Cl HCO3 Research Articles

Hydrogeochemical evolution and heavy metal characterization of groundwater from southwestern, Nigeria: An integrated assessment using spatial, indexical, irrigation, chemometric, and health risk models

This study examines the hydrogeochemical and heavy metal parameters of groundwater in Ojo District to determine its suitability for use, potential sources, and human health implications. Ten groundwater samples were assessed, and hydrogeochemical modelling was performed via the Aquachem software. The chemical ions were in the following order: EC > (107.78–448.65 μS/cm) > TDS (182.02–320.77 mg/l) > TH (46.22–182.45 mg/l) > pH (5.55–6.35); HCO3− (64.13–125.82 mg/l) > Na+ (36.87–96.49 mg/l) > Ca2+ (47.65–58.88 mg/l) > SO42− (19.94–53.67) > NO3− (15.55–44.25 mg/l) > Cl− (20.43–27.16 mg/l) > Mg2+ (11.09–16.87 mg/l) and K+ (2.55–7.86 mg/l). The concentrations of heavy metals in groundwater were in the range of: Fe (0.11–0.27 mg/l) > Mn (0.003–0.16 mg/l) > Ni (0.05–0.12 mg/l) > Zn (0.003–0.05 mg/l) > Pb (0.001–0.03 mg/l) > As (0.001–0.005 mg/l) > Cr (0.002–0.005 mg/l) > Cd (0.001–0.003 mg/l) and Cu (0.001–0.0002 mg/l), with Pb, Mn, and Ni exceeding their allowable limits. The Schoeller and Gibbs plots revealed that the major mechanisms controlling the aquifer groundwater in Ojo region are geological rock weathering and mineralization, with a minimal influence of saltwater intrusion. The piper trilinear diagram also revealed that none of the cation was dominant while the anions were strongly dominated by HCO3− (weak acids). The hydrogeochemical facies which describes the geochemical characteristics of the groundwater were classified into 3 types; “Ca2+–Mg+–HCO3– (65 %)”, “mixing zones (30 %)”, and “Na+–K+–Cl––HCO3– (5 %)”. The hydrogeochemical modelling revealed that the groundwater is characterized by forward cation exchange, while rock–water interactions (silicate dissolution) were heavily involved in the geochemical processes. The single pollution index showed that Pb, Ni, and Mn contributed significantly to contamination, and the multi–pollution indices showed that the groundwater was slightly-moderately polluted. The integrated groundwater quality index revealed that only 10 % were clean, 50 % were poor or moderately unclean, 30 % were highly unclean, and only 10 % were extremely unclean (unfit for utilization). The water pollution index showed that 70 % of the groundwater was good. The irrigation indices suggest that the groundwater would enhance soil quality and support plant growth. Multivariate analysis revealed that the groundwater is being influenced by geogenic factors and anthropogenic activities. The health risk assessment (Hazard Quotient and Hazard Index) showed that exposure of adults to the investigated groundwaters could result in noncarcinogenic adverse effects. The cancer risk values also exceeded the minimum limit (1.0 x 10−6) and thresholds (1.0 x 10−4) for adults, indicating the carcinogenic potential of the groundwater.

The origin of high salinity and hydrogeochemical characteristics of groundwater in semi-arid area of the Linta Basin, Southwestern Madagascar

The Linta Basin, located in the Southwestern Madagascar, is a semi-arid area where groundwater in fractured media bedrock aquifer constitutes the main source of water supply. In the last two decades, highly mineralized groundwater was identified in this area; however, the origin of the salinity was not clear. The purpose of the study was to clarify the origin of salinity and to identify hotspots with groundwater unsuitable for water supply. Groundwater quality in this basin was investigated by hydrogeochemical and isotopic methods accompanied by mineralogical study. In total, 32 groundwater samples were collected and analyzed. The results showed that groundwater temperature varied from 25.2 °C to 31.7 °C. Values of pH and TDS varied from 6.55 to 8.24 and 221 to 5612 mg/L, respectively. The aquifer, which is mainly fractured, showed 7 groundwater types, namely Mg–HCO3,Na–HCO3 and also Na–C1, Mg–Cl, Na–Cl–HCO3, Mg–Cl–HCO3-, and Ca–Mg–HCO3. Two groups of variables have been identified by factor analysis; the factor F1 comprises EC, Ca2+, Mg2+, SO42−, and Cl− whereas the factor F2 comprises HCO3−, K+, and Na+, and they were interpreted in terms of hydrogeochemical processes. Values of saturation indices (SI) for carbonate minerals were generally positive, indicating their possible precipitation. Based on the Gibbs diagram and factor analysis, groundwater mineralization is affected by water-rock interactions and evaporation, respectively. The important role of evaporation is confirmed by enrichment of stable isotopes with δ18O values up to 1.2 ‰. Processes such as base ionic exchange process and reverse ionic exchange process may also be important locally. The main origin of groundwater mineralization is the hydrolysis of silicate minerals such as feldspars and micas coupled with evaporation. In several wells, salinity is too high for water supply and nitrate concentration is above the WHO limit for drinking water. Results of the study highlighted groundwater chemistry formation processes and are applicable in other African countries with bedrock aquifers.

Reservoirs and Hydrogeochemical Characterizations of the Yanggao Geothermal Field in Shanxi Province, China

Geothermal water is the product of deep circulation within the crust, and the understanding of its hydrogeochemical process can provide effective information for integrated research on its circulation pattern and formation mechanism. Based on the geothermal geological conditions of the Yanggao geothermal field, this study analyzed water samples from thermal springs and geothermal wells in the geothermal field, ascertaining their hydrochemical components, along with their hydrogen and oxygen isotopes. Using methods like piper diagrams, ionic component ratio characterization, Na–K–Mg equilibrium diagrams, and reverse path simulations, this study elucidated the recharge source of geothermal water in the study area, revealed the water–rock interactions the geothermal water experienced, and evaluated the geothermal reservoir temperatures. The results show that the geothermal water has hydrochemical types of Na–Cl–HCO3 and Na–HCO3–Cl, and is primarily recharged by the atmospheric precipitation in the northern mountainous area. The geothermal water has experienced extended water runoff and deep thermal circulation, and its hydrochemical composition primarily results from the weathering and dissolution of silicate rocks and evaporites. The major hydrogeochemical processes of the geothermal water involve the dissolution of calcite, dolomite, gypsum, and kaolinite. In addition, the canon-exchange also changes the chemical component of the geothermal water. The SiO2 Geothermometer, a multimineral equilibrium diagram, and the silica–enthalpy model reveal the presence of deep and shallow geothermal reservoirs in the study area, which exhibit temperatures of 73 °C and ranging from 125 to 150 °C, respectively. The open geothermal reservoir environment results in the mixing of geothermal water and cold water, with shallow and deep geothermal water mixing with cold water at ratios of 57% and 76%, respectively.

Seasonality of hydrogeochemical evolutions and isotopic variabilities (δ18O, δ2H and d-excess) in the surface water as well as groundwater from tropical central-south Mexico

Due to adverse impact of the global warming on hydrological resources, we intended to document the hydrogeochemical evolutions of surface and groundwater at tropical central-south Mexico in terms of seasonality of rock-water interaction, precipitation/evaporation variation and moisture source by evaluating the major ion chemistry in Piper and Gibbs plots, Durov diagram and through estimation of the chloro-alkaline indices as well as assessing the stable isotope compositions (δ18O and δ2H) in samples from different seasons of a year. Surface water of the Lake Coatetelco shifted from mostly Ca–Mg–HCO3 facies in wet summer-autumn to Na–HCO3–Cl facies in the dry spring due to elevated Na, Cl and HCO3. Greater evaporation in spring led to a maximum δ18O enrichment of ca.7‰ compared to the other seasons, and much depleted deuterium excess (−40.92‰ to −39.20‰). Interaction of the lake water with subsurface carbonate lithologies, and comparable isotopic compositions reflected the enhanced interaction between the surface water body and aquifers in the wet autumn. Effect of seasonality, however, was unclear on the groundwater facies, and its heterogenous composition (Ca–Mg–HCO3, Na–HCO3–Cl and Na–HCO3) reflected the interactions with different lithologies. Fractionations in isotope compositions of the groundwater were caused from recharge at different elevations, seasonality of moisture sources and moisture recycling. The water-mineral saturation index was an efficient proxy of seasonality as the lake water and groundwater (avg SIcalcite > 0.5) of the dry autumn were saturated with calcite. This vital information about carbonate precipitation, pCO2 and chemical facies would be useful for the better interpretation of paleoclimate archives in this region.

Hydro-chemical characteristics and groundwater quality evaluation in south-western region of Bangladesh: A GIS-based approach and multivariate analyses

The study focuses on the chemistry of groundwater and if it is suitable for drinking and for use in agriculture using water quality indices, GIS mapping, and multivariate analyses in Sharsa Upazila, Jashore district, Bangladesh. In this study, the concentration of NH4+, K+, Ca2+, EC, Turbidity overstep BDWS drinking standards in 69 %, 14 %, 100 %, 40 % (WHO), 73 % of samples respectively. The value of Water Quality Indices (WQI) results inferred that the maximum specimen was held good quality for drinking uses, and the values distributed central eastern part to the south-eastern part were good quality water in the selected studied area. The study area's PH, EC, SAR, Na (%), TH, and NO3− values were mapped using GIS tools to show their spatial distribution. The cluster and correlation matrix analyses are used to validate for Principle Component Analysis (PCA). The five PCA results exhibited that the presence of EC, turbidity, K+, SO42− and NO3− was significant and was caused by both geogenic (rock weathering and cation exchange) and anthropogenic (agrochemicals, animal feedback) factor. According to the hydro-geochemical data, the maximum number of samples is of the Ca–Mg–HCO3–Cl type and is dominated by rocks. The irrigation water indices like MH, KR, SAR, and %Na indicate show high-quality groundwater for irrigation purposes. Most of the samples were satisfactory and compiled with WHO and Bangladeshi criteria for standard drinking water guideline values.

Hydrochemistry, controlling mechanisms and water quality index in hot springs of the Kullu-Manali region, India

The present study highlights the unique chemical characteristics of hot springs and their comparison with cold springs, surface water, and groundwater in the same area. The hot springs' temperature ranges from 27 to 96 °C, which induce variable degree of hydrochemical alteration of hot springs' water. The concentrations of Na+ and K+ are highly correlated with Cl−, HCO3−, and SO42− in hot springs, while Ca2+ and Mg2+ behave erratically. The Na/Cl ionic ratios give clues of a restricted geological environment of thermal waters, mixing in cold springs and groundwater, and a meteoric origin of the surface water. The SiO2 behave conservatively, with little change in different water types except surface water. The concentrations of SiO2, highest in the hot springs and lowest in the surface water, help draw depth profiling of different water types. Mixing of ascending hot springs with overlying waters of different origins creates ambiguity in chemical interpretations. Due to mixing with different water types, Chalcedony thermometry better represents hot springs than Na–K–Mg geothermometry. As a result, hot springs alter from Na–Cl and Na–Cl–SO4 type facies with high SiO2 and gradually evolved in Ca–Mg–Na–HCO3–Cl type water. Similarly, most cold springs show mix-type and Ca–HCO3 water types. The chemical characteristics of cold springs are similar to groundwater and equally sensitive to seasonal variation due to mixing with meteoric recharge. The surface water is characterized by Ca–Cl2 type water. All water types acquire unique chemical signatures due to the combined effect of geological formations, depth, temperature, degree of meteoric recharge, and, to some extent, anthropogenic pollution. The Water Quality Index (WQI) assessment revealed that three samples from the Kullu and Kalath regions fall in poor WQI, requiring immediate protection from anthropogenic pollution.

Co-occurrence of arsenic and fluoride in groundwater of Guide basin in China: Genesis, mobility and enrichment mechanism

Endemic arsenic poisoning and fluorosis caused by primary high arsenic (As) and high fluoride (F−) groundwater have become one of the most serious environmental geological problems faced by the international society. High As and high F− groundwater exists in Neogene confined aquifers in Guide basin, with concentrations of 355 μg/L and 5.67 mg/L, respectively, and showing a co-occurrence phenomenon of As and F− in the groundwater. This poses a double threat to the health of tens of thousands of local residents. In this study, based on the systematic collection of groundwater and borehole sediment samples, analysis of hydrochemistry and isotope indexes, combined with laboratory tests, purpose of this study is to reveal the migration rule and co-enrichment mechanism of As and F− in aquifers, and finally establish a hydrogeochemical conceptual model of the enrichment process of As and F−. The main conclusions are as follows: hydrochemical type of unconfined and confined groundwater in Guide basin is Ca–Na–HCO3 and Na–Cl–HCO3 type, respectively. Main minerals in sediments are quartz and plagioclase. Concentrations of As and F− are lower in unconfined groundwater, but higher in confined groundwater, and which show a gradual increasing trend along the groundwater flow path. The mineralization of natural organic matter in confined aquifer causes iron and manganese oxide minerals containing As to dissolve gradually, which leads to the gradual release of As into groundwater. Large amount of HCO3− produced by mineralization of organic matter precipitate with Ca2+ in groundwater, resulting in reduction of Ca2+ content, promoting the dissolution of fluoride-containing minerals such as fluorite (CaF2), and continuously releasing F− into groundwater. Meanwhile, competitive adsorption reactions in confined aquifers causes more As and F− to be released from mineral surface into groundwater, which gradually migrate and accumulate along groundwater flow. Finally, it is established that a conceptual model for the formation of high As and F− groundwater in the confined aquifer of Guide basin. The research results not only help to improve our understanding of the formation and evolution of groundwater with high As and F− with similar geological background, but also provide scientific basis for rational development and utilization of groundwater, and prevention and control of chronic As and F− poisoning in local and similar areas.

Multi-isotopic and hydrochemical evidence of water resources evolution and recharge estimation in the tropical coastal aquifer

The study integrates hydrochemical and isotopic (δ18O, δ2H, 3H, and δ13C) techniques to investigate water evolution in the North Kelantan River basin. Groundwater facies were mainly classified as Ca–Mg–Cl, Ca–Mg–Cl–HCO3, and Na–Cl during the rainy season and shift toward Ca–Mg–HCO3 and Na–Ca–HCO3–Cl during the dry season in surface water and shallow aquifer, while facies in intermediate and deep aquifers were classified as Na–HCO3 and Na–Cl. The δ18O and δ2H compositions of most groundwater samples have not deviated significantly from NKMWL (δ2H = 8.4 δ18O + 11.5) with slightly depleted isotopic values due to the humid climate. Isotopically, evaporation does not impact recharged water significantly. However, shallow aquifers are slightly enriched than deep aquifers of the study area. The estimated recharge was 20.17% and 22.52% of annual rainfall based on the CMB and δ18O values, respectively. The recharge mainly occurs during the wet season and is influenced mostly by the amount of rain. Aquifers clustered in distinct groups based on their isotopic signatures and hydrochemical results. The decomposition of organic matter is the primary carbon source in the study area. Building on this, by utilizing isotope hydrology to study water resources, we can gain a deeper insight into the susceptibility of groundwater in coastal aquifers of monsoonal tropical humid regions.

Evaluation of water from Lake Coatetelco in central-south Mexico and surrounding groundwater wells for drinking and irrigation, and the possible health risks

Due to an increasing reduction of hydrological resources across Mexico and their growing contamination from global warming and anthropogenic activities, this study evaluated water from the perennial Lake Coatetelco (Ca–Mg–HCO3) in tropical central-southern Mexico and groundwater (Ca–Mg–HCO3 and Na–HCO3–Cl) from the surrounding wells for drinking as well as irrigation qualities. Comparison with the WHO guidelines and the estimated water quality indices (DWQI and IWQI) grouped almost all the samples collected after the warm season rainfall in excellent and good categories (DWQI < 100) for drinking, even though fluoride remained > 1.5 mg/L in 50% samples. Except for one groundwater sample, all showed > 25% permeability (classes I and II) in Donnen classification indicating their suitability for irrigation. USSL and Wilcox classifications, however, catalogued some in the high-salinity hazard group and some as doubtful for irrigating regular plants. Samples from about 53% wells were also in high and severe restriction categories of IWQI for the irrigation. Total Hazard Quotient Index (THQI) for estimating the non-carcinogenic risk (HQfluoride > 1) showed that at least one lake water sample and 53% of groundwater might expose the adult and child population to dental and skeletal fluorosis. This water quality assessment data posterior to the rainfall season could be useful as a baseline for both the short- and long-term monitoring in attention to the United Nation’s Sustainable Development Goal 6.

Assessment of groundwater hydrochemistry, water quality, and health risk in Hainan Island, China

Groundwater is an important source of water for human sustenance. The determination of groundwater quality at island sites is an urgent priority in China, but there are lacking systematic reports relating to them. Here, 63 groups of groundwater samples were collected and analyzed of Hainan Island. The groundwater in the study area is weakly alkaline, mainly comprising hard and soft freshwater. The predominant anions and cations are HCO3−, and Ca2+ and Na+, respectively, and the main water chemistry types are HCO3–Cl–Na and HCO3–Cl–Na–Ca. The chemical evolution of groundwater is mainly affected by water–rock interactions, cation exchange, and human activity. The groundwater is mostly of high quality and, in most areas, is suitable for drinking and irrigation. Contrastingly, the water quality in the west of the island is relatively poor. The spatial distribution of the risk coefficient (HQ) is consistent with the spatial variation in the NO3− concentrations in the groundwater. Notably, there are unacceptable health risks for different groups of people, with infants having the greatest level of impact, followed by children, teenagers, and adults. This study provides a valuable reference for the development and utilization of groundwater resources, as well as the improvement of aquatic ecological conditions on Hainan Island and other island areas worldwide.

Assessment of Hydrogeochemical Characteristics and Seawater Intrusion in Coastal Aquifers by Integrating Statistical and Graphical Techniques: Quaternary Aquifer, West Nile Delta, Egypt

The Quaternary aquifer in the western Nile Delta is threatened by seawater intrusion. Few studies have integrated diverse techniques for the assessment of seawater intrusion in this aquifer. The present study aims to determine the geochemical processes and impact of seawater intrusion on this aquifer. To accomplish this investigation, the integration of hydrogeochemical, statistical, multivariate statistical, and graphical tools were implemented on 75 groundwater samples and 5 soil samples. The physicochemical variables were analyzed using hierarchical cluster analysis (HCA), saturation index (SI), ionic ratios, ionic relationships, the seawater intrusion index (SWI) and the correlations among 16 hydrochemical parameters, to identify the influencing processes of groundwater quality in the study area. According to the statistical study, the groundwater is divided into four groups. Those are distributed, from north to south: Group1 (G1), Group2 (G2), Group4 (G4), and Group3 (G3). The samples of G1 and G2 are distinguished by Na–Cl chemical type. While G4 has two main ion associations, HCO3–Ca–Mg and Cl–SO4–Na, G3 is characterized by HCO3–Cl–SO4–Ca–Na type. The processes that affect the chemistry of the groundwater are the seawater intrusion, ion exchange, silicate and Ca-rich mineral weathering, and mineral deposition. G1 and G2 groups are primarily influenced by seawater incursion, evaporation, and the ion exchange mechanism. In addition, the weathering of silicate minerals has a substantial effect on G3 and G4 groups, resulting in the creation of carbonate minerals.

Hydrogeochemical assessment and groundwater quality in a shallow aquifer: A case study of San Luis Potosí Valley, Mexico

The chemical composition of groundwater is the product of the evolution and incorporation of major ions, the product of natural hydrogeochemical processes or human interference that occurs in an aquifer. To establish the hydrogeochemical groundwater characteristics and suitability, 47 samples were collected from shallow wells in the study area. The objective was to determine the hydrogeochemical assessment of the groundwater in the shallow aquifer and establish the water quality and pollution associated with the dissolved organic matter in the San Luis Potosí sub-basin. The water quality assessment has been carried out by evaluating the physicochemical parameters such as temperature, pH, EC, TDS, and the main ions, which present the following trend: Ca2+>Na+>K+>Mg2+, HCO3− > SO42− > Cl− > NO3. The type of water in the area is mainly of four types: Ca–Na–HCO3–Cl (32%), Ca–Na–SO4–HCO3 (19%), Na–Ca–HCO3–Cl (13%), Ca–Na–HCO3–SO4 (11%). The content of NO3− (4.0–50.0 mg L−1), NH4+ (0.03–40.0 mg L−1), SO42− (20.0–276.0 mg L−1) y PO43− (0.01–45.5 mg L−1) indicate contamination that may come from inorganic and organic matter. Organic matter of anthropogenic origin was identified by 3D fluorescence. The results of this study demonstrate that the main processes that affect and control the chemical composition of the water in the shallow aquifer of SLP are silicate weathering, albite weathering, and reversible ion exchange.

Hydrogeochemical and isotopic investigation of the multilayer aquifer system: a case study of the Quaternary and the Campanian aquifers of the Mateur plain, Northern Tunisia

Abstract The Mateur multi-aquifer system, consisting of a Quaternary alluvial aquifer and a Campanian limestone aquifer, is one of the most significant aquifer systems in northern Tunisia, providing domestic and agricultural water supply for the entire Mateur region. The present study aims to unveil the various factors and mechanisms controlling the groundwater chemistry of such a system. Indeed, integrated hydrogeochemical and isotopic approaches are used herein to identify the alluvial and limestone aquifer waters mixing and evolution in the Mateur region. Results show that despite the difference in aquifer lithology, there is little difference in the major ion geochemistry and stable isotope ratios of groundwater within the Mateur plain. Waters from the Quaternary alluvial aquifer are classified into two predominant facies: mixed facies (Ca–Na–SO4–Cl and Ca–Na–HCO3–Cl) and Na–Cl facies. Similarly, waters from the limestone aquifer have also mixed facies (Ca–Na–SO4–Cl) and sodium chloride facies (NaCl). Groundwater δ18O and δ2H values show more homogeneous values along the groundwater flow direction, indicating inter-aquifer mixing processes. Tritium contents of the Campanian aquifer are lower than those of the Quaternary aquifer, indicating a relatively older age or mixture with recent waters. This validates a concept of the hydraulic continuity between the Quaternary aquifer and the Campanian aquifer which is consistent with the geochemical analytical results.

PRDX6: A protein bridging S-palmitoylation and diabetic neuropathy

Diabetic neuropathy is regarded as one of the most debilitating outcomes of diabetes. It can affect both the peripheral and central nervous systems, leading to pain, decreased motility, cognitive decline, and dementia. S-palmitoylation is a reversible posttranslational lipid modification, and its dysregulation has been implicated in metabolic syndrome, cancers, neurological disorders, and infections. However, the role of S-palmitoylation in diabetic neuropathy remains unclear. Here we demonstrate a potential association between activating protein palmitoylation and diabetic neuropathy. We compared the proteomic data of lumbar dorsal root ganglia (DRG) of diabetes mice and palmitoylome profiling data of the HUVEC cell line. The mapping results identified peroxiredoxin-6 (PRDX6) as a novel target in diabetic neuropathy, whose biological mechanism was associated with S-palmitoylation. Bioinformatic prediction revealed that PRDX6 had two palmitoylation sites, Cys47 and Cys91. Immunofluorescence results indicated PRDX6 translocating between the cytoplasm and cell membrane. Protein function analysis proposed that increased palmitoylation could competitively inhibit the formation of disulfide-bond between Cys47 and Cys91 and change the spatial topology of PRDX6 protein. Cl–HCO3- anion exchanger 3 (AE3) was one of the AE family members, which was proved to express in DRG. AE3 activity evoked Cl- influx in neurons which was generally associated with increased excitability and susceptibility to pain. We demonstrated that the S-palmitoylation status of Cys47 could affect the interaction between PRDX6 and the C-terminal domain of AE3, thereby regulating the activity of AE3 anion exchanger enzyme in the nervous system. The results highlight a central role for PRDX6 palmitoylation in protection against diabetic neuropathy.

Geogenic enrichment of fluoride in groundwater of hard rock aquifer in fluorosis prevalent area of Balangir district, Odisha, India

Hydrogeochemical characterization of groundwater has been carried out in a hard rock aquifer from Balangir district, a fluorosis-affected area of Odisha, India with the aim of understanding the sources and processes controlling fluoride (F−) enrichment. A total of 37 groundwater (tube wells) and 7 surface water (pond) samples were collected during the pre-monsoon period. Groundwaters are mostly categorized as moderate to very hard water types with alkaline nature. The enhanced Na+ and HCO3− concentration in groundwater is mostly a result of silicate weathering. The F− concentration in groundwater ranged from 0.4 to 4.29 mg/l, with 38% of samples exceeded the drinking water limit (1.5 mg/l; as prescribed by the World Health Organization, 2011), in contrast to very low F− (<0.9 mg/l) in surface water. High F− concentrations in underlying granitic bedrocks (up to 700 mg/kg), which spatially corresponds to F− rich groundwater, suggest that lithological composition is the main control of F−. Fluoride-rich waters are mostly Na–HCO3 type, followed by mixed Na–Ca–HCO3 (Cl) type with Na+/Ca2+ ratio >1. The significant positive correlations of F− with Na+, HCO3−, and pH indicate that the weathering of sodium-rich silicate minerals and increase of pH mobilizes F− ion. Geochemical modeling indicates that the activity of F− in groundwater increased by precipitation of calcite, dolomite, and aragonite. Fluoride risk assessment indicates that 38% of groundwater samples can cause a high prevalence of dental fluorosis with children being at greater risk than adults. Henceforth, it is advisable to treat this contaminated groundwater before consumption or provide alternative drinking water to avoid further fluorosis risks in the concerned area.

Predicting and analysing the quality of water resources for industrial purposes using integrated data-intelligent algorithms

The continuous increase in the rate of industrialization in developing countries, in recent times, calls for continuous industrial water quality assessment and prediction. This is to create more awareness and ensure cleaner and sustainable industrial production. Water quality for industrial uses is often described in terms of corrosion and scaling potentials (CSPs). In this paper, optimized artificial intelligence models (e.g. multiple regressions (MR), hierarchical clusters (HCs), and artificial neural networks (ANNs)) for assessing and predicting the CSPs of water resources were developed, for Ojoto suburb (SE Nigeria). Indices used in evaluating the CSPs are chloride–sulphate mass ratio (CSMR), Larson-Skold index (LSI), Langelier index (LI), aggressive index (AI), Ryznar stability index (RSI), Puckorius scaling index (PSI), and Revelle index (RI). This work is the first of its kind to utilize predictive models in simultaneously predicting the industrial water quality indices. Prior to the predictive modeling, R-mode HCs, correlation, principal component, and factor analyses were used to analyze the relationships between the physicochemical variables (pH–T–EC–TDS–TH–Ca–HCO3–Cl–SO4–Fe–Zn–Pb) and the CSP indices. Q-mode HCs effectively identified the spatiotemporal water corrosion/scaling risk classification and distribution in the area. Both MR and ANN models suitably predicted the CSP indices. However, both models better predicted AI, LI, RSI and PSI than LSI, RI and CSMR. The MR models’ performances were analyzed using R, R2, adjusted R2 and F-ratio values whereas the ANN models were verified using parity plots, R2, RMSE, and residual error plots. For the ANN modeling, scaled-conjugate-gradient optimizer outperformed gradient-descent optimizer. Also, ANN models outperformed the MR models. The practical implications of the present research findings were also discussed.

Enrichment mechanisms for the co-occurrence of arsenic-fluoride-iodine in the groundwater in different sedimentary environments of the Hetao Basin, China

Abnormal levels of co-occurring arsenic (As), fluoride (F−) and iodine (I) in groundwater at the Hetao Basin are geochemically unique. The abnormal distribution of As, F− and I is obviously related to the sedimentary environment. It is necessary to study the enrichment mechanisms for the co-occurrence of As, F− and I in groundwater under the influence of the sedimentary environment in Hetao Basin. In this study, 499 groundwater samples were collected. Sedimentary environments, hydrogeochemical process, isotopes were analyzed to elucidate their enrichment mechanisms. The environment of groundwater is weakly alkaline. The hydrochemical types of groundwater are mainly Na–Cl–HCO3. The distribution of isotope δ18O demonstrates that irrigation from the Yellow River is the main recharge source. The main drainage channel is the discharge area in the Hetao basin. Based on the clay-sand ratio (R), the number of clay layers (N) and terrain slope (S), Hetao Basin was divided into four sedimentary environmental zones. The distribution of As (0–916.70 μg/L), F− (0.05–8.60 mg/L) and I (0.01–3.00 mg/L) was featured by a clear zonation of the sedimentary environment. The high As and high I groundwater were mainly distributed in the paleochannel zone of the Yellow River, with exceedance rates of 80.28% and 52.58%, and the median values of 73.91 μg/L and 0.11 mg/L, respectively. In the reducing environment, the release of As initially adsorbed on iron hydrogen and iron oxide, the reductive of iron hydroxide itself, rock weathering and evaporation are the key factors affecting the enrichment of As in groundwater. In this area, large amounts of aquatic organisms and plankton deposited in the sediment and channel filling deposits abundant with organic matter is the premise of high-I groundwater. The reduction of iodate and nitrate directly leads to the high concentration of I in groundwater. The high F− groundwater was mainly distributed in the piedmont alluvial-pluvial fan and the north margin of Ordos Plateau, with exceedance rates of 58.62% and 43.30%, and the median values of 1.10 mg/L and 0.86 mg/L, respectively. High F− groundwater in the two zones is affected by the abundant biotite and hornblende in Langshan Mountain and Ordos Plateau. Under evaporation, the precipitation rate of CaF2 and pH plays key roles in the enrichment of F− in groundwater. In the Hetao Basin, sedimentary environment is the main controlling factor for the co-mobilization of As, F− and I in groundwater.

Changes in Serum Electrolytes Following Permanent or Temporary Ileostomy

Background: Patients with ileostomies are well known to be susceptible to extracellular fluid volume depletion as a result of fluid and solute losses that are greater than intake. However, electrolyte disorders accompanying these episodes of volume depletion are not well delineated. Objective: To find out serum electrolytes changes observed in patients undergone permanent or temporary ileostomy. Method: This prospective observational study was carried out in the Department of Colorectal Surgery, BSMMU, Dhaka, from January 2018 to December 2018. Fifty patients underwent permanent or temporary ileostomy and postoperatively treated with intravenous fluid and electrolytes at least up to 3rd POD along with gradual resumption of oral intake or ileostomy feeding and managed at least for 5 days were included in this study. Electrolyte was measured preoperatively and 3rd and 5th POD and observed the changes. Result: Males were predominant than females (1.17:1). Most of the patients were in age group 31 – 40 years. Mean age was 42.4±12.5 years. Serum sodium (Na) and serum potassium (K) were reduced at POD 3 and at POD 5 compared to pre-operative level. Serum sodium concentration was 136.6±3.75 mmol/L pre operatively and reduced to 135.1 ±2.98 mmol/L at 3rd POD and 134.8±3.04 mmol/L at 5th POD. Similarly, serum potassium concentration was 4.0±0.49 mmol/L pre operatively and reduced to 3.8±0.70 mmol/L at 3rd POD and 3.8±0.50 mmol/L at 5th POD. Both serum Na and serum K level reduced significantly in POD 3 and in POD 5 in comparison to pre-operative values (p&lt;0.05). Regarding serum Cl and serum HCO3 level no statistically significant difference were observed (p&gt;0.05). Conclusion: Serum sodium and potassium concentration reduced statistically significantly after permanent ileostomy. Bangladesh Med Res Counc Bull 2021; 47(1): 78-81

Seasonal and Spatial Variations of δ13CDIC Values in the Mun River, Northeast Thailand

As an important part of the global carbon cycle, dissolved inorganic carbon (DIC) concentration and its stable carbon isotopic composition (δ13CDIC) have been used to constrain the sources of DIC in rivers. In this study, we systematically investigated the water chemistry, DIC contents, and δ13CDIC values in a tropical agricultural river in northeast Thailand. The water temperature ranged from 20.3 to 31.3 °C, and water pH values ranged from 6.4 to 8.4, with seasonal variations. Based on the major ion compositions, the hydro-chemical type of the Mun River water was a unique Na–Ca–Cl–HCO3 type, controlled by evaporite and silicate weathering. Seasonal variation of DIC concentrations and its carbon isotopic composition was obvious; DIC and δ13CDIC were significantly lower in the wet season (135 to 3146 μmol/L and −31.0‰ to −7.0‰) compared to the dry season (185 to 5897 μmol/L and −19.6‰ to −2.7‰). A high level of 12C-enriched DIC/CO2 from soil respiration and organic matter oxidation may cause the low pH values, δ13CDIC values, and high partial pressure of CO2 (pCO2) in the middle and lower reaches during the wet/rainy season compared to the dry season. This may be responsible for the seasonal and spatial variations of DIC concentrations and δ13CDIC values in the Mun River. According to the relationship between pCO2 and δ13CDIC values, CO2 outgassing may be more significant in the dry season, due to the greater influx of groundwater with higher pCO2 levels; and the rapid CO2 diffusion into the atmosphere will continuously increase the δ13CDIC values and decrease pCO2 levels. These results show that riverine biologic effects and CO2 outgassing play important roles in the DIC and δ13CDIC evolution of this typical agriculturally-dominated watershed.

Groundwater quality assessment and hydrochemical characteristics in Wera Didjo, Southern Ethiopia

Groundwater quality assessment study was conducted in Wera Dijo, Southern Ethiopia. The study's objective is to understand water chemistry suitability for domestic and irrigation activities. In the study area, only regional hydrochemistry work has been done; hence this study focused on the detailed water chemistry of the study area. Twenty-eight shallow and deep water samples were collected, and major physical and chemical parameters were studied. The important hydrochemical facies of water present throughout this region are Ca–Mg–HCO3, Ca–Mg–SO4 and Na–HCO3–Cl. Except for fluoride, sodium, and potassium ion, the levels of major cation and anion were found to be below the World Health Organization's allowable limits for drinking purposes in the majority of the study area. The fluoride ion in groundwater exceeded the highest allowable amount of 1.5 mg/L for drinking water in fifteen of the samples. The sodium percentage, permeability index, sodium absorption ratio and The United States Salinity Laboratory (USSL) categorization were used to evaluate the water in this study location for irrigation purposes. Based on several water quality parameters overall, the research area water chemistry was suitable for drinking, agricultural activity and industrial use.