Chemical speciation analysis of 129I in seawater and a preliminary investigation to use it as a tracer for geochemical cycle study of stable iodine

A method was developed for the determination of the I-129 and I-127 in iodide and iodate species in seawater. Iodide and iodate were first separated by anion exchange method from seawater; the separated fractions of various chemical species of iodine were further concentrated by solvent extraction and then converted to LiI irradiation target. The concentrations of I-129 and I-127 in various fractions were determined by neutron activation analysis using nuclear reactions of I-129 (n, gamma)I-130 and I-127(n, gamma) I-128, respectively. Surface and bottom seawater samples from three locations in the Kattegat and Baltic Sea were analyzed for I-129 and I-127 in both iodide and iodate species and total inorganic iodine. Levels as low as 2.3 X 10(-15) M I-129 and 7 nM I-127 were measured. The possibility of using this method to study the geochemical cycle of iodine in the ocean was investigated. The preliminary results indicate that this is possible, and that this method can be also used for the investigation of the transport, dispersion and mixture of water masses by using I-129 discharged from reprocessing facilities as a tracer. (C) 2001 Elsevier Science B.V. All rights reserved.