Although precipitation is the main pathway of iodine to the earth's surface continental reservoirs, little is known about the distribution of the element in the atmosphere of Europe. A similar situation is encountered with the distribution of the radioactive isotope 129I. As seas represent the main reservoir of iodine, precipitation along coastal regions is expected to be more enriched with iodine than inland areas. The complex chemical forms, relatively rapid transformation of iodine compounds and short residence time in the atmosphere contribute to the difficulty of understanding the atmospheric distribution. Furthermore, the presently not well-known amount of direct atmospheric release of 129I is another obstacle in understanding the isotopic atmospheric distribution. With the aim of elucidating part of the problem, we present in this study new data and an overview on distribution and inventory of 129I over Europe that represents the major global atmospheric 129I reservoir. The study covers latitudes 37°N to 70°N (southern Spain to northern Sweden) and includes both rain and snow. The results show a general increase in 129I concentration with proximity to release (reprocessing facility at Sellafield and La Hague) and/or moisture source (oceans and seas). Furthermore, high concentrations of 129I seem to persist in precipitation irrespective of occurrence in high (70°N) or low (37°N) latitude. Precipitation sampled from high altitude region is generally depleted in 129I compared with samples from low altitude, although more data are needed to evaluate this trend. The total amount of 129I provided annually by precipitation over Europe composes, however, only a tiny portion of the annual marine and/or atmospheric discharge from the nuclear reprocessing facilities. The preliminary data presented here indicate that systematic and long lasting time series analysis of 129I in several parts of Europe and the world are needed in order to achieve a coherent picture about the distribution of the isotope in precipitation and also in dry fallout. Such data sets will provide vital information not only about 129I, but also about eventual hazardous release of 131I.
See more of Poster Session II
See more of The 10th International Conference on Accelerator Mass Spectrometry (September 5-10, 2005)