Main content area

Iodine-129, Iodine-127 and Cesium-137 in seawater from the North Sea and the Baltic Sea

Daraoui, A., Tosch, L., Gorny, M., Michel, R., Goroncy, I., Herrmann, J., Nies, H., Synal, H.-A., Alfimov, V., Walther, C.
Journal of environmental radioactivity 2016 v.162-163 pp. 289-299
anion exchange, cesium, explosions, gamma spectrometry, iodine, isotopes, radioactivity, radionuclides, salinity, seawater, sediments, Baltic Sea, English Channel, North Sea, United Kingdom
In this study, new data are presented for the iodine isotopes (¹²⁷I, ¹²⁹I and their isotopic ratios) and Cesium (¹³⁷Cs) in water samples of the North Sea and the Baltic Sea in 2005 and 2009. This study supplements and extends the study of Michel et al. (2012). Iodine isotopes were separated from their matrix by using an anion exchange method and were determined by applying ICP-MS and AMS. ¹³⁷Cs in seawater was determined after cesium ion exchange procedure enrichment by gamma-spectrometry. The concentrations of ¹²⁷I in seawater of the North and Baltic Sea are fairly constant in each Sea with averages of (44 ± 2) and (21 ± 1) ng g⁻¹, respectively, depending on the salinity. However, large variations of ¹²⁹I concentrations in these areas were detected, which decreased along the French, Belgian, Dutch, German, and Danish shores. ¹²⁹I/¹²⁷I isotope ratios in the Baltic Sea are about 10 times lower than in the North Sea in 2009. The highest isotopic ratios (2.7 × 10⁻⁶) was detected in the English Channel east of the nuclear reprocessing plant at Cap de la Hague. The results confirm the result of our early study that the sources of ¹²⁹I in the North Sea are primarily the nuclear reprocessing facilities at Sellafield (UK) and La Hague (F), and that in the Baltic Sea the inflow of water from North Sea through the Danish Straits dominates the occurrence of ¹²⁹I.In 2009, the activity concentration of ¹³⁷Cs was at least 6 times higher in the Baltic Sea (37 Bq m⁻³) than in the North Sea (5.9 Bq m⁻³), due to release of ¹³⁷Cs from sediments in the Baltic Sea, which were contaminated by the Chernobyl accident and – to a minor degree – the atmospheric explosions of atomic bombs. The results are discussed by comparing the results of our previous work and the current study demonstrating the continuing disequilibrium of ¹²⁹I/¹²⁷I atomic ratio in the environmental compartments.