129I levels in soils from Ukraine and Slovenia in the last decade

Abstract

129I is important as an environmental tracer of the biogeochemical cycling of iodine and of the dissemination of nuclear pollution, because anthropogenic 129I has been released from only few point sources and with its short mixing time its distribution therefore reveals the movement of 129I in the environment. A radiochemical neutron activation analysis method was developed to measure the concentration of 129I in soil samples. A procedure to pre-concentrate iodine from up to 150 g of soil was developed and validated using IAEA standard reference material IAEA-375 (Chernobyl soil). The method was applied to determine 129I/127I isotopic ratios as well as 129I and 127I concentrations in soils from several locations in Ukraine collected in 2006, 1996, 1993 and 1989, and from Slovenia, collected at various places in 2009 and 2006. The 127I concentrations in surface soils from Ukraine were in the range 2.3–23.1 µg g−1 and for 129I (11.1–245.7) · 10−8 µg g−1 dry matter with the highest value of 1.47 · 10−3 µg g−1 found in a soil sample collected in Yaniv, Ukraine in July 1993. In soil samples from Slovenia 127I concentrations ranged 0.73–130 µg g−1 and 129I (8.0–245.7) · 10−8 µg g−1. The 129I/127I isotopic ratios of surface soils from Ukraine were in the range of the order of 10−9–10−5 and of 10−10–10−8 for soils from Slovenia. The highest isotopic ratio 13.6 · 10−5 was found in a soil sample collected in Yaniv, Ukraine in July 1993.