*2.3. Chemical Analysis and Data Processing*

The samples were analyzed for physical and chemical parameters, including temperature, pH, electrical conductivity (EC), total hardness (TH), total dissolved solids (TDS), major ions (Na<sup>+</sup> , K<sup>+</sup> , Ca2+, Mg2+, Cl−, SO<sup>4</sup> <sup>2</sup>−, HCO<sup>3</sup> <sup>−</sup>, NO<sup>3</sup> <sup>−</sup>, NO<sup>2</sup> <sup>−</sup> and F−), and Cr6+ . Some parameters such as pH, EC and temperature were recorded on the field by portable multi-parameter devices. Drying and weighing approach was used to measure TDS. Na<sup>+</sup> and K<sup>+</sup> were determined using flame atomic absorption spectrometer and TH, Ca2+ , and Mg2+ were analyzed using EDTA titrimetric methods. Spectrophotometer and ion chromatography were used to determine the enrichment of NO<sup>2</sup> <sup>−</sup>, NO<sup>3</sup> <sup>−</sup>, and SO<sup>4</sup> <sup>2</sup>−, respectively. Standard titration method using AgNO<sup>3</sup> as a reactant solution was used to determine the concentration of Cl−. Traditional titrimetric and ion selective electrode methods were used to determine HCO<sup>3</sup> −, and F−, respectively. Ion chromatographic-colorimetric analytical principle was used to determine Cr6+ .

The evaluation of water suitability for drinking purposes was based on the concentrations of physical and hydrochemical characteristics of the considered samples compared to the limits of physicochemical parameters recommended by the WHO [14,41,42]. The groundwater quality standards set by the Ministry of Health of the People's Republic of China, and the Standardization Administration of the People's Republic of China [43] were also considered in this study.
