Ca-HCO3 Water Type Research Articles

Major Ions and Trace Elements Characterization of Groundwater in Shallow Aquifers, Yaoundé Urban City, Cameroon

Purpose: This study assessed the suitability of groundwater in parts of Yaoundé city for drinking and domestic purposes, investigating the factors controlling its composition. Materials and Methods: Water samples were collected during the dry season and analyzed for physicochemical parameters and major ions. Findings: Results showed an acidic aquifer with generally fresh water, dominated by Ca-HCO3, Na-Cl, Ca-NaHCO3, and Ca-Cl water types. While most major ions were within WHO guidelines, nitrates exceeded safe limits in most samples, and some trace elements like aluminum, manganese, and iron were also above recommended levels. Implications to Theory, Practice and Policy: The study concludes that groundwater quality is influenced by water-rock interaction, ion exchange, and anthropogenic activities, particularly nitrate and chloride pollution. Therefore, proper groundwater management strategies are crucial to ensure the sustainability and safety of this vital resource.

Hydrogeochemical and microbial constituents of groundwater in Lephalale municipality, Limpopo province, South Africa

This study assessed the hydrogeochemical characteristics and microbial constituents of groundwater in Lephalale Municipality, South Africa. A total of 71 borehole water samples were collected from 15 villages within the Lephalale Municipality between April 2019 and October 2020. The results of the parameters such pH, EC, TDS, and alkalinity range from 6.69 to 7.87, 620.30 to 1937.00 μS/cm, 330.35 to1035.50 mg/L and 50.00-390.00 mg/L, respectively. The mean values of major cations and anions were found to be in the order of Na+>Ca2+>Mg2+>K+ and HCO3−>Cl−>NO3−>SO42−>F−, respectively. About 35 % of the tested samples had F− concentrations above 1.5 mg/L recommended by the world health organization (WHO) to eliminate the risk of fluorosis. The hydrogeochemical facies determined using a piper diagram revealed the dominance of mixed CaMgCl and CaHCO3 water types. The Gibbs plot analysis revealed that the main composition-controlling hydrogeochemical processes in the study area is the rock-water interaction. The microbial constituent's analysis showed that faecal coliform in groundwater samples were ranging between 0 and 71 CFU/ 100 mL with an average of 0.56 CFU/100 mL, while total coliform (TC) counts were between 0 and 360.5 CFU/100mL with the average of 30.81 CFU/100mL, respectively. This study revealed that groundwater in some boreholes from Lephalale Municipality poses risk of fluorosis and pathogen related diseases. Therefore, the study recommends improving of water quality within the study area prior to consumption.

Active CO2 emissions from thermal springs in the Karakoram fault system and adjacent regions, western Tibetan Plateau

Large-scale intra-continental strike-slip faults provide the pathways for groundwater circulation and the release of CO2-rich fluids through thermal springs, which is a significant type of deep CO2 emissions into the atmosphere and hydrosphere. India-Asia collision created numerous strike-slip faults and thermal springs in the Tibetan Plateau and adjacent regions, but their CO2 origins and fluxes are still not well understood. Here, we present a quantitative study on CO2 emissions from thermal springs in the Karakoram fault system (KKFS) and adjacent regions, western Tibetan Plateau, with the aim of revealing the origins of CO2-rich fluids and estimating the dissolved and gaseous CO2 fluxes. Hydrogen and oxygen isotopic data show that the geothermal waters were recharged by local precipitation (e.g., rainfall and snow-melt water) and experienced variable degrees of water-rock interaction, giving rise to the dominant Na–HCO3 type and minor Na–Cl and Ca–HCO3 type waters discharging from thermal springs. Spatially, the thermal springs within or close to the KKFS (Group 1 and Group 2) have larger circulation depths of 1.3–5.1 km, while those away from the KKFS (Group 3) exhibit shallow (0.6−0.8 km) groundwater circulation. Mass balance calculations reveal high deeply-sourced carbon inputs (60.4−94.3%) to dissolved inorganic carbon (DIC) of the Group 1 and Group 2 samples, while the Group 3 samples have higher shallow carbon contributions (50.4−60.9%) to DIC via dissolution of carbonate and organic carbon. This is consistent with higher Δ14CDIC values (−788.6‰ to −692.1‰) in Group 3 samples and the lack of radioactive 14C in Group 1 and Group 2 samples (Δ14CDIC = −999.9‰ to −985.9‰). Based on chemical compositions and fluxes of spring water and bubbling gases, the total CO2 output from thermal springs (including dissolved and gaseous CO2) in the KKFS is estimated to be ∼2332 t a−1, in which the endogenic carbon such as metamorphic CO2 accounts for ∼1863 t a−1. Our results provide the first estimate of deep CO2 flux for the KKFS and would contribute to a better understanding of active CO2 emissions facilitated by strike-slip faulting processes in continental collision zone.

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.

Hydro-geochemistry and Related Processes Controlling the Composition of Thermal Waters in the Lake Natron Basin, Northern Tanzania

Lake Natron Basin (LNB) forms part of the eastern branch of the East African Rift System (EARS) in Tanzania. The basin is endowed with thermal springs flowing towards the lake from the western, northwestern, southwestern and eastern parts. The western, northwestern and south-western thermal springs emanate from fractures in the basaltic rocks while in the east, they originate from the western flank of the Gelai volcano. There are limited studies on these springs, thus their geochemical differences and distributions of physicochemical parameters are not well understood. A hydrogeochemical study was conducted to interpret available geochemical data from the LNB springs, including cold and thermal water to allow their geochemical characterization. Results have shown that LNB water is dominated by sodium (Na+), chloride (Cl-) and bicarbonate (HCO3-) ions. Three hydro-chemical facies have been identified forming Na-Cl, Na-HCO3 and Ca-HCO3 water types. This study has also revealed that thermal water in the north-western part of the basin is highly mineralised and gradually becomes diluted toward south-west and south due to groundwater incursion. Water-CO2-rock interaction affects the overall chemistry of thermal water leading to HCO3- water, particularly in the east of the basin. While few springs from the western side of the basin indicated maturity of the thermal waters, other springs indicated mixed Cl-HCO3/peripheral water; while the cold waters are HCO3 type. It is recommended to take precautions when planning geothermal projects to avoid corrosion and scaling of production facilities. Similarly, mixing or dilution of thermal water with shallow groundwater can affect the temperature and the composition of Cl-.

Groundwater Quality and Potential Pollution in the Southern Shimabara Peninsula, Japan

Nitrate pollution in groundwater is a severe problem in Shimabara Peninsula, Nagasaki Prefecture, Japan. Previous studies have investigated water quality characteristics in the northern part of the peninsula and shown serious effects of nitrate pollution in the groundwater. The present study aimed to investigate the groundwater quality in the southern areas of the peninsula for improved understanding of the water quality status for the entire peninsula. Groundwater samples were collected at 56 locations in Minami-Shimabara City from 28 July to 4 August 2021. The spatial distribution of water quality constituents was assessed by Piper-trilinear and Stiff diagrams for major ion concentrations. One agricultural area in the western parts exceeded Japanese recommended standards for water. According to the Piper-trilinear diagram, 44 sampling sites (78.6%) were classified as alkaline earth carbonate type, nine sites (16.1%) as alkaline earth non-carbonate type, and three sites (5.3%) as alkaline carbonate type. Stiff diagrams displayed Ca-HCO3 water type for most of the sites. Na-HCO3 and Mg-HCO3 types were found in coastal areas. Principal component analyses showed that the first component corresponded to dissolved constituents in groundwater and denitrification, the second effects of ion exchange and low nitrate pollution, and the third effects of severe nitrate pollution. Hierarchical cluster analysis was used to classify the groundwater into five groups. The first group included sites with relatively high nitrate concentration. The second group had relatively low ion concentration, distributed from center to eastern parts. The third group included intermediate ion concentration, distributed at lower altitudes along the coastal line. The fourth and fifth groups had a higher ion concentration, especially characterized by high sodium and bicarbonate concentration.

Natural occurrence and controls of arsenic in groundwater in a semiarid basin in the Mexican Altiplano

The sources, mobility, and controlling processes of arsenic (As) in an aquifer system in the Cerritos-Guadalcazar area of Central Mexico were investigated. High As concentrations (up to 128 μg/L) in groundwater were found to be associated with both primary sources (rocks and tailings) and secondary sources (soil and sediments). The high As concentrations in the otherwise pristine Cerritos shallow granular aquifer are the result of a distant source of As-rich sediments eroded from a mineralized area in the recharge zone of a karstic aquifer. An intermediate groundwater flow system delivers the As load from the karstic to the granular aquifer. In addition, identification of a Na–Cl water type in the shallow granular aquifer indicates a regional flow; however, additional information is needed to corroborate this assumption. Local flows in the karstic aquifer are Ca–HCO3 water type with low (<1 μg/L) dissolved As concentrations. Principle axis factor analysis shows distinct groupings associated with different aquifer characteristics. The sulfate factor dominates in the southern area of the granular aquifer, which explains 30% of the total variance. The arsenic-uranium factor is expressed in samples from deep and dug wells tapping the basin sediments. A conceptual model was developed where the path of the As is shown. Three groups of samples showed negative correlation among deuterium excess and As concentrations. Evaporation modeling to simulate the As enrichment showed that evaporation processes play an important role in As behavior. This research can provide a tool for further studies in the Sierra Madre Oriental.

Integrated Hydrogeochemical Analysis of Stream Water in Parts of Proterozoic Shillong Basin Meghalaya, India

Hydrogeochemical surveys were conducted in parts of the Proterozoic Shillong basin in Meghalaya to locate the unconformity-related uranium deposits, related alteration patterns, and the influence of the rock formations on the groundwater solute chemistry. Shillong Basin comprises Proterozoic metasediments and felsic volcanics of Tyrsad Formation, undeformed arenaceous Barapani Formation with intrusive granites, and metabasic sills and dykes. The groundwater quality is determined for drinking, and domestic-agro-industrial utilities using hydrogeochemical tools and physicochemical parameters. The water is acidic to slightly alkaline and has an oxidizing redox environment, Electrical Conductivity (EC), Total Dissolve Solids (TDS), and major ions fell below the World Health Organization (WHO) and Indian Standards Institute (ISI) acceptable limits except for Zn, Fe, and SiO2 showing higher concentrations.The sequences of abundance of major cations and trace elements are Fe&gt;Zn&gt;SiO2&gt;Ca2+&gt;Na+ &gt;Mg2+&gt;K+ &gt;U and anions as HCO3&gt;Cl- &gt;SO4 2- .Groundwater character was assessed by ion exchange, simple dissolution, and unusual dissolution mechanisms. The area has dominant CaHCO3, NaHCO3, and restricted CaMgHCO3 type water. Plagioclase dissolution and high SiO2 and cation exchange of Ca for Na were identified. The groundwater indices of Sodium Percent, Kelley’s Index, Sodium Adsorption Ratio, Magnesium Ratio, Electrical Conductivity, TDS, USSL, and Wilcox index were found suitable for agro-industrial uses. Permeability Index is found to be suitable in most areas and the Corrosivity Ratio shows the areas of galvanized pipes and PVC pipes to be used for water supply. AHC analysis shows three distinct groups of water types, as well as the factor analysis, also shows the three prominent factors of water types defining the dimensionality of water types. Magnesium metasomatic alteration zones and Zn anomalous zones are delineated.

Characterizing the Groundwater Flow Regime in a Landslide Recharge Area Using Stable Isotopes: A Case Study of the Urbas Landslide Area in NW Slovenia

Slope stability strongly depends on the prevailing hydrological and hydrogeological conditions. The amount and intensity of precipitation and changing groundwater levels are important landslide triggering factors. Environmental tracers, including the chemical and stable isotope compositions of precipitation and groundwater, were used to gain insight into the groundwater dynamics of the Urbas landslide. The landslide is situated in a mountainous area with steep slopes and high precipitation amount and poses a high risk for the safety of the Koroška Bela settlement that lies downstream. The stable isotope analyses of oxygen-18 (18O) and deuterium (2H) in the precipitation and groundwater were used to estimate the groundwater mean residence time and the average altitude of the landslide recharge area. This information will help to plan and prioritize remedial landslide measures aiming to reduce the recharge of the landslide body and, thus, lower the risk of transformation of the sliding material into debris flow. The results of the chemical analysis of samples taken from springs and a piezometer show a Ca–HCO3 water type. This indicates low water–rock interaction in a landslide area composed of Upper Carboniferous and Permian clastic rocks and points to upper laying carbonate rocks and scree deposits as the main recharge area. Water samples for stable isotope analyses of δ18O and δ2H were collected from a rain gauge, springs, and a piezometer over a two-year period (2018–2020). The estimated mean recharge altitude of the groundwater at sampling points was from approximately 1700 to 1800 m a.s.l. with a mean residence time of 2–5 months.

Catchment-scale impacts of shallow landslides on stream water chemistry

Catchment water quality plays an important role in ecosystem and water resource management in mountainous areas. Shallow landslides triggered by earthquakes or heavy rainfall can cause a sudden and long-term deterioration in stream water quality by releasing contaminants into streams. Although many studies have been undertaken on the relationship between a single landslide and the water chemistry of a nearby river, little is known about the impact of densely distributed shallow landslides on stream water chemistry at the catchment scale. To this end, this study determined the major ion concentrations and isotopic compositions of stream water along with the shallow landslide area/catchment area ratio (LCR) in 37 headwater subcatchments in the southern part of Hokkaido, Japan, where an earthquake caused more than 6000 shallow landslides on September 6, 2018. In subcatchments with a high LCR, stream water exhibited significantly higher Ca2+ and HCO3− concentrations, while there was no correlation between the LCR and concentrations of Na+ and Cl−. The δ18O and δD values of stream water plotted between the local meteoric water lines of summer and winter precipitation, indicating that they originated from meteoric water. Shallow landslides formed sliding surfaces, landslide deposits, and landslide-dammed lakes, which enhanced the interaction between the surface soil and stream water, leading to Ca–HCO3 type water. The results showed that shallow-landslide-driven changes in stream water quality could be linearly approximated by the fraction of the landslide area at the catchment scale, which is a more versatile approach than the local framework of a single landslide and a nearby stream. In future research, these findings could be combined with a slope stability model and the background climatic, geological, topographical, and water quality conditions of a watershed to evaluate water pollution triggered by shallow landslides at the catchment scale.

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+ &gt; Ca2+ &gt; Mg2+ &gt; K+ and HCO3-&gt; Cl-&gt; 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.

Groundwater quality assessment using principal component analysis and hierarchical cluster analysis in Alaçam, Turkey

Abstract This study assessed groundwater quality in Alaçam, where irrigations are performed solely with groundwaters and samples were taken from 35 groundwater wells at pre and post irrigation seasons in 2014. Samples were analyzed for 18 water quality parameters. SAR, RSC and %Na values were calculated to examine the suitability of groundwater for irrigation. Hierarchical cluster analysis and principal component analysis were used to assess the groundwater quality parameters. The average EC value of groundwater in the pre-irrigation period was 1.21 dS/m and 1.30 dS/m after irrigation in the study area. It was determined that there were problems in two wells pre-irrigation and one well post-irrigation in terms of RSC, while there was no problem in the wells in terms of SAR. Piper diagram and cluster analysis showed that most groundwaters had CaHCO3 type water characteristics and only 3% had NaCl- as the predominant type. Seawater intrusion was identified as the primary factor influencing groundwater quality. Multivariate statistical analyses to evaluate polluting sources revealed that groundwater quality is affected by seawater intrusion, ion exchange, mineral dissolution and anthropogenic factors. The use of multivariate statistical methods and geographic information systems to manage water resources will be beneficial for both planners and decision-makers.

Multi-isotopic (O, H, C, S, Sr, B, Li) characterization of waters in a low-enthalpy geothermal system in Havza (Samsun), Turkey

In this study, multi-isotopic (O, H, C, S, Sr, B, Li) compositions were used to perform geochemical characterization, determine the source and reservoir rocks, and explain the water-rock interaction mechanisms for geothermal fluids in the low-enthalpy Havza (Samsun) geothermal field (HGF) in Turkey. The geothermal water of Na-HCO3 water type has a wellhead temperature of 53°C, pH of nearly 7.7 and an EC value of 1140 µS/cm. The geothermal springs of Ca-HCO3 water type have an EC value of nearly 667 µS/cm and a temperature of nearly 26°C. The reservoir temperatures of the HGF geothermal system were calculated as 60–90°C and 108–160°C by silica and SO4-H2O oxygen isotope geothermometers, respectively. Stable isotope compositions (δ2H and δ18O) show that the geothermal well water is mixed with deeply circulated waters fed from higher elevations (∼ 830–1260 m), while the geothermal spring water is mixed with shallow cold water. The positive δ13C value (+3.01‰) indicates that the dissolved inorganic carbon (DIC) in the geothermal well water has no contribution from the atmospheric CO2 but originates in the metamorphic CO2 and marine limestones. However, the DIC in the geothermal springs is derived from C3 plants and silicate weathering. The values of 34SCDT show that the sulfate in the geothermal waters is due to the dissolution of sulfate minerals. The values of δ11B (-1.12 to +9.37 ‰) in the geothermal well and spring waters reflect both leaching of surrounding rocks and mantle-derived B. The reservoir rock may be Late Cretaceous-Permian limestones and Jurassic sandstones considering 87Sr/86Sr ratios (0.707108–0.707688) and δ7Li values (-7.44 to +6.18 ‰), whereas it might be Jurassic sandstones based on δ11B values. The strontium isotope composition of the geothermal spring water indicates the mixing of deep geothermal waters and cold groundwaters.

Arsenic contamination of irrigation wells and associated human health hazards in the Punjab plains of Pakistan

In the present study, the tubewell water quality, emphasizing on As contamination, were investigated in the Punjab plains of Pakistan. The Na-Cl water type is dominated in Doabs (Rechna and Chaj) whereas Ca-HCO3 water type is dominated in Ravi flood plain. Concentrations of As in well water (65 ± 32 μg/L) are higher in the floodplains of the Ravi River compared to the Chenab (13 ± 9 μg/L) and Jhelum (4 ± 5 μg/L) rivers, as well as in the intervening Rechna (6 ± 6 μg/L) and Chaj doabs (0.8 ± 0.2 μg/L). The average Hazard quotients (HQ) is 9.09E+00 and Potential Cancer Risk (CR) is 4.09E−03 in Ravi flood plain which indicates the potential health risk to the consumers of well water for drinking purposes and also long term irrigation with this water will result As accumulation in paddy soil. Based on average values, the Sodium Adsorption Ratio (SAR), Magnesium Hazard (MH), %Sodium (%Na) and Kelly Ratio (KR) follows the sequence Rechna Doab>Chaj Doab>Chenab floodplain>Jhelum floodplain>Ravi floodplain in 5 geographic units, suggesting low salinity water in floodplains and saline water in Doabs.

Genesis of thermal waters from the Taşkesti-Sarıot geothermal prospect in Mudurnu (Bolu, NW Turkey)

The Taşkesti–Sarıot study area is located in northwest Turkey, about 23 km NW of Mudurnu town in the Bolu province. The thermal waters of the Taşkesti–Sarıot were investigated by means of field measurements, chemical analyses and isotope investigations. An area of 20 km2 was geologically mapped around the spa and characteristics of thermal and cold-waters were determined. The Taşkesti-Sarıot thermal waters, (T °C = 63, and flowrate of 1.70 L/sec) emanates along a secondary fault in the North Anatolian Fault Zone (NAFZ). Geothermal water reservoirs are present within fractured limestone, micaschists, diorite, tonalite, serpentinite, gabbropegmatites and graywacke which have the secondary porosity and permeability. Based on the main consitituents, the thermal waters can be classfied as Na(Ca)SO4 types, whereas the cold and stream waters were characterized as a Ca(Mg)HCO3 type waters. Geochemical processes responsible for the genesis of the hydrochemical features of the waters include dissolution, mixing, oxidation and loss of energy by heat conduction. Chemical geothermometers suggest deep temperatures close to 100 °C for the deepest geothermal well (SK-1: 63 °C at the surface) water in the region and thus the Taşkesti-Sarıot geothermal system can be classified as a low temperature resource.These thermal waters are of meteoric origin that circulate and restores heat through the fault zone due to the geothermal gradient and discharge to the surface. The thermal waters are derived from advective flow as indicated by the δ2H and 18O isotope data, which plot on the meteoric water line showing a significant downward shift if compared with a local reference point thus indicating recharge by infiltration derived from a high standing (colder) terrain. The recharge area for the thermal waters is estimated to be nearly 1000 – 1600 m from the northeast part of the study area. Moreover, there is no evidence for isotope exchange between hot waters and reservoir rock. Tritium data confirm the deep origin of the thermal waters. Finally, a conceptual geochemical model of the geothermal system is proposed.

Evaluation of Seasonal Groundwater Quality Changes Associated with Groundwater Pumping and Level Fluctuations in an Agricultural Area, Korea

This study was conducted to evaluate seasonal groundwater quality due to groundwater pumping and hydrochemical characteristics with groundwater level fluctuations in an agricultural area in Korea. Groundwater levels were observed for about one year using automatic monitoring sensors, and groundwater uses were estimated based on the monitoring data. Groundwater use in the area is closely related to irrigation for rice farming, and rising groundwater levels occur during the pumping, which may be caused by the irrigation water of rice paddies. Hydrochemical analysis results for two separate times (17 July and 1 October 2019) show that the dissolved components in groundwater decreased overall due to dilution, especially at wells in the alluvial aquifer and shallow depth. More than 50% of the samples were classified as CaHCO3 water type, and changes in water type occurred depending on the well location. Water quality changes were small at most wells, but changes at some wells were evident. In addition, the groundwater quality was confirmed to have the effect of saltwater supplied during the 2018 drought by comparison with seawater. According to principal component analysis (PCA), the water quality from July to October was confirmed to have changed due to dilution, and the effect was strong at shallow wells. In the study areas where rice paddy farming is active in summer, irrigation water may be one of the important factors changing the groundwater quality. These results provide a qualitative and quantitative basis for groundwater quality change in agricultural areas, particularly rice paddies areas, along with groundwater level and usage.

The Influence of Non-Engineered Municipal Landfills on Groundwater Chemistry and Quality in Bloemfontein, South Africa.

This study assessed the groundwater quality around two municipal solid waste landfill sites, in the city of Bloemfontein, Free State Province, South Africa. The two landfill sites are located in two contrasting geological terrains, with both lacking some basic facilities found in a well-designed landfill. A total of eight groundwater samples were collected from pollution monitoring boreholes near the two landfill sites, with five samples representing the northern landfill site and three samples representing the southern landfill site. The samples were collected in the autumn and winter seasons to assess any possible seasonal variations. They were analysed for physicochemical (pH, electrical conductivity (EC), total dissolve solids (TDS), chemical oxygen demand (COD) and total organic carbon (TOC)) and microbiological parameters (Escherichia coli, total coliform). The results of the analysis showed that the waters from both landfills were generally dominated by Ca, Mg, SO4, and HCO3 ions. Some of the major anions and cations in the water samples were above the South African National Standard (SANS241:2015) and World Health Organisation (WHO) permissible limits for drinking water. Majority of the boreholes had total dissolved solids and electrical conductivity values exceeding the SANS 241:2015 and WHO permissible limits. Piper trilinear plots for the two landfill sites showed that Ca(Mg)HCO3 water type predominates, but Ca(Mg)SO4 and Ca(Mg)Cl were also found. These water types were further confirmed with expanded Durov diagrams, indicating that that the boreholes represented a water type that is seldom found which is undergoing ion exchange, typical of sulphate contamination. From the SAR diagrams, boreholes in the northern landfill site had a high salinity hazard with only one borehole in the southern landfill site having a high salinity hazard. The geology was found to play a significant role in the distribution of contaminants into the groundwater systems in the study area. The study concluded that the northern landfill site had a poorer water quality in comparison to the southern landfill site based on the analysed physicochemical parameters. However, the southern landfill site showed significant microbial contamination, due to the elevated amount of E. coli and total coliform concentrations. The high permeability of the weathered dolerites in the northern landfill site might have enabled the percolation of contaminants into the groundwater resulting in the poorer water quality.

An assessment of the effects of excessive groundwater abstraction on the quality of groundwater resources of the Zanjan Plain, Iran

In the present study, the quality of groundwater and the effects of pumping on the phreatic surface beneath the Zanjan Plain located in northwestern Iran were investigated by measuring water levels in 81 observation wells as well as various physicochemical parameters including electrical conductivity (EC), total dissolved solids (TDS), total hardness (TH) and pH. In addition, the results of the chemical analysis of major anions and cations from 53 boreholes that were sampled during the period 2004–2018 were evaluated. The water level measurements indicated that the elevation of the phreatic surface had declined by up to about 8 m during the studied period, indicating an average decrease of about 0.57 m per year. A comparison of the measured physicochemical parameters with WHO, ISIRI, and EPA standards for drinking water quality showed that some parameters including EC, TDS, TH, SO4, and Cl in the northwestern and central parts of the plain exceeded the allowable level. An assessment of water quality index (WQI) values showed that most parts of the Zanjan Plain lie in the “good” quality class, although in some parts, the water quality of “poor” quality class, most likely due to the effects of urban activities. A comparison of the results from a Schoeller diagram assessment with WQI values showed some differences between the results of the qualitative classification of some parts of the Zanjan Plain groundwater based on the two mentioned methods. The results of the present study showed that groundwater of some areas of the Zanjan Plain is not suitable to be used for irrigation of agricultural lands with limited drainage. The Piper diagram also indicated that the dominant groundwater quality facies on the Zanjan Plain were Ca–Na–HCO3 and Ca–HCO3 water types. The results of the Spearman correlation analysis also showed a high correlation of most anions with cations. Analysis of the volume changes versus qualitative changes in groundwater also showed a general decreasing trend of water quality with decreases in the volume of groundwater in storage in the aquifer, although in some conditions due to changes in solubility of water-soluble materials because of the changes in groundwater level, other trends were also observed.

Non-carcinogenic health risk assessment with source identification of nitrate and fluoride polluted groundwater of Wardha sub-basin, central India

In order to understand the pollution status of groundwater with geochemical evolution and appraisal of its probable public health risk due to nitrate (NO3–) and fluoride (F–), a total of 93 groundwater samples were collected during pre-monsoon (May) period from Wardha sub-basin, central India. By employing Piper plot, transition from Ca–HCO3 type water (recharge waters) to Na–Cl (saline water) type water through mixed Ca–Na–HCO3, mixed Ca–Mg–Cl (reverse ion exchange waters) and Ca–Cl types (leachate waters), were observed. The Geogenic processes such as silicate, dolomite, halite and carbonate weathering along with calcite precipitation and ion exchange process were identified as major controlling factors for evolution and alteration of groundwater chemistry. The Saturation index highlighted that the groundwater in the area is oversaturated with respect to the mineral calcite and dolomite, and under saturated with gypsum, fluorite and halite. The high NO3– and F– concentration overpassing the permissible limit were found in 54.8% and 18.5% of samples. The plot of F– with Na+/Ca2+, Na+/Mg2+ and F–/Cl– established fluoride bearing rock weathering is responsible for F– contamination. Based on the cluster analysis, the groundwater was grouped into Cluster-I Ca–Na–HCO3 type (61.3%) and Cluster-II Na–Ca–HCO3–Cl type (30.1%). The total hazard index (HI) based on human health risk assessment (HHRA) model for cumulative NO3– and F– toxicity through oral and dermal pathways were computed as 100%, 97.85% and 96.77% for children, female and male populations respectively. The HQ(nitrate) > 1 through ingestion pathway were in 84.95%, 68.82% and 62.37%, and HQ(fluoride) > 1 in 83.87%, 62.37% and 43.01% of the groundwater samples were recorded for children, female and male population respectively. The risk assessment study highlighted very high toxicity and severe health impact of ingestion of contaminated groundwater on public health.

Evaluation of shallow groundwater for drinking purpose based on water quality index and synthetic pollution index in Changchun New District, China

Due to the impact of human agricultural production and climate and environmental changes, the applicability of groundwater for drinking purposes has attracted widespread attention. In order to quantify the hydrochemical characteristics of groundwater in Changchun New District and evaluate its quality for drinking purposes, 53 shallow groundwater samples were collected and analyzed. The results show that groundwater in aquifers in the study area is weakly alkaline. The abundance is in the order Ca2+ > Na+ > Mg2+ for cations, and HCO3− > Cl− > SO42− for anions. Ca-HCO3•Cl water type dominated the area, constituting about 26.41% of the total samples; Ca-HCO3 water type constituted about 22.64%; Ca•Na-HCO3 and Ca•Na-HCO3•Cl water types constituted 15.09% each, whereas Ca•Na-HCO3•Cl•SO4, Ca-HCO3•Cl•SO4, and Ca-SO4•Cl types made up 22.64% each. Correlation analysis (CA) and principal component analyses (PCA) show that rock weathering and dissolution, and human activities are the main reasons affecting the chemical composition of water in Changchun. The high concentrations of Pb, NO2−, Fe, and Mn must be widely concerned and may become the main environmental geological problems in the area. The analysis of water samples based on the water quality index model revealed that about 5.66%, 56.60%, 15.09%, 18.86%, and 3.77% of the shallow groundwater samples were excellent, good, poor, very poor, and unsuitable for drinking purposes, respectively. The analysis of groundwater samples based on the synthetic pollution index model showed that more than 37.74% of the groundwater samples were moderately polluted. The spatial distribution maps of the water quality index and the synthetic pollution index show that most of the shallow groundwater resources in the study area are clean and suitable for drinking, despite the risks of the shallow groundwater in the southeast of the study area.