Main Hydrogeochemical Processes Research Articles

Hydrogeochemical processes, and health risk assessment of groundwater, in Santa María del rio aquifer: A case study of San Luis Potosí valley, Mexico

The main objectives of this research were to the hydrogeochemical processes that control the groundwater chemistry, groundwater quality, and assessment of health risks of water. The drinking water that supplies the community of Santa María del Rio, S.L.P., comes from groundwater, in some municipality localities, groundwater Fluorine and arsenic are reported. Twenty-one representative groundwater samples were taken. Physicochemical parameters in situ: pH, OD, ORP, Alkalinity, STD, EC, Salinity, Total Coliforms, and E-coli, were analyzed, and in the laboratory, the heavy metals, metalloids and major constituents, cations: calcium, sodium, magnesium, and potassium, were determined by the ICP, and anions: chlorides, and sulfates, by colorimetry techniques. The results of the analyses were compared with the Mexican and EPA drinking water standards to verify their suitability and ensure that they do not exceed the permitted limit values. The results of the chemistry of the principal groundwater ions in the study area suggest that the main hydrogeochemical process that controls the variation of groundwater quality is the rock–water interaction. Groundwater has been classified into two hydrochemical facies, CaMgHCO3 and NaHCO3, consistent with the type of rock. The samples with the CaMg–HCO3 facie are associated with less evolved waters located in areas with local recharge. The dominant reactions in the aquifer are calcite, dolomite, and gypsum solutions. The presence of the N–NO3- ion is associated with agricultural and urban zone influence, which indicates that this activity has impacted the water quality. The risk index (HI) results show that values > 0.1 < 1 of HI, for Pb present low chronic risks for adults and children. In contrast, HI values > 4 for both population groups represent high chronic risk. Excessive use of fertilizers should be controlled in the study area to prevent groundwater contamination by heavy metals and metalloids and be measured regularly to check drinking water quality.

River–Spring Connectivity and Hydrogeochemical Processes in a Karst Water System of Northern China: A Case Study of Jinan Spring Catchment

Frequent surface water–groundwater interactions and prevalent anthropogenic inputs make karst water systems vulnerable to human disturbance. As a typical karst region in North China, the Jinan Spring Catchment has become increasingly threatened due to rapid population growth and urban expansion. In this study, the local river–spring interaction and its interference with the hydrogeochemical evolution of groundwater are evaluated based on water stable isotopes and hydrochemistry. Twenty-two karst groundwater, eleven Quaternary pore water, sixteen spring water, and thirty-two surface water samples were collected during low- and high-flow conditions over the course of a year. The isotopic signatures of four different water types display significant differences, reflecting the recharge–discharge relationship of the karst water system. Mountainous springs feature lighter isotopes, whereas urban springs have significantly heavier isotopes. The result of end-member mixing analysis shows that the surface–groundwater interaction varies spatially and temporally within the spring catchment. Urban springs receive considerable replenishment from the surface water, especially after rainy episodes (up to 50%), while mountainous springs show little hydraulic dependence on surface water leakage (4~6%). Local mineral dissolution (including calcite, dolomite, gypsum, and halite), CO2 dissolution/exsolution, and cation exchange are the main hydrogeochemical processes constraining water chemistry in the spring catchment. The deterioration of water quality can be attributed to anthropogenic influences involving the discharge of domestic effluents, agricultural activities, and irrigation return flow. The findings of this work can improve our understanding of the complex karst water system and serve as a reference for sustainable groundwater management in other karst areas of northern China.

Hydrochemical Characteristics and Formation Mechanism of Groundwater in the Western Region of Hepu Basin, Beihai City

Beihai City is a typical coastal city where groundwater provides a strong support for social and economic development. Studies on the hydrochemical characteristics and formation mechanism in Beihai City play an important role in the scientific management of water resources and coastal ecological environment protection. In this study, we revealed the main hydrogeochemical processes controlling groundwater quality by means of groundwater survey and water sample collection in the western region of Hepu Basin, Beihai City, combined with hydrochemistry and isotope theories and methods. The results showed that groundwater had the remarkable features of low pH value and low mineralization degree. For pore water, hydrochemistry type by primarily NO3 type water and concentrations of Na+ and Cl- were modestly increased along the flow path. Ca-HCO3, Ca-Cl·HCO3, Ca·Na-HCO3, and Na-Cl·HCO3 types were predominant in fissure water. The groundwater was of meteoric origin, hydrogeochemical evolutions were mainly affected by water-rock interactions, cation exchange, and anthropogenic activities. Na+, K+, and Cl- were mainly derived from evaporite and silicate rocks; Ca2+, Mg2+, HCO3-, and SO42- were from carbonatite and evaporite; and NO3- principally arose from anthropogenic activities. This study suggests that the groundwater pollution prevention and control should be carried out as soon as possible in the area where the NO3 type water occurs to avoid the further deterioration of water quality.

The hydrogeochemical characteristics and formation mechanism of high-fluoride mine water

Excessive fluoride ion (F−) concentrations in mine water affected by the geologic processes and coal mine activity prevent the reusage of it as domestic and production water resources. There are few researches on the accumulation mechanism of fluoride in mine water. In this study, 71 water samples and 39 rock samples were collected from 9 mines of the Inner Shaanxi-Mongolia Contiguous area for chemical analyses and laboratory experiments. Results indicate that the concentration of F− in mine water increased with the gradual increase of the coal mining depth. The average concentration of F− in no.3-1 coal mine water is higher than that in no.2-2 coal mine water. And concentrations of F− exceed the China national standard for drinking water quality (upper limit of 1 mg/L), which is closely related to fluoride in the no.3-1 coal roof groundwater and water-rock interaction in the goaf. The main hydrogeochemical processes include mineral dissolution (fluorapatite and hornblende), desorption of exchangeable F− from clay minerals (mica, illite, kaolinite and chlorite) and cation exchange between Ca2+ and Na+. Furthermore, long-term further water–rock interactions result in F− accumulation in mine water. Alkaline environments, decreased particle size of rock, and increased temperature all favor release of F− from clay mineral surface into mine water. Finally, conceptual model of high-fluoride mine water was first proposed, and the formation of high-fluoride mine water can be summed as two stages including water-rock interaction in groundwater and secondary water-rock interaction in goaf. This study helps to improve our understanding of genesis of high-fluoride mine water and our capability of predicting the future concentration, which may provide foundation for manage and utilization of mine water.

Assessment of some bottled natural mineral waters and spring waters in Algeria using multivariate statistical analysis, hydrogeochemical approaches and water quality index (WQI)

ABSTRACT In Algeria, the consumption of mineral waters has grown enormously, indicating that these waters have safe quality for drinking use. The objectives of the present study are to evaluate the physicochemical characteristics of 43 bottled mineral waters and to identify the main hydrogeochemical processes governing water chemistry using a combination of geochemical techniques and multivariate statistical approaches. The results revealed that the abundance order of cations and anions (mg/L) are Ca2+> Na+> Mg2+> K+, HCO3 −> SO4 2−> Cl−> NO3 −. In addition, the comparison between the obtained results and World Health Organization (WHO) standards showed that the analysed physicochemical parameters (pH, Na+, Cl−, SO4 2−, NO3 −) are within the acceptable limits of the World Health Organization (WHO) for drinking except TDS, Ca 2+, Mg2+, K+, HCO3 −, which exceed the WHO permissible limits in few water samples. Hydrogeochemical types in the study area were Ca2+-HCO3 −, Ca2+-Mg2+-HCO3 −, Ca-Mg2+-SO4 2—Cl-, Na+-HCO3 − and Na+-Cl−types, with a low mineral and intermediate mineral contents based on Van der Aa’s classification. The Gibbs plot specifies that almost all samples (93%) fall in water–rock interaction dominance. The major hydrogeochemical processes acting are dissolution of carbonate minerals, ion-exchange mechanisms and silicate weathering. Principal component analysis (PCA) was applied to hydrochemical data of mineral water samples. The results suggest that hydrochemistry in the region is affected not only by geogenic processes but also is impacted by anthropogenic activities. The comparative evaluation of the different water quality indices (WQI) shows that there is a difference between indices values for the same water sample, which may be attributed to the weighting methods, aggregation methods, and the limits of classes used in the calculation of each index. The results from this study can provide the basis for local decision-makers to develop suitable water management strategies and protection against any pollution risk.

Hydrogeochemical processes and groundwater evolution of the São Sebastião-Marizal aquifer system in the Tucano Central Basin, Bahia, Brazil

• New hydrogeochemical and physicochemical data for 35 samples of the São Sebastião-Marizal Aquifer System. • Ca–Na–Mg–HCO 3 –Cl facies of recharge zones evolves to Mg–Ca–Cl and Na–Cl facies along groundwater flow in the Marizal and São Sebastião aquifers, respectively. • Silicate weathering exerts a dominant control on groundwater composition. • Water-rock interaction is the main hydrogeochemical process. • Physicochemical parameters are more variable within the unconfined Marizal aquifer. • Alkaline to alkaline earth ratios indicate that reverse ion exchange predominates in the Marizal aquifer. • The hydrogeochemical signature indicates that silicate weathering and ion exchange processes contribute equally in the São Sebastião aquifer.

Both natural and anthropogenic factors control surface water and groundwater chemistry and quality in the Ningtiaota coalfield of Ordos Basin, Northwestern China.

An understanding of the vertical variations in hydrogeochemical processes in various aquifers and quality suitability assessment is crucial for the utilization of groundwater in the Ningtiaota coalfield of Ordos Basin, Northwestern China. Based on 39 water samples collected from surface water (SW), Quaternary pore water (QW), weathered fissure water (WW), and mine water (MW), we conducted self-organizing maps (SOM) algorithm, multivariate statistical analysis (MSA), and classical graphical methods to elucidate the mechanisms controlling the vertical spatial variations in SW and groundwater chemistry and conducted a health risk assessment. The findings indicated that the hydrogeochemical type showed a transition from the HCO3--Na+ type in SW to the HCO3--Ca2+ type in QW, then to the SO42--Mg2+ type in WW, and back to HCO3--Na+ type in MW. Water-rock interaction, silicate dissolution, and cation exchange were the main hydrogeochemical processes in the study area. Additionally, groundwater residence time and mining operations were critical external factors that affect water chemistry. Contrary to phreatic aquifers, confined aquifers featured greater circulation depth, water-rock interactions, and external interventions leading to worse quality and higher health risks. Water quality surrounding the coalfield was poor, causing it to be undrinkable, with excessive SO42-, arsenic (As), and F-, etc. Approximately 61.54% of SW, all of QW, 75% of WW, and 35.71% of MW can be used for irrigation.

Hydrogeochemistry of the Umm er Radhuma Unconfined Aquifer, Western Desert Iraq- Saudi border

The Umm Er Radhuma unconfined aquifer Hydrogeochemistry in the Saudi – Iraq border desert was studied to identify the main hydrogeochemical processes and rock-water interaction. The measurements were done using standard APHA procedures. The results indicated that Na+ and Cl- are the dominant ions in the groundwater. The average contribution of cations in the aquifer is Na+ + K+ ( 26 %), Ca2+ (14 %), and Mg2+ (10%) ; whereas anions contribution is Cl- (24 %) , SO42- (20 %), and HCO3- (6 %). The results reflect that the examined water is hard water of neutral to slightly alkaline, slightly brackish, with mineralized pH conditions. The main conclusion of chemical reactions indicated carbonates, evaporate dissolution, and clay minerals water interaction through ionic exchanging.

Characterisation of Hydro-Geochemical Processes Influencing Groundwater Quality in Rural Areas: A Case Study of Soutpansberg Region, Limpopo Province, South Africa

Groundwater is often the main or only source of fresh water supply in arid to semi-arid rural areas owing to decreasing rainfall patterns, reduced availability of surface water and socioeconomic activities. It is important to understand the hydro-geochemical processes influencing groundwater quality for improved management and sustainability of resources and to improve rural livelihoods. To understand the hydro-geochemical process influencing the hydro-geochemistry of the Soutpansberg region, this study assessed groundwater quality data from 12 boreholes and 2 geothermal springs collected between 1995 and 2017. This study indicated that the majority of the samples were classified as fresh groundwater dominated by Ca-HCO3 and mixed Ca-Mg-Cl types. Gibbs diagrams, Pearson correlations, bivariate plots and saturation indexes suggested that rock dominance processes, such as weathering of silicates, dissolution of carbonates and halite minerals and ion exchange processes, were the main hydro-geochemical processes influencing the groundwater quality in the Soutpansberg region. The high concentration of F− in the geothermal spring was attributed to the dissolution of fluorite mineral. Point source anthropogenic inputs from fertilisers were attributed to the high concentration of NO3− in the groundwater. This study recommends that research outputs should be used to influence and support policy change and groundwater allocation in arid to semi-arid rural environments for improved management of resources and livelihoods. This study further recommends that suitable deflouridation and denitrification techniques be applied to improve the quality of groundwater for drinking purposes.

Geochemical Characteristics and Driving Factors of High-Iodine Groundwater in Rapidly Urbanized Delta Areas: A Case Study of the Pearl River Delta

The source of iodine in the groundwater of coastal urbanization areas is complex, and high-iodine groundwater is a potential threat to the safety of drinking water. Based on this, this study took the Pearl River Delta, which is developing rapidly in urbanization, as the research area. Additionally, the occurrence characteristics and driving factors of iodide in shallow groundwater of different aquifers and different urbanization levels in the Pearl River Delta were studied using mathematical statistics, principal component analysis, and other methods. The results showed that the concentration of iodide in the shallow groundwater was 2.34 mg·L-1 and undetected in the form of I-. Among 1567 groundwater samples in the study area, there were 120 groups of groundwater with high iodine content greater than 0.1 mg·L-1, accounting for 7.7%. Among them, 84 and 36 groups were detected in shallow porous and shallow fissure high-iodine groundwater, respectively, whereas no high-iodine groundwater was detected in the karst aquifer. The proportion of high-iodine groundwater was 8.0% in the shallow porous aquifer and 7.5% in the shallow fissure aquifer. Both the porous aquifer and the fissured aquifer with high iodine content were mainly distributed in the urbanized areas, the proportion of which was more than three times that of the non-urbanized areas. The chemical types of the high-iodine groundwater were mainly HCO3·Cl-Ca·Na and Cl-Na type water, which have the characteristics of high pH and low redox potential. The reduction and dissolution of iodine-containing Fe/Mn (oxygen) hydroxides and the decomposition of iodine-rich organics in sediments may be the main sources of high-iodine groundwater in the shallow porous aquifers of the Pearl River Delta Plain. The degradation and urbanization of organic matter in carbonate-rich rocks is accompanied by the leakage of reducing sewage, which may be the main source of high-iodine groundwater in shallow fissured aquifers. The neutral to weakly alkaline reduction environment with rich organic matter was the main cause of high-iodine groundwater in the Delta Plain area. Weathering, leaching, cation exchange, and sea-land interactions are the main hydrogeochemical processes in the evolution of high-iodine groundwater in the Pearl River Delta.

Groundwater Chemical Characteristics and Salinization Mechanism in the Coastal Plain of the South Bank of Laizhou Bay

Based on 59 groundwater samples which were collected on the south bank of Laizhou Bay, the main ionic ratios analysis and the main ionic Piper three-line diagram was done. The results show that from offshore to nearshore, groundwater hydrochemical is mainly freshwater, brackish water, salt water, and brine. And the ion type transforms from HCO3-Ca to HCO3·Cl-Ca, then converted to HCO3·Cl-Na and further transformed into Cl·HCO3-Na, then changed to Cl-Na regularity. By calculating some conventional water ion ratios which include Na/CL, K/CL, Ca/CL, SO4/CL, the hydrogeochemical effects of water-rock interactions, the source of groundwater salinity and the mechanism of groundwater salinization were investigated in this study. The anion-cation exchange reaction in the groundwater of the brackish water transition zone in the northern part of the monitoring section is more obvious than that in the southern underground freshwater. The main hydrogeochemical processes occurring in the brackish water transition zone are the dissolution of minerals (calcite, anhydrite and rock salt), precipitation of gypsum and dissipation of carbon dioxide. And the main cation exchange in this area is Ca-Na exchange.

Deep carbon degassing in the Matese massif chain (Southern Italy) inferred by geochemical and isotopic data.

The Italian Apennines are among the most important sources of freshwater for several Italian regions. With evidences of deep CO2-rich fluids intruding into aquifers in the nearby central-southern Apennines, a thorough investigation into the geochemistry of groundwater became critical to ensure the water quality in the area. Here, we show the main hydrogeochemical processes occurring in the Matese Massif (MM) aquifer through the investigation of 98 water samples collected from springs and water wells. All waters were classified as HCO3 type with Ca dominance (from 50% up to 97%) and variable amount of Mg (from 1% up to 49%). A multivariate statistical approach through the application of the factor analysis (FA) highlighted three main hydrogeochemical processes: (i) water-carbonate rock interactions mostly enhanced in peripheral areas of the MM by CO2 deep degassing; (ii) addition of NaCl-rich components linked to recharging process and to water mixing processes of the groundwater with a thermal component relatively rich in Cl, Na, and CO2; (iii) anthropogenic activities influencing groundwater composition at the foothills of MM. Furthermore, the first detailed TDIC, pCO2, and δ13C-TDIC distribution maps of the MM area have been created, which track chemical and isotopic anomalies in several peripheral areas (Pratella, Ailano, and Telese) throughout the region. These maps systematically highlight that the greater the amount of dissolved carbon occurs the heavier the C isotope enrichment, especially in the peripheral areas. Conversely, spring waters emerging at higher altitudes within MM are only slightly mineralized and associated with δ13C-TDIC values mainly characterized by recharging processes with the addition of biogenic carbon during the infiltration process through the soil.

Hydrogeochemical characteristics, temporal, and spatial variations for evaluation of groundwater quality of Hamedan–Bahar Plain as a major agricultural region, West of Iran

This study was conducted to assess the suitability of groundwater resources for drinking and irrigating purposes in Hamedan–Bahar Plain, west of Iran as a major agricultural district, in the spring and summer of 2018. In so doing, a total of 60 water specimens were collected from the semi-deep water wells of the study area with an average depth of 50–75 m and then the hydrogeochemical characteristics of groundwater samples and their suitability were investigated. The evaluation of the groundwater quality was carried out by assessing the physicochemical variables notably temperature (T), pH, electrical conductivity (EC), total dissolved solids (TDS), total hardness (TH), and by measuring the rates of major ions including Ca2+, Cl−, HCO3−, K+, Mg2+, Na+, NO3−, PO43−, and SO42− and trace elements, such as arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn). The results indicated that the groundwater specimens were somewhat alkaline and brackish. The cationic trend of the specimens in the spring season was found to be Ca > Mg > Na > K > Pb > As > Cu > Zn > Ni > Fe > Cr > Mn > Cd, while, in the summer season it manifested itself as Ca > Mg > Na > As > K > Pb > Cu > Zn > Fe > Ni > Cr > Mn > Cd. However, the trend of anionic contents in both seasons was HCO3 > NO3 > SO4 > Cl > PO4. The analysis of the data showed that Na–Cl–HCO3 was the dominant groundwater type in both seasons. The studied specimens were also described in terms of some indices, including the total hardness (TH), Kelley’s ratio (KR), magnesium hazard (MH), permeability index (PI), the residual sodium carbonate (RSC), sodium adsorption ratio (SAR), soluble sodium percentage (SSP), and maximum permissible limit (MPL). The results indicated that groundwater samples have suitable quality for the main uses. Based on the values obtained for chloro-alkaline indices (CAI-1 and CAI-2), chemical weathering was suggested as the main hydrogeochemical process controlling calcium, magnesium, sulfate, and carbonate distribution in the groundwater supplies.

Response of a Coastal Groundwater System to Natural and Anthropogenic Factors: Case Study on East Coast of Laizhou Bay, China.

With a shifting climate pattern and enhancement of human activities, coastal areas are exposed to threats of groundwater environmental issues. This work takes the eastern coast of Laizhou Bay as a research area to study the response of a coastal groundwater system to natural and human impacts with a combination of statistical, hydrogeochemical, and fuzzy classification methods. First, the groundwater level dynamics from 1980 to 2017 were analyzed. The average annual groundwater level dropped 13.16 m with a descent rate of 0.379 m/a. The main external environmental factors that affected the groundwater level were extracted, including natural factors (rainfall and temperature), as well as human activities (irrigated area, water-saving irrigated area, sown area of high-water-consumption crops, etc.). Back-propagation artificial neural network was used to model the response of groundwater level to the above driving factors, and sensitivity analysis was conducted to measure the extent of impact of these factors on groundwater level. The results verified that human factors including irrigated area and water-saving irrigated area were the most important influencing factors on groundwater level dynamics, followed by annual precipitation. Further, groundwater samples were collected over the study area to analyze the groundwater hydrogeochemical signatures. With the hydrochemical diagrams and ion ratios, the formation of groundwater, the sources of groundwater components, and the main hydrogeochemical processes controlling the groundwater evolution were discussed to understand the natural background of groundwater environment. The fuzzy C-means clustering method was adopted to classify the groundwater samples into four clusters based on their hydrochemical characteristics to reveal the spatial variation of groundwater quality in the research area. Each cluster was spatially continuous, and there were great differences in groundwater hydrochemical and pollution characteristics between different clusters. The natural and human factors resulted in this difference were discussed based on the natural background of the groundwater environment, and the types and intensity of human activity.

Hydrochemical and isotopic characteristics of thermal groundwater at Farafra Oasis, Western Desert, Egypt

Groundwater from the Nubian sandstone aquifer at Farafra Oasis in the Western Desert of Egypt has been investigated using chemical tracers and environmental isotopes to clarify the hydrochemical features of this aquifer. The majority of the collected samples are characterized by Ca-Cl water type, which may be attributed to dissolution of the carbonate-rich sediments. Calculated saturation indices show that the main hydrogeochemical processes were the dissolution of carbonates and evaporites and the precipitation of Fe-rich minerals. Temperatures calculated using the K-Mg geothermometer show that the reservoir temperature ranges from 58°C to 121°C. The groundwater samples have δD and δ 18 O values similar to the isotopic content of the Nubian aquifer palaeowater in the Western Desert. Additionally, the isotopic composition suggests that there is no active potential current recharge from the local precipitation. Gamma spectrometry of 226 Ra, 232 Th and 40 K activities indicates that the groundwater of the Nubian aquifer is safe with respect to radioactivity. Groundwater in Farafra Oasis is the main source of irrigation and drinking water for local residents. All the samples are excellent for irrigation uses for all types of crops. It is suggested that the water samples may require some treatment regarding the high iron content before usage as drinking water. Supplementary material: Locations of the collected groundwater samples and their Na-K-Mg ternary cation plot is available at https://doi.org/10.6084/m9.figshare.c.4938252

Hydrogeochemical Characterization of a Warm Spring System in a Carbonate Mountain Range of the Eastern Julian Alps, Slovenia

The Alps represent an area where many deep groundwater circulations occur as thermal springs. In the Bled case study, the thermal water temperature, at it is discharged to the surface, is between 19–23 °C. In order to determine the extent (e.g., geometry) and the origin of the pronounced deep circulation system in the Bled area, chemical and isotopic measurements of waters from different hydrogeological systems were performed (e.g., surface water, thermal water, fresh groundwater). Hydrogeochemical methods were used to tie together the above-mentioned parameters. The results have shown that thermal outflow in Bled is determined by the presence of a deep-water circulation system, where the dissolution of carbonates minerals is the main hydrogeochemical process affecting chemical components of natural water flow. The correlation of the major ions suggests that the recharge area is represented by both limestone and dolomite rocks. Moreover, the results of δ18O and δ2H of all samples indicate that the recharge is mainly meteoric precipitation. The recharge altitude was estimated for two sampled fresh groundwater springs. The isotopic compositions of those two springs suggest the range from δ18O = −8.68‰, δ2H = −57.4‰ at an elevation of 629 m to δ18O = −9.30‰, δ2H = −60.1‰ at an elevation of 1216 m. The isotopic analysis has confirmed that the thermal water recharges from altitudes of 1282–1620 m a.s.l.

Groundwater Hydrogeochemical Processes and the Connectivity of Multilayer Aquifers in a Coal Mine with Karst Collapse Columns

Understanding groundwater hydrogeochemical processes and the connectivity of multilayer aquifers in a coal mine with karst collapse columns (KCCs) is very important for mine safety and groundwater resource management. In this study, 52 groundwater samples from the main aquifers in the Xieqiao coal mine (Anhui Province, China) were analyzed using hydrochemical, multivariate statistical methods, and stable isotope analyses. In the Permian aquifer, the main hydrogeochemical processes are halite and silicate dissolution and sulfate reduction, followed by cation exchange, while in the Carboniferous and Ordovician aquifers, the main hydrogeochemical processes are carbonate, gypsum, and halite dissolution, followed by cation exchange. This causes the hydrochemical characteristics of these two aquifers to be similar. The Permian aquifer contains less SO42−, more HCO3− concentration, and a concentration ratio of SO42− to HCO3− less than 0.25 due to sulfate reduction, which allows the Permian aquifer to be distinguished easily from the other two. Both hierarchical cluster and stable isotope analysis show that water samples from both aquifers appear to have been mixed via the KCCs, which may serve as a potential channel for groundwater inrush into the coal mine. These results may assist in accurately predicting potential water inrush sources in this coal mine as well as in other mines.

Applying multivariate statistics for identification of groundwater chemistry and qualities in the Sugan Lake Basin, Northern Qinghai-Tibet Plateau, China

The Sugan Lake Basin is located in the inland arid region of northwestern China, in which groundwater is of great significance to human and ecology. Therefore, it is necessary to understand the chemical characteristics and quality of groundwater in the basin. Based on samples collected from 35 groundwater wells in Sugan Lake Basin, the spatial distribution characteristics of groundwater chemistry, main hydrogeochemical processes and groundwater quality have been discussed in this paper by using the multivariate statistics and hydrochemistry analysis methods. The results showed that the groundwater is weakly alkaline, and its total dissolved solid (TDS) and total hardness (TH) are high, with the average values of 1244.03 mg/L and 492.10 mg/L, respectively. The types of groundwater are mainly HCO3−-SO42−-Ca2+ type in the runoff area and Cl−-SO42−-Na+ type in the catchment area. Rock weathering and ion exchange are the main controlling factors of regional groundwater chemistry, followed by evaporative crystallization, and human activities have less impact on groundwater. The spatial difference of groundwater quality is obvious, the water quality of the catchment area is not suitable for drinking, and the suitability for plant growth is also poor. The groundwater in the runoff area can be used for drinking, but the hardness is slightly higher, which is more suitable for ecological purpose.

Hydrochemical and Isotopic Evolution of Groundwater Flowing Downstream of the Daqing River (Liaodong Bay, China)

Guo, Q.; Zhang, J.; Hu, Z., and Zhou, Z., 2020. Hydrochemical and isotopic evolution of groundwater flowing downstream of the Daqing River (Liaodong Bay, China). Journal of Coastal Research, 36(3), 608–618. Coconut Creek (Florida), ISSN 0749-0208.Hydrochemistry and specific environmental isotope ratios (δD, δ17O, and δ18O) were employed to investigate the hydrochemical and isotopic characteristics of groundwater in the downstream coastal plain of the Daqing River, China. The relative abundance of the major cations and anions of groundwater along the Daqing River changed from Ca2+, Mg2+ to Na+, Ca2+ and from to Cl–, respectively. The samples, divided into different groups on the basis of correlation coefficients, showed that the chemical composition of the groundwater samples near the Daqing River is approximately consistent with that of the Daqing River. The saturation indices calculated by PHREEQC software indicated that the main hydrogeochemical processes are evaporation and concentration along groundwater flow paths from the upper zone to the middle zone of the Daqing River basin. However, in the down zone, calcite, anhydrite, and dolomite become supersaturated. Isotopic data reveal that the groundwater is affected by the strong evaporation along the Daqing River. In the down zone of the Daqing River, the groundwater is polluted by the seawater.

Hydrogeochemistry and Usability of Groundwater at the Tista River Basin in Northern Bangladesh

Objectives: A study on groundwater of Lalmonirhat Sadar Upazila, Bangladesh has been conducted to explore the groundwater hydrochemistry and suitability for potable water and agricultural uses. Methods/statistical analysis: During the dry season, fifty groundwater samples were collected from different shallow tube wells adjacent to Tista River, Bangladesh. Water samples were analysed according to the standard procedures. We calculated some parameters required for assessing irrigation water quality. The correlation matrix, hierarchical cluster analysis (HCA), and principal component analysis (PCA) were used for better understanding of groundwater chemistry and categorizing the water samples. Findings: The Ca2+–Mg2+–CO3 2−–HCO3 − was the dominant water type, and carbonate weathering was the main hydro geochemical process in the study area. The contributions of ion exchange and reverse ion exchange were almost equal. Groundwater characteristics were influenced by precipitation and not affected by seawater intrusion. The results of all the measured and calculated parameters clearly indicated the suitability of all ground water samples for irrigation. Based on all analysed parameters including hardness, all waters were suitable for drinking and domestic uses. Applications: The groundwater of the study area might be suitable for irrigation, drinking and domestic uses until the waters are otherwise polluted. Keywords: Hydrogeochemistry, Groundwater, Irrigation, Drinking, Bangladesh