Iodine-129:: Sample preparation, quality control and analyses of pre-nuclear materials and of natural waters from Lower Saxony, Germany

Sample preparation procedures for AMS measurements of I-129 and I-127 in environmental materials and some methodological aspects of quality assurance are discussed. Measurements from analyses of some pre-nuclear soil and thyroid gland samples and of a systematic investigation of natural waters in Lower Saxony, Germany, are described. Although the up-to-now lowest I-129/I-127 ratios in soils and thyroid glands were observed, they are still suspect to contamination since they are significantly higher than the pre-nuclear equilibrium ratio in the marine hydrosphere. A survey on all available I-129/I-127 isotopic ratios in precipitation shows a dramatic increase until the middle of the 1980s and a stabilization since 1987 at high isotopic ratios of about (3.6-8.3) x 10(-7). In surface waters, ratios of (57-380) x 10(-10) are measured while shallow ground waters show with ratios of (1.3-200) x 10(-10) significantly lower values with a much larger spread. The data for I-129 in soils and in precipitation are used to estimate pre-nuclear and modern 129I deposition densities. (C) 2000 Elsevier Science B.V. All rights reserved.