Anthropogenic 129I concentration and 129I/127I ratio in rainwater from Seville (Spain) in the period 2005-2008 as affected by airborne releases from Sellafield and La Hague facilities

Abstract

129I is a very long-lived radionuclide (T 1/2=15.7×10 6 years) that is present in the environment both because of natural and anthropogenic sources. In this work 129I concentration and 129I/ 129I ratio have been determined in rainwater samples collected at Seville (south-western Spain) during the period 2005-2008. Typical 129I concentration range from (0.26-8.86)×10 8 atoms/L, while 129I deposition are normally in the order of 10 7-10 8 atoms/m 2d. Variability in the isotopic ratio 129I/ 129I indicates a range of (0.17-8.71)×10 -8. Temporal evolution of the 129I deposition seem to be related with the history of the 129I gaseous releases from the European reprocessing facilities at Sellafield and La Hague. The results obtained in this work are lower than the reported in previous works for the same location during the period 1996-1999, probably due to the reduction of the total gaseous 129I releases emitted by Sellafield and La Hague. The study of the dependence of the 129I deposition with some atmospheric parameters suggests that deposition seems to be more important in wet than in dry periods and that also depends in the wind direction, being more important for winds with north to south component. The agreement between the 129I concentration and the 129I/ 129I ratio suggest that the gaseous 129I emitted by the reprocessing plants has enough time to equilibrate with the 127I present in the atmosphere before arriving to southern Spain, probably due to the distance between Seville and these reprocessing plants. © 2012 Elsevier Ltd.