RADIOCAESIUM SOIL-TO-WOOD TRANSFER IN COMMERCIAL WILLOW SRC ON CONTAMINATED FARM LAND

The feasibility of the application of willow short rotation coppice (SRC) for energy production as a revaluation tool for severely radiocaesium contaminated land was studied. The effect of crop age, clone and soil type on the radiocaesium levels in the wood was assessed following sampling in 14 existing willow SRC fields, planted on radiocaesium contaminated land in Sweden following Chernobyl deposition. There was only one plot where willow stands of different maturity and clone were sampled and no significant differences were found. The soil types differed in texture, radiocaesium sorption characteristics, organic matter content and/or nutrient status, yet differences in soil characteristics were not extreme. The soil-to-wood transfer factor (TF) of radiocaesium differed significantly between soil types. The TF recorded was generally small (0.00086-0.016 kg kg-1), except for willows established on sandy soil (0.19-0.46 kg kg-1). Apart from the weak yet significant exponential correlation between the Cs-TF and the solid/liquid distribution coefficient (R²=0.54) or the radiocaesium interception potential, RIP (R²= 0.66), no single significant correlations between soil characteristics and TF were found. The wood – soil solution 137Cs concentration factor (CF) was significantly related to the potassium concentration in the soil solution. A different relation was, however, found between the sandy Trödje soils and the other soils. Differences in the ageing rate of radiocaesium in the soil, the soil K-status and the ammonium concentration in the soil solution are put forward as potential factors explaining this difference. Though from the dataset available, it was not possible to unequivocally predict the Cs-soil-to-wood-transfer, the generally low TFs observed, points to the particular suitability for establishment of SRC on radiocaesium contaminated land.