The abundance and activity of microorganisms in the soil under at increasing radioactive contamination

Abstract

The research was conducted at two landfills with different levels of contamination by radioactive substances. Landfill 1 is located on the border with the Exclusion Zone of the Chornobyl nuclear power plant. Within landfill 1, three soil sampling points were selected, differing in the degree of radioactive soil contamination. Landfill 2 (four sampling points) is located in the Chornobyl Exclusion Zone directly near the area of the so-called "Red Forest". At this landfill, the sites identified for soil sampling are characterized by a significantly higher level of radionuclide contamination compared to those at landfill 1.It was found that low levels of radioactive contamination contributed to the activation of the development of microorganisms. Within landfill 1, the accumulation of microbial mass was the smallest with low contamination and the biggest with higher contamination. At the same time, the soil of landfill 2 showed significantly lower (within one order) indicators, especially at the point with the highest contamination.Determination of the dynamics of the number of fungi in the studied soils shows similar changes in indicators depending on the level of radioactive contamination. Thus, the number of fungi in the soil of landfill 1, as a rule, increases with increasing levels of pollution. However, in the soil of landfill 2, the lowest number of micromycetes among the studied variants was noted during the entire period of research. At the same time, the number of fungi is 10-100 times lower than the corresponding indicator for the soils of landfill 1, depending on the sampling points.The feature noted for fungi is also characteristic of cellulolytic bacteria, however, due to their very low quantity, they may have an insignificant role in the processes of destruction of plant residues under the studied conditions.When determining the number of ammonifying microorganisms, it was found that this group of representatives of the soil microbiota becomes more active withthe increasing levels of radionuclide contamination at landfill 1. At the same time, the development of ammonifying microorganisms is suppressed in the soils of landfill 2, especially at the point with the highest level of pollution. Therefore, the peptolytic pathway of the destruction of organic residues (ammonification) is generally consistent with the course of development of pathogens of the saccharolytic pathway (primarily fungi).The conducted studies indicate the dependence of the development and functioning of microorganisms – destructors of plant mortmass on the level of ionizing radiation. Relatively low absorbed dose rates in the soil of landfill 1 (up to 1.6 μGy/hour) stimulated the development of microorganisms and contributed to the accumulation of their biomass. High absorbed dose rates in the soil of landfill 2 (from 3.7 to 84.0 μGy/hour) negatively affect the studied indicators.