Chemical speciation analysis of I-129 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 iodi de and iodate species in seawater. Iodide and iodate were first separated b y anion exchange method from seawater; the separated fractions of various c hemical species of iodine were further concentrated by solvent extraction a nd then converted to LiI irradiation target. The concentrations of I-129 an d 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 iodi de 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 m ethod to study the geochemical cycle of iodine in the ocean was investigate d. The preliminary results indicate that this is possible, and that this me thod can be also used for the investigation of the transport, dispersion an d mixture of water masses by using I-129 discharged from reprocessing facil ities as a tracer. (C) 2001 Elsevier Science B.V. All rights reserved.