Major anions
In a study area, major dominance of anions is in the order of nitrate> chloride> sulphate> bicarbonate> fluoride > carbonate. The concentration of chloride ranges between 25 to 893 mg/L with a mean of 282.73 mg/L. The spatial analysis reveals that, 268.29 sq.km is acceptable and 398.66 sq.km (Fig.4c) is permissible as per WHO (2011) and BIS (2012). The sulphate concentration varies from 15 to 322 mg/L, with an average of 100.01 mg/L, and 659.94 sq.km area (Fig.4d) is an acceptable limit for drinking purposes. Both the chloride and sulphate ions in the study region was observed that within the permissible limit and doesn’t affect the nature of groundwater for drinking purpose. Bicarbonate concentration varies from 195.2 to 732 mg/L, with an average of 41.35 mg/L. The high concentration of bicarbonate is due to weathering of rock and rock water interaction. Nitrate is the most significant pollutant of groundwater for both drinking and agriculture uses. The concentration of nitrate varies from 5 to 73 mg/L, with a mean of 34.16 mg/L. One-third of the sample locations are highly affected due to a higher concentration of nitrate ions. In the study area, dumping of waste in open land from residents, sewage disposal, utilization of chemical fertilizers are the major factors that cause the nitrate contamination in groundwater. The spatial analysis reveals that 101.14 sq.km area (Fig.4e) is undesirable for drinking uses. Continuous consumption of nitrate contaminated water leads the major diseases such as heart problems and blue baby syndrome (Tian et al., 2019). The concentration of fluoride ion range between 0.12 to 1.79 mg/L with an average of 0.58 mg/L. about 10% of the sample locations (9.05 sq.km) exceeds the permissible limit of fluoride for drinking purposes (Fig.4f).