Comparative physicochemical characterization and water quality assessment of drinking water from wells in Songino-Khairkhan District, Ulaanbaatar, Mongolia

ABSTRACT Groundwater is an important drinking-water source in peri-urban areas where centralized water supply systems are limited. This study evaluated the hydrochemical characteristics and trace-element composition of groundwater in Khoroos 32 and 33 of Songino-Khairkhan District, Ulaanbaatar, Mongolia. Thirty-four groundwater samples were collected from domestic wells and analyzed for physicochemical parameters, major ions, and trace elements using ICP-OES. Results were compared with the Mongolian Drinking Water Standard and WHO guidelines. Among nine trace elements analyzed (As, Ba, Sb, Mn, Ni, Sr, U, Zn, and Mo), Sr exceeded the applicable guideline value in five wells (S3, S5, S6, S14, and S17), while U exceeded the guideline value in one well (S2). Elevated Ca, Mg, Cl, Sr, and U concentrations occurred mainly in Khoroo 32, particularly in the Emeelt area. Arsenic ranged from 0.03 to 8.79 μg/L (mean 1.67 μg/L) and remained below the WHO guideline of 10 μg/L. The highest mineralization occurred at S5. Spatial and chemical variations indicate that groundwater composition is primarily influenced by mineral dissolution and water–rock interactions, although localized anthropogenic contributions cannot be excluded. These findings provide baseline information for groundwater-quality management and emphasize continued monitoring of wells with elevated Sr and U.