Bavarian Forest: mushrooms still contaminated with radioactivity – Bavaria

The chestnut bolet or Imleria badia is a very popular edible mushroom. This is of course primarily due to its intense, tasty, nutty aroma. In addition, chestnut boletus can not only be freshly prepared. But also drying and grinding and even freezing. And they are among the most common mushrooms in this country. Even less knowledgeable mushroom friends can identify them with certainty. Because with their hemispherical dark brown hats they look like chestnuts, which is why they are often just called chestnuts. But Imleria badia is not without risk.

The mycologist Claus Bässler, who oversees fungal studies in the Bavarian Forest National Park and teaches nature conservation biology at the Goethe University in Frankfurt, has now discovered chestnuts that contain up to 3100 Bequerel cesium per kilogram as part of a study in the protected area. That is five times as much as the limit of 600 Bequerel, above which mushrooms are no longer allowed on the market. What is special about the study is that the researchers not only measured the cesium contamination of the fungi, but also that of the soil on which they grew. To do this, they defined sample areas 36 across the national park and took samples of both mushrooms and the soil.

The high values ​​of the Bayerwald-Schwammerl surprised Bässler and his employees very much. At the same time, they assume that the burden in other regions of the Free State will not be significantly lower. The Chernobyl nuclear disaster was 35 years ago. During the GAU on April 26, 1986 in the Soviet nuclear power plant in what is now the Ukraine, enormous amounts of radioactive substances were released and some of the soils in Bavaria were extremely heavily contaminated – especially in Swabia and Old Bavaria. The result was an equally rapid and sometimes immense burden, especially of mushrooms, but also of game, especially wild boar, especially with the long-lived cesium.

A third of the mushroom samples for the study have broken the limit.

“Of course, it was to be expected that the cesium would migrate down into the deeper soil layers over time, thus reducing the burden on plants and animals,” says Bässler. “But that did not happen.” And not only when it comes to the chestnut boletus. In porcini mushrooms (Boletus edulis), the second type of fungus examined in the study, which naturally absorbs significantly less radioactivity than Imleria badia, the researchers discovered cesium concentrations of up to 600 bequerels per kilo. All in all, a third of the mushroom samples for the study broke the limit. “That’s a lot,” says Baessler, who likes to eat mushrooms himself – “but not very often,” as he immediately added, “the health risk is simply too high for me because of the radioactivity”.

So far there have only been hypotheses about the reasons why the cesium remains up in the forest floor. “It probably has to do with the metabolism of plants, animals and fungi,” says Bässler. “They take it in, as it were, in a perpetual cycle, excrete it, take it up again, excrete it and so on.” This obviously prevents the radioactive material from reaching deeper soil layers over time, where it can no longer be reached by plants, animals and fungi. For Bässler it is also clear “that the burden will certainly remain with us longer than many assumed”.

Open detailed view

The load on soils and fungi can change very quickly from region to region.

But that’s not the only surprise the researchers have experienced. They have also found that the loads on soils and fungi can change regionally very quickly and, moreover, do not automatically correspond with one another. “In the old area of ​​the national park, between Lusen and Rachel, the soil is less contaminated than in the expansion area around the Falkenstein,” says the mycologist. “On the other hand, in the Rachel-Lusen area, it is the fungi in the higher elevations that are more heavily contaminated, while on the Falkenstein it is those in the lower elevations.” Bässler suspects that the contamination of the soil is not the only reason for the pollution of the fungi. “The very different growth conditions, including the microclimate, in the respective locations could also play a role,” he says. “But more studies would be needed to clarify this.”

Bässler Mushroom friends can already advise this much: “If you don’t want to take in too much cesium, you should curb your passion in the future”, says the mycologist. “And you should focus on species like the boletus, which is not very good at accumulating cesium.” This does not mean that only porcini mushrooms should ever go into the saucepan. Also the very popular real chanterelle (Cantharellus cibarius) is usually comparatively lightly polluted. “However, you should be familiar with the chanterelles,” says Bässler. “The trumpet chanterelle, a sister species of the real chanterelle, which is admittedly not so in the focus of mushroom hunters, can be equated with chestnuts in terms of radioactivity.”