Abstract

Uranium concentration in groundwater of the Goesan area was anticipated high because the area contains Ogcheon metamorphic rock zone which partly includes coal bed bearing high uranium content and nearly half of the area is covered by granitic rocks. Groundwater samples collected from 250 wells in five 5 lithology (Ogcheon meta-sandy rock zone (Og1), Ogcheon lower phyllite zone (Og2), Ogcheon pebble bearing phyllite zone (Og3), Jurassic granite (Jgr), Cretaceous granite (Kgr)), of the area were analyzed and equivalent uranium concentrations (e(U)) from 200 rocks near sampled wells were measured using portable gamma spectrometry. Higher median value of e(U) (8.2 mg/kg) was found on Kgr outcrops. The median e(U) value of Og2 was not as high as that of Kgr and similar to those of Jgr, Og1, and Og3 (3.05~3.90 mg/kg). The uranium level in groundwater of the area ranged from 0.01 to 293.0 μg/L with a median value of 0.87 μg/L which is similar to the national median uranium level of 0.74 μg/L. The uranium concentration was high in the samples from the Kgr (median 4.74 μg/L) and low samples from the Og1, Og2, and Og3 (median 0.35~0.74 μg/L). The percentage of total samples having uranium level above 30 μg/L was 2.8%, on the other hand, that of Kgr is 20.7%, reflecting additional survey on the Kgr area is needed.

Keywords groundwater, uranium concentration, Jurassic granite (Jgr), Cretaceous granite (Kgr), Ogcheon metamorphic rock zone