Hydrogeochemistry and Occurrences of Uranium and Radon in Ground-water of Mungyeong Area

The occurrence of natural radionuclides like uranium and radon in groundwater was hydrochemically examined based on 40 well groundwaters in Mungyeong area. The range of electrical conductivity (EC) value in the study area was 68 similar to 574 mu S/cm. In addition to the increase of EC value, the content of cations and anions also tends to increase. Uranium concentrations ranged from 0.03 similar to 169 mu g/L (median value, 0.82 mu g/L) and radon concentrations ranged from 70 similar to 30,700 pCi/L (median value, 955 pCi/L). Only 1 out of 40 wells (2.5%) showed uranium concentration exceeding the maximum contaminant level (MCL; 30 mu g/L) proposed by the US Environmental Protection Agency (EPA). Radon concentrations of eight wells (20%) exceeded AMCL(Altemative maximum contaminant level) of the US EPA (4,000 pCi/L). Four out of those eight wells even exceeded Finland's guideline level (8,100 pCi/L). When concentrations of uranium and radon were investigated in terms of geology, the highest values are generally associated with granite. The uranium and radon levels observed in this study are low in comparison to those of other countries with similar geological settings. It is likely that the measured value was lower than the actual content due to the inflow of shallow groundwater by the lack of casing and grouting.