Abstract

The concentration of natural radioactivity in the sediment of the Geum River was investigated. The river and lake sediment samples were collected at 23 points during September to November, 2015 and March to April, 2015, respectively. The gamma-rays emitted from the 226Ra and 232Th decay series and 40K were measured with a high purity germanium (HPGe) gamma detector. The average radioactivity concentrations of the 226Ra, 232Th decay series and 40K for the river sediment was found to be 15.6 ± 0.6, 33.8 ± 1.2, 789.8 ± 26.0 Bq/kg, respectively, while for the lake sediment, the concentrations were 17.1 ± 0.5, 37.8 ± 1.1, 269.4 ± 9.6 Bq/kg, respectively. Spearman’s correlation was conducted to compare the radioactivity concentration and properties of the sediment. The radioactivity concentration of the 232Th decay series showed a negative correlation with the particle size of the sediment, and was measured to be higher than the 226Ra decay series according to mobility of the radionuclides. The radioactivity concentration of 40K showed a negative correlation with organic matter content. The concentration of 40K in the lake sediment was lower than that in the river sediment.