Spatial Variation in Physico-Chemical Characteristics of Groundwater
The analytical results obtained during physico-chemical analysis were compared with WHO standards to understand their suitability for drinking purposes.
Physical Parameters
Results reveal that pH lies between 6.3 and 8.1, which is acceptable for drinking purposes (Fig. 2a). pH in groundwater is less than the desired value suggested by WHO only in Central Saunda (6.3), which indicates that groundwater is slightly acidic. EC in the area ranged between 138 and 1154 µS/cm. Around 32% of the groundwater samples exceed the desirable limit (500 µS/cm). The spatial distribution reveals that EC is low in the northeast and southern part of the study area, whereas it is high in the northwest part of the area (Fig. 2b). Extremely high EC (> 1000 µS/cm) is reported in 4% of the samples which include Ichat Bazar (1035 µS/, 662mg/l), Barhi (1154 µS/cm, 739mg/l) and Siyarkoni (1103 µS/cm, 706mg/l). The TDS in the area ranges from 88 to 739. Around 36% of the samples report TDS greater than 500, with the highest values being reported in Barhi (739mg/l) (Fig. 2c). Around 66% of the samples report TH higher than 200mg/l, which is of great concern. Chauparan reports TH greater than 600 (Fig. 2d) which is more than the maximum permissible limit suggested by WHO.
Major Cation Chemistry
Calcium concentration in the groundwater of the area ranges from 10 to 161 mg/l. 37% of the samples have calcium values more than the desirable limit (75mg/l) suggested by WHO. Such high concentrations result in kidney stones as well as cardiovascular diseases. The spatial variation reveals higher concentrations in the southern part of the study area in Gola, and central parts in Daru (Fig. 3a). Concentration of magnesium is more than the desirable limit (50mg/l) in the sites in Hazaribagh (50.4mg/l), Ichakdih (50.57mg/l) and Siyarkoni (84mg/l). The northwestern part has the highest values of magnesium (Fig. 3b). 95% of the sampling sites have a concentration of magnesium within the desirable limit suggested by WHO. The groundwater of the area contains sodium in desirable quantity (5-105mg/l), making it fit for human consumption. The northwestern part of the area contains a relatively higher concentration of sodium than the rest of the areas (Fig. 3c). Concentration of potassium in the groundwater is rather low for a large part of the study area. The lowest concentration is observed in the north-west and southern part of the area (Fig. 3d). Higher than permissible concentrations of potassium have been observed in Pakrih Barwadih (18mg/l), Pahej (12.99mg/l), Ichakdih (12.45mg/l) and Kharanti (26mg/l), which may have a laxative effect on the human. The spatial variation of ammonium in groundwater in the area reveals decreasing values of ammonium from north to south (Fig. 3f). The northern part of the area, comprising of Hazaribagh district has comparatively higher concentrations of ammonium with the highest value being observed in Jhumra (4.43mg/l).
Major Anion Chemistry
The concentration of bicarbonate in the study area is within the desirable limit suggested by WHO. The spatial distribution of bicarbonate in the area reveals higher values in the western and northwestern part of the area (Fig. 4c). The concentration of chloride (mean 71mg/l), is within the desirable limit suggested by WHO in 98% of the samples. Similar concentrations of chloride have also been observed in Dumka and Jamtara districts (Singh et al. 2012), and parts of Udaipur in Rajasthan (Bhuiyan and Champati Ray 2017). The concentration of chloride is low in the southern and northeastern parts of the area. The higher concentration is observed in only certain pockets in sample 76. (Fig. 4a) may be attributed to contamination by untreated mine waste effluents. The primary objection to the presence of excessive chlorides in drinking water is that it imparts a salty taste to water. Chlorides in drinking water are not normally detrimental to health, although high concentrations may be harmful to some people suffering from heart or kidney diseases (McKee and Wolf 1963). While sulphate alters physical attributes like smell and taste, it also has a detrimental impact on human consumption like cathartic effects. The concentration of sulphate (1-273mg/l) in the groundwater of the area is within the desirable limits as per WHO norms in 98% of the samples. This concentration is spatially diverse; higher concentration can be observed in the southern part of the area (Fig. 4e). This may be attributed to the weathering of sulphide ores, gypsum, and anhydrite (Todd and Mays 2005), and the presence of coal mining in the area. This reflects the anthropogenic influence on the geochemistry of groundwater. Phosphate is negligible in the majority of the groundwater samples. It ranges from 0.023 to 3.5mg/l, having higher concentrations in the south and southeastern part of the area (Fig. 4f).
The concentration of fluoride ranges from 0.2 to 6.72 mg/l. Fluoride is present beyond the permissible limit (1.5mg/l) suggested by WHO in 70% of the samples. Previous studies conducted in parts of Hazaribagh have also revealed higher concentrations of fluoride (1.89–3.84 mg/l) in groundwater (Kumar and Sadhu 2013). The concentration of fluoride is higher in the southeast part, and lowest in the northwestern part of the area (Fig. 4b). Higher fluoride could be due to the weathering of fluoride-bearing minerals including biotite, fluorite, and apatite, which are present as secondary minerals in granite and granitic gneiss rocks of the area (Singh et al. 2010). In the study area, the concentration of nitrate in groundwater ranged from 0.41 to 273.69 mg/l. 64% of the samples contain nitrate more than the permissible limit suggested by WHO. The spatial distribution of nitrate reveals pockets of high concentration in the northern and central part of the area (Fig. 4d). Higher concentrations may be due to biological fixation, application of fertilizers and pesticides as well as sewage from industries.
Groundwater Quality For Drinking Purposes
The analysis of the concentration of individual ions concerning WHO standards is vital, but it is also observed that water is found suitable for one ion and unsuitable for the other. Thus, to understand the overall suitability of water for drinking purposes, the present study analyzes its quality involving a combination of various physical and chemical parameters with the help of WQI.
As per WQI, good-quality water dominates the area (Table 3). This comprises 4100.38 sq. km. of area, which is around 84% of the total area. Excellent water is observed in around 10% of the area, comprising 42.65 sq km of the area. A similar study conducted in Bist Doab region of Punjab revealed the presence of excellent water in one-third of the area (Gautam et al. 2021). 23% of the samples covering 751.56 sq. km. of the area consist of poor-quality water covering the area of Daru, Tatijhariya, Keredari, Barkagaon, Chalkusa, and Gola. Poor-quality water is present in 0.77% of the area comprising the Chauparan block. The higher concentrations of EC, TH, chloride, fluoride, and nitrate impart poor quality to the groundwater of these regions. Spatial variation of WQI (Fig. 5) reveals that the eastern and southern part of the area comprises water suitable for drinking, while the central and northwestern part of the area has a poor-quality of groundwater.
Table 3
Classification of groundwater as per Water Quality Index
Water Type | WQI | No. of samples |
Excellent Water | < 50 | 7 (9.59%) |
Good Water | 50–100 | 48(65.75%) |
Poor Water | 100–200 | 17(23.29%) |
Very Poor Water | 200–300 | 1(1.37%) |
Water Unsuitable for Drinking | > 300 | 0 |
Human Health Risk Assessment
In countries like India, most people depend on groundwater as a source for drinking purposes. Consequently, the presence of fluoride and nitrate in groundwater poses a non-carcinogenic risk to human health, which has become a serious issue. The residents of the area depend on groundwater for drinking purposes (Heena and Rai 2020). The concentration of fluoride and nitrate are beyond the permissible stipulations of WHO in most of the samples. On account of that, it becomes extremely vital to assess the health risk due to fluoride and nitrate using the universally established criteria for fluoride and nitrate. The present study computes the non-carcinogenic health risks due to nitrate and fluoride for different sections of the population (male, female, and children).
Exposure Dose
The exposure dose of fluoride and nitrate was calculated for males, females and children. The exposure dose of nitrate in males ranged from 0.015 to 10.52 (mean 1.55) for males, 0.014 to 9.95 (mean 1.47) for females, and 0.01 to 12.7 (mean 1.88) for children (Table 4). Higher values of nitrate were observed in Chauparan, while the least exposure of nitrate was noticed at Dadi. The exposure dose of fluoride in males ranged from 0.009 to 0.25 (mean 0.06), 0.0093 to 0.24 (mean 0.05) in females (Table 4). The range of exposure dose is 0.01 to 0.31 (mean 0.07) in children, which is similar to that observed in Agra (0.07-0.31mg/kg/day) (Yadav et al. 2019). The highest exposure level of fluoride was observed in Barkagaon, while the least exposure to fluoride was noticed in Churchu.
Table 4
Computation of Exposure duration
| Male | Female | Children |
EDF | EDN | EDF | EDN | EDF | EDN |
Minimum | 0.009 | 0.015 | 0.09 | 0.014 | 0.01 | 0.01 |
Maximum | 0.25 | 10.52 | 0.24 | 9.95 | 0.31 | 12.7 |
Mean | 0.06 | 1.55 | 0.05 | 1.47 | 0.07 | 1.88 |
Hazard Quotient And Total Hazard Index
The hazard quotient for nitrate varied from 0.009 to 6.57 for males (mean 0.97) (Table 5), which is lower than observed values in South India (1.71) (Karunanidhi et al. 2019). The observed hazard quotient varies from 0.009 to 6.22 for females (mean 0.91) (Table 5) and 0.01 to 7.98 for children (mean 1.17), which is higher than values observed in Thoothukudi district, Tamil Nadu (mean 0.9) (Selvam et al. 2021). The calculated values of HQ are greater than 1 in 31.43% of the samples for males and children, while 30% of the samples in females. As the northern and central parts of the area have a higher concentration of nitrate, the health risk is also higher in that area. Nitrate concentrations higher than 11 ppm in the body may be the cause of anoxemia, asphyxia, and blue baby disease. It could have such negative implications that it may even cause death to infants (< 4 months old). Excess nitrate could have equally negative repercussions for older infants and adults, as it can be the cause of gastric cancer (Comly 1945; Gilly et al. 1984).
Table 5
Computation of Hazard Quotient for adult male, females and children
| Male | Female | Children |
HQF | HQN | HQT | HQF | HQN | HQT | HQF | HQN | HQT |
Minimum | 0.16 | 0.01 | 0.01 | 0.16 | 0.01 | 0.01 | 0.20 | 1.18 | 0.01 |
Maximum | 4.31 | 6.58 | 7.46 | 4.07 | 6.22 | 7.06 | 5.23 | 0.01 | 9.05 |
Mean | 1.00 | 0.97 | 1.89 | 0.95 | 0.92 | 1.79 | 1.22 | 7.98 | 2.30 |
The hazard quotient for fluoride varied from 0.16 to 4.30 for males (mean 1.01), and 0.15 to 4.07 for females (mean 0.95) (Table 5). The hazard quotient calculated for children lies in the range of 0.19 to 5.22 (mean 1.22) (Table 5), which is higher than those observed in South India (0.01 to 3.25) (Karunanidhi et al. 2019). The hazard quotient is more than the reference dose in 38.5% of the samples in males and children, and 37.14% of the samples in females. This suggests that the majority of the residents of the area are prone to dental and skeletal fluorosis. Previous studies conducted in parts of Hazaribagh reveal the presence of dental fluorosis among children (Kumar and Sadhu 2013). This reveals the grim situation of the health of the residents of the area. The presence of fluoride in water in concentrations less than 0.5mg/l creates another problem; it promotes dental carries in children especially in the formative stages of permanent teeth (Bhattacharya 1988), osteoporosis, and growth retardation. In terms of general health, in communities where drinking water is excessively high in fluoride, the most prominent adverse effects are skeletal fluorosis and bone fracture, low IQ, and deformities in growth, especially in infants (Marshall et al. 2004).
As per USEPA, the Total Hazard Index (THI) should not exceed 1, as it denotes non-carcinogenic risk to human health. The THI ranges from 0.01 to 7.46 (mean 1.89) for males (Table 5), which is higher than the Thoothukudi district, Tamil Nadu (1.6). THI in the area ranges from 0.009 to 7.05 (mean 1.79) and 0.01 to 9.05 (mean 2.3) (Table 5) for females and children, respectively. Assessment of non-carcinogenic danger based on THI indicates that 83.56%, 78.08%, and 89.04% of the samples surpass the allowable limit for males, females, and children respectively. The vulnerability of total hazard is maximum in children followed by females and then males. Studies conducted in Shanmuganadhi in South India (Karunanidhi et al. 2019) also reveals that children are most vulnerable to health risk. Spatial variation in the overall non-carcinogenic risk as depicted by THI is maximum in Chauparan and minimum in Dadi. Lower values are observed in the northwestern part of the study area (Fig. 6a,b,c).