Various mushroom samples, lichens and pteridophytes are collected nationwide in 2017 and their contents of artificial radionuclides (137Cs, 238Pu, 239,240Pu and 90Sr) are measured to address the growing concerns regarding the radioactive contamination of food products in Korea.
The analysis shows that the activity concentrations of 137Cs range from minimum detectable activity (MDA) to 77 Bq/kg of fresh weight and the highest concentration was found in the Sarcodon imbricatus. The activity concentrations of 239,240Pu in the mushrooms varied from MDA to 0.13 Bq/kg of fresh weight. Among the samples, Umbilicaria escu¬lenta (lichen) showed the highest concentration. On the other hand, the activity concentration of 90Sr in the mushrooms showed the MDA to 19.6 Bq/kg of fresh weight, the highest concentration of 90Sr was found in the Phellinus linteus.
The activity ratio ratios of 238Pu/239,240Pu vary from 0.023 to 0.038, with a mean of 0.028. This ratio is consistent to the global fallout ratio (0.020-0.030) within 2σ. In addition to the activity ratio of 238Pu/239,240Pu, the atom ratio of 240Pu/239Pu will be reported later as a supplement to identify the sources.