Four decades after the accident at the nuclear power plant located in Prypiat, the animals of Chernobyl they continue generating fascination. These survivors in one of the most contaminated regions in Europe they surprise us in many ways, but if there is an enigmatic species in this place it is the wild boar.
One of the most radioactive species from Chernobyl.
Solving the mystery. In 2023 it appeared a new trackrevealed by a team of researchers, about these animals: we finally know why their radioactivity is greater than that of other species. The answer has less to do with the nuclear accident itself than with something that happened long before.
More radioactive? There is very little we still know about the animals of Chernobyl. One of the most curious enigmas was that of wild boars. To understand why we have to talk about one of the most polluting radioactive isotopes, caesium 137 (Cs137).
The half-life of this isotope (the time in which half of the atoms we have of the material will have disintegrated) is just over 30 years. The concentration of cesium in the food chain should in principle be reduced even further since the atoms tend to leach into the soil or be carried away by water into rivers.
Going down. That is why the level of radioactivity in animals such as deer or roe deer has decreased significantly in the area. Not only has this situation not occurred in wild boar populations: their radiation levels have remained almost constant, that is, the decrease is not even in line with what the semi-disintegration of Cs137 would imply. It is the “wild boar paradox”.
Nuclear tests and radioactive truffles. The answer comes from cesium 135. The team that solved this mystery did so by focusing not on the radiation levels but on its origin. They verified that it was this other isotope of cesium that was behind this phenomenon. Cs135 has a much longer half-life, which explains why the reduction had been smaller.
This also makes it more difficult to detect the presence of Cs135. As explains the responsible team From the study, each type of nuclear incident has its own “signature.” It is estimated that 90% of the Cs137 present in Europe was released by the Chernobyl accident, but this is not the case for Cs135. The origin of this is 68% in the nuclear tests carried out in the context of the cold war.
Just the right depth. The diet of wild boars has also been one of the key factors when it comes to understanding the reason for their radiation levels. These animals feed on a type of truffle (Elaphomyces) that grows in the subsoil, at depths of between 20 and 40 centimeters.
As we pointed out before, part of the radioactive cesium It was seeping year after year into the soil of the area. At the rate of a few millimeters a year, cesium (both from nuclear tests and from the accident) has been advancing towards these depths, contaminating these mushrooms, a source of food for wild boars.
From Chernobyl to Bavaria. The study that clarified this mystery was carried out by analyzing a population of 48 wild boars in the state of Bavariasouthern Germany. The analysis details were published in the magazine Environmental Science & Technology.
In the long term. The results of the study invite us to think that the situation will not change in the short term. That is, it is unlikely that the radioactivity levels of wild boars will begin to decline in the coming years until they are equal to those of other similar animals such as deer or roe deer.
The greater radiation present in these animals has made hunters resist their capture. This implies that the populations of these wild boars will go increasing in the future. Perhaps their expansion through central Europe will cause the radiation levels of these animals to decline generation after generation but, from what we have seen, this process could still continue for decades.
Image | Joachim Reddemann / Кирилл Пурин
*An earlier version of this article was published in July 2024
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