Dominant Water Type Research Articles

Coupling multivariate analysis and Bayesian isotope mixing model to assess the origin and quality of groundwater in the Freetown Layered Complex, Sierra Leone

The current study combined the water quality index, multivariate statistical techniques, environmental isotopes, and the Bayesian isotope mixing model to determine the extent of groundwater pollution, origin, age, and proportional source contribution to groundwater recharge in the Freetown peninsula. The water quality index analysis depicts that all the groundwaters are excellent and suitable for drinking purposes. The Gibb’s diagram suggests that water-rock interaction and precipitation are the dominant sources impacting the groundwater chemistry while sodium chloride and magnesium bicarbonate are the dominant water types in the Freetown peninsula. This study finds that saltwater and anthropogenic contamination from agriculture and domestic sewage significantly impact the groundwater quality in the study area. Two (2) clusters were delineated; cluster 1 showed the characteristics of groundwater while cluster 2 demonstrated the characteristics of estuary water. A plot of 2H versus 18O showed that the groundwaters in the study area are of meteoric origin. The Bayesian model (SIMMR) output revealed that precipitation (83%) was the dominant source of groundwater recharge in the study area. The tritium analysis revealed that the majority of the groundwaters (83.3%) are young and of recent recharge. This study serves as a baseline to evaluate the percentage sources of salinity in groundwater.

Hydrogeochemistry and quality evaluation of groundwater and its impact on human health in North Tripura, India.

Groundwater contamination becomes an alarming threat to the provision of ecosystem services and natural resources. A very high level of groundwater contamination has been observed in the northeastern states particularly in North Tripura district. Therefore, the present study considered the region as a case study to evaluate the hydrogeochemical facies, heavy metal pollution and irrigation indices, and their impact on human health. For the investigation, we have collected a total of 35 groundwater samples from North Tripura district. Hydrogeochemical facies through Piper plot reflect Ca2+-Mg2+-HCO3- and Na+-HCO3- as dominant water types. Gibbs plot identifies the dominance of rock-water interaction process in groundwater hydrochemistry. Geochemical plots indicate the dominance of silicate weathering, ion exchange and carbonate dissolution processes in groundwater mineralisation. The order of trace metal contaminations follows Fe > As > Zn > Mn > Cu > Pb. Results of heavy metal indices suggest above 80% samples are at high risk due to high Fe contamination. The risk of the heavy metal indices is associated with rising elevation in southern part of North Tripura. Findings of health risk assessment study imply that children face much carcinogenic and non-carcinogenic risks than adults because of unsafe levels of Fe and As. Multivariate statistical tools are applied to unravel interrelationships among all ions and trace metals as well as probable hydrogeochemical processes in groundwater. Results of Wilcox and USSL plots suggest 77% samples meet irrigation suitability criteria. Besides, the analysis suggests a better insight to identify hydrogeochemical processes controlling groundwater chemistry and the suitability of groundwater for irrigation and drinking purposes. The study also suggests treatment and sustainable management of groundwater resources is compulsory to reduce trace metal contaminations before public use.

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

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

Rare earth element patterns in a rapidly changing karst environment

Samples of surface water, groundwater and rocks were collected along the Louros River karst system in Greece to study the evolution of the chemical composition of groundwater. It was found that the hydrochemistry is closely related to the lithology of the host rocks. Emphasis was placed on the study of REEs due to the presence of phosphate-rich rocks in the area. A distinctive feature that was also taken into account was the high velocities of surface and groundwater in this rapidly changing karst environment.The carbonate formations of the Ionian Zone determine the hydrogeology of the catchment, particularly the Senonian, Vigla and Pantokrator limestones, through which groundwater mainly moves at relatively high velocities, play a key role. From the northernmost areas at the upper part of the catchment to the southernmost areas at the river's mouth, a multitude of springs, along the river, mark the main base level, above which a common aquifer is formed on either riverbed, hydraulically and locally connecting those geological formations.The chemical composition of the water is mainly controlled by the dissolution of calcite, dolomite and gypsum, with Ca–HCO3 being the dominant water type. Elevated pH values (>7), increased concentrations of dissolved oxygen and low concentrations of Fe and Mn indicate a karst system with oxidising alkaline waters. Groundwater type changes when it encounters gypsum in the area, or when the process of dedolomitisation takes place and, together with the phosphate minerals contributes to the release of REEs into the water. ΣREEs range from 0.22 in anhydrite to 33.8 ppm in the sandstones. The REE concentrations in the 0.45 μm-filtered surface and groundwater samples range between 50 and 260 ng/L. REEs concentration in groundwater is controlled by pH.The European shale normalised REE profiles of the rock samples are enriched in LREEs compared to HREEs and show a slightly negative Ce anomaly, which is explained by an oxidising sedimentation environment. The positive Eu anomaly of the same samples was attributed to the presence of phosphate minerals. Positive anomalies in both Ce and Eu were observed in the corresponding profiles of surface and groundwater samples. The effect of carbonate species, especially HCO3−, on surface and groundwater resulted in their enrichment in HREEs. In general, an enrichment of HREEs in surface and groundwater was observed in proportion to the distance covered.

Hydrochemical characterization and evaluation of groundwater quality of zamfara area, northwest, nigeria

This study deals with hydrochemical assessment of groundwater within the lithological framework underlain Zamfara State, Northwestern Nigeria with the aim of ascertaining its suitability for human consumption. Groundwater samples were collected from boreholes tapping the aquifer of the area and analyzed for various physico-chemical parameters, such as total dissolve solids, electrical conductivity (Ec), pH, temperature, Na+, K+, Ca2+, Mg2+, HCO3, Cl-, SO4, NO3, PO4, and trace elements (Mn, Cu, Zn, Fe, Pb and Cr). The results obtained were subjected to multivariate statistical analysis, water quality index method, and hydrochemical variation plots for proper characterization. As far as suitability is concerned most of the studied physic-chemical parameters trace elements (iron, lead and chromium ions) revealed average concentrations lower than the permissible limit set for domestic water use by World Health Organization. However, the compiled overall water quality index for the studied groundwater shows ‘very poor water quality’. Due to the fact that WQI rating reflect the composite influence of different water quality parameters. The result of the multivariate statistical analysis, as applied to the chemical data set of the studied groundwater provides an insight into the underlying controlling hydrochemical processes in the area. Four factors including factor-1 (total hardness, chloride, nitrate, manganese, bicarbonate and alkalinity), factor-2 (TDS, conductivity, total hardness, magnesium and calcium), factor-3 (Temperature, sodium, potassium, copper, zinc, iron and chromium), factor-4 (calcium, magnesium and nitrate) represents the signatures from dissolution of bedrock through which the groundwater passes, ionic mixing, leaching from the lateritic overburden, agricultural activities (fertilizer application) and effluent from waste dumpsites in the study area. The distribution of major ions in the groundwater shows relative abundance of cations: Na++K+ > Ca2+ > Mg2+; while the relative abundance of the anions is: Cl- > HCO3- > SO42-. Groundwater in the aquifer of the study area are majorly of evolved type with mixing of ionic concentrations. Alkali’s are more in abundant to that of alkaline earth, while Cl and HCO3 dominate SO4 and NO3 concentration. The water samples are basically ‘Alkali waters’ with ‘Earth Alkaline’ components that are predominantly HCO3- and Cl-.The relative abundance of the three (3) dominant water types are as thus: Na-HCO3-Cl > Ca-Mg-HCO3-Cl > Na-Ca-Cl. Simple mineral dissolution or mixing processes is mainly responsible for the variation in the hydrochemistry of the groundwater of the study area.

Water quality indices and multivariate statistical analysis of urban groundwater in semi-arid Sokoto Basin, Northwestern Nigeria

Drinking water is limited in quantity and quality in fast-growing cities in developing countries. Water quality has been impacted by competing demands by industry, municipal supplies, and agriculture. This study investigates groundwater quality in three urban centres in the semiarid Sokoto Basin, North-Western Nigeria. The study employed in situ and laboratory analyses and 30 water samples were analysed. Physical parameters (pH, Temp., EC, and TDS) were analysed using hand-held metres during sampling. Separate water samples were collected to determine chemical parameters (Ca2+, Cu2+, Fe3+, K+, Mg2+, Na+, Zn2+, Cl−, CO32−, HC03-, NO3−, PO43− and SO42−). Results indicate that most sampling locations in the study area have good quality water; 10% of sampling locations fell in the poor water class based on the Water Quality Index (WQI). Iron (Fe3+) and NO3− were the major pollutants and occurred at concentrations above (WHO, 2011) and (NSDWQ, 2007) reference guidelines. Hydrogeochemical facies revealed Ca–Mg–SO4–Cl and Ca–Cl water types. There is no dominant water type in the cation triangle, though the Cl-water type is formed in an anion triangle. Rock weathering controls groundwater quality primarily, as revealed by multivariate statistical analysis and the Gibbs model. The HCA results showed that, though clusters 1 and 2 can be classified as NO3− polluted boreholes, the boreholes ARG7 and ARG10 revealed relatively different groundwater compositions. The study, therefore, concludes that despite the increased urbanisation in the semiarid Sokoto basin, there is little evidence of groundwater quality deterioration. The WQI and multivariate statistics provide a framework for researchers who may require more accurate results while considering multiple groundwater quality parameters. This approach can be applied in other urban centres, mainly in arid and semiarid environments.

Genesis of uranium containing groundwater in the Brahmaputra floodplain of Assam: Hydrogeochemistry and its associated health risk

Groundwater uranium (U) content and the major hydrogeochemical processes were evaluated for six districts of Assam, lying mostly on the central and northern region of the Brahmaputra floodplain. A total of 504 groundwater samples were collected using the grid sampling technique. Uranium concentrations analysed using LED fluorimeter model LF-2a, ranged from below detection limit (BDL) to 13.5 μgL−1. All the U concentrations were found to be well below the prescribed limits of AERB, WHO and USEPA. The highest groundwater U was recorded in a sample from Nagaon, a central Brahmaputra floodplain district. The SEM-EDX spectra of the sediment samples revealed geogenic presence of U in the floodplain. A comparative assessment between the relationships of U with other groundwater parameters revealed that shallow aquifers provided more feasibility for elemental interactions and hence more mobility of U species. The correlation statistics in shallow aquifers depicted the importance of alkalinity on U release and mobilization. Uranium release during weathering of the geological strata was signified by the relationship of U with EC, TDS and salinity. The role played by pH and ORP in dissolution of U in the floodplain was not strong. The dominant water type in the study was Mg–HCO3, which was associated with higher U concentration. This revealed the positive role of carbonate dissolution towards U release in the floodplain. Hydrogeochemical investigation further implied for greater silicate weathering and ion exchange compared to that of carbonate weathering and reverse ion exchange processes. The calculated undersaturation of calcite, dolomite and gypsum explained their role as source minerals in the floodplain. Uranium dissolution and mobilization was found to have positive association with carbonate weathering, as depicted by its significant relationship with calcite, dolomite and gypsum. Health risk, both radiological and chemical, relating to U ingestion through drinking water was absent within the floodplain.

Assessing groundwater quality in peri-urban Accra, Ghana: Implications for drinking and irrigation purposes

In many developing countries, cities are faced with rising water demand due to rapidly increasing population, inadequate municipal water supply and growing sanitation pressure. Consequently, groundwater resources are being heavily relied on to meet the demand. However, the long-term supply and quality of groundwater are threatened by multiple anthropogenic pressures. This study assessed the quality and suitability of groundwater available to more than 600,000 inhabitants in several peri-urban communities in Accra, the capital city of Ghana. Thirty-six (36) borehole samples were analysed for their suitability for domestic and irrigation purposes based on relevant physicochemical parameters. In addition, water quality index (WQI), sodium absorption ratio, and relevant statistical plots were employed to assess the groundwater's quality and suitability for domestic and irrigation purposes. The results indicate that almost all parameters measured were within the WHO recommended limits for drinking water for most samples. This is reflected in the classification of 92% of water samples as good or excellent quality for domestic purposes using WQI. The abundance of ions in groundwater followed the trend: Na+ > Ca2+ > Mg2+ > K+ for cations, and Cl− > SO42− > HCO3− > F− > NO3− for anions. By using principal component and hierarchical cluster analyses, the study identified mineral dissolution and anthropogenic activities as the main factors influencing groundwater chemistry in the study area. These factors resulted in mixed water types, viz: Na–Ca–Mg–Cl and Na–Ca–Mg–SO4, and Na–Cl as the dominant water type. Classifications based on the Wilcox and USSL diagrams suggest that groundwater in the study area is generally suitable for irrigation. Given that these boreholes are new, the results from this study represent background levels and have important implications for groundwater development and management in the rapidly developing capital of Ghana.

Surface water quality analysis using multivariate statistical techniques: a case study of Fars Province rivers, Iran.

This study aimed to transform the input of a large dataset into the output of interpretable information. Hence, multivariate statistical methods were carried out to analyze physicochemical parameters in 34 rivers during a 17-year period (1997-2014). Cluster analysis divided the study area into spatially different riverine water quality sub-regions described in ascending order of water quality as severely polluted (SP), highly polluted (HP), polluted (P), moderately polluted (MP), lightly polluted (LP), and not polluted (NP). By diagnosing threats and identifying fragile zones, water contamination sources responsible for impaired water quality in the study area recognized as natural pollutants in LP, municipal wastes in P, discharge of industrial effluents in MP, natural geochemical formations in SP and HP, and superficial flows of agricultural lands in SP, HP, and MP. The dominant water type in each zone wasclassified into Na-Cl, Na-Cl, Na-Mg-Ca-Cl-SO4, Na-Ca-Mg-Cl-SO4, Na-Ca-Cl, and Ca-Mg-HCO3-SO4 groups for SP, HP, P, MP, LP, and NP, respectively. To explore aesthetic aspects of drinking water application, hazard quotient (HQ) was applied for children and adults in terms of ingestion and dermal exposure. Overall health risk assessment revealed the order of impacts of the secondary water quality parameters as Cl- > Na+ > total dissolved solids (TDS) > Ca2+ > SO42- > Mg2+. Furthermore, hazard index (HI) ranged from 0.011 to 31.439 and 0.010 to 30.122 for children and adults, respectively, indicating a potential health risk regarding chloride throughout the whole region excluding NP. To identify significant agents in water quality, principal component analysis extracted 3 varifactors (VFs), with the eigenvalues of 4.74, 1.19, and 0.85, respectively, explained about 83% of the variance. The most important parameters in the first factor were TDS, electrical conductivity, SAR, TH, Na+, Cl-, and SO42- accounting for 58% of the total variance. The most influenced parameters in the second and third factors were pH and HCO3-, respectively, with variance coverage of 26%. These factors indicated that the hydrochemical characteristics of the water originated by natural interactions (existing salt domes, evaporation, weathering, and soil erosion) and anthropogenic activities (fertilizer-rich flows of agro-fields and domestic/industrial disposals), which must be minimized in rivers to supply the population with hygienic water.

Hydrochemical characteristics and identification of groundwater pollution sources in tropical savanna.

Groundwater pollution of the watershed is mainly influenced by the multifaceted interactions of natural and anthropogenic processes. In this study, classic chemical and multivariate statistical methods were utilized to assess the groundwater quality and ascertain the potential contamination sources affecting the groundwater quality of Galma sub-watershed in a tropical savanna. For this purpose, the data set of 18 groundwater quality variables covering 57 different sampling boreholes (BH) was used. The groundwater samples essentially contained the cations in the following order of dominance: Ca2+ > Na+ > Mg2+ > K+. However, the anions had HCO3- > Cl- > SO4-2 > NO3- respectively. The hydrochemical facies classified the groundwater types of the sub-watershed into mixed Ca-Mg-Cl type of water, which means no cations and anions exceeds 50%. The second dominant water type was Ca-Cl. The Mg-HCO3 water type was found in BH 9, and Na-Cl water type in BH 29 of the studied area. The weathering of the basement rocks was responsible for the concentrations of these ions in the groundwater chemistry of the sub-watershed. Hierarchical cluster analysis (HCA) grouped the groundwater samples (boreholes) into five clusters that are statistically significant regarding the similarities of groundwater quality characteristics. The principal component analysis (PCA) extracted two major principal components explained around 65% of the variance and suggested the natural and anthropogenic processes especially the agricultural pollutants including synthetic fertilizers, and leaching of agricultural waste as the main factors affecting the groundwater quality. The integrated method proved to be efficient and robust for groundwater quality evaluation, as it guaranteed the precise assessment of groundwater chemistry in the sub-watershed of the tropical savanna. The findings of this investigation could be useful to the policy makers for developing effective groundwater management plans for the groundwater resources and protection of the sub-watershed.

Groundwater flow and geochemical processes affecting its quality in the basement (Oban Massif) and sedimentary (Mamfe Embayment) environments, southeastern Nigeria

Groundwater flow and geochemical processes that affect its quality were investigated in Oban Massif and Mamfe Embayment, southeastern Nigeria. Physical parameters of water samples such as acidity (pH), turbidity, temperature and total dissolved solids (TDS) were measured in the field using potable kits. The waters tested acidic with a pH ranged from 5.59 to 7.23, which is not in agreement with World Health Organization (WHO 2011) permissible limit (6.5–8.5) for drinking water. The sedimentary area shows TDS, turbidity, fluoride (F) and chloride (Cl−) ions exceeding permissible limits of 500 mg/l, 5 mg/l, 1.5 mg/l and 250 mg/l, respectively stipulated by WHO (2011) for drinking water. Ionic ratios of SO4/Cl contoured on topographic map decreased to the center indicating that groundwater flow is from east to west and Cl/HCO3 increased towards the center. Cl/HCO3 also increases towards the west reflecting eastern to western direction of groundwater flow. Existing water table values also showed that groundwater flow direction is from eastern in the basement to western sedimentary part of the study area. Ionic ratio plots and Gibbs plots show that geochemical processes such ion exchange, evaporation, crystallization; precipitation and rock weathering affect water chemistry and quality within the study. Silicate weathering and rock-water interactions are the dominant geochemical processes affecting water chemistry and quality. Multivariate statistical analysis confirmed that the source of elements in water is from geochemical processes such as silicate weathering from basement rocks, saline water intrusion, interaction of rock with aquifer materials and human inputs. Piper diagram revealed that the dominant water types are Ca–Na–HCO3- and Ca2+ + Mg2+-HCO3-. Evaluation of water quality for irrigation using percent sodium (% Na), Magnesium ratio, sodium absorption ratio (SAR), potential and salinity hazards show the water is suitable for irrigation. Water quality in the basement is more suitable for agriculture and domestic uses compared to the sedimentary area. This method used in evaluating groundwater quality is useful for local and regional study here in Nigeria and elsewhere on the globe.

Mechanism of arsenic enrichment and mobilization in groundwater from southeastern Bangladesh: Water quality and preliminary health risks assessment

To understand the mechanistic pathway of arsenic (As) enrichment and mobilization in groundwater (southeastern Bangladesh) and to evaluate the water quality as well as associated health risks, a suite of systematically collected groundwater samples (depth: 17–61 m) were analyzed. Arsenic concentrations (μg L−1) in the groundwater samples were ranged from 6 to 581 with a mean value of 199 which is significantly higher than the recommended values. The assessment of water quality using entropy water quality index and irrigation water quality indices revealed that the groundwater in the studied region was not recommended for drinking and irrigation, respectively with few exceptions. Dominant water types in the studied area were Ca–Mg–HCO3, Na–HCO3, and Na–Cl types. Various forms of water-rock interactions, leaching of evaporates, and the confined nature of the aquifer mostly control the hydro-chemical parameters. Fe/Mn bound As are likely to be released in the aquifer through the dissolution of carbonate minerals of Fe/Mn while the higher degree of water-rock interaction and probable oxidation of organic materials helped to elevate As concentration. The probable longer residence time of groundwater guided by topographic slope and the neighboring clayey aquitard govern the As mobilization in the aquifer. Probabilistic health risk assessment revealed that groundwaters from the studied area can cause both non-carcinogenic and carcinogenic health risks.

Groundwater quality mapping for drinking and irrigation purposes using statistical, hydrochemical facies, and water quality indices in Tercha District, Dawuro Zone, Southern Ethiopia

When groundwater quality is good, it may be a substantial water supply for various applications. However, no systematic research on hydrogeochemistry and water quality features for drinking and irrigation has been undertaken in the present study area. As a result, the current study looked at hydrogeochemical variables and groundwater quality for drinking and irrigation in Tercha district, Dawuro Zone, Southern Ethiopia. Forty-seven groundwater samples were collected and tested to satisfy the required target for various physicochemical properties. The hydrogeochemical features of the groundwater in the study region were assessed using in-situ testing and laboratory analysis of physicochemical parameters. Groundwater samples from the research region were slightly acidic to slightly basic, with the principal cations and anions decreasing in sequence: Na+ > Ca2+ > Mg2+ > K+ and HCO3-> Cl-> SO42-. The hadrochemical facies of the studied region evolved from mildly mineralized dominant highland Ca-HCO3 water types to moderately mineralized mixed Ca-Na-HCO3 water types to highly mineralized deep rift floor Na-HCO3 water types. Additionally, the World Health Organization and the Ethiopian Standard Agency were utilized to compare the drinking water quality. Except for NO3- (4.25 %), Fe (8.51 %), and F- (2.12%), all groundwater samples from the research region were determined to be within permitted limits and appropriate for drinking. According to the Water Quality Index, about 80.86% of groundwater samples are excellent, and 19.14% are good drinking water. Sodium absorption ratio (SAR), sodium (Na) percentage, residual sodium carbonate RSC, permeability index (PI), and magnesium hazard were among the irrigation water quality indicators calculated (MH). The great majority of groundwater samples are suitable for agricultural use.

Geochemical modeling unravels the water chemical changes along the largest Mexican river

Tropical Usumacinta River is the tenth largest in North America and Mexico's principal river. Diverse and increasing anthropogenic activities (e.g., land-use change, agriculture, urban development) occur along the river and most likely alter its water quality. We used inverse geochemical models (PHREEQC code) and chemical diagrams to determine the water chemistry in the mainstream and principal tributaries, the principal geological and anthropic causal factors, and the effects of tropical seasonality. The dominant chemical water type in the river is Ca-Mg-SO4-HCO3 in the dry season, while Ca-Mg-HCO3-SO4 in the rainy season. The water-rock interaction processes in the dry season are: 1) gypsum, halite, and sylvite precipitation, and Mg2+ to Na+ ion exchange in the middle basin; 2) calcite, kaolinite, and SiO2(a) precipitation, CO2, dolomite, gypsum, halite, sylvite, and K-feldspar dissolution, nitrification, and Ca2+ to Na+ ion exchange in the lower basin. In the rainy season, the processes are: 1) plagioclase and sylvite precipitation, calcite, dolomite, gypsum, halite, kaolinite, and K-feldspar dissolution in the middle basin; 2) kaolinite precipitation, dolomite, gypsum, halite, K-feldspar, and sylvite dissolution, and nitrification, in the lower basin. The model outcome reveals the water-rock interactions that control the chemical composition in the river are mainly the carbonate and secondly the silicate weathering in the dry season. In contrast, in the rainy season, the weathering of carbonate and silicate rocks have the same weathering proportion. At the same time, the model of the dry season reveals the influence of saline water intrusion in the lower basin. The effects caused by agricultural activities as nitrification are evident in the lower basin of the dry season. In contrast, it is not present in the rainy season most likely associated to the river flow dilutes the nitrates. The results of this research are slightly different from other tropical rivers with similar geology, with a predominance of Ca2+ and Mg2+ cations, and HCO3- and SO42- anions. This investigation is the first to present the major ions composition, chemical water types, and water-rock interactions in the tropical Usumacinta River. The methodology herein used proved to be useful to understand the chemical changes in rivers with various geological materials that could be applied in other tropical and temperate rivers.

QUALITY ASSESSMENT AND HYDROGEOCHEMICAL PROPERTIES OF GAZLIGÖL (İHSANIYE-AFYONKARAHISAR, TURKEY) WATER RESOURCES

The study area includes Gazlıgöl (İhsaniye) and its surroundings located approximately 21 km north of Afyonkarahisar province. In this study, it is aimed to determine the hydrochemical properties of the water resources in the study area and their usability for different purposes. With this scope, pH, electrical conductivity (EC), main anion-cation and NO3 contents of a total of 19 groundwater samples in the region were determined. According to the results obtained, the pH values of the water resources in the region vary between 7.1 and 8.1 and the average is 7.7, which is basic water. The electrical conductivity values are between 110 and 1927 µS/cm, with an average of 461 µS/cm. The dominant water types in the region are Ca-Na-HCO3, Ca-Mg-HCO3, Ca-Mg-HCO3-SO4, Na-Ca-HCO3 and Na-Ca-HCO3-SO4. World Health Organization (WHO) and Turkish Standards Institute (TSE 266) standards were used to evaluate the usability of water resources in the study area as drinking water and it has been determined that only the samples H16 and H18 can be unfavorable to use as drinking water. Electrical conductivity, sodium percentage, sodium adsorption rate, residual sodium carbonate, Kelley index, permeability index parameters, Wilcox and US Salinity Laboratory Diagrams were used to evaluate the suitability of water resources as irrigation water. According to the results obtained, it was determined that all waters were suitable for irrigation water, except for samples HG16 and HG18. In addition, in terms of the industrial use properties of the water resources, HG1, HG11 and HG19 samples are in the "bubbling waters when boiling" class, while the HG16 and HG18 samples are in the "highly foaming waters when boiling" class. HG9, HG10, HG11, HG13, HG16, HG18 and HG19 samples in the class of “carbonate precipitations occur” and this type of water can cause rotting and calcification.

Investigation of the hydrogeochemistry, groundwater quality, and associated health risks in industrialized regions of Tripura, northeast India

The aim of this study was to elucidate the contaminant sources and the processes controlling the groundwater quality and risk assessment of heavy metals posed on humans by statistical indices. The groundwater sampling was performed at Bodhjungnagar Industrial Estate, A.D. Nagar, Dukli and Badharghat Industrial Cluster, Tripura, India during pre-monsoon and post-monsoon in the year 2017. A total of 21 water quality parameters (Temp, pH, TDS, Ca, Mg, TH, Na, K, HCO3, Cl, SO4, PO4, NO3, F, Fe, Mn, Pb, Cd, As, Cu, Zn, and Cr) were determined from collected samples. The statistical and graphical methods were employed to assess the suitability of water. The water quality index (WQI) suggested that the majority of the samples are suitable for drinking purpose. The WATEQ4F model was applied to compute the saturation index (SI) of different minerals present in the water samples. Based on Piper plot the dominant water type is Ca-Cl in the study area. The Nemerow integrated pollution index (NIPI) indicates that the groundwaters of both industrial sites have moderately to highly deteriorated water with heavy metals. The hazard index (HI) revealed that amongst the population, chronic health risk was greater for children and considering the seasons, the risk was higher during the pre­monsoon season.

Using a linear discriminant analysis (LDA)-based nomenclature system and self-organizing maps (SOM) for spatiotemporal assessment of groundwater quality in a coastal aquifer

In this study, a linear discriminant analysis (LDA) - based nomenclature system have been used for the classification of groundwater samples in a coastal aquifer. The capability of three models (7 hlr, 7 M conc, and Greater molar conc) in determining the water types has been investigated. The results show that Ca-HCO3, Na-Cl, and Na-HCO3; and Ca-HCO3, Na-HCO3, and Na-Cl are the three dominant water types for the wet and dry seasons, respectively. The results of 7 hlr (basic + hybrid) model as the best option show that 42 and 27 water types can be identified for wet and dry seasons, respectively. Twenty-four physicochemical components have been used for the hydrogeochemical study of selected water resources based on Kohonen’s self-organizing map (SOM) method. The k-means clustering tool detected 7 and 6 clusters using the Davies-Bouldin index (DBI) for the wet and dry seasons, respectively. Hydrogeochemical assessment of duplicated samples showed that the seasonal changes can not cause significant changes in the chemical composition of groundwater resources of this aquifer. Radar diagrams of physicochemical variables showed some changes in the chemical composition of groundwater in some locations due to water–rock interaction as well as pollutants produced by human activities. Comparison of the results of classification of water samples by SOM and principal component analysis (PCA) shows that both methods can perform clustering of samples correctly. However, the SOM method provides more accurate clustering without any overlap between different clusters.

Comparative Hydrochemical Evaluation of Water At Ilokun Village and Ado-Ekiti Metropolis, Southwestern Nigeria.

This study focused on comparative hydrochemical evaluation of water in Ado-Ekiti metropolis and Ilokun Village (where there is an open refuse dump), Southwestern Nigeria. Fifteen groundwater samples from Ado-Ekiti Metropolis, four groundwater samples and three stream water samples from Ilokun village were collected and analyzed for physico-chemical parameters. In-situ parameters (Temp. (°C), EC (µS/cm), pH and TDS (mg/L)) were measured using Multi-parameter Testr™ 35 Series S/NO: 1382654. Major cations and anions were determined employing Atomic Absorption Spectrometer and Colorimetric methods respectively. The pH revealed that water in Ado-Ekiti was slightly acidic to alkaline while that of Ilokun village was alkaline.  The order of major ions concentrations in Ado-Ekiti metropolis and Ilokun village were Mg<K<Na<Ca and Mg<K<Ca<Na and HCO3<Cl<SO4<NO3 and Cl<HCO3<SO4<NO3 respectively. EC (µS/cm) values of all sampled water were <1000 except in a location at Ilokun village close to the refuse dump signifying local anthropogenic contamination. CaCl (54.55%) was the dominant water type and all were Ado-Ekiti groundwater. CaHCO3 (9.10 % Ado-Ekiti groundwater, 9.10% Ilokun water), NaCl (13.60 % Ilokun water), CaNaHCO3 (4.55% Ado-Ekiti groundwater) and CaMgCl (4.55% Ado-Ekiti groundwater, 4.55% Ilokun water) represent minor water types. The water chemistry in the study area may have modified from weathering materials derived from the underlying bedrocks. Based on graphical evaluation and estimated irrigation parameters, both Ado-Ekiti groundwater and Ilokun water were suitable for irrigation purposes. Hydrochemical parameters and all estimated irrigation parameters showed marked quality differences with respect to Ado-Ekiti groundwater and Ilokun water.  

Solute transport and solutional denu-dation rate of carbonate karst in the semi-arid Zagros region (southwes-tern Iran)

We conducted a one-year-long study of solute load measured three times per month in three neighboring subwatersheds (Alashtar, Khorram Abad, and Biranshahr) located in the Karkheh River basin in the Zagros region of southwestern Iran. Research was focused on the chemical composition of water (solute load), karst denudation rate, spatial and temporal variability, as well as comparison of solute load with suspended load. Results show that Ca-Mg-HCO3 is the dominant water type that reflects the lithological characteristics of the catchment areas. Lack of seasonal fluctuation of solute load and absence of dilution during high water levels but evident seasonal course of discharge defines the highest solute flux during the annual maximum of discharge in spring months. The highest solute flux is related to flood events. High annual variation of Na1 concentration compared to conservative Cl2 as well as Chloro-Alkali indexes (CAI and CAI2) suggests that Na1 adsorption and desorption during ion-exchange reactions occur in the regolith. This Na+ variability, to some extent, explains weak Ca21 and Mg21 dilution effect during high water levels. During the measurement period (2014-2015), solute flux calculated per catchment area amounted to 49-69 t km-2 a-1 (tons per km per year). The chemical composition of water and discharge shows by far the highest chemical denudation of limestones and dolomites (87−89 %), while dissolution of gypsum is of minor importance (11−13 %). As a result, the carbonate karst solutional denudation rate is between 0.010 and 0.040 mm a21 , where the higher values are more probable for longer periods due to the relatively low discharge during the spring of 2015. Comparison of dissolved and suspended loads indicates that the transport of suspended load is an order of magnitude less than transport of the dissolved load; the only exception is one flash flood event when suspended load exceeded the dissolved load. Besides a small decrease in solute flux as well as carbonate karst dissolution rates from NW to SE, no large hydrochemical differences between the three subwatersheds were detected.

Groundwater quality evaluation of the alluvial aquifers using GIS and water quality indices in the Upper Blue Nile Basin, Ethiopia

Groundwater (GW), which contributes to the quality of life, economic development, improved food security, and rural society stability, is essential to improving rural water supply access and quality. Given its multi-purpose uses, GW quality has been degraded and polluted by global climate change, population growth, human activities, land use land cover (LULC) transition. GW quality, therefore, should be evaluated and tracked continuously to secure its multi-purpose uses. Herein, this study aims to assess the shallow GW standard using water quality indices (WQI) and GIS techniques in the northwestern boundary of Lake Tana, Upper Blue Nile (UBN) of the Amhara Region, Ethiopia. The water samples were collected from 30 sites, and physico-chemical parameters such as pH, electrical conductivity (EC) were measured in situ. Calcium (Ca+), magnesium (Mg+), sodium (Na+), potassium (K+), chlorine (Cl−), sulphate (SO4−2), nitrate (NO−3), bicarbonate (HCO3−), carbonate (CO3−2) concentraions were determined. Irrigation water quality indices, including sodium adsorption ratio (SAR), sodium soluble percentage (SSP), residual sodium carbonate (RSC), permeability index (PI), magnesium adsorption ratio (MAR), Kelley's ratio (KR), and Na% were calculated. The results show that EC (46.7%), SAR (97%), KR (53%), SSP (53.3%) MH (100%) and Na+ (50%) are suitable for irrigation. The overall WQI for drinking purposes ranges from 46 to 67.5, which confirms that 22%, 38.8%, and 39.2% of samples fall under very good, good, and poor quality, respectively. The hydrochemical facies indicated that, the dominant water type (43% of samples) is type-III (Na-K-Cl-SO4) and mixed type. Most shallow wells near Lake Tana are unsuitable for drinking purpose. Further, the government should monitor contamination sources, including agricultural activities, domestic wastes and landfills for sustainable GW quality.