Uranium concentrations (a total of 82 samples) in groundwater in Icheon, middle Korea, showed a wide range from 0.02 to 1640 μg/L with a mean of 56.77 μg/L, a median of 3.03 μg/L, and a standard deviation of 228.63 μg/L. Most groundwater samples had quite low concentrations: 32.9% were below 1 μg/L, while 15.9% exceeded 30 μg/L, the maximum contaminant level (MCL) of the US EPA (Environmental Protection Agency). Radon concentrations also ranged widely from 1.48 to 865.8 Bq/L. Although the standard deviation of radon was large (151.8 Bq/L), the mean was 211.29 Bq/L and the median was 176.86 Bq/L. Overall, 64.6% of the samples exceeded the alternative maximum contaminant level (AMCL) of the US EPA (148 Bq/L). According to statistical analyses, there was no close correlations between uranium and radon, but there were correlations between uranium and redox potential (Eh) (−0.54), dissolved oxygen (DO) (−0.50), HCO₃⁻ (0.45), Sr (0.65), and SiO₂ (−0.44). Radon showed independent behavior with respect to most components in groundwater. Uranium concentrations in groundwater increased with increasing water–rock interactions. Anomalously high uranium and radon concentrations in groundwater are preferentially localized in granite areas and spatial distributions are remarkably heterogeneous.

Bottled waters have been becoming increasingly popular in Korea over the last two decades due to the high demand for safe drinking water. Hydrochemical characterization of groundwater is essential for understanding quality properties of bottled waters. We investigated hydrochemistry of 60 manufacture factories for bottled waters in relation to geology. The mean EC value is highest in groundwaters of Ogcheon metamorphic rocks (213.6 μS/cm) > Precambrian gneiss (177.8 μS/cm) > Cretaceous granite (160.4 μS/cm) > Jurassic granite (131.3 μS/cm) > Quaternary Jeju Island volcanic rocks (99.2 μS/cm). The groundwater types are commonly classified as Ca-HCO₃, Ca-Na-HCO₃, or Ca-Mg-HCO₃ types depending on bed rocks. Based on correlation matrix, the groundwater chemistry was controlled by water–rock interactions. We established relationships between groundwater compositions and bedrock geology in Korea.

Radon concentrations in the raw water and treated water used for 59 brands of bottled water produced in South Korea were analysed. The radon levels in 59 raw water samples ranged from 3.7 to 476.8 Bq/L, with a geometric mean of 49.0 Bq/L. The mean radon levels in raw water samples were high in Jurassic granite aquifers and low in volcanic rock aquifers. However, the maximum radon levels were observed in metamorphic rock aquifers. The concentrations in 55 treated water samples ranged from 0.1 to 239.4 Bq/L, with a geometric mean of 7.7 Bq/L. In treated water, radon levels decreased by 16.0–98.9% (average, 74.9%) due mainly to storage in water tanks and treatment with granular activated carbon (GAC) filters. The radon levels in raw water and treated water samples exceeded the US EPA alternative maximum contaminant level (AMCL) of 148 Bq/L by 16.9% and 1.8%, respectively. Considering the radon reduction rate, it is anticipated that the radon concentrations in bottled water in stores will not exceed 148 Bq/L because it takes about 1–2 weeks for treated water to reach the customer as bottled water.