The 1986 Chernobyl nuclear catastrophe significantly affected Central Europes forest ecosystem. Post-accident, high radioactive contamination led to advisories against consuming mushrooms and impacted wild video game meat for years. Over time, the radioactivity in deer and roe deer meat reduced as anticipated, but wild boar meat continued to reveal all of a sudden high radioactivity levels, surpassing safety limitations in some cases even today.
The ratio of the two types of cesium is not constantly the same– for example, the fallout from the Chernobyl nuclear accident had an isotope finger print different from that of the nuclear weapons tests of the 1960s. Therefore, the contamination of wild boar meat is likewise not expected to reduce substantially in the next couple of years, since some of the cesium from Chernobyl is only now being included into the truffles.
Recent research has actually uncovered that the relentless radioactive contamination in Central Europes swine meat, an outcome of the Chernobyl disaster, is also substantially affected by cesium from 1960s nuclear weapons tests, highlighting complicated eco-friendly interactions and the important function of exact scientific analysis. Credit: Joachim Reddermann/ TU Wien
Years following the Chernobyl nuclear disaster, wild boar meat continues to exhibit all of a sudden high levels of radioactivity. The option to the riddle: a crucial other cause had been overlooked.
The 1986 Chernobyl nuclear disaster substantially affected Central Europes forest environment. Post-accident, high radioactive contamination resulted in advisories against consuming mushrooms and affected wild video game meat for several years. In time, the radioactivity in deer and roe deer meat decreased as expected, however wild boar meat continued to reveal suddenly high radioactivity levels, surpassing safety limitations sometimes even today.
This consistent abnormality, referred to as the “wild boar paradox,” baffled experts for years. Recent in-depth research studies by TU Wien (Vienna) and the Leibniz University of Hannover have uncovered a description: It is a late consequences of the nuclear weapons tests from the 1960s.
More radiation than physics permits?
” The most important component for the radioactivity of the samples is cesium-137, with a half-life of about 30 years,” says Prof. Georg Steinhauser of TU Wien. “Hence, after 30 years, half of the product has actually decomposed all by itself.” Radiation direct exposure to food, nevertheless, usually declines much quicker.
The cesium has distributed since Chernobyl, was washed out by rainwater, bound to minerals, or possibly migrated deep into the soil, so it is no longer absorbed by plants and animals in the very same quantities as it was instantly after the reactor accident. Thus, after one half-life, most food samples show not merely just half the initial activity concentration, however much less.
When it comes to wild boar meat, nevertheless, things are different: there, the radiation levels have actually remained practically constant. They reduce far more slowly than would be anticipated from the natural radioactive decay of cesium alone– a result that at first glimpse appears totally contradictory from a physical point of view.
To this day, samples of wild boar meat are still determined that disagree for usage because their radiation levels clearly go beyond the allowed limit. This might also be a reason for the fact that swines experience less hunting pressure in some areas and their overpopulation often causes great damage to farming and forestry.
In search of the cesium finger print
Prof. Georg Steinhauser, who moved from Leibniz Universität Hannover to TU Wien in 2022, and his group set out to get to the bottom of this puzzle: By making new, more precise measurements, they wished to figure out not only the quantity but also the origin of the radioactivity.
” This is possible because various sources of radioactive isotopes have different physical finger prints,” explains Dr. Bin Feng, who performs his research at the Institute of Inorganic Chemistry at Leibniz Universität Hannover and the TRIGA Center Atominstitut at TU Wien. The ratio of the two types of cesium is not constantly the exact same– for example, the fallout from the Chernobyl nuclear mishap had an isotope fingerprint different from that of the nuclear weapons tests of the 1960s.
“Since it has such a long half-life and seldom decomposes, you cant just find it with radiation detectors,” says Georg Steinhauser. “You have to work with mass spectrometric methods and go to reasonably great lengths to differentiate it precisely from other atoms.
The outcomes revealed that while a total of about 90% of the cesium-137 in Central Europe comes from Chernobyl, the percentage in the wild boar samples is much lower. Rather, a big percentage of the cesium in swine meat is attributable to nuclear weapons screening– approximately 68% in some samples.
The deer truffle is (most likely) to blame
The reason for this lies in the very special food preferences of swines: they especially like to collect deer truffles from the ground, and the radioactive cesium builds up in these subterranean mushrooms with a veteran hold-up. “The cesium migrates downwards through the soil extremely slowly, sometimes only about one millimeter each year,” states Georg Steinhauser.
Deer truffles, which can be discovered at depths of 20-40 centimeters, are therefore just now soaking up the cesium that was released in Chernobyl. The cesium from “old” nuclear weapons tests, on the other hand, has actually currently gotten here there some time back.”
Hence, there is a complex interaction of various effects: Both the cesium from the nuclear weapons tests and the cesium from Chernobyl spread through the soil, and the truffles are hence reached by two different “cesium fronts” that gradually move through the soil. On the other hand, the cesium decomposes over the years.
” If you include up all these results, it can be explained why the radioactivity of deer truffles– and subsequently of pigs– stays relatively consistent for many years,” says Georg Steinhauser. Hence, the contamination of swine meat is likewise not anticipated to decrease significantly in the next couple of years, due to the fact that a few of the cesium from Chernobyl is only now being integrated into the truffles. “Our work reveals how made complex the correlations in natural environments can be,” says Georg Steinhauser, “however likewise exactly that the answers to such riddles can be found if your measurements are adequately precise.”
Recommendation: “Disproportionately High Contributions of 60 Year Old Weapons-137Cs Explain the Persistence of Radioactive Contamination in Bavarian Wild Boars” by Felix Stäger, Dorian Zok, Anna-Katharina Schiller, Bin Feng and Georg Steinhauser, 30 August 2023, Environmental Science & & Technology.DOI: 10.1021/ acs.est.3 c03565.