Fig. (4) Box-and-whisker plots showing nitrate (top left), sulphate (top right), fluoride (down left) and chloride (down right) concentrations in the various sampling sites of Nzhelele River. SANS permissible limit of nitrate, sulphate, chloride and fluoride in drinking water are >40 mg/L, 250 mg/L, 300 mg/L and 1.5 mg/L, respectively.