Hydrochemical characteristics and distribution of uranium in groundwater of the Geum River Basin, South Korea

Abstract In the Geum River basin in Korea, local groundwater contamination has been occurring due to the complex influence of urbanization and agricultural activities. For proper utilization as a water resource, this study identified major influencing factors of groundwater hydrochemistry in the bedrock aquifer by statistical analysis and regional uranium (U) distribution as a redox-sensitive contaminant. The H-3 concentration of the groundwater was high in the plains and low in the mountain areas; thus, it was deemed to be affected by the residence time of groundwater after precipitation recharge. The hydrochemical properties and factor loading values of the principal components indicated that the major factors were water‒rock interactions and residence time, but a positive correlation of K-NO3 and Mg-Cl showed the influence of agricultural activities. Cl− increased as it moved downstream, while NO2− was found to decrease from upstream to midstream, and NO3− showed no regularity. Thus, the main groundwater pollutants upstream and downstream in the Geum River basin were likely to be contributed by agricultural activities and seawater infiltration, respectively. The U in groundwater existed in the UO2(CO3)22− (namely, uranyl ion), and the highest concentration was observed at neutral pH. It had a positive correlation with HCO3, pH, and Ca and a weak negative correlation with NO3.