Table 2 shows the minimum, maximum, average, and standard deviation values of the water quality indicators obtained in January 2020.
All of the water quality metrics in the study area varied greatly in space. Groundwater contamination from anthropogenic sources such as industry, open home sewerage systems, and agricultural activities accounted for the majority of the regional variance. Furthermore, surface water resources such as tanks and rivers have an impact on water quality through groundwater recharge. The geographic variance in water quality metrics recorded over the study period is detailed further below.
pH (Hydrogen ion concentration)
It is a measurement of the concentration of Hydrogen (or) Hydroxyl ions in water. It influences the solubility of mineral matter and other anthropogenic pollutants. Hence it plays a major role in the mineralization of ground water and it is expected to increase along its flow path. The pH scale has a range of 0 to 14 on it. Water with a pH of 7 is neutral; water with a pH of greater than 7 is basic; water with a pH of less than 7 is acidic. A ten-fold difference in hydrogen-ion concentration is represented by a 1-unit change in pH..
The pH values in the study area ranged from 7.86 to 9.86, with an average of 8.27, indicating that the samples were somewhat alkaline overall. The pH of ground water is normally controlled by the equilibrium between the dissolved carbon dioxide – bicarbonate – carbonate species. As the ground water moves along its flow path, consumption of carbon dioxide shifts the equilibrium to the right side, which results in the pH to increase. In addition to the natural control, industrial pollution could also contribute the pH to increase or decrease, depending on the waste generated.
Electrical conductivity (EC)
At 25 degrees Celsius, electrical conductivity in the research region ranged from 703 to 15280 µS/cm at 25 o C. Distribution of Electrical conductivity is shown as a contour map in Figure.6. EC values showed a wide variation in space. Table 3 shows the classification of ground water based on electrical conductivity.
Total dissolved solids (TDS)
Total cations and total anions are added together to calculate TDS. Ionic species such as Na, K, Ca, Mg, CO3, HCO3, Cl, SO4, NO3 and other trace elements are included in this. Major cations and anions, on the other hand, typically made up more than 90% of the TDS. Table 4 shows groundwater classifications based on TDS as determined by . In the absence of other sources, the desirable level is 500 mg/L and the highest allowable limit is 2000 mg/L, according to the Bureau of Indian Standards' drinking water specification. Table 5 shows the TDS-based suitability of groundwater for drinking.
Total hardness, Calcium and Magnesium
The presence of alkaline earth metals and other polyvalent cations in water causes it to be hard. Calcium and magnesium ions are abundant in the majority of groundwater. The following classification in (Table 6) characterizes the soft & hard water. The bulk of groundwater samples fell into the hard water category, according to total hardness categorization. With respect to the classification of Table 7, about 76.0 % of the samples are categorized as very hard water. The details of samples compared with BIS drinking water standard is given in Table 8.
In groundwater, chloride is one of the most common anions. Chloride ions are present in water due to the rapid mobility of the ion and the high solubility of chloride salts. About 15% of the samples were above the permissible limit of 1000 mg/L.
Sulphate is one of the principal anions found in groundwater, and due to solubility controls, its concentration levels are generally lower than those of chloride and bicarbonate. The concentration of sulphate ranged between 18 and 1850 mg/L, with mean value of 294 mg/L. Figure 7 depicts the regional distribution of sulphate.
One of the most important markers of pollution from anthropogenic sources is nitrate. Its persistent nature and transit through the ground water flow path are aided by its negative charge and high mobility. The spatial distribution contour of nitrate (Figure.8) is parallel to electrical conductivity contour, which indicates that the source is same. It is also noticed that the concentration of nitrate is more in irrigation wells than that of domestic wells.
Assessment for Nitrate
The presence of nitrate content in groundwater can be mainly through two sources either geogenic or anthropogenic activities. Because nitrogen is one of the most important components of fertilizer; agricultural operations are a major source of nitrate leaching into groundwater. . The poisoning of agricultural land by leaching of nitrate is a major problem in India, since seventy percent of the population relies on horticultural activities .Table 9showing THI values for nitrate calculated using both oral and dermal HQ.
Health risk assessment for Fluoride
Fluorine is a prevalent element in the earth's crust, accounting for around 0.32 percent of the total (WHO 2017) and in some lithological compositions, higher levels are found. Table 10 showing THI values for fluoride calculated using both oral and dermal HQ.