Analysis of 129I and 127I in soils of the Chernobyl Exclusion Zone, 29 years after the deposition of 129I

Shaw, G. et al. (2019) Analysis of 129I and 127I in soils of the Chernobyl Exclusion Zone, 29 years after the deposition of 129I. Science of the Total Environment, 692, pp. 966-974. (doi: 10.1016/j.scitotenv.2019.07.319) (PMID:31540000)

Abstract

The Chernobyl Exclusion Zone (CEZ) represents a unique natural laboratory that received significant 129I contamination across a range of soils and land-use types in a short time period in 1986. Data are presented on 129I and 127I in soil samples collected from highly contaminated areas in the CEZ in 2015. The geometric mean (GM) total concentration of stable iodine (127I) was 6.7 × 10−7 g g−1 and the (GM) total concentration of 129I was 2.39 × 10−13 g g−1, equivalent to 1.56 mBq kg−1. GM total 127I concentration is below the European average soil concentration of 3.94 × 10−6 g g−1, while 129I is significantly higher than the pre-Chernobyl activity concentration for 129I of 0.094 mBq kg−1. Significant differences were found in the extractability of native, stable 127I and 129I almost 30 years after the introduction of 129I to the soils. Both 127I and 129I were predominantly associated with alkaline-extractable soil organic matter, established using a three-step sequential extraction procedure. Whereas 127I was significantly correlated with gross soil organic matter (measured by loss on ignition), however, 129I was not. The ratio of 129I/127I was significantly lower in extracts of soil organic matter than in more labile (soluble and adsorbed) fractions, indicating incomplete equilibration of 129I with native 127I in soil humic substances after 29 years residence time in the CEZ soils. The initial physico-chemical form of 129I in the CEZ soils is unknown, but the widespread presence of uranium oxide fuel particles is unlikely to have influenced the environmental behaviour of 129I. Our findings have implications for long-term radiation dose from 129I in contaminated soils and the use of native, stable 127I as a proxy for the long-term fate of 129I.

• Item Type: Articles
• Additional Information: This work was carried out within the TREE (Transfer-Exposure-Effects) consortium, one of three projects within the Radioactivity and the Environment (RATE) programme funded jointly by the Natural Environment Research Council, Radioactive Waste Management Ltd. and the Environment Agency (grant no. NE/L000504/1). We thank M. D. Bondarkov and J. Makluk (Chornobyl Center for Nuclear Safety, Radioactive Waste and Radioecology, Slavutych) and Thawatchai Itthipoonthanakorn (Office of Atoms for Peace, Bangkok, Thailand) for their kind assistance. Finally, we thank four anonymous reviewers for their help in improving the manuscript.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Xu, Dr Sheng and Freeman, Professor Stewart
• Authors: Shaw, G., Bailey, E., Crout, N., Field, L., Freeman, S., Gaschak, S., Hou, X., Izquierdo, M., Wells, C., Xu, S., and Young, S.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Science of the Total Environment
• Publisher: Elsevier
• ISSN: 0048-9697
• ISSN (Online): 1879-1026
• Published Online: 21 July 2019
• Copyright Holders: Copyright © 2019 Elsevier B.V.
• First Published: First published in Science of the Total Environment 692:966-974
• Publisher Policy: Reproduced under a Creative Commons License