Accumulation of 137Cs and 90Sr radionuclides by dominants and co-dominants of birch-pine forest communities in Northern Ukraine

Investigation of the post-Chernobyl accumulation of radionuclides in forest communities not only sheds light on the specific ecological aftermath of the disaster but also holds broader significance for enhancing our knowledge of radioactive contamination in natural environments and informing strategies for mitigating its impacts. The study was carried out in an area with soil contamination exceeding the pre-accident level for the isotopes cesium (137Cs, 5.0-15.0 Ci km-2) and strontium (90Sr, 0.15-3.0 Ci km-2) in the Semenivka State Forestry (Chernihiv Region, Northern Ukraine). Four experimental plots with an area of 400 m2 each were established in a birch-Scots pine forest, where dominant trees, herb and shrub layers, and mosses were analyzed for radionuclide bioaccumulation. Our results indicate a larger accumulation of 137Cs compared to 90Sr in the forest ecosystem. The highest 137Cs and 90Sr accumulation was detected in the fern Pteridium aquilinum, and the lowest in Pinus sylvestris. Based on our results, we hypothesized that the processes of accumulation and dispersion of 137Cs among the different vegetation layers are more complex compared to 90Sr. MANOVA regression analysis revealed significant differences in the accumulation of radionuclides between different layer levels, plant species and plant parts in the studied forest areas. According β coefficient analysis, both 137Cs and 90Sr are influenced by the site (area type) but in different ways. For 90Sr, the negative β coefficient implies that certain area types are associated with lower Sr accumulation, while for 137Cs the effect of area type may be more complex or context-dependent. These contrasting results suggest that Cs accumulation is more sensitive to changes in layer level compared to Sr. This could be due to differences in the environmental behaviour of these radionuclides, their chemical properties or differences in soil-plant transfer mechanisms. The significant effect of plant species on 137Cs/90Sr accumulation highlights that species-specific characteristics may play a role in radionuclide uptake. Moreover, we found significant differences in 137Cs/90Sr accumulation between different plant parts. Further research on the mechanisms of accumulation and distribution of these radionuclides are essential for better understanding their impact on human health and the environment.