HCO3 Water Type Research Articles

Assessment of groundwater quality and the main controls on its hydrochemistry in some Voltaian and basement aquifers, northern Ghana

Groundwater resources play the single most important role in the delivery of potable water to rural communities in northern Ghana, especially during the long dry season and where surface water sources are polluted or non-existent. This study sought to assess the quality and main controls on groundwater chemistry in parts of Sawla-Tuna-Kalba District in the Savannah Region of Ghana. Multivariate statistical analysis and conventional hydrochemical plots were employed in the analysis of 112 groundwater samples from the study area. Conventional graphical methods, R-mode Hierarchical Cluster Analysis (HCA) and Principal Component Analysis (PCA) identified dissolution of silicates and the influence of agrochemicals and domestic wastewaters as the main sources of variations in the hydrochemistry in the study area. Q-mode HCA coupled with Stiff diagrams identified Ca–HCO3 water type in recharge areas, and Mg–Ca–HCO3 water type, which evolves into a Ca–Na–K–HCO3 water type in discharge areas in the groundwater flow regime. Mineral stability diagrams indicate the groundwater is stable in kaolinite, which suggests little or no restricted groundwater flow conditions. Groundwater quality for domestic purposes was assessed using the weighted arithmetic index approach. The computed water quality indices (WQIs) from the data suggest that 94% of the sampled boreholes provide groundwater of “excellent” quality for drinking purposes, whereas 5% and 1% present water of “good” and “poor” quality respectively. Spatial interpolation of the estimated WQIs suggests the quality of the groundwater in the study area is suitable for domestic purposes. The assessment of the groundwater quality for irrigation purposes suggests the water is of “excellent” to “permissible” quality and may be used for irrigation without prior treatment.

Biogeochemical and reactive transport modeling of arsenic in groundwaters from the Mississippi River delta plain: An analog for the As-affected aquifers of South and Southeast Asia

Abstract Arsenic (As) concentrations and speciation were measured in groundwaters from the upper Chicot aquifer in southern Louisiana to: (1) ascertain the geochemical processes responsible for its mobilization into the groundwater; and (2) investigate the fate and transport of As in the aquifer following its mobilization into solution. Ancillary geochemical parameters, including dissolved iron (Fe) concentrations and speciation, major solutes, pH, and alkalinity were also quantified in the groundwaters, along with the mineralogy and geochemistry of the aquifer sediments. Arsenic concentrations as high as 644 nmol kg−1 (48.2 μg kg−1) were measured in the groundwaters, with the arsenite oxyanion (H3AsIIIO30) accounting for ca. 60%, on average, of the total dissolved As, and the remaining ca. 40% consisting of the arsenate oxyanion (i.e., H2AsVO42−). The groundwaters are Na – HCO3 type waters of slightly alkaline pH (8.09 ≤ pH ≤ 8.34), moderately high mineralization (7.3 mmol kg−1 ≤ I ≤ 13.7 mmol kg−1), and high Fe(II) concentrations (18 μmol kg−1 ≤ Fe(II) ≤ 47 μmol kg−1), and thus are compositionally similar to As-affected groundwaters from South and Southeast Asia (e.g., Bangladesh, West Bengal, India, and Vietnam). Groundwaters with the highest As concentrations also have the highest Fe(II) concentrations, which is consistent with reductive dissolution of Fe(III) oxides/oxyhydroxides releasing sorbed or co-precipitated As into the groundwaters. Biogeochemical reactive transport modeling that employs rates laws for microbial respiration indicates that dissimilatory reduction of Fe(III) oxides/oxyhydroxides coupled to organic matter oxidation can explain the high As concentrations along the mid-reaches of the studied flow path. Geochemical analysis of the aquifer sediments further demonstrates that the bulk of the environmentally mobile As in the aquifer is associated with Fe(III) oxides/oxyhydroxides and/or chemisorbed (i.e., inner-sphere surface complexed) onto aquifer mineral surfaces. Model calculations confirm that mobilization of 2–8% of this labile As could support the high As concentrations measured in these groundwaters. Reactive transport modeling coupled to the generalized double-layer surface complexation model predicts that As(III) could be transported ca. 10 km down gradient from the current location of the As “hot-spot” after 150 years, whereas As(V) is predicted to move between 2.4 km and 8.5 km depending on the composition of Fe(III) oxides/oxyhydroxides in the aquifer. Reactive transport modeling also illustrates how retardation and attenuation of As(III) and As(V) along flow paths in aquifer systems is strongly dependent on the type and content of Fe(III) oxides/oxyhydroxides present in the aquifer with higher contents of amorphous to poorly crystalline forms leading to greater retardation and attenuation of both As species. The data and modeling indicate that although As is readily mobilized by microbial reduction of Fe(III) oxides/oxyhydroxides, its tendency to form strong, inner sphere surface complexes on Fe(III) oxides/oxyhydroxides remaining in the aquifer will control the fate and transport of As once released into solution. We suggest that these observations may help explain the “patchy” spatial distributions of As concentrations commonly observed in As-affected aquifers, such as those of South and Southeast Asia.

Shallow groundwater quality evolution after 20 years of exploitation in the southern Lake Chad: hydrochemistry and stable isotopes survey in the far north of Cameroon

Two field hydrogeological surveys were conducted in 1992 and 2013 using hydrochemistry and isotope techniques in the far north region of Cameroon which corresponds to the southern part of Lake Chad basin. The dataset relates to shallow groundwaters of the Quaternary and substratum aquifers that were sampled at the same locations to potentially reveal any temporal variation in the chemical and isotopic characteristics of the groundwater resource. Groundwater shows mainly a CaMg–HCO3 water type but CaMg–Cl–NO3 and NaK–HCO3 water types can also be found. The mineralization is governed essentially by cation exchange processes. However, we also observe dissolution processes of carbonates. Strong anthropogenic contamination of groundwater with nitrates, chlorides, and sulfates is highlighted. It is found that the nitrate content after 20 years has increased by an average factor of 6. These high concentrations in nitrate (up to 600 mg/l) are related to local anthropogenic activities and to the very bad conditions of maintaining of wells and boreholes. The isotopic content is ranging from − 6.46‰ to + 0.46‰ for 18O in 2013 and from − 5.57‰ to + 0.37‰ in 1992 without noticeable evolution. The stable isotope approach underlined the hydraulic connection between basement and quaternary aquifers. Stable isotopes also demonstrated that groundwater in the region is recharged by modern precipitation, but also by evaporated surface waters from rivers during flood episodes. After 20 years, the evolution in Cl−, SO42−, and NO3− concentrations in groundwater is worrying in terms of public health and the government is encouraged to develop a monitoring of this transboundary resource.

Hydrochemistry with special reference to fluoride contamination in groundwater of the Bongo district, Upper East Region, Ghana

This study was conducted to understand the hydrochemistry of groundwater in the Bongo district and unravel the source of fluoride in the groundwater using an integrated hydrochemical analysis and multivariate geostatistical analysis. A total of thirty (30) borehole water samples were collected in various communities in the district during the dry season. The district is dominated by Upper Birimian (Paleoproterozoic) metavolcanics and granitoids known as the Bongo granitoids. Hydrochemical facies identified in the area include Ca–Na–HCO3 (70%) and Ca–Mg–HCO3 (30%) water types. The Ca–Na–HCO3 water types are hosted in fractured bedrocks of the Upper Birimian metavolcanics and the K-feldspar rich Bongo granitoids, whereas the Ca–Mg–HCO3 water types are within the Upper Birimian volcanic/metavolcanic sequences. All the hydrochemical parameters show acceptable concentrations for drinking purposes except fluoride (1.71–4.0 mg/L). The high fluoride concentrations in the groundwater are largely due to intense dissolution of the Bongo granitoids, which contain biotite and muscovite as the dominant fluoride-bearing minerals. The pH, Ca2+, SO42−, HCO3− and CO32− concentrations have weak positive correlations with F− concentrations of the groundwater implying some dependent relationship and different source for the fluoride. Principal component analysis performed on the hydrochemical data resulted in three principal components (PCs), which explain 76.251% of the total variance. The three PCs represent the dominant processes influencing the groundwater chemistry, which include water–rock interaction, mineral dissolution, and ion exchange reactions, respectively, with water–rock interaction as the most dominant process. However, anthropogenic sources such as the use of phosphate fertilizers cannot be precluded from contributing to the groundwater fluoride contamination.

Evaluation and characterization of the groundwater quality and hydrogeochemistry of Ogbaru farming district in southeastern Nigeria

The aim of this study was to evaluate and characterize the hydrogeochemistry and quality of groundwater (for human consumption) in Ogbaru district, southeast Nigeria. Borehole samples were subjected to physicochemical, bacteriological, hydrogeochemical, and statistical analysis. The physicochemical characteristics of the water were below standard maximum permissible limits for drinking water. Moreover, heavy metals were found in low concentrations (below their permissible limits) in all of the samples. However, majority of the samples have pH values below the allowable limits of 6.5–8.5, indicating they are slightly acidic waters. The dominance of cations and anions is in the order: Ca > Mg > Na > K and HCO3 > Cl > NO3 > SO4 > PO4 > NO2, respectively. Mg–Ca–HCO3 water type dominated the area, constituting about 47.4% of the total samples. Ca–Mg–HCO3 water type constituted about 16%; Mg–Ca–Na and Ca–Mg–Na–HCO3 water types constituted 10.5% each, whereas Ca–Mg–Cl, Mg–Ca–Cl–NO3, and Ca–Mg types made up 5.2% each. The possible sources and influencers (both anthropogenic and geogenic) of the physical and chemical water quality parameters were identified by correlation and principal component analyses. Although most of the groundwater samples are of good quality based on the physicochemical properties, the presence of coliforms indicates that their quality is questionable and hence not safe for drinking. Therefore, treating them before use is recommended.

Geochemical and isotopic characteristics of geothermal discharges in the Emet Basin, Western Anatolia, Turkey

The geochemical and isotopic compositions of low-temperature thermal waters in the N–S-oriented Emet Basin, located in Western Anatolia, Turkey, were comprehensively investigated. Three distinct physicochemical processes affecting the chemical composition of the thermal waters were distinguished at this site: dissolution of CaCO3, gradual transformation of Ca–HCO3-type waters to Ca–SO4-type waters by the addition of SO4, and mixing of deep Na–HCO3-type waters with Ca–SO4-type waters. The first two processes are associated with the dissolution of carbonates and evaporites, respectively, and predominantly control the chemistry of thermal waters in the basin. The third process is observed locally and is manifested as CO2-rich thermal waters with relatively higher total ionic concentration.The majority of the thermal waters lie close to the local meteoric water line with a deuterium excess of +17‰. The single CO2-rich thermal water in the basin, located in the Yeniceköy area, shows a slight enrichment in 18O and a shift from the local meteoric water line. The δ34SSO4 and δ18OSO4 values of the dissolved sulfate range from 14.49‰ to 22.46‰ (vs. V-CDT) and 11.9‰–17.8‰ (vs. V-SMOW), respectively, which indicates that the source of sulfate in the thermal waters is evaporites such as gypsum and anhydrite in the basin. The δ13CDIC values of the thermal waters vary between −0.63‰ and −10.36‰ (vs. V-PDB). By using a binary mixing model, the δ13C value of the deep carbon source associated with the formation of CO2-rich thermal waters was calculated as 0‰, which is a typical value of marine limestones. Thermal decomposition of marine limestones and dissolution of carbonates dominate the carbon budgets of thermal waters, whereas the organic carbon contribution is generally less than 20% and the mantle-derived carbon contribution was found to be insignificant.Air-corrected 3He/4He ratios of the thermal waters ranging from 0.34 RA to 1.57 RA indicate that radiogenic (crustal) helium is dominant in the region, although up to 19.4% of the total helium is of mantle origin. The 3He/heat ratios vary from 0.4 × 10−15 cm3 STP/J to 13.2 × 10−15 cm3 STP/J, which are very close to the ratios in the continental environment. This indicates that the dominant heat source in the region is radiogenic.

Hydrochemical and isotopic studies to understand quality problems in groundwater of the Niğde Province, Central Turkey

This study seeks to decipher the hydrochemistry, recharge sources, and the possible factors controlling the chemistry of groundwater in Nigde Province of central Turkey. This was done by conducting hydrochemical, multivariate statistical, and stable isotope analysis on 37 well and spring water samples collected in the wet and dry seasons of 2016. The major ion abundance in the groundwater is in the order Ca2+ > Na+ > Mg2+ > K+ and HCO3− > SO42− > Cl−. This accounted for the dominance of Ca–SO4–HCO3 water type with other mixed water types, reflecting the geology of the area, which is predominated by carbonate lithologies. All the physico-chemical parameters generally comply with the WHO and Turkish national guideline values for drinking water except TDS, Ca2+, SO42−, NO3−, and As. The elevated amounts of TDS, SO42−, and NO3− were largely from anthropogenic sources. The studied well and spring water samples are suitable for irrigation purposes in terms of their sodium hazard, but with regard to salinity hazard, the well water samples are not suitable for irrigation purposes due to their high salinity values. Three factors that explain 85.2% of the total variance of the data point to water–rock interaction and mixing with thermal waters as the principal factors controlling the chemistry of the groundwater. Metal pollution load was significantly higher in the wet season than in the dry season with arsenic as the key contaminant (0.69–391.14 µg/L and 0.29–43.6 µg/L in the wet and dry seasons, respectively). The tritium concentrations reveal that the well waters have longer residence time and water–rock interaction than the spring waters and are thus recharged from older groundwater sources.

Hydrogeological Modelling of Geothermal Waters in Cesme and Environs, Western Anatolia, Turkey

The geothermal fields of Çeşme are located in the western part of province capital of Izmir and can be considered as important tourist resorts with a great number of thermal hot springs which are used for thermal bathing since several years. Nowadays, the geothermal waters in the fields are used for district heating and greenhouses. In the area of Çeşme, there are sedimentary and volcanic rocks predominantly. The basement rocks are of Devonian age and consists of intercalations of sandstones, greywackes and limestones overline by Upper to Middle Triassic carbonate rocks with intercalations of sandstones and claystones. These rocks are overlain by Neogene volcanic and terrestrial sedimentary rocks. In 1995, we have measured in-situ parameters in many locations of groundwaters and geothermal waters with collection of a great number of samples for these waters. The geothermal waters are of Na-Cl, Na-(Cl)-HCO3, Na-Ca-Cl, Na-Mg-(Cl)-HCO3, Na-Mg-Ca-(Cl)-HCO3 and Ca-Na-Mg-(Cl)-HCO3 type waters during the groundwaters display Na-Cl, Na-HCO3, Na-Mg-(Cl)-HCO3, Na-Mg-HCO3, Na-Mg-Ca-(Cl)-HCO3, Mg-Ca-Na-(Cl)-HCO3 and Mg-Ca-Na-(Cl)-HCO3 type waters. The Na-Cl type waters are originated from deep reservoir during the others can be considered as diluted Cl-HCO3 water type. The plot of δ18O versus δD shows that the geothermal waters are enriched in δ18O and δD and located on the mixing trend between groundwaters and seawaters indicating mixing of these both different waters. The proportion of seawaters in geothermal waters seems to be very higher than groundwaters. The shift in the δ18O values are related to δ18O exchange between the deeply circulating meteoric waters and reservoir rocks in the area. The increase of δD is related to the contribution of seawaters. The geothermal waters in the area fall into fields of immature to partially equilibrated waters. In general, the reservoir temperature of the area of Çeşme is estimated to be 80 to 120 °C.

Using regional datasets of isotope geochemistry to resolve complex groundwater flow and formation connectivity in northeastern Alberta, Canada

In the southern Athabasca Oil Sands (SAOS) Region, located in Alberta Canada, individual in-situ oil sands operators have conducted local geochemical and isotope groundwater studies to establish baseline characteristics and to improve understanding of the connectivity of water supply and disposal formations within individual leases. Canada's Oil Sands Innovation Alliance (COSIA) initiated this study to combine the data from these individual studies along with public information into a comprehensive unified dataset to evaluate conceptual models of regional groundwater flow and the degree of interaction and separation between important water supply and disposal aquifers. The unified dataset comprised over 293 groundwater samples from the main water source and disposal hydrostratigraphic units and included geochemical and isotopic tracers that can be used to identify sources (δ18O and δ2H) and age of water (3H) and associated solutes (14CDIC, 36Cl), as well as the sources of salinity and diagenetic processes (δ13CDIC, δ34SSO4, 87Sr/86Sr, δ11B, δ37Cl and δ81Br) and dissolved organics (δ13CDOC). The TDS and stable isotope composition (δ18O and δ2H) of groundwater from several Cretaceous formations were used to identify three main mixing controls. i) Areas where locally recharged groundwater mixes with glaciogenic water were identified by lower δ18O and δ18O values, high TDS, Cl:Br and δ34SSO4, 87Sr/86Sr, and δ37Cl values consistent with dissolution of evaporites. These areas were situated where vertical pathways through otherwise competent formations are likely to occur. ii) Mixing with paleo-waters characterized by high TDS and higher δ18O and δ2H signatures indicating groundwater recharged under warmer climate periods and/or evaporative enrichment were identified in the south, and southwestern portions of the study area. The presence of these paleo-waters indicate slow-moving groundwater zones with limited lateral and vertical connectivity. iii) Areas with potential connectivity to shallow aquifers were identified by their lower TDS values, modern meteoric δ18O and δ2H signatures, HCO3 type waters, and δ34SSO4 and 87Sr/86Sr signatures, consistent with weathering of shallow aquifer material. Geochemical and isotopic indicators suggest that in areas where the Colorado Group aquitard is thin or absent, there is greater connectivity between the Grand Rapids Formation and the shallower aquifers. Interpretation of the new unified dataset has improved understanding of the extent that glacial recharge had on Devonian aquifers, and overlying Cretaceous formations, and identified zones with relatively stagnant groundwater flow, both of which have implications for regional groundwater resource development, monitoring and potential wastewater disposal.

Hydrogeochemical characteristics and spatial distribution of groundwater quality in Arusha well fields, Northern Tanzania

Arusha aquifers have been exploited intensively serving as the main source of domestic water supply in the city. But the quality of groundwater is not clearly documented for future planning and management. Hydrogeochemical assessment was carried out to establish groundwater quality and its spatial distribution with the aid of geostatistical techniques. Groundwater samples were collected and analyzed for major cations and anions using conventional methods of water analysis. Well lithology and geological map were considered for hydrogeological interpretation of the area. The results of piper diagram revealed Na–K–HCO3 water type with sodium and bicarbonate ions dominating in all samples. High fluoride concentrations and general groundwater chemistry are mainly controlled by aquifer lithology than anthropogenic activities. The levels of anthropogenic pollution indicators such as nitrate, chloride and sulfate in deep wells are generally low and most likely coming from natural sources. The geological sections indicate two potential aquifers (volcanic sediment and weathered/fractured formation) both yield water containing significant concentration of fluoride. Fluoride concentrations were higher than WHO guidelines (1.5 mg/l) and Tanzanian standards (4.0 mg/l) by 82 and 36% of the analyzed groundwater samples, respectively. The southern part of the study area yields groundwater of better quality for human consumption than northern zones which is at high elevation on the foot of Mt. Meru. With exception of fluoride, the quality of groundwater in the study area is generally suitable for drinking purpose and other socioeconomic uses.

Groundwater quality assessment using water quality index and GIS technique in Modjo River Basin, central Ethiopia

Groundwater is main sources of water supply in Modjo River Basin. In this study, 31 groundwater samples were collected and analyzed to determine suitability of groundwater for drinking and irrigation uses. Spatial variation map of major cations (Ca2+, Mg2+, Na+, K +) and anions (HCO3−, NO3−, SO42−, F−, Cl−) were produced using IDW interpolation in GIS. Piper pilot show that, Ca–Na–HCO3, Na–Ca–HCO3 (mixed) and Na–HCO3 water types are found in study area. Ca2+ and Mg2+ are dominant in highland aquifer whereas Na+ is dominant in rift valley aquifer. HCO3− is the dominant anion in all samples. Rock-water interaction and cation exchange along groundwater flow path are responsible for the current characteristics of hydrogeochemical facies. Water quality index using quality rating scale to evaluate the suitability of water for drinking purpose shows that 3.23% and 93.54% of groundwater samples fall within excellent and good water quality, respectively. On the other hand 3.23% of groundwater samples fall within poor water quality. From the computation of SAR values it was found that 97% of groundwater samples are in suitable class and the remaining 3% constituting doubtful class for irrigation use. RSC value shows that, 9.67% of groundwater samples fall in good categories for irrigation use. Whereas, 41.93% samples falls in doubtful and 48.38% samples falls in unsuitable categories for irrigation use. In general, geogenic process and anthropogenic activities such as urban sewages and fertilizers are factors governing groundwater chemistry of study area.

Hydrogeochemistry and groundwater quality assessment of the multilayered aquifer in Lower Kelantan Basin, Kelantan, Malaysia

Continual expansion of population density, urbanization, agriculture, and industry in most parts of the world has increased the generation of pollution, which contributes to the deterioration of surface water quality. This causes the dependence on groundwater sources for their daily needs to accumulate day by day, which raises concerns about their quality and hydrogeochemistry. This study was carried out to increase understanding of the geological setup and assess the groundwater hydrogeochemical characteristics of the multilayered aquifers in Lower Kelantan Basin. Based on lithological data correlation of exploration wells, the study area can be divided into three main aquifers: shallow, intermediate and deep aquifers. From these three aquifers, 101 groundwater samples were collected and analyzed for various parameters. The results showed that pH values in the shallow, intermediate and deep aquifers were generally acidic to slightly alkaline. The sequences of major cations and anions were Na+ > Ca2+ > Mg2+ > K+ and HCO3− > Cl− > SO42− > CO32−, respectively. In the intermediate aquifer, the influence of ancient seawater was the primary factor that contributed to the elevated values of electrical conductivity (EC), Cl− and total dissolved solids (TDS). The main facies in the shallow aquifer were Ca–HCO3 and Na–HCO3 water types. The water types were dominated by Na–Cl and Na–HCO3 in the intermediate aquifer and by Na–HCO3 in the deep aquifer. The Gibbs diagram reveals that the majority of groundwater samples belonged to the deep aquifer and fell in the rock dominance zone. Shallow aquifer samples mostly fell in the rainfall zone, suggesting that this aquifer is affected by anthropogenic activities. In contrast, the results suggest that the deep aquifer is heavily influenced by natural processes.

Understanding fluid behavior through ion and isotope data from the Yitong Basin, Northeast China

To evaluate ion origins and fluid behavior, the chemical properties of thermal water sampled from the Eocene reservoir in the Yitong Basin (YB), Northeast China, were investigated. The thermal water samples are classified as Na–HCO3-type water and were fully equilibrated, except for Sijixiangkang (SJXK) and Yitong (YT). The cations originate mainly from water–rock interactions (e.g., albitization and weathering of plagioclase), while the anions originate from magmatic volatiles and leaching of limestone and granite, which were heated by hot magmatic volatiles and exhibited an evaporation-like pattern in the Gibbs diagrams. The existence of magmatic volatiles was verified by the high ion ratio, the minor-element origins, δ13C values of HCO3, and δ34S values of SO4, which flowed upward along lithospheric faults, with higher fluxes in the northeast than in the southwest (the δ13C value of the Chaluhe depression (CD) is 0.93‰ lower than that of the Moliqing depression (MD, 1.63‰)). Furthermore, according to the Br/Cl and HCO3−/Cl ratios and the δ13C values, we speculate that a deep Permian limestone reservoir exists below the granitic unit. Based on the ion origins and fluid potentials, we conclude that the CD and MD are open systems rather than closed systems. The recharged water migrates from the margin to the center in the plane, and in the vertical direction, it migrates from the Yongji (E2y) and Sheling (E2sh) strata to the overlying strata and underlying Shuangyang (E2s) strata along faults. By summarizing all of the available data, we proposed a conceptual model of fluid migration.

Hydrogeological Modelling of Some Geothermal Waters of Ivrindi, Havran and Gönen in the Province Capital of Balikesir, Western Anatolia, Turkey

In this study, hydrogeological, hydrogeochemical and isotope geochemical features of Havran, Gönen and Ivrindi within the province capital of Balıkesir, Turkey were investigated in detail. The Early Triassic Karakaya formation in the study area of Havran forms the oldest rocks consisting of spilitic basalts, diabases, gabbros, mudstones, cherts and radiolarites. There are limestone blocks in this formation with intercalations with sandstones and with feldspar contents, quartzite, conglomerates and siltstones. Oligocene to Miocene granodiorite intrusions were generated in association with intensively volcanic events in the area. Between Upper Oligocene and Early Miocene, andesitic and dacitic pyroclastic rocks cropped out due to intensively volcanism. Later, conglomerates, sandstones, claystones, marls and limestones as lacustrine sediments formed from Middle to Upper Miocene in the study area. In the study area of Gönen, the Lower Triassic Karakaya formation consists of basalts, diabases, gabbros, mudstones, cherts and radiolarites and forms the basement rocks overlain by Upper Jurassic to Lower Cretaceous sandy limestones. Upper and Middle Miocene volcanics which can be considered intensive Biga Peninsula volcanos outcrop in the area. These andesitic lava flows are of black, gray and red color with intensive fissures. Neogene lacustrine sediments consist of conglomerates, sandstones, marl, claystone and clayey limestones. Upper Miocene to Pliocene rhyolitic pyroclastics and dacitic lava flows are the volcanic rocks which are overlain by Pliocene conglomerates, sandstones and claystones. In the study area of Ivrindi, the Çaldağ limestones are the oldest formation in Permian age. Çavdartepe metamorphic rocks are of Lower Triassic in which can be observed marbles sporadically. The Kınık formation consisting of conglomerates, sandstones, siltstones and limestones are of Lower Triassic age and display a lateral Stratigraphic progress with volcanic rocks. Upper Miocene to Pliocene Yürekli formation consists of dacites and rhyodacites. Upper Miocene to Pliocene Soma formation is composed of clayey limestone, marl, siltstone, intercalations of sandstone, agglomerate and andesitic gravels and blocks cemented by tuffs. Quaternary alluvium is the youngest formation. The samples of geothermal waters in the area of Havran can be considered as Na-Ca-(SO4)-HCO3, Na-(SO4)-HCO3 and Na-SO4 type waters. In comparison, the geothermal waters in Gönen are of Na-(SO4)-HCO3 and Na-HCO3 type waters. The geothermal waters of Ivrindi are considered as Na-Ca-HCO3 type waters. In the area, a groundwater sample is of Ca-Mg-HCO3 type water.The geothermal waters belong to the cations of Na+K>Ca>Mg in Havran, Gönen and Ivrindi and to the anions of SO4>HCO3>Cl in Havran, HCO3>SO4>Cl in Gönen and SO4>HCO3>Cl in Ivrindi. In the diagram of Na-K-Mg1/2, the geothermal waters in Havran, Gönen and Ivrindi of the province capital of Balıkesir can be classified as immature waters.

English

Groundwater compositions could be altered significantly due to geogenic and anthropogenic inputs from rock and human respectively. Such impacted water may be injurious to health if consumed. Studies of groundwater within the lateritic overburden on migmatite gneiss and pegmatised schist in Ibadan area were undertaken with the aim of determining their physico-chemical composition and portability. Groundwater within lateritic profiles over NE-SW trending migmatite and pegmatised schist were sampled. The temperature of the water ranged from 23.9 to 32.7°C, electrical conductivity from 60 to 580 µS/cm, pH from 5.5 to 7.3 and TDS from 55 to 422 mg/L. The concentrations of cations in mg/L ranged for Ca2+ (62.2-79.4), Mg2+ (7.5-15.3), Na+ (28.2-54.3), and K+ (55.0-85.1) while the anions are HCO3- (116.1-149.2), SO42- (0.0-1.1), Cl- (8.2-22.1) and NO3- (0.3-2.2) mg/L. These chemical data are characteristic of Na-(K)-HCO3 water type. The cations, anions and the trace metals of the groundwater are generally within the WHO standards. The low level of chemical constituents in the groundwater reflects geogenic input arising from weathering of the basement rocks. The water is good for domestic, industrial and irrigation purposes. Key words: Groundwater, water portability, migmatite, pegmatised schist, hydrochemistry.

Hydrochemical investigations of groundwater quality for drinking and irrigational purposes: two case studies of Koprivnica-Križevci County (Croatia) and district Allahabad (India)

The hydrochemical study was conducted to outline the suitability of groundwater for drinking and irrigational purposes of two distinctly located geographical areas, Koprivnica-Križevci County, Croatia and district Allahabad, India. A total 160 groundwater samples were collected from sources (in hot and cold seasons) of both countries during 2 years (2011–2012) to evaluate the recent hydrochemical status of groundwater. Samples were analyzed for 12 various physico-chemical parameters.The Koprivnica-Križevci County has Ca–HCO3 water type, whereas in Allahabad it prevails as Mg–HCO3. All the parameters were below the maximum acceptable value (MAV) of standards (WHO, US EPA, Indian and Croatian Standards). The usage and consumption of groundwater should be of no concern with regard to inorganic pollutants. Irrigational indices (residual sodium carbonate content, magnesium hazard, permeability index, exchangeable sodium percentage, and salinity hazard) showed that groundwater is suitable for irrigational purposes. Hierarchical clustering analysis (HCA) has resulted into four groups due to the processes on natural and anthropogenic factors. The principal component analysis (PCA) has shown that first factor (all physico-chemical analyzed variables) explains 27.75% of the total variability and another factor (geographical distribution) accounts only for 10.46%. We found that local environmental conditions are more important predictor than geographical distribution. The present study may be helpful in dealing for further studies concerning groundwater quality issues in the distinctly located geographical areas. The groundwater quality is essential for management and sustainability of water resources, economic development, and human health.

Geochemical evaluation of thermal springs in Odisha, India

The Indian state of Odisha has a number of thermal springs. These thermal springs are located at eight places (Attri, Tarabalo, Deulajhari, Magarmuhan, Bankhol, Badaberena, Taptapani and Boden) and belong to Mahanadi Geothermal Province, which is an Archean/Pre-Cambrian Geothermal Province. The thermal water discharging from these springs shows moderately acidic to moderately alkaline character (pH: 5.05–8.93) and the temperature ranges from 28 (Boden) to 58 °C (Tarabalo). Total dissolved solids (TDS) also shows a wide variation between 16.9 (Bankhol) and 595 mg/L (Deulajhari). A wide variation in the chemical characteristics of the thermal waters has been observed as they are located in different geological settings. Based on water chemistry, all the thermal springs can broadly be grouped into three water types: Na–Cl, Ca–HCO3 and Na–HCO3. The thermal spring water from Attri, Tarabalo and Deulajhari belongs to Na–Cl water type which is due to the circulation through granitic rocks. Higher concentrations of Cl and F in these thermal waters further suggest limited mixing and longer residence time as compared to the other areas where Ca–HCO3 and Na–HCO3 water types were found. Anion variation diagram clearly indicates that the thermal waters from Attri, Tarabalo and Deulajhari are fast ascending and fall in the mature water field; thus, their chemical signatures can be used to determine the reservoir temperature. However, in other areas, water chemistry is shaped by near-surface groundwater mixing processes and thus the chemical geothermometers may not be applicable to determine the reservoir temperature. No appreciable temporal variations have been observed in the water chemistry of the thermal waters.

Integrated approach for identifying the factors controlling groundwater quality of a tropical coastal zone in Kerala, India

The present study examined the factors controlling shallow groundwater quality in two coastal panchayaths (viz., Chennam-Pallippuram and Thykkattussery) of Alappuzha district, Kerala, India, for three sampling seasons: pre-monsoon, monsoon and post-monsoon. The hydrochemical analysis shows significant seasonal fluctuations in groundwater quality, which are principally controlled by the climatic seasonality, contributed by the monsoon phenomenon. The groundwater is highly polluted due to organic load, which is manifested as high total and fecal coliform (TC and FC) contents, especially during MON. Fresh water recharge during MON contributes Ca–Mg–HCO3 type waters, whereas Ca–Mg–Cl and mixed cations-Cl types during PRM imply interaction between groundwater and saline/brackish water of the lake surrounding the study area. Such interaction is also evident by various ionic ratios (e.g., Mg2+/Ca2+, Na+/Cl−) as well as the correlation between Cl− and SO4 2−. The Ca2++ Mg2+ versus TZ+ relationship indicates significance of weathering of carbonate and silicate minerals as well as interaction between groundwater and aquifer matrix, which is also supported by the positive chloro-alkaline indices. Isotopic composition of the groundwater and lake water also suggests the influence of fresh water recharge (mainly during monsoon) as well as interaction of groundwater with lake water in controlling groundwater quality. Factor analysis proposes three dominant processes controlling groundwater quality of the region: (1) interaction of groundwater with brackish water of the Vembanad Lake, (2) geogenic/atmospheric sources, such as weathering, groundwater interaction with aquifer matrix, atmospheric inputs and fresh water recharge and (3) diverse anthropogenic sources of contamination (e.g., domestic waste, septic tanks, and agricultural residues). However, relative influence of these factors on groundwater quality varies temporally to form groundwater with differing chemical composition among the seasons. The present study underscores the exigency to ensure availability of safe drinking water for the coastal zones.

Hydrochemical characteristics of groundwater and surface water for domestic and irrigation purposes in Vea catchment, Northern Ghana

The Vea catchment, mainly underlain by crystalline basement rocks, is located in Northern Ghana. Hydrogeochemical studies were carried out in this area with the objective of identifying the geochemical processes influencing water quality and suitability of surface and groundwater for agricultural and domestic uses. Sixty-one groundwater and four surface water samples were collected from boreholes, dams and rivers and analysed for Ca2+, Mg2+, Na+, K+, HCO3 −, Cl−, and SO4 2−, Fetot, PO4 3−, Mntot, NH4 +, NO3 −, NO2 −. In addition, pH, total dissolved solids, electrical conductivity, total hardness, turbidity, colour, salinity and dissolved oxygen were analysed. Chloro-alkaline indices 1 and 2, and characterization of weathering processes suggest that the chemistry of groundwater is dominated by the interaction between water and rocks. Cation exchange and silicate weathering are the dominant processes controlling the chemical composition of the groundwater in the area studied. Mineral saturation indices indicate the presence of at least three groups of groundwater in the Vea catchment with respect to residence time. The meteoric genesis index suggests that 86% of the water samples belong to the shallow meteoric water percolation type. The findings further suggest that the groundwater and surface water in the basin studied are mainly Ca–Mg–HCO3 water type, regardless of the geology. Compared to the water quality guidelines of WHO, the study results on sodium absorption ratio, sodium percentage, magnesium hazard, permeability index and residual sodium carbonate indicate that groundwater and surface water in the Vea catchment are generally suitable for drinking and irrigation purposes.

Geochemistry and Hydrothermal Contamination of the Atemajac-toluquilla Groundwater System (Guadalajara, Mexico)

Chemical and isotopic data were used to explain the geochemistry and the hydrothermal influence in a groundwater system in Guadalajara, México. According to the measured parameters and the characteristics of the groundwater, four water groups were identified: i) thermal waters with high temperatures and high concentrations of Cl, Na, HCO3 and the presence of Li, Mn, F and Mg, apparently of old age with a long residence time; ii) mixed waters of Na-HCO3 to HCO3 water type, which represent a mixture of cold water and thermal water; iii) polluted water characterized by high concentrations of nitrate and sulfate derived from urban and agricultural return flow; iv) cold water characterized by low temperature values, low concentration of Cl, Na and salinity, of Na-HCO3 type. This last group represents modern water located in the recharge zone. Finally, major proportions of hydrothermal fluids are largest in the well waters of the first group varying from 1.9 to 12.5%. The other groups show hydrothermal fractions below 1.7%. Groundwater with elevated hydrothermal proportions is located to the southeastern area of the Toluquilla aquifers. This study identifies some processes that govern the groundwater and hydrothermal mixing.