Distribution and source of 129I, 239,240Pu, 137Cs in the environment of Lithuania

Fifty five soil samples collected in the Lithuania teritory in 2011 and 2012 were analyzed for 129I, 137Cs and Pu isotopes in order to investigate the level and distribution of artificial radioactivity in Lithuania. The activity and atomic ratio of 238Pu/239,240Pu, 129I/127I and 131I/137Cs were used to identify the origin of these radionuclides. The 238Pu/239+240Pu and 240Pu/239Pu ratios in the soil samples analyzed varied in the range of 0.02-0.18 and 0.18-0.24, respectively, suggesting the global fallout as the major source of Pu in Lithuania. The values of 10−9 to 10−6 for 129I/127I atomic ratio revealed that the source of 129I in Lithuania is global fallout in most cases though several sampling sites shows a possible impact of reprocessing releases. Estimated 129I/131I ratio in soil samples from the southern part of Lithuania shows negligible input of the Chernobyl fallout. No correlation of the 137Cs and Pu isotopes with 129I was observed, indicating their different sources terms. Results demonstrate uneven distribution of these radionuclides in the Lithuanian territory and several sources of contamination i.e. Chernobyl accident, reprocessing releases and global fallout.