Hydrogeochemical Characteristics of Uranium and Radon in Groundwater from the Goesan Area of the Ogcheon Metamorphic Belt (OMB), Korea

Byong-Wook Cho, Dong-Soo Kim, Moon-Su Kim, Jae-Hong Hwang and Chang-Oh Choo
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Byong-Wook Cho: Groundwater Research Center, Korea Institute of Geoscience and Mineral Resources, Daejeon 34132, Korea
Dong-Soo Kim: Soil and Groundwater Research Division, National Institute of Environmental Research, Incheon 22689, Korea
Moon-Su Kim: Soil and Groundwater Research Division, National Institute of Environmental Research, Incheon 22689, Korea
Jae-Hong Hwang: Geoscience Data Center, Korea Institute of Geoscience and Mineral Resources, Daejeon 34132, Korea
Chang-Oh Choo: Department of Earth and Environmental Sciences, Andong National University, Andong 36729, Korea

Sustainability, 2021, vol. 13, issue 20, 1-19

Abstract: Uranium and radon concentrations in groundwater from the Goesan area of the Ogcheon Metamorphic Belt (OMB), central Korea, whose bedrock is known to contain the highest uranium levels in Korea, were analyzed from 200 wells. We also measured the uranium concentrations in the bedrock near the investigated wells to infer a relationship between the bedrock geology and the groundwater. The five geologic bedrock units in the Goesan area consist of Cretaceous granite (Kgr), Jurassic granite (Jgr) and three types of metasedimentary rocks (og1, og2, and og3). The percentages of the groundwater samples over 30 μg/L (maximum contaminant level, MCL of US EPA) were 2.0% of the 200 groundwater samples; 12% of Kgr and 1.8% of Jgr exceeded the MCL, respectively. Overall, 16.5% of the 200 groundwater samples exceeded 148 Bq/L (alternative maximum contaminant level, AMCL of US EPA); 60.0% of Kgr and 25.0% of Jgr exceeded the AMCL, but only 0% of og1, 7.9% of og2, and 2.6% of og3 exceeded the value, respectively. No direct correlation was found between uranium concentration and radon concentration in water samples. Radon has a slightly linear correlation with Na (0.31), Mg (−0.30), and F (0.36). However, uranium behavior in groundwater was independent of other components. Based on thermodynamic calculation, uranium chemical speciation was dominated by carbonate complexes, namely the Ca 2 UO 2 (CO 3 ) 3(aq) and CaUO 2 (CO 3 ) 3 2− species. Although uraniferous mineral phases designated as saturation indices were greatly undersaturated, uranium hydroxides such as schoepite, UO 2 (OH) 2 and U(OH) 3 became possible phases. Uranium-containing bedrock in OMB did not significantly affect radioactive levels in the groundwater, possibly due to adsorption effects related to organic matter and geochemical reduction. Nevertheless, oxidation prevention of uranium-containing bedrock needs to be systematically managed for monitoring the possible migration of uranium into groundwater.

Keywords: uranium; radon; groundwater; Goesan area; Ogcheon Metamorphic Belt; uranium chemical speciation; saturation indices (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2021
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