BIOSPHERIC I-129 CONCENTRATIONS IN THE PRE-NUCLEAR AND NUCLEAR-AGE

In order to detect characteristic regional differences or temporal cha nges of I-129 concentrations in the biosphere, thyroids from humans, g razing livestock, and herbivorous wildlife species (reindeer and roede er) were collected in various areas of the world which are not affecte d by reprocessing plants. For reasons of comparison, all samples were analyzed for their I-129:I-127 atom ratios. Human and bovine thyroids taken from the 10th region in Southern Chile (39-degrees-41-degrees So uth) indicated values of the I-129:I-127 atom ratio between 1.1 x 10(- 9) and 2.0 x 10(-9) and between 1.2 x 10(-10) and 9 x 10(-9), respecti vely. They showed no significant increase in the concentration of bios pheric I-129 in comparison with that established in the pre-nuclear ag e. Atom ratios found in human thyroids collected in Lower Saxony (Fede ral Republic of Germany), which is a region not directly affected by r eprocessing plants, exhibited I-129:I-127 values between 8 x 10(-9) an d 6 x 10(-8) from February 1988 to September 1990. Thyroid glands of r eindeer and roedeer as well as heather, moss, and lichen were taken fr om the Vilhelmina, Heby, and Gavle communes in Sweden and analyzed for I-129 and I-127. All three communes were found to be seriously contam inated by fallout from the Chernobyl accident. Highest I-129:I-127 ato m ratios between 3.5 x 10(-7) and 1 x 10(-6) were found in the Gavle c ommune (approximately 150 km northwest of Stockholm) where the highest Cs-137 ground deposition (70-80 kBq m-2) was measured. Two soil sampl es taken from Krasnaya Gora and Mirny locations in Russia (approximate ly 200 km northeast of Chernobyl) exhibited ratios of about 1 x 10(-6) . These locations showed a Cs-137 ground deposition of 370 and 1,300 k Bq m-2, respectively.