controlling surface water and groundwater chemical characteristics and irrigation suitability in the Yarkant River Basin, northwest China

This study investigated the geochemical processes and the suitability for irrigation purposes of surface water and groundwater in the Yarkant River Basin, northwest China. The results showed that the surface water was moderately alkaline and neutral to slightly alkaline in the groundwater. The mean values for most ions in the groundwater were higher than those in the surface water. Geochemical method and hydrogen and oxygen isotope revealed that hydrochemical were mainly affected by dissolved evaporite minerals, ion exchange processes, and anthropogenic activities. Still, the geochemical processes of in surface water and groundwater were different. Additionally, three and four factors were extracted by factor analyses of surface water and groundwater, respectively, which distinguished the hydrochemical from natural origins and anthropogenic activities in more detail. The surface water and some groundwater in the south of the study area were suitable for irrigation processes. However, many groundwaters in the north were unsuitable for irrigation, because of their high sodium levels and salinity. The study results provide a theoretical basis for the sustainable utilization of regional water resources.

Impact of Dumpsites on Groundwater Contamination in Selected Settlements in Irewole and Isokan Local Government areas, Osun State, Nigeria

This study examined the spatio-temporal variation in the physico- chemical characteristics of ground water across the study area. This was with a view to determining the impact of dumpsites on ground water quality in the study area. Ground water samples were taken twice (once in the dry season and once in the wet season). These samples were taken from wells within 150 m proximity of a dumpsite using 1 litre high density polyethylene bottles. A control point was purposely picked, 1 km away from any noticeable dumpsite. The water samples were analyzed for physical and chemical parameters according to APHA, 1992 standard. The result of Analysis of Variance between values exhibited at the sampled points in Apomu and Ikire showed that there was no statistically significant difference in ground water pH values between the two communities in both wet (F = 0.102, P > 0.05) and dry (F = 0.471, P > 0.05) season. The result showed that the distance of the sample points to the dumpsite did not have a direct influence on water quality in that some parameters that were tested were found to exist more in the control samples than in the mean of the experimental samples. The results also showed that some of the tested parameters existed in higher quantities than both Nigerian and WHO standards for drinking water quality. The study concludes that the dumpsites in the study area has led to contamination of ground water as a result of leachate percolation from the dumpsites

Spatial estimation of groundwater quality, hydrogeochemical investigation, and health impacts of shallow groundwater in Kabul city, Afghanistan

The management of groundwater in densely populated areas with no centralized water treatment is critical for the prevention of diseases and maintaining sanitation. Here, we determine the bacteriological and chemical characteristics of groundwater in Kabul city, a resource that 4.1 million individuals rely on. Groundwater samples were analyzed from 41 newly established piezometric wells across Kabul, and data were compared with the last detailed study, undertaken in 2007, to understand contamination trends in an area that has undergone significant development and social changes. Piper diagrams, Gibbs diagrams, correlation analysis, and bivariate plots examine the hydrogeochemical and natural occurring processes of groundwater. The average concentration of cations followed the order Na+ > Mg2+ > Ca2+ > K+, and anions HCO3− > NO3− > Cl− > SO42− > F with Gibbs diagrams indicating mainly rock-weathering influence groundwater chemistry. An increase in nitrate (NO3−) and E. coli indicates anthropogenic activities impacting the shallow groundwater quality, with significantly elevated nitrate (over 50 mg/L) and E. coli (up to 250 CFU/100 mL). The increasing presence of E. coli and NO3− in the shallow groundwater of Kabul city in turn suggests problematic links to the prevalence of waterborne diseases. Additionally, the water quality index (WQI) was used to assess groundwater quality, and rank its suitability for drinking purposes. The WQI analysis showed that less than 35% of shallow groundwater samples had good water quality. The findings of this study are crucial for the development and sustainable management of groundwater in the city. In short term, we propose interventions such as point-of-use (POU) water purification which may offer temporary respite for waterborne disease prevention. Kabul city requires immediate attention to developing sustainable groundwater management policies, expansion of the water supply network, groundwater quality monitoring, and wastewater management.

Multivariate statistics and hydrogeochemistry of deep groundwater at southwestern part of Bangladesh

Multivariate statistics and GIS alone with geochemical modeling were applied to investigate the hydro-geochemical characteristics of groundwater and their spatial distribution in the deep aquifer system of Bagherpara Upazila, Bangladesh. This Upazila consists of an area of 308.3 km2 and local people mostly rely on groundwater to meet the drinking water requirements. Water samples from one hundred randomly selected deep tube wells (152–198 m) were collected and analyzed for 14 water quality parameters to characterize the hydro-geochemical properties. The groundwater shows slight alkaline in nature throughout the study area. Most of the water samples were turbid and 68% of them failed to meet the drinking water quality standard prescribed by the World Health Organization (WHO). TDS concentration ranges between 280 mg/L and 1040 mg/L, with a mean value of 446.20 (±122.19) mg/L. The general order of cation and anion along the study area were Ca2+>Mg2+>Na+>K+ and HCO3->Cl−>PO43->SO42->NO3- respectively. Carbonate weathering is the dominant process for releasing ions in groundwater. Besides, the ion exchange process is active in the study area, which leads to the reduction of Na+ ions. Gibb's plot suggests a rock dominance inheritance controls the dissolution and precipitation of minerals along with the ion-exchange process, and ultimately dictates the groundwater chemistry. Besides, the Piper diagram showed that Ca2+-Mg2+-SO42- is the dominant water type in 65% of the samples followed by Ca2+-Mg2+–HCO3- water type (35%). The abundance of Ca2+ and Mg2+ ions and the alkaline nature of groundwater indicate mixed geochemical facies and reverse exchange reactions. The principal component analysis (PCA) reveals that weathering and leaching of host rocks was the main natural source, while municipal solid waste dumping, sewage discharge, and fertilizer application could be other anthropogenic factors that affect the groundwater geochemistry. In fine, the chemical characteristics of groundwater were acquired through rock dissolution, percolation, and reverse exchange process.

Hydrochemical Characteristics and Genetic Analysis of Shallow High-Fluorine Groundwater in Fuyang River Basin

In order to understand the sustainable and effective utilization of groundwater resources in Fuyang River Basin, the chemical characteristics and genetic evolution process of characteristic shallow fluoride groundwater in the region were carried out. The results show that the chemical characteristics of groundwater are zonal in horizontal direction. From the piedmont plain to the central plain, the hydrochemical types of the first and second aquifers are mainly HCO3-Ca-Mg-type water, HCO3-Cl-Ca-Mg-type water, Cl-SO4-Na-Ca-type water, and Cl-SO4-Na-Mg-type water. The main mineral sources of hydrochemical ions are salt rock, carbonate rock, sulfate rock, and silicate rock. F- has a significant positive correlation with HCO3- while it is negatively correlated with K+. In the strong evaporation and alkaline environment created by climatic conditions in the study area, F- mainly comes from the dissolution of minerals. Gypsum and fluorite are in a relatively stable dissolved state continuously providing F- and Ca2+ for groundwater; the adsorption of cation was gradually strengthened from the piedmont plain to the central plain. The high HCO3- content is also conducive to F- desorption in alkaline environments. The samples with F- concentration greater than 1 mg·L-1 accounted for 35.7% and mainly distributed in the south of the study area. In summary, the chemical characteristics of shallow groundwater in Fuyang River Basin are affected by the combined effects including leaching effect, evaporation concentration, ion exchange-desorption, and human factors.

Chemical Evolution Process and Quality Assessment of Seepage Groundwater in Tunnel Crossing Gas-Bearing Coal Seams

The chemical characteristics of groundwater in the gas coal seam section of the tunnel have rich geological significance. To study the chemical evolution process and controlling factors of groundwater in the gas-bearing coal seam section of the tunnel, and the influence of tunnel coal removal on the groundwater quality, field investigations and laboratory experiments were carried out on the groundwater in the coal measure strata and the high-gaseous section and surrounding aquifers. Through hydrochemical analysis, correlation analysis, hydrochemical simulation, and other methods, the chemical origin of groundwater in coal measure strata and other aquifers was revealed. The water quality of groundwater was analyzed by water quality index (WQI), sodium adsorption rate (SAR), percentage of soluble sodium (Na+%), and participation of sodium carbonate (RSC). The results show that the water samples of each aquifer are weakly alkaline. Influenced by formation lithology and mineral redox reactions, the genesis of coal formation water is more complex than that of natural karst groundwater. The water chemistry characteristics show obvious differences among aquifer groups, with low correlation of HCO3-, Ca2+, and Mg2+. The central drainage ditch is dominated by dolomite dissolution, and the sloping shaft side ditch is dominated by calcite dissolution, and ion exchange effects are prevalent in different water sources. In terms of irrigation water quality, the permeability index (PI), magnesium hazard (MH), and Kelly index (KI) calculations show that 45.8% of the water samples are in the “unsuitable” condition. This study helps to fully understand the quality of coal seam water in tunnels and can provide a reference for groundwater utilization.

Response of groundwater chemical characteristics to land use types and health risk assessment of nitrate in semi-arid areas: A case study of Shuangliao City, Northeast China

Groundwater is an important source of water, especially in semi-arid areas. The assessment of the chemical characteristics of groundwater under different land use types the associated risk to human health is of important significance for water resources utilization and protecting the ecological environment. The present study analyzed the hydrochemical characteristics and ion sources of groundwater, taking Shuangliao City as an example. The analysis was based on the field investigation (82 water samples), descriptive statistics, correlation analysis, ion proportionality coefficient method, and principal component analysis (PCA). The results indicated that the concentrations of most ions in the aquifer had wide spatiotemporal variation and were susceptible to environmental influences. NO3− showed the highest spatial variability, with concentrations ranging from 0.0 to 529.48 mg·L−1. The processes contributing the most to the chemical composition of groundwater were leaching/dissolution and cation exchange. The spatial distribution of groundwater chemistry types was visually obtained through the combined use of Piper trilinear charts and a Digital Terrain Model (DTM). The HCO3—Ca type dominated. Groundwater Cl−, SO42−, and Ca2+ were negatively correlated with the Normalized Difference Vegetation Index (NDVI) due to the absorption of inorganic salt by vegetation roots, indicating that land use types affect groundwater hydrochemistry in the area. The hazard quotient (HQ) used in the human health risk assessment (HHRA) model indicated children (0.0010–6.4162) to be at the highest risk, followed by adult females (0.0007–4.0396), with adult males (0.0005–3.0863) under the lowest risk. The spatial distribution of groundwater nitrate was shown to pose risks to children, adult females, and adult males across 62.97%, 50.01%, and 39.34% of the study area, respectively. This study can improve the understanding of groundwater evolution and the relationship between water chemistry and land use types. This study can also guide the development and utilization of groundwater resources and conservation of water quality in semi-arid areas.