Hydrogeochemical Characteristics and Natural Radionuclides in Groundwater for Drinking-water Supply in Korea

A total of 247 samples were collected from groundwater being used for drinking-water supply, and hydrogeochemistry and radionuclide analysis were performed. In-situ analysis of groundwaters resulted in ranges of 13.7~25.1∘C for temperature, 5.9~8.5 for pH, 33~591 mV for Eh, 66~820μS/cm for EC, and 0.2~9.4 mg/L for DO. Major cation and anion concentrations of groundwaters were in ranges of 0.5~227.6 for Na, 1.0~279.3 for Ca, 0.0~9.3 for K, 0.1~100.1 for Mg, 0.0~3.3 for F, 0.9~779.1 for Cl, 0.3~120.4 for SO₄ , 0.0~27.4 for NO₃ -N, and 6~372 mg/L for HCO₃ . Uranium-238 and radon-222 concentrations were detected in ranges of N.D- 131.1μg/L and 18-15,953 pCi/L, respectively. In case of some groundwaters exceeding USEPA MCL level ( 30μg/L ) for uranium concentration, their pH ranged from 6.8 to 8.0 and Eh showed a relatively low value(86~199 mV) compared to other areas. Most groundwaters belonged to Ca-(Na)- HCO₃ type, and groundwaters of metamorphic rock exhibited the highest concentration of Na, Mg, Ca, Cl, NO₃ -N, U, and those of plutonic rock showed the highest concentration of HCO₃ , and Rn. Uranium and fluoride from granite areas did not show any correlation. However, uranium and bicarbonate displayed a positive relation of some areas in plutonic rocks( R² =0.3896).