The presence of Cs-137 in Austria is primarily attributable to the Chernobyl nuclear disaster in 1986, although the extent of contamination depended heavily on local rainfall patterns immediately following the accident. As a result, the regions of Upper Austria, Salzburg, north-western Styria and parts of Carinthia in particular still exhibit significantly elevated soil radioactivity levels today. A smaller proportion of the Cs-137 originates from above-ground nuclear weapons tests carried out between the 1950s and 1980s. As radionuclides in forests are scarcely removed from the ecosystem by agricultural cultivation, they remain in the humus layer for a particularly long time and can be taken up by plants and fungi there.

The study is based on extensive sampling carried out in 2022 and 2023. Two projects were conducted. One project involved mushroom monitoring commissioned by the Federal Ministry of Social Affairs, Health, Care and Consumer Protection (BMASGPK). This focused on determining caesium-137 levels in chanterelles, porcini, bay boletes and parasol mushrooms. To this end, samples were taken from many areas across Austria, covering all federal states (except Vienna). Care was taken to ensure that the mushrooms were collected from sites affected to varying degrees by the Chernobyl disaster.

In the second project, entitled ‘Distribution of Radionuclides in the Forest Ecosystem’, commissioned by Department V/8 Radiation Protection of the then Federal Ministry for Climate Protection, Environment, Energy, Mobility, Innovation and Technology (BMK), which is now part of the Federal Ministry of Agriculture and Forestry, Climate and Environmental Protection, Regions and Water Management (BMLUK), sites were selected that had been more severely affected by Chernobyl. Various wild mushrooms were sampled, such as the false morel, golden bolete, ochre bolete, snow cap, bread-crust fungus, trumpet chanterelle and violet lacquer funnel.

Overall, the study shows that forest ecosystems retain radionuclides for decades and that fungi play a central role in the transfer of these substances. The behaviour of Cs-137 and its uptake by fungi is complex and highly variable. However, for future radiological incidents, the transfer factors obtained provide an important basis for rapidly estimating how high potential fungal contamination levels might be and which species would be affected to what extent.