Abstract
This work is the first report on activity concentrations of (40)K in Inonotus obliquus sampled in a virgin forest of Siberia. The results have shown that the chaga conk is characterized by high activity concentrations of (40)K, averaging 1,641 Bq/kg dry weight (DW) and peaking at 3,502 Bq/kg DW. Activity concentrations of (40)K in chaga conks have been defined to increase from the near-trunk stratum to the crust of the conk with increased exposure to the solar radiation. Our measurements have revealed the samples to be mildly contaminated with (137)Cs. Intensive assimilation of (40)K by chaga conks has been shown as a normal and innate feature of the wild chaga mushroom.