Soil fertilisation with Cs-137-contaminated and uncontaminated wood ash as a countermeasure to reduce Cs-137 uptake by forest plants

The purpose of present study was to find out whether wood ash with a high pH value and neutralizing capacity reduces Cs-137 uptake by forest plants many years after the radionuclide fallout. The effects of one-time point fertilisation with Cs-137-contaminated and uncontaminated wood ash alone or in combination with KCl on Cs-137 transfer from soil to young leaves and green shoots of various dwarf shrubs and tree species were examined in a long-term fertilisation experiment (2012-2021) conducted in Bazar mixed forest, around 70 km from Chernobyl nuclear power plant. The results indicated minor effects of soil fertilisation, although there were differences between Cs-137 uptake by species and years. Soil amendment with Cs-137-contaminated wood ash generally did not affect Cs-137 uptake by young shoots and leaves of plants over the growing season in the first year and only slightly decreased Tag for Cs-137 in the following years. The effect of a single application of Cs-137-uncontaminated wood ash on reducing Cs-137 uptake by plants was generally negligible. Application of Cs-137-contaminated wood ash in combination with KCl reduced plant Cs-137 uptake by about 45%, however, such reduction was only significant in some years for bilberry berries, young leaves and green shoots of lingonberry and alder buckthorn. Thus application of wood ash to Cs-137-contaminated forest soil many years after radionuclide fallout generally does not reduce Cs-137 uptake by forest vegetation in a mixed forest ecosystem and this countermeasure should be applied with caution.