Comparing the Radioactive Contamination of Marsh Labrador Tea (Ledum Palustre L.) Over Different Periods Since Chernobyl Accident

Radioactive contamination of the above-ground phytomass of marsh Labrador tea (Ledum palustre L.) in different periods after the Chernobyl accident was studied. Marsh Labrador tea is widely used in official and folk medicine. The studied species grows in over-moistened pine (less mixed) forests and open oligotrophic and mesotrophic marshes. It was found that in the first four years since the beginning of observations (1991), the magnitude of the specific activity of 137Cs in above-ground vegetative phytomass of marsh Labrador tea, depending on a permanent sample area (PSA), decreased by 1.2–1.4 times. After 10 years, it decreased by 1.6–1.7 times, after 16 years by 1.9–2.1 times, after 21 years by 2.7–3.1 times, and after 27 years by 3.1–6.5 times. An increase in the magnitude of transitions factors was also observed on all PSA over time. Thus, the minimal increase within 1991–2018 was recorded in PSA 11 – by 1.2 times and on PSA 13 – by 1.4 times. The maximum decrease in the magnitude of transition coefficient was observed in PSA 16 – by 2.7 times, in PSA 15 – by 3.0 times, and in PSA 18 – by 2.0 times. It was found that marsh Labrador tea belongs to the group of plants that are characterized by the high content of 137Cs in the above-ground vegetative phytomass. Within the observation period (1991–2018), this content significantly exceeds the admissible levels of radionuclide content in plant medicinal raw materials that are used for manufacturing medical preparations. In the PSA with maximum magnitudes of soil contamination density (400.5±50.73 kBk·m-2) this excess made up 158.4 times in 1991, and 33.7 times (166.9±23.56 kBk·m-2) in 2018. For 27 years of observations, there has been a decrease in the density of radioactive soil contamination by 2.1–2.7 times, which is due to radionuclide decomposition, its vertical migration in the soil, and towards the components of forest ecosystems.