Residual sodium bicarbonate (RBSC)
Gupta (1983) classified the groundwater for irrigation use based on the relation between the bicarbonate and calcium ions. The excess concentration of sodium bicarbonate leads to a harmful effect on soil (Rahman et al., 2017). In the study area, the RBSC value ranges from -11.96 to 7.21 meq/L, with an average of -0.05 meq/L (Table.4). About 90% of the sample locations are suitable, and 10% of samples are the marginal state of contamination (Table.6). The spatial distribution of RBCS 660.00 sq.km area falls under suitable, and 6.95 sq.km area is a marginally contaminated type of groundwater (Fig.11e). A higher value of RBSC indicates the dissolution of organic matter in the soil.