An evaluation of ratio systems in radioecological studies

Replicate samples of soil, Juncus squarrosus and Calluna vulgaris were taken within a grid system on an organic peatland soil site in Ireland. A similar sampling survey was carried out on an organic rich forest soil site in Sweden, where Vaccinium myrtillus and Vaccinium vitis-idaea with corresponding soil samples were taken within a Picea abies stand. The data were used to investigate the relationship between soil and plant Cs-137 content and to examine the validity of using ratios to describe this relationship. Findings from both countries were in agreement. There were no significant changes in plant Cs-137 concentration associated with increasing soil content. When data from both countries were merged and treated as a single data set, a significant overall positive correlation (95% confidence level) between soil and plant Cs-137 levels was observed. Concentration ratios and transfer factors were calculated for Cs-137 and K-40 uptake from soils to plants. Both ratio types exhibited a clearly defined decrease associated with increasing soil concentrations for both radionuclides. Findings demonstrate serious problems with the use of ratios for the evaluation of radionuclide transfer.