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

129 I 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 129 I concentration and 129 I/ 129 I ratio have been determined in rainwater samples collected at Seville (south-western Spain) during the period 2005–2008. Typical 129 I concentration range from (0.26–8.86)×10 8 atoms/L, while 129 I deposition are normally in the order of 10 7 –10 8 atoms/m 2 d. Variability in the isotopic ratio 129 I/ 129 I indicates a range of (0.17–8.71) × 10 −8 . Temporal evolution of the 129 I deposition seem to be related with the history of the 129 I 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 129 I releases emitted by Sellafield and La Hague. The study of the dependence of the 129 I 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 129 I concentration and the 129 I/ 129 I ratio suggest that the gaseous 129 I emitted by the reprocessing plants has enough time to equilibrate with the 127 I present in the atmosphere before arriving to southern Spain, probably due to the distance between Seville and these reprocessing plants. ► 129 I and 129 I/ 127 I were determined in rainwater from Seville during 2005–2008. ► The results are lower than previous ones for the same location during 1996–1999. ► 129 I deposition is more important in wet periods and depends on the wind direction. ► Southern Spain was affected by airborne 129 I releases from Sellafield and La Hague.