Soil-to-plant transfer factors of radioactive Ca, Sm and Pd isotopes: critical assessment of the use of analogies to derive best-estimates from existing non-specific data

• Published in: Journal of environmental radioactivity Vol. 136; pp. 152 - 161
• Main Authors: Henner, Pascale, Hurtevent, Pierre, Thiry, Yves
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.10.2014; Elsevier
• Subjects: Assessments; Calcium; Calcium - metabolism; Calcium Radioisotopes - metabolism; Conservation; Earth sciences; Earth, ocean, space; Exact sciences and technology; Isotopes; Life Sciences; Mathematical models; Models, Theoretical; Palladium; Palladium - metabolism; Phylogeny; Plants (organisms); Plants - metabolism; Radiation Monitoring; Radioactive Waste; Radioactivity; Radioisotopes - metabolism; Radionuclides; Samarium; Samarium - metabolism; Soil (material); Soil Pollutants, Radioactive - metabolism; Soil-to-plant transfer factor; Soils; Surficial geology; Use of analogues; Waste Disposal Facilities; Radionuclides; Palladium; Use of analogues; Samarium; Calcium; Soil-to-plant transfer factor; risk assessment; samarium; calcium; cerium; Plantae; radionucleids; biosphere; classification; variability; subtropical zone; rare earths; temperate zone; prediction; palladium; radioactive isotopes; soils
• ISSN: 0265-931X; 1879-1700
• DOI: 10.1016/j.jenvrad.2014.06.003

45Ca, 151Sm and 107Pd are three radionuclides present in low to intermediate in activity radioactive wastes for which no soil-to-plant Transfer Factors (TF) values are available to be used in biosphere models for Ecological Risk Assessment. In the absence of specific radioecological studies, this work reviews and analyzes the existing literature for stable isotopes of Pd, Sm and Ca in order to derive best estimates for TF values that could be used as Transfer Factors. Alternative methods of extrapolation are also critically assessed. The values have been classified according to climatic zone, plant class and soil type for each element. The overall geometric mean TF values (for all plants and conditions) was calculated as 8.4E-02 for Pd, for which the value of radioRu in TRS-472 is also available. The mean TF for Sm was 4.2E-04. This value was lower than the TF values for radioactive Ce that are proposed as alternative values for Sm in TRS-472. The former may be relevant for long term assessments and the latter could possibly used to describe the short term 151Sm post-release behaviour. The mean value for Ca is 2.3E-01 but varies considerably among plants of a given class due to the variety of plant Ca uptake behaviors. Alternatively, to limit this variability, Ca data content for dry plant matter, as analyzed using the phylogenetic method, could be used to derive TF values if the conservation of isotopic ratio of 45Ca to stable Ca in soils and in plants hypothesis is taken into account. The TF for Ca in sub-tropical zones is 10-fold lower than in temperate zones. There is a lot of data available about exchangeable Ca in soil, which mean that we could calculate an available TF. The analysis shows that Ca bioavailability is also a key factor within transfer. •Derivation of TF values for Pd, Sm and Ca based on stable isotope literature.•Assessment of alternative values for Pd based on radioactive Ru values from TRS-472 (IAEA).•Assessment of alternative values for Sm based on stable Ce values and radioactive Ce values from TRS-472 (IAEA).•Phylogenetic analysis of plant Ca content to help to derive TFs.•Conclusions on the use of values based on scenarios (radioactive discharge vs long term assessment).