Accumulation of 137Cs after potassium fertilization in plant organs of Salix viminalis L. and in combusted ash

The effect of potassium (K) application at a common rate on 137Cs uptake and distribution within basket willow (Salix viminalis L.) and 137Cs activity in willow ash was studied in a three-year field experiment on a sandy soil. Experimental plots fertilized with 60 kg N and 48 kg K per ha were compared with a control with similar N but no K fertilization. There was no significant difference in 137Cs activity concentrations in plants growing on plots with or without fertilizer K. Higher concentrations of 137Cs activity were found in roots and leaves of willow than in stems and cuttings. The highest 137Cs activity concentration was detected in the fine roots (size 0–1 mm). The transfer factor (TFg) of 137Cs in different plant organs varied between 0.1 × 10−3 and 2.6 × 10−3 m2 kg−1. After combustion, 137Cs activity concentrations in ash produced from wood chips from K-fertilized plots were significantly lower than those in ash originating from plots without K fertilization. Fly ash had higher 137Cs concentrations than bottom ash and all ash samples had 137Cs concentrations that were well below the 10 000 Bq kg−1 Swedish limit for spreading on land.