A weighted bootstrap method for the determination of probability density functions of freshwater distribution coefficients (Kds) of Co, Cs, Sr and I radioisotopes

• Published in: Chemosphere (Oxford) Vol. 65; no. 8; pp. 1308 - 1320
• Main Authors: Durrieu, G., Ciffroy, P., Garnier, J.-M.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.11.2006; Elsevier
• Subjects: Applied sciences; Biological and physicochemical phenomena; Cesium - analysis; Cesium - chemistry; Cobalt - analysis; Cobalt - chemistry; Distribution coefficient; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Fresh Water - chemistry; Hydrogen-Ion Concentration; Iodine - analysis; Iodine - chemistry; Natural water pollution; Phase Transition; Pollution; Pollution, environment geology; Probability; Radioisotopes - analysis; Radioisotopes - chemistry; Radionuclides; Risk assessment; Statistical analysis; Strontium - analysis; Strontium - chemistry; Time Factors; Water Pollutants, Radioactive - analysis; Water Pollutants, Radioactive - chemistry; Water treatment and pollution; Database; Radionuclides; Distribution coefficient; Statistical analysis; Risk assessment; Uncertainty; Radioactive pollution; Pollutant behavior; Cesium; Partition coefficient; Conditional probability; Radioisotope; Cobalt; Strontium; Surface water; Probability density function; Bootstrap; Stream; Phase partition; Water pollution; Iodine
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2006.04.028

The objective of the study was to provide global probability density functions (PDFs) representing the uncertainty of distribution coefficients (Kds) in freshwater for radioisotopes of Co, Cs, Sr and I. A comprehensive database containing Kd values referenced in 61 articles was first built and quality scores were affected to each data point according to various criteria (e.g. presentation of data, contact times, pH, solid-to-liquid ratio, expert judgement). A weighted bootstrapping procedure was then set up in order to build PDFs, in such a way that more importance is given to the most relevant data points (i.e. those corresponding to typical natural environments). However, it was also assessed that the relevance and the robustness of the PDFs determined by our procedure depended on the number of Kd values in the database. Owing to the large database, conditional PDFs were also proposed, for site studies where some parametric information is known (e.g. pH, contact time between radionuclides and particles, solid-to-liquid ratio). Such conditional PDFs reduce the uncertainty on the Kd values. These global and conditional PDFs are useful for end-users of dose models because the uncertainty and sensitivity of Kd values are taking into account.