Effects of 137Cs and 90Sr on structure and functional aspects of the microflora in agricultural used soils

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At long sight, 137Cs and 90Sr are the primary radionuclides contaminating agricultural soils due to nuclear power plant core melts, such as those at Chernobyl and Fukushima. Once deposited, these radionuclides persist in the upper soil layer for decades, where microbial activity is highest due to favorable conditions like organic matter, warmth, and gas exchange. Consequently, microorganisms in these upper layers, such as the plow layer in agricultural fields, face significant exposure to radioactivity. However, the impact of realistic levels of 137Cs and 90Sr on microbial communities and their functions remains largely unexplored. This dissertation examines the effects of radioactive contamination on microbial community structure and functions in soils. Typical agricultural soils, including an Orthic Luvisol and a Gleyic Cambisol, were artificially contaminated with varying concentrations of 137Cs and 90Sr, alongside radiolabeled substrates, and incubated in controlled laboratory microcosms. The lower concentrations mirrored those in the Chernobyl exclusion zone, while the higher levels reached up to 50 times the maximum hotspots for 137Cs in that area. The study involved three experiments assessing ionizing radiation effects on bacterial and fungal community structures, degradation of labeled substrates, fungal biomass development, and soil organic matter composition. Some microcosms were autoclaved and reinoculated with nat