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).