Analysis: the area is ideal for researchers studying the long-term ecological effects of a nuclear disaster, but war has made it inaccessible
By Alexandre de Menezes, University of Galway and Olena Pareniuk, National Academy of Sciences of Ukraine
There is a renewed threat of nuclear explosions and radiation contamination in Europe because of the war in Ukraine. During the early stages of the war, the Russian army invaded the Chornobyl Exclusion Zone (its name in Ukrainian), damaged research laboratories, and threatened radiation containment procedures. Later, the Zaporizhzhia nuclear power plant, the largest in Europe, was also occupied and its physical integrity was put at risk.
We need to better understand how radiation affects people and ecosystems so that we can prepare for future scenarios where widespread environmental radiation contamination occurs. To do this, there is no better place than Chornobyl.
Despite an overall decrease in radiation levels, the radiation contamination in local soils remains very high today in some areas. The continuing existence of highly contaminated sites has led to some speculation that high radiation would lead to dangerous mutations in the DNA of bacteria and other microorganisms, turning the Chornobyl area into a hotspot for the emergence of new infectious diseases. However, this threat has not materialised nearly 37 years since the accident.
On the other hand, radiation may have more subtle effects on the local microorganisms, with consequences that are hard to predict. High radiation in soil may favour microorganisms better able to cope with increased biological stress, and since soil microbes carry out many key ecological processes, this could have knockdown effects on the whole ecosystem.
One essential microbial ecological process is the decomposition of organic matter from dead organisms. In some areas with very high radiation, leaf litter was found to decompose more slowly than in less contaminated sites. However, another study found the opposite situation, with greater organic matter breakdown in more radioactive sites, which was attributed to the microorganisms overcompensating the damaging effect of radiation and becoming more efficient at decomposing organic matter.
Soil microbes and forest fires
The Chornobyl ecosystem allows researchers to study unique ecological questions. One of these questions is how radiation stress can affect the stability of the ecosystem against further ecological disturbances. Changing weather patterns have made the summers drier and hotter, and the Chornobyl region has been increasingly afflicted by forest fires.
In 2017, I was able to join collaborators on an expedition to study how the local forests are being affected by the fires. I characterised the soil microbial community by DNA sequencing and found that radiation is one of the factors that correlates with the diversity of soil microorganisms.
Currently I am evaluating how fire affected the soil microorganisms differently in high radiation areas, however, more research is needed to untangle the effect of fire from those caused by other factors. Unfortunately, research is one of the casualties of this war, and access to the Chornobyl Exclusion Zone to carry out further experiments is currently impossible.
Microbes and radiation safety in Chornobyl power plant
A more pressing issue is how microbial activity may be compromising the integrity of the concrete structure built to contain the large amount of radioactive material remaining in the reactor 4 of the nuclear power plant. This is because the lifetime of the steel bearing constructions inside the containment shelter was calculated based on physical and chemical properties of the materials and did not take into account biocorrosion caused by bacteria.
My Ukrainian collaborator Olena Pareniuk is concerned that the high radiation environment inside the concrete shelter may be leading to the evolution of bacteria with increased ability to corrode the containment structures. If this is true, the radiation containment shelter may not last as long as expected, requiring a re-evaluation of the containment strategy.
While studying the bacteria living inside the exploded reactor is difficult due to the extreme levels of radiation, it is crucial for the long-term management of the site and may reveal novel microbial properties with applications in science and technology. We are hoping that calmer times will soon return to Ukraine so that we can resume our study of this fascinating region and its microbial inhabitants.