Groundwater Chemistry Research Articles

Boron adsorption in clay minerals: Implications for martian groundwater chemistry and boron on Mars

Boron has been detected on Mars in calcium-sulfate veins found within clay mineral rich rocks on Mars by the Mars Science Laboratory (MSL) Curiosity rover using Laser Induced Breakdown Spectroscopy (LIBS) analysis. Borates play a vital role in stabilizing ribose on Earth and has been suggested as a key requirement for life. Borate ions readily adsorb to phyllosilicate clay minerals. The discovery of boron on Mars in proximity to phyllosilicate-bearing bedrock may have strong implications for potential past prebiotic conditions on Mars. In this study we generated a suite of clay minerals with adsorbed borate, including both typical terrestrial clay minerals (montmorillonite) and Mars-analog clay minerals (nontronite, saponite, griffithite), to understand controls on borate adsorption and to analyze with LIBS to compare with MSL data. Clay minerals were subjected to mineralogical and chemical analysis before and after adsorption. Adsorption analysis revealed that the Mars analog clay minerals adsorbed less boron than terrestrial counterparts, but within comparable amounts to those detected on Mars and in meteorites. Post-adsorption analysis by X-ray diffraction (XRD) revealed slight changes in the interlayer spacing of many of the clay minerals. Based on the adsorption analysis of the Mars-analog clay minerals, phyllosilicate-bearing bedrock in Gale crater may contain up to 90-110 ppm B. A series of borate-enriched samples were created for analysis of LIBS spectra from ChemCam on the Curiosity rover and SuperCam on the Perseverance Rover. The results of this study may provide insight into martian groundwater geochemistry processes and the mobility of a key molecule connected with life.

ROS production upon groundwater oxygenation: Implications of oxidative capacity during groundwater abstraction and discharging

Production of reactive oxygen species (ROS), such as hydrogen peroxide (H2O2) and hydroxyl radical (•OH), has been increasingly discovered upon oxygenation of reduced species in anoxic soil and sediment pore waters. We therefore hypothesize that H2O2 and •OH can be produced during groundwater abstraction and discharging due to oxygenation. To evaluate the capacities of H2O2 and •OH accumulation during groundwater oxygenation, here we measured H2O2 and •OH accumulations during dark oxygenation of groundwater abstracted from different depths of 11 wells adjacent to the Han River. This abstraction could simulate the scenarios of groundwater abstraction by riverside pumping and also of groundwater discharging in hyporheic zones. Results showed that H2O2 and •OH formed during oxygenation of the groundwater with low Eh values (< 63 mV), and only H2O2 (< 3.37 μM) formed for the groundwater with high Eh values (63–206.5 mV). Statistical analysis indicated that dissolved Fe(II) was mainly accountable for the production of measurable •OH in the low Eh locations. The aquifer conditions (i.e., aquifer lithology) and external environmental factors (i.e. pumping disturbance) within short-term abstraction process had negligible influence on ROS production. The relationship between ROS production and groundwater chemistry was further explored by multiple linear regression, which deduced the quantitative models for estimating ROS production upon oxygenation of groundwater from different sources with different chemistry. Using the abstracted groundwater in western Bengal basin as an example, the estimated results indicated that ROS production had a great potential to oxidize the typical contaminant of As(III). As ROS, particularly •OH, represents strong oxidants, our findings implicate an overlooked oxidative capacity during groundwater abstraction and discharging in hyporheic zones or other areas, which could lead to the oxidative transformation of substances and the oxidative stress of microbial metabolism and associated biogeochemical processes in the environments suffering from groundwater oxygenation. This oxidative capacity is particularly important when the groundwater with low Eh values, i.e., under strongly reductive conditions, were abstracted and oxygenated in the surface.

Hydrogeochemical processes and groundwater evolution in complex volcanic highlands and alluvio-lacustrine deposits (Upper Blue Nile), Ethiopia.

Lake Tana basin encompasses a wide regional volcanic aquifer system, in the northwestern highlands of Ethiopia. It has significant water resource potential for water supply and irrigation purposes. The objective of this study was to assess the physiochemical characteristics of the surface water-groundwater and investigate the processes controlling groundwater chemistry. A total of 273 water samples were collected from different water points for major ions and stable isotope analysis, representing different physiographic and hydrogeologic regions. Multivariate statistical, graphical methods, saturation and speciation modelling were used jointly to characterize water chemistry and to define hydrogeochemical processes. The Piper plots in combination with cluster analysis and isotope hydrological data indicate that, generally, the groundwater chemistry of the basin can be classified into (1) low TDS Ca-HCO3, Ca-Mg-HCO3, and Ca-Na-Mg-HCO3 type water which is relatively enriched in δ18O-δ2H and depleted in δ13C. These are recharge waters, which are characterized by low rock-water interaction; (2) brackish Mg-Na-Ca-HCO3 type water which is relatively depleted in δ18O-δ2H and enriched in δ13C; and (3) low TDS Na-(Ca)-HCO3 and Na-HCO3 type water which varies from less to more depleted in δ18O-δ2H and is characterized by relatively enriched δ13C. The cross-plots of the major cations vs. HCO3- and stability diagrams show that the primary processes controlling the groundwater evolution in the Lake Tana basin are alumino-silicate weathering and dissolution. Studying the hydrogeochemical characteristics of a complex geologic system with integrated approach helps to understand the complex groundwater flow system and flow dynamics, which in turn helps for proper groundwater utilization and future management.

Chemical Characteristics and Controlling Factorsof Groundwater in Chahannur Basin

This paper studies the spatial distribution characteristics and controlling factors of groundwater chemistry in the Chahannur Basin. One hundred and seventy shallow groundwater samples (50 m shallow) are collected, and seven ions, pH, TDS, TH, iron, manganese, COD, barium and other indicators, are detected. Piper triplex graph, Gibbs model, ion ratio, analysis of variance and Kriging interpolation are used to carry out the research. The results show that bicarbonate water is the main water chemical type in the Chahannur Basin, in which bicarbonate water accounts for 65.23%, chloride water accounts for 15.15% and sulfate water accounts for 19.62%. Bicarbonate water is mainly distributed in the mountainous areas in the north and south of the basin, and the main controlling factor is rock weathering. Sulfate-type water is mainly distributed in the lower reaches of the northern mountains of the basin, and the main controlling factors are rock weathering and evaporation concentration. The chloride water is mainly distributed in the Chahannur Lake area and the shallow groundwater buried area in the central region of the basin. The main controlling factors are evaporation concentration and human influence. Na+ is mainly derived from atmospheric precipitation and rock salt leaching, Ca2+ and Mg2+ are mainly derived from carbonate minerals leaching, and silicate minerals leaching is less. The pH of groundwater in the basin ranges from 6.3 to 9.18, with an average value of 7.50. The TDS in the basin ranges from 227 to 22,700 mg/L, with an average of 1661 mg/L. Iron in the catchment ranges from 0.01 to 15.343 mg/L, with a mean of 0.837 mg/L. The manganese content in the basin ranges from 0.005 to 3.802 mg/L, with an average value of 0.254 mg/L. COD in the basin ranges from 0.71–32.72 mg/L, with an average value of 3.49 mg/L. Barium in the basin ranges from 0.005 to 0.312 mg/L, with an average of 0.075 mg/L. The research results provide basic scientific data support for groundwater hydrochemistry research in the Chahannur Basin and show that the types of water chemistry in the study area are complex and diverse, and although the distribution is still controlled by terrain and geological conditions, the area affected by human activities accounts for a high proportion, so attention should be paid to the impact of human activities on groundwater in this area.

Spatial evolution analysis of groundwater chemistry, quality, and fluoride health risk in southern Hebei Plain, China.

The present study investigated ion and fluoride concentrations in groundwater and their associated health risks to local populations in the southern Hebei Plain during 2018-2020. A total of 336 groundwater samples were collected from monitoring wells at 112 different locations. Statistical analysis, Gibbs diagram, principal ion ratio, and saturation index were carried out to clarify the chemical characteristics and control mechanism of groundwater. The results indicated that the groundwater types in the study area were mainly HCO3-Ca, Cl-Na, and SO4-Ca. The concentrations of cations and anions were Na+ > Ca2+ > Mg2+ > K+ and HCO3- > SO42- > Cl- > NO3- > F-, respectively. Based on the water chemical parameters, the pollution index of groundwater (PIG) was used to comprehensively evaluate the water quality. The results showed that during the study period, 60.41% of groundwater samples were suitable for drinking purposes, and 39.59% needed purification treatment to meet the requirements of drinking water standards. The groundwater quality in the western pre-hill plain areas was good, while the water quality in the northeastern and southeastern areas was poor and contaminated to varying degrees. Groundwater quality was mainly affected by the combined effect of total dissolved solids (TDS), Na+, Mg2+, Cl-, SO42- and HCO3- concentrations. Fluoride concentrations in the groundwater samples ranged from 0.07 to 8.51mg/L, with 44% of the samples containing fluoride below the recommended limit of 0.5mg/L, which would put the population at risk of dental caries. Also, 8% of the samples exceeded the permissible limit for fluoride in drinking water (1.5mg/L), which would expose the local population to the risk of fluorosis. The human health risk evaluation of fluoride showed significant differences in non-carcinogenic effects between two different groups of children and adults. HIin values ranged from 0.08 to 10.19 for children and 0.03 to 4.65 for adults, with hazard indices greater than 1 at 29.16% and 10.11%, respectively. This indicates that children have a greater exposure risk than adults, and the entropy of higher risk is mainly distributed in the northeast of the study area. Based on the above analysis of the spatial evolution of groundwater chemistry, water quality, and fluoride health risks in the southern Hebei Plain region, corresponding protection and management measures were proposed, which also provided reference significance for the effective use of drinking water and health risk prevention in the region.

Application of statistics to correlate groundwater chemistry with land use on O'ahu, Hawai'i.

This study compiles commonly available groundwater chemistry data from the Pearl Harbor Sole Source Aquifer (SSA), Hawai'i-O'ahu's primary drinking water source-and applies hierarchical clustering analysis (HCA), principal component analyses (PCA), piper diagrams, and box plots with geospatial analysis to better define groundwater regions and correlate groundwater chemistry in those regions with land use. Groundwater in this aquifer recharges and flows through chemically similar soil and rocks, such that anthropogenic activities are a primary influence on the chemical variability of the aquifer's differing regions. Our analyses link specific chemical species in groundwater to land use/cover categories: urban, agriculture, and natural and anthropogenically-induced saline water intrusion. To create distinct statistical groupings with different groundwater chemistry compositions, it was important that the suite of parameters used in the statistical analysis do not covary. In our case, Cl- covaried with several major ions; however, by including F-, alkalinity, and SiOx that do not covary with Cl- in the covariance matrix, we produced improved spatial grouping of HCA clusters and stronger affinities to land use designations. Results show that dominant groundwater chemistry changes with land use along flow paths. These results pertain to areas where groundwater flows from conservation land in high recharge areas of O'ahu's mountain ranges to urban and agricultural land use regions: groundwater retains its source characteristics until about 3-6km into agricultural and urban zoned lands. Ultimately, this study outlines a simple method for water quality regulators to use groundwater chemistry to identify risks of target contaminants based on land use.

Influence of Dissolved Oxygen, Water Level and Temperature on Dissolved Organic Carbon in Coastal Groundwater

The quality of groundwater has been severely impacted by urbanization around coasts. The change in climate and land use patterns has deteriorated the quality and availability of groundwater. One of the main issues in contemporary groundwater quality research is dissolved organic carbon (DOC) in the water. The influence of DO, water level and water temperature on DOC in groundwater was identified in the current study by sampling 68 groundwater samples. The analytical results revealed that ~18% of total samples have DOC &gt; 5 mg/L. The groundwater samples represented in the urban regions show high DOC. The samples with higher DOC correlated positively with dissolved inorganic ions, such as Ca, K, NO3, Fe and DO. Domestic wastewater, agricultural runoff and local geology all have an impact on the DOC of groundwater. Groundwater chemistry is shown to be controlled by both aerobic and anaerobic conditions based on the DOC’s interactions with other ions. The study interrelates various sources, such as land use, geology, water level and temperature, to the DOC in groundwater and infers that the levels are higher in shallow groundwater, predominantly around the built-up region followed by the agricultural region. The temperature changes enhance the DOC in groundwater due to the variation in microbial activity. The shallow water level with a lower temperature shows the maximum DOC. Apart from the sediment organic matter and microbes, the study also attributes land use pattern to the source of DOC in groundwater.

Hydro-chemical Characteristics of Melt Water Draining from Glaciers of Rongdo Basin, Shyok Valley, Ladakh

Abstract Physico-chemical parameters of meltwater of 20 water samples from glaciers of Rongdo basin, Shyok valley are presented here. The concentration of cations and anions of the two valleys were found in the order Ca&amp;gt;Mg&amp;gt;Na&amp;gt;K and HCO3&amp;gt;SO4&amp;gt;Cl&amp;gt;NO3 respectively. Significant altitudinal variation was found in major ions as indicated by the increase of TDS of glacial melt and stream water samples downstream. Gibbs plot shows chemical weathering of the rock forming minerals as the main cause for contributing ions to the melt water. The dominant order of hydrogeochemical water types identified is Ca-HCO3, is due to the water rock interaction which leads to the easy dissolution of carbonate and silicate minerals. However, few glacial melt and stream water have the influence of precipitation and meltwater runoff on chemistry. The hot spring falls in Na-HCO3 type, a typical of deeper groundwater influenced by ion exchange processes. Scatter plots of HCO3+SO4 vs. Ca/Na Plot and Ca/Na vs. HCO3/Na clearly indicates that the weathering of carbonate and silicate play a dominant role on groundwater chemistry. Two chloro-alkaline indices indicate reverse exchange reaction between Na+, K+, Mg2+and Ca2+. The physical parameters and major ions are within the permissible concentrations as per WHO and BIS indicating water is good for drinking and domestic purposes. The groundwater is suitable for irrigation as per the quality parameters and plots including EC, sodium percent (Na%) and sodium adsorption ratio (SAR).

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.

Quality and groundwater contamination of Wadi Hanifa, central Saudi Arabia

In arid and semi-arid regions, freshwater is mainly acquired from groundwater. Over the years, human activities have reduced the latter's quality, making it a threat to health. Heavy metal pollution index (HPI), metal index (MI), groundwater quality index (GWQI), sodium absorption ratio (SAR), magnesium ratio (MR), Kelly's ratio (KR), and sodium percentage (Na%) were applied as pollution parameters and indices in assessing the groundwater's suitability for irrigation and drinking purposes in Wadi Hanifa in Saudi Arabia. Samples were collected from 26 sites, and a physicochemical analysis and heavy metal analysis were conducted. The results showed a concentration of SO42-, Cl-, Ca2+, HCO3-, Na+, Mg2+, and K+, which is higher than the WHO standards for drinking water. 96.15% of the water samples (n = 25) fell under the Ca-Cl groundwater dominant facies type, and one model fell under the mixed type. According to the GWQI classification, 16.66%, 50%, and 26.92% of the collected samples are categorized as very poor, poor, and generally unsuitable for human consumption, respectively. Parameters such as SAR, KR, and Na% are indicative of irrigation water. The study's primary factors affecting the groundwater chemistry included the natural processes of precipitation or dissolution of the silicates, carbonates, and evaporites alongside anthropogenic activities and soil leaching.

Hydrogeochemical characterization and natural background level determination of selected inorganic substances in groundwater from a semi-confined aquifer in Midwestern Burkina Faso, West Africa.

Hydrogeochemical processes that govern selected inorganic substances distribution in a semi-confined aquifer were characterized using traditional hydrogeochemical approaches and natural background levels (NBLs). Saturation indices and bivariate plots were used to investigate the effects of water-rock interactions on natural evolution of the groundwater chemistry, whereas Q-mode hierarchical cluster analysis and one-way analysis of variance classified the groundwater samples into three distinct groups. To highlight the groundwater status, NBLs and threshold values (TVs) of the substances were calculated using pre-selection method. Piper's diagram showed that the Ca-Mg-HCO3 water type was the only hydrochemical facies of the groundwaters. Although all samples, except a borewell with a high NO3- concentration, had major ion and transition metal concentrations within the World Health Organization's recommended guideline values for drinking water, Cl-, NO3- and PO43- exhibited scattered distribution patterns, reflecting their nonpoint anthropogenic sources in the groundwater system. The bivariate and saturation indices revealed that silicate weathering and possible gypsum and anhydrite dissolution contributed to the groundwater chemistry. In contrast, NH4+, FeT and Mn abundance appeared to be influenced by redox conditions. Strong positive spatial correlations between pH, FeT, Mn and Zn suggested that mobility of these metals was controlled by pH. The relative high F- concentrations in lowland areas may imply the impact of evaporation on this ion's abundance. Contrary to TVs of HCO3-, those of Cl-, NO3-, SO42-, F- and NH4+ were below the guideline values, confirming the influence of chemical weathering on the groundwater chemistry. Based on the present findings, further studies that take into account more inorganic substances are required for NBLs and TVs determination in the area, thereby setting up a robust sustainable management plan for the regional groundwater resources.

Hydrochemical Characterization of Surface Water and Groundwater in the Crystalline Basement Aquifer System in the Pra Basin (Ghana)

The quality of groundwater resources in the Pra Basin (Ghana) is threatened by ongoing river pollution from illegal mining. To date, there are very limited data and literature on the hydrochemical characteristics of the basin. For the first time, we provide regional hydrochemical data on surface water and groundwater to gain insight into the geochemical processes and quality for drinking and irrigation purposes. We collected 90 samples from surface water (rivers) and groundwater (boreholes) and analysed them for their chemical parameters. We performed a water quality assessment using conventional water quality rating indices for drinking water and irrigation. Cluster and factor analysis were performed on the hydrochemical data to learn the chemical variations in the hydrochemical data. Bivariate ion plots were used to interpret the plausible geochemical processes controlling the composition of dissolved ions in surface water and groundwater. The water quality assessment using Water Quality Index (WQI) revealed that 74% of surface water and 20% of groundwater samples are of poor drinking quality and, therefore, cannot be used for drinking purposes. For irrigation, surface water and groundwater are of good quality based on Sodium Adsorption Ratio (SAR), Wilcox diagram and United States Salinity (USSL) indices. However, Mn and Fe (total) concentrations observed in most surface water samples are above the acceptable limit for irrigation and therefore require treatment to avoid soil acidification and loss of availability of vital soil nutrients. Manganese and iron (total) are identified as the main contaminants affecting the basin’s water quality. The hierarchical cluster analysis highlights the heterogeneity in the regional hydrochemical data, which showed three distinct spatial associations based on elevation differences. Groundwater composition chemically evolves from a Ca–HCO3 to a Na–HCO3 and finally to a Na–Cl water type along the flow regime from the recharge to the discharge zone. The bivariate ion plot and the factor analysis underscore silicate weathering, carbonate dissolution and ion exchange as the most likely geochemical processes driving the hydrochemical evolution of the Pra Basin groundwater. Going forward, geochemical models should be implemented to elucidate the dominant reaction pathways driving the evolution of groundwater chemistry in the Pra Basin.

Identification of the hydrochemical features, genesis, water quality and potential health hazards of groundwater in Dawen River Basin, North China

Groundwater resources fulfill a key role in socioeconomic development and residential water use in the Dawen River Basin (DRB). This study sampled and tested three types of groundwater in the DRB, including pore groundwater (PGW), fissure groundwater (FGW), and karst groundwater (KGW). Groundwater in the DRB was assessed for hydrochemical characteristics, quality, and hazards to human health by nitrate contents. Results identified the dominant groundwater anion and cation to be HCO3− and Ca2+, respectively, whereas groundwater was generally weakly alkaline hard-fresh water. The groundwater contents of main chemical components during wet season exceeded those in the dry season, with the rank of groundwater types by chemical component contents being: PGW > KGW > FGW. A Durov diagram indicated groundwater in the DRB to be mixed HCO3-Ca and HCO3·SO4–Ca·Mg types. Rock weathering (silicate and carbonate rocks) was found to be the predominant process regulating groundwater chemistry of the DRB, whereas human activities also had a significant impact, particularly for high NO3− related to agricultural activities. Groundwater quality of the DRB was relatively good overall, falling into the good and moderate classification grades, with that of the PGW the worst. Long-term human direct consumption or exposure to groundwater of DRB poses certain health risks due to groundwater nitrate, with the risk for children highest. The spatial variations in quality of groundwater and nitrate health hazard in the DRB were relatively consistent, with better quality and lower health risk of PGW and FGW in the east than in the west, and that of KGW better in the center than in the east and west. The present study can provide some reference for groundwater safety and protection management in DRB and other similar areas in the world.

Geochemical characterisation and geostatistical evaluation of groundwater suitability: a case study in Perambalur District, Tamil Nadu, India

Groundwater is a naturally occurring potential source for drinking, irrigation, agricultural and industrial purposes. The population growth and accelerated development of industries and agriculture activity degrade groundwater quality. The groundwater quality of an area was determined by the physical and chemical parameters, influenced by geology, soil, land use, land cover and anthropogenic activities. Perambalur district in Tamil Nadu has been selected as a study area with a total geographical area of around 1757 km2. In the study area, groundwater quality decreases due to the usage of chemical fertilisers and pesticides in agricultural land and miningactivities. So, the hydrogeochemical assessment will help to determine the groundwater suitability for drinking. Forty-eight groundwater samples were collected from the study area during the pre-monsoon (July 2021) and post-monsoon season (January 2022). Samples were analysed using the standard methods prescribed by the American Public Health Association for pH, electrical conductivity (EC), total dissolved solids (TDS), calcium, magnesium, sodium, potassium, carbonate, bicarbonate, chloride, sulphate, nitrate and fluoride. The spatial distribution of major physiochemical parameters is mapped using the inverse distance weighted (IDW) interpolation technique. The evaluation of hydrochemical facies from piper plots revealed that the major cation and anion were in the order of Ca2+ > Mg2+ > Na+ > K+ and Cl- > HCO3- > SO42- > NO3- in both seasons, respectively. Further, the plot explains the presence of both permanent and temporary hardness in the groundwater. The evaluation of hydrochemical facies from the piper plot emphasises that the reverse ion exchange controls groundwater chemistry. The assessment of chloro-alkaline indices reveals that the sodium and potassium in groundwater get substituted with magnesium and calcium in the parent rock, which determines the groundwater composition. The values of saturation indices reveal that calcite and dolomite are supersaturated and tend to precipitate. From principal component analysis, the principal components have an eigenvalue of more than 1, containing 79.8% and 79.2% in the total variance in pre-monsoon and post-monsoon, respectively. Most physiochemical parameters like TDS, EC, Na+, Mg2+, Cl- and SO42 - have strong positive loading and are responsible for the changes in groundwater chemistry. Finally, the calculation of the water quality index identified that groundwater quality in post-monsoon tends to decline compared to pre-monsoon.

Hydrogeological conditions of Irpin and their influence on the city’s engineering protection and construction assessment

The scheme of engineering-construction assessment, which is created based on engineering geological zoning of the city’s territory is desirable among additional graphic materials in the design of master plans projects as determined by state building norms [State…, 2012]. Engineering geological zoning provides for different ranks’ selection of taxonomic engineering-geological (EG) units, which have a particular range of common engineering geological conditions that ultimately determine the construction sites’ affiliation to a specific suitability category. Geological-lithological structure and hydrogeological conditions of the Irpin city, Kyiv region are investigated, and the types and degrees ofgroundwater aggressiveness, chemical composition, and mineralization of groundwater, the depths of the first aquifers from the day surface are highlighted in this article. A variant of the creation of large-scale maps of groundwater depth and chemistry based on a hydrogeological survey conducting is presented. The analysis of hydrogeological circumstances of the city’s territory lays the foundations for the selection of engineering-geological sites based on the comparison of this information with geomorphological, engineering-geological and geodynamic data. Complexity assessment of hydrogeological conditions and accounting of hydrogeological factors for the construction assessment scheme and selection of corresponding measures of engineering training and protection of the problem construction sites has become an ultimate result.

Hydrochemical characteristics, quality and health risk assessment of nitrate enriched coastal groundwater in northern China

Groundwater quality is an essential factor restricting regional sustainable development owing to water resource scarcity, especially in coastal regions. Coastal groundwater is affected by natural conditions and strong human activities, and the evolution of water quality is extremely complex. Information on the hydrochemistry evolution and nitrate contamination status of coastal groundwater under the conjunctive effects of natural processes and human activities is a vital requirement for groundwater resource management in coastal regions. Thus, this study integrated traditional hydrochemical analysis approaches, the entropy-weight water quality index (EWQI), and the health risk assessment model to analyze hydrochemical characteristics, quality, and nitrate health risks in a typical coastal region (i.e., southern Laizhou Bay) simultaneously affected by seawater intrusion and anthropogenic activities, as well as to explore the dominant mechanisms controlling groundwater quality. The results indicated that the concentrations of major hydrochemical constituents in groundwater exhibited wide variability. The NO3− concentration varied from 0.59 to 824.80 mg/L; it surpassed the WHO drinking water standard (50 mg/L) at 89.47% of sampling sites. The predominant hydrochemical types of groundwater were SO4•Cl–Ca•Mg and HCO3–Ca•Mg. Governing factors influencing groundwater chemistry were recognized as rock weathering, inverse cation exchange and anthropogenic activities, and nitrate contents were largely controlled by agricultural practices. The computed EWQI showed that 55.26% of groundwater samples possessed EWQI values greater than 57, which is relatively poor-quality groundwater. The poor-quality groundwater was concentrated in the southwestern part of the study area. Non-cancer risks of nitrate in 96.71%, 94.74%, 89.47%, and 89.47% of the groundwater samples were unacceptable for infants, children, teens, and adults, and the spatial distribution of the hazard quotient (HQ) was in accordance with the spatial pattern of nitrate concentration. These findings can guide the exploitation and utilization of groundwater resources and water quality conservation in coastal regions.

Impact of soil salinity on groundwater chemistry in semi-arid regions in Western India: Insights from major ion and stable isotopic [formula omitted] characteristics.

Detailed geochemical and stable isotopic (δDH2O, δ18OH2O, and δ13CDIC) study of groundwater samples (n = 74) from a semi-arid region in Western India was carried out to constrain their solute sources and sub-surface weathering processes. Na+, Cl−, and HCO3− dominate major ion chemistry. This type of chemistry points to a significant solute supply from the salt-affected soils and bedrock dissolution. The average δ18O and δD in our groundwater samples are similar to their corresponding values in precipitation samples. Spatial variability of the δ18O and δD data depicts the impact of continental effect and variable extent of evaporation in this region. The δ18O-δD cross-plot yields a lower slope (5.2 ± 0.5) than that of the global meteoric water line (∼8), confirming the significant impact of evaporation on groundwater hydrology. δ13CDIC values vary between −7.3‰ and −16.4‰ (average = −9.7‰ ± 1.7‰), and first-order binary mixing calculation shows that about 75 (±16) % of the DIC in these samples are supplied via carbonate dissolution (range: 35–100%). Inverse model calculations involving elemental ratios of major ions show that the solutes are mainly supplied through salt-affected soils (30 ± 22%), with sub-ordinate contributions from rain (31 ± 13%), silicate (23 ± 12%) and carbonate (15 ± 13%). These estimates are consistent with the formation of salt-affected soils via evaporative water loss in semi-arid regions and the faster dissolution kinetics of these soil salts. The outcomes of this study underscore distinctly different compositions of semi-arid groundwater reservoirs, which has implications for drinking and irrigation usage.

Hydrogeochemical evolution of the shallow and deep basaltic aquifers in Tamborine Mountain, Queensland (Australia)

Tamborine Mountain, Queensland (Australia), is a prime example of a basalt fractured-rock aquifer. Yet very little is known about the hydrochemistry of this groundwater system. Both analytical (major ions and stable isotopes) and multivariate (hierarchical cluster analysis, principal component analysis and factor analysis) analyses were used in this study to investigate the factors that interact within this aquifer system, in order to determine groundwater hydrogeochemistry. A new approach was applied to the data by classifying hydrographs by water type to clearly identify differing aquifer zones. Three distinct groundwater chemistry types were identified, and they were differentiated by variations in depth. Shallow bores were dominated by Na–Cl waters, deep bores were dominated by Na–HCO3 and Ca–HCO3 waters, and the two deepest bores were dominated by mixed water types. The evaluation of hydrogeochemical data has determined that both mineral weathering processes and groundwater/surface-water interaction had a strong influence on the hydrogeochemistry. Seasonal effects were minimal in the study area based on physicochemical parameters and ion chemistry. However, stable isotopic data show temporal trends. Increased rainfall events during the wet season produced a depletion in δ18O and increased d-excess values. The opposite is found during the dry season as a result of higher evaporation rates that are not hindered by intense rainfall events.

Hydrogeochemical characterization of groundwater in the shallow aquifer system of Middle Ganga Basin, India

Middle Ganga Basin (MGB) is lifeline for millions of inhabitants relying heavily on the groundwater. This has resulted in depletion of water quality and quantity at a very rapid scale. The present study has emphasized on hydrogeochemical evolution of groundwater in the Middle Ganga Basin, covering an area of 99,058 sq. km. Around 400 water samples were evaluated to determine the geochemical evolution of the shallow groundwater in MGB. The weighted average water quality index (WAWQI) shows 20.2% of the groundwater are unsuitable for drinking purposes. The Ca–HCO3 water facies dominates in northern region in the interfluves of Ghaghara and West Rapti rivers whereas more evolved water types such as Mg–HCO3, Na–HCO3 are found in the interfluves area of Ghaghara, Ganga, Yamuna, and Gomati Rivers. The occurrence of more mineralized water with increasing residence time in the flow direction suggests geogenic control and evolution follow the Chebotarev sequence. The saline water type is observed in and around the settlement reflecting the in-situ enrichment due to stagnation and anthropogenic activities. Hierarchical cluster analysis classified the regional groundwater data into three distinct major groups G1, G2, and G3. Factor 1 is attributed to anthropogenic inputs and associated with subgroup G2B and group G3. Factor 2 is attributable to the geogenic factors and is associated with subgroups G1A, G1B, and G2A. The various bivariate plots confirm the dominance of silicate weathering over carbonate weathering in the study area. Geochemical mass balance modeling suggests calcite and dolomite are in saturation to oversaturation conditions, restricting their further dissolution and primary silicate minerals controlling the groundwater chemistry. Our work reveals hydrogeochemical evolution on a regional scale in the shallow groundwater which will help to develop sustainable groundwater management strategies.

Groundwater characterization of the eastern Minesing Wetlands in support of the endangered Hine’s emerald dragonfly (Somatochlora hineana)

The Minesing Wetlands contain Canada’s only known population of Hine’s emerald dragonfly (HED), a species listed as endangered since 2011. The HED relies on groundwater discharge areas to complete its life cycle and therefore the population is potentially sensitive to changes in groundwater. The goals of this study were to, (1) characterize groundwater discharge to the eastern portion of the Minesing Wetlands, which corresponds to the HED habitat, (2) document any significant changes in groundwater chemistry since a 1998 study, and (3) establish a comprehensive baseline water quality data set to facilitate future comparisons. Consistent with HED habitats in the USA, the chemistry of Minesing Wetlands groundwater was dominated by calcium and bicarbonate. Low groundwater chloride and nitrate concentrations indicated minimal impact from activities such as road salt application and fertilizer use. Nitrate was generally only found at the wetland margin where groundwater springs emerged from the base of the uplands. The dominant form of inorganic nitrogen in wetland groundwater was ammonium (max = 1.5 mg N/L), and soluble reactive phosphorus concentrations were also relatively high (8 to 122 µg/L). The most consistent change in wetland groundwater chemistry between the 1998 study and samples collected in 2015–2017 was that chloride concentrations in 10 of 23 wells increased over time, however the maximum mean well chloride (11.6 mg/L) remained well below the guideline for the protection of aquatic life (120 mg/L). To preserve HED habitat, potential impacts to groundwater need to be considered during land use planning for the recharge area.