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Having safe drinking water is a fundamental human right, which affects directly the human health. In view of this, an effort has been made for understanding the spatial distribution of quality of groundwater in a rural dry climatic region of Andhra Pradesh, South India, and associated health risks with respect to pollutants of NO3− and F−, which cause the potential production of non-carcinogenic risk, using entropy-weighted water quality index (EWWQI) and total chronic hazard index (TCHI), where the population rely on the groundwater resource for drinking purpose. Groundwater quality observed from the present study region has an alkaline character with brackish type. The concentrations of K+, HCO3−, TDS, Na+, NO3−, F−, Mg2+ and Cl− come under the non-permissible limits in 100%, 100%, 96.67%, 90%, 73.33%, 46.67%, 13.33% and 6.67% of the groundwater samples, which deteriorate the groundwater quality, causing the health disorders. The overall groundwater quality computed, using EWWQI, ranges from 53.64 to 216.59 (122.22), which classifies the region spatially into 55%, 10% and 35% due to influences of the geogenic and anthropogenic pollutants, which are the respective medium, poor and very poor groundwater quality types prescribed for potable water. According to the TCHI evaluated with respect to pollutants of NO3− and F−, the values of TCHI for men (1.194 to 4030), women (1.411 to 4.763) and children (1.614 to 5.449) are more than its acceptable limit of one. So, the health risk of non-carcinogenic is spatially in the decreasing order of children > women > men, depending upon their sensitiveness to pollutants and also their body weights. Further, the spatial distributions of both TCH1 and EWWQI are more or less similar, following the pollution activities, which help for establishment of the fact to recognize the intensity of various vulnerable zones. Therefore, the present study suggests the suitable environmental safety measures to control the NO3−- and F−-contaminated drinking water and subsequently to increase the health conditions.

Quality of groundwater is assessed from a part of Prakasam district, Andhra Pradesh, India. Groundwater samples collected from thirty locations from the study area were analysed for pH, electrical conductivity (EC), total dissolved solids (TDS), calcium (Ca2+), magnesium (Mg2+), sodium (Na+), potassium (K+), bicarbonate (HCO3-), chloride (Cl−), sulphate (SO42-), nitrate (NO3-) and fluoride (F−). The results of the chemical analysis indicate that the groundwater is alkaline in nature and are mainly characterized by Na+–HCO3- and Na+–Cl− facies. Groundwater chemistry reflects the dominance of rock weathering and is subsequently modified by human activities, which are supported by genetic geochemical evolution and hydrogeochemical relations. Further, the chemical parameters (pH, TDS, Ca2+, Mg2+, Na+, HCO3-, Cl−, SO42-, NO3- and F−) were compared with the drinking water quality standards. The sodium adsorption ratio, percent sodium, permeability index, residual sodium carbonate, magnesium ratio and Kelly’s ratio were computed and USSL, Wilcox and Doneen’s diagrams were also used for evaluation of groundwater quality for irrigation. For industrial purpose, the pH, TDS, HCO3-, Cl− and SO42- were used to assess the impact of incrustation and corrosion activities on metal surfaces. As a whole, it is observed that the groundwater quality is not suitable for drinking, irrigation and industrial purposes due to one or more chemical parameters exceeding their standard limits. Therefore, groundwater management measures were suggested to improve the water quality.

Evaluation of groundwater quality and related health hazards is a prerequisite for taking preventive measures. The rural region of Telangana, India, has been selected for the present study to assess the sources and origins of inferior groundwater quality and to understand the human health risk zones for adults and children due to the consumption of nitrate ( NO 3 - )- and fluoride (F − )-contaminated groundwater for drinking purposes. Groundwater samples collected from the study region were determined for various chemical parameters. Groundwater quality was dominated by Na + and HCO 3 - ions. Piper’s diagram and bivariate plots indicated the carbonate water type and silicate weathering as a main factor and man-made contamination as a secondary factor controlling groundwater chemistry; hence, the groundwater quality in the study region is low. According to the Groundwater Quality Index (GQI) classification, 48.3% and 51.7% of the total study region are excellent (GQI: < 50) and good (GQI: 50 to 100) water quality types, respectively, for drinking purposes. However, NO 3 - ranged from 0.04 to 585 mg/L, exceeding the drinking water quality limit of 45 mg/L in 34% of the groundwater samples due to the effects of nitrogen fertilizers. This was supported by the relationship of NO 3 - with TDS, Na + , and Cl − . The F − content was from 0.22 to 5.41 mg/L, which exceeds the standard drinking water quality limit of 1.5 mg/L in 25% of the groundwater samples. The relationship of F − with pH, Ca 2+ , Na + , and HCO 3 - supports the weathering and dissolution of fluoride-rich minerals for high F − content in groundwater. They were further supported by a principal component analysis. The Health Risk Index (HRI) values ranged from 0.20 to 20.10 and 0.36 to 30.90 with a mean of 2.82 and 4.34 for adults and children, respectively. The mean intensity of HRI (> 1.0) was 1.37 times higher in children (5.70) than in adults (4.16) due to the differences in weight size and exposure time. With an acceptable limit of more than 1.0, the study divided the region into Northern Safe Health Zone (33.3% for adults and 28.1% for children) and Southern Unsafe Health Zone (66.7% for adults and 71.9% for children) based on the intensity of agricultural activity. Therefore, effective strategic measures such as safe drinking water, denitrification, defluoridation, rainwater harvesting techniques, sanitary facilities, and chemical fertilizer restrictions are recommended to improve human health and protect groundwater resources.

A qualitative approach, including geochemical and multivariate statistical approaches, is applied to evaluate the groundwater quality and human health risk, based on analytical data of 72 samples collected from a semi-arid region of eastern Maharashtra, India. The shifting of hydrochemical type from Ca2+–Na+–HCO3- to Na+–Ca2+–Cl− type was observed along different flow paths. The main controlling processes observed from the chemical characterisation of the groundwater are water–rock interactions, dedolomitisation and reverse ion exchange. Simulation analysis (mass transfer) exposes the dissolution of dolomite, gypsum, halite, k-feldspar and CO2 down the simulated pathways. Around 77% of the total variance was observed from the first three principal component analyses. The high positive loadings of EC, TDS, Na+, K+, Ca2+, Cl−, NO3- and SO42- of PC1 revealed silicate weathering and reverse ion exchange followed by human activities as the contamination sources. The sources identified for high positive loadings on HCO3- and SO42- of PC2 are soil CO2 and human activities. The high loadings of pH and F− in PC3 revealed fluorite dissolution and calcite precipitation. The human health risk calculated for NO3- revealed that 58% and 44% of the total groundwater samples surpassed the tolerance limit for non-carcinogenic risk of 1.0 in children and adults. The human health risk assessment for fluoride showed high hazard index values in 40% and 23% of the total groundwater samples for children and adults, respectively. The study suggests some management measures for protection of groundwater resources.

Assessment of pollutants and groundwater quality has attracted much attention worldwide as it is directly linked to human health. In view of this, groundwater samples were collected from a part of Guntur district, Andhra Pradesh, India, to assess groundwater pollution levels and groundwater quality, using Water Pollution Index (WPI) and Water Quality Index (WQI), respectively. Groundwater chemical composition results indicated that groundwater quality was characterized by alkaline and very hard categories with Na+ > Mg2+ > Ca2+ > K+: HCO3- > Cl - > SO42- > NO3- > F - facies. TDS, TH, Ca2+, Mg2+, Na+, K+, HCO3-, Cl -, NO3-, and F - were above the recommended threshold limits in 100%, 100%, 35%, 100%, 100%, 100%, 100%, 95%, 85%, and 75% of groundwater samples, respectively, for drinking purposes. The geochemical diagram showed base exchange water type (Na+–HCO3-) in 50% of groundwater samples resulting from weathering and dissolution of plagioclase feldspars under the influence of soil CO2 and ion exchange process. The remaining groundwater samples showed saline water type (Na+–Cl -) due to the influence of evaporation, sewage sludge, septic tank leaks, irrigation-return flows, agrochemicals, etc. Ionic relationships of Ca2+/Na+vs HCO3-/Na+, Ca2+/Na+vs Mg2+/Na+, higher Na+ than Ca2+, and occurrence of CaCO3 concretions further supported geogenic processes that alter groundwater chemistry. The positive linear trend of TDS vs Cl - + NO3-/HCO3- and the relationship of TDS with TH showed anthropogenic input as the main factor, causing groundwater contamination. The WPI indicated two categories of water quality: moderately polluted water (WPI: 0.75–1.00) and highly polluted water (WPI: > 1.00) in 60% and 40% of groundwater samples, which were 81.49% and 18.51% of the study area, respectively. Hierarchical cluster analysis identified three clusters: Cluster I (pH, F -, Ca2+, K+, NO3-, Na+, and SO42−), Cluster II (TH, Mg2+, Cl -, and HCO3-), and Cluster III (TDS) support WPI. Following WQI, 75% and 25% of groundwater samples fell under poor groundwater quality type (WQI: 100–200) and very poor groundwater quality type (> 200), respectively, especially due to the increased concentrations of Mg2+, Na+, K+, HCO32−, Cl -, NO3-, and F - ions, thereby increasing salinity (TDS) and hardness (TH) in groundwater. Spatially, they covered 85.84% and 14.06% of the study area. The quality of this groundwater is not suitable for drinking purposes. Therefore, the present study suggests preventive measures (safe drinking water supply, desalinization, defluoridation, denitrification, calcium food, and rainwater harvesting) to protect human health.

The present study is a part of hard rock aquifer of Telangana, South India, where the groundwater is withdrawn heavily for drinking, irrigation, and small-scale industrial purposes. Geochemical characteristics explain the chemical processes, which control the groundwater chemistry and consequently the groundwater quality, while the chemical quality of groundwater is adversely affected by anthropogenic activities, which damage the water environment. The focus of the present study was, thus, to know the origin of geochemical characteristics and also to evaluate the quality of groundwater for various purposes for taking the suitable remedial measures to provide safe water to the local community. Geochemical relations (GR) and hierarchical cluster analysis (HCA) were used to assess the geochemical characteristics. Entropy weighted groundwater quality index (EWGQI), United States Soil Salinity Laboratory Staff (USSLS)’s diagram, and groundwater quality criteria for water supply pipes (GQCW) were used to evaluate the groundwater quality for drinking, irrigation, and industrial purposes, respectively. The study found that the water-rock interactions associated with ion exchange and evaporation were the prime geochemical factors controlling the geochemical characteristics and the anthropogenic activities as the secondary factor. These observations were further supported by HCA. According to the EWGQI, 34.97% of the spatial area was found to have the poor and very poor groundwater quality zones for drinking purpose, because of the dominance of TDS, Na + , Cl − , SO 4 2 − , NO 3 − , and F − contents in the groundwater system. Based on the USSLS’s diagram, 79.55% of the present study area was observed to be poor and very poor water quality type for irrigation utilization due to salinity hazard. The GQCW demonstrated that the 7.91% and 8.82% of the areas were not suitable for industrial purpose due to influence of incrustation based on HCO 3 − and SO 4 2 − , respectively, and 1.85%, 12.32%, and 1.25 of the areas are unfit due to influence of corrosion based on pH, TDS, and Cl − , respectively. Therefore, boiling, activated carbon filter, rainwater harvesting, suitable coatings on metal surfaces of water supply pipes, etc. are the important suggested effective strategic measures to provide safe water for drinking, irrigation, and industrial purposes.

A survey on quality of groundwater was carried out for assessing the geochemical characteristics and controlling factors of chemical composition of groundwater in a part of Guntur district, Andhra Pradesh, India, where the area is underlain by Peninsular Gneissic Complex. The results of the groundwater chemistry show a variation in pH, EC, TDS, Ca 2+ , Mg 2+ , Na + , K + , HCO 3 − , Cl − , SO 4 2− , NO 3 − and F − . The chemical composition of groundwater is mainly characterized by Na + −HCO 3 − facies. Hydrogeochemical type transits from Na + –Cl − –HCO 3 − to Na + –HCO 3 − –Cl − along the flow path. Graphical and binary diagrams, correlation coefficients and saturation indices clearly explain that the chemical composition of groundwater is mainly controlled by geogenic processes (rock weathering, mineral dissolution, ion exchange and evaporation) and anthropogenic sources (irrigation return flow, wastewater, agrochemicals and constructional activities). The principal component (PC) analysis transforms the chemical variables into four PCs, which account for 87% of the total variance of the groundwater chemistry. The PC I has high positive loadings of pH, HCO 3 − , NO 3 − , K + , Mg 2+ and F − , attributing to mineral weathering and dissolution, and agrochemicals (nitrogen, phosphate and potash fertilizers). The PC II loadings are highly positive for Na + , TDS, Cl − and F − , representing the rock weathering, mineral dissolution, ion exchange, evaporation, irrigation return flow and phosphate fertilizers. The PC III shows high loading of Ca 2+ , which is caused by mineral weathering and dissolution, and constructional activities. The PC IV has high positive loading of Mg 2+ and SO 4 2− , measuring the mineral weathering and dissolution, and soil amendments. The spatial distribution of PC scores explains that the geogenic processes are the primary contributors and man-made activities are the secondary factors responsible for modifications of groundwater chemistry. Further, geochemical modeling of groundwater also clearly confirms the water–rock interactions with respect to the phases of calcite, dolomite, fluorite, halite, gypsum, K-feldspar, albite and CO 2 , which are the prime factors controlling the chemistry of groundwater, while the rate of reaction and intensity are influenced by climate and anthropogenic activities. The study helps as baseline information to assess the sources of factors controlling the chemical composition of groundwater and also in enhancing the groundwater quality management.

The present study region comprises granite and granite gneisses aquifer system constituted by Precambrian rocks. Groundwater is the primary source for drinking and other domestic purposes. Many developing regions in the world suffer from lack of safe drinking water. A rural part of Wanaparthy District in Telangana State, India, is one of them. For this reason, the groundwater samples collected from the study region were analyzed for pH, TDS, Ca2+, Mg2+, Na+, K+, HCO3−, Cl−, SO42−, NO3− and F− and evaluated groundwater quality criteria, using ionic spatial distribution (ISD), entropy water quality index (EWQI) and principal component analysis (PCA). The ISD maps show that some locations are not suitable for drinking purpose due to exceeding concentrations of TDS, Mg2+, Na+, K+, HCO3−, Cl−, NO3−and F−, compared to those with national drinking water quality standards. According to the EWQI, about 3%, 47%, 43% and 7% of the total area come under the excellent, good, medium and extremely poor water quality types for drinking purpose, respectively. Chadha’s diagram classified the area as carbonate hardness (63%), non-carbonate alkali (17%), carbonates alkali (13%) and non-carbonate hardness (7%) zones. The binary diagrams (Na+ + K+ vs TC, Na+ vs Ca2+ and HCO3− vs TC) indicate that the quality of groundwater is controlled by influences of water–rock interactions, mineral weathering and dissolution, ion exchange and evaporation as well as the impact of anthropogenic sources. The PCA transferred the chemical variables into three principal components accounts for about 81% of the total variance. The high positive loadings of PC1 (Cl−, TDS, SO42−, Na+, NO3−, Mg2+ and HCO3−) stand for processes of silicate weathering and dissolution, ion exchange and evaporation, and the influence of domestic waste waters, irrigation return flows and chemical fertilizers on the groundwater system, the PC2 (F− and pH) signifies the alkaline nature of groundwater, which causes fluorosis, and the PC3 (K+) is a result of potassium fertilizers. The study helps to take remediate measures at a specific site and hence suggests the treatment of water before its drinking and also the recharge of the aquifer artificially to improve the groundwater quality.

Impacts of geogenic and anthropogenic sources change seriously quality of groundwater. Inferior groundwater quality directly affects the human health, agricultural output and industrial sector. The aim of the present study is to evaluate the groundwater quality for drinking purpose and also to identify the pollutants responsible for variation of chemical quality of groundwater, using pollution index of groundwater (PIG). Groundwater samples collected from a rural part of Telangana State, India, were analyzed for pH, total dissolved solids (TDS), calcium (Ca2+), magnesium (Mg2+), sodium (Na+), potassium (K+), bicarbonate (\\[ {\\text{HCO}}_{3}^{ - } \\]), chloride (\\[ {\\text{Cl}}^{ - } \\]), sulfate (\\[ {\\text{SO}}_{4}^{2 - } \\]), nitrate (\\[ {\\text{NO}}_{3}^{ - } \\]) and fluoride (\\[ {\\text{F}}^{ - } \\]). The groundwater is characterized by Na+ and \\[ {\\text{HCO}}_{3}^{ - } \\] ions. The values of TDS, Mg2+, Na+, K+, \\[ {\\text{HCO}}_{3}^{ - } \\], \\[ {\\text{Cl}}^{ - } \\], \\[ {\\text{SO}}_{4}^{2 - } \\], \\[ {\\text{NO}}_{3}^{ - } \\] and \\[ {\\text{F}}^{ - } \\] are more than their threshold limits prescribed for drinking purpose in a few groundwater samples. The computed values of PIG varied from 0.69 to 1.37, which classify the 80% of the present study area into the insignificant pollution zone (PIG: < 1.0) caused by geogenic origin associated with rock-weathering, mineral dissolution, ion exchange and evaporation processes, and the rest (20%) into the low pollution zone (PIG: 1.0 to 1.5) due to influence of anthropogenic source (waste waters and agricultural activities) on the groundwater system, which are proved by ANOVA test. The diagrams (Ca2+ + Mg2+) versus (\\[ {\\text{HCO}}_{3}^{ - } \\] + \\[ {\\text{SO}}_{4}^{2 - } \\]), Na+ versus (Ca2+ + Mg2+), Na+ versus \\[ {\\text{Cl}}^{ - } \\], Ca2+ versus \\[ {\\text{SO}}_{4}^{2 - } \\] and Ca2+ versus Mg2+ support the geogenic origin, whereas the diagram TDS with (\\[ {\\text{NO}}_{3}^{ - } \\] + \\[ {\\text{Cl}}^{ - } \\])/\\[ {\\text{HCO}}_{3}^{ - } \\] confirms the impact of anthropogenic activities on the aquifer chemistry, which substantially proved the explanation of PIG. The characterization of geochemical evolution of groundwater, using trilinear diagram, also further supports the assessment of PIG in the variation of groundwater quality. From this study, the TDS, Mg2+, Na+, \\[ {\\text{Cl}}^{ - } \\], \\[ {\\text{SO}}_{4}^{2 - } \\] and \\[ {\\text{NO}}_{3}^{ - } \\] are considered as indicators in assessing the groundwater pollution sources.

Hydrogeochemistry is an important tool for the evaluation of the effect of human activities on aquifer system. Sixty eight groundwater samples were collected from bore wells during pre- and post-monsoon from Nagpur , a fast growing city in India, to assess the spatial controlling processes of groundwater contamination using principal component analysis (PCA). Groundwater has variable total dissolved solid (TDS) and total hardness (TH) values classifying them from fresh to saline and moderately hard to very hard types. About 36 and 33 % of the total groundwater samples during pre- and post-monsoon, respectively, are not suitable for drinking purpose. The graphical presentation of groundwater chemistry has indicated Ca–HCO₃, mixed Ca–Na–HCO₃ and mixed Ca–Mg–Cl types. The PCA summarizes the chemical variables of pH, EC, TDS, TH, TA, Na⁺, K⁺, Ca²⁺, Mg²⁺, HCO₃ ⁻, Cl⁻, SO₄ ²⁻ and NO₃ ⁻ into two PC loadings, accounting for 61.33 and 62.09 % of the total variance during pre- and post-monsoon, respectively. The first PC shows high loadings of EC, TDS, TH, Cl⁻, NO₃ ⁻, Ca²⁺ and Mg²⁺, which considered as pollution-controlled processes of anthropogenic sources. Second PC has high loadings of Na⁺ and HCO₃ ⁻, which is taken as alkalinity and pollution-controlled processes of geogenic and anthropogenic sources, respectively. The PC scores suggest the causes of variation in the groundwater chemistry. Negative values of chloro-alkaline indices suggest the prevalence of reverse ion exchange irrespective of the season, silicate weathering and anthropogenic activities over the controlling of groundwater quality which further PCA. Thus, the PCA helps as a tool to assess the controlling processes of the groundwater quality.