Search

International audience; The molecular environment of iodine in reference inorganic and organic compounds, and in dry humic and fulvic acids (HAs and FAs) extracted from subsurface and deep aquifers was probed by iodine L 3-edge X-ray absorption spectroscopy. The X-ray absorption near-edge structure (XANES) of iodine spectra from HAs and FAs resembled those of organic references and displayed structural features consistent with iodine forming covalent bonds with organic molecules. Simulation of XANES spectra by linear combination of reference spectra suggested the predominance of iodine forming covalent bonds to aromatic rings (aromatic-bound iodine). Comparison of extended X-ray absorption fine structure (EXAFS) spectra of reference and samples further showed that iodine was surrounded by carbon shells at distances comparables to those for references containing aromatic-bound iodine. Quantitative analysis of EXAFS spectra indicated that iodine was bound to about one carbon at a distance d (I–C) of 2.01(4)–2.04(9) A ˚ , which was comparable to the distances observed for aromatic-bound iodine in references (1.99(1)–2.07(6) A ˚), and significantly shorter than that observed for aliphatic-bound iodine (2.15(2)–2.16(2) A ˚). These results are in agreement with previous conclusions from X-ray photoelectron spectros-copy and from electrospray ionization mass spectrometry. These results collectively suggest that the aromatic-bound iodine is stable in the various aquifers of this study.

As a long-lived beta-emitting radioisotope of iodine, I-129 is produced both naturally and as a result of human nuclear activities. At present time, the main part of I-129 in the environment originates from the human nuclear activity, especially the releases from the spent nuclear fuel reprocessing plants, the I-129/I-127 ratios have being reached to values of 10(-10) to 10(-4) in the environment from 10(-12) in the pre-nuclear era. In this article, we review the occurrence, sources, inventory, and concentration level of I-129 in environment and the method for speciation analysis of I-129 in the environment. Measurement techniques for the determination of I-129 are presented and compared. An overview of applications of I-129 speciation in various scientific disciplines such as radiation protection, waste depository, and environmental sciences is given. In addition, the bioavailability and radiation toxicity (close to thyroid) of I-129 are discussed. (C) 2008 Elsevier B.V. All rights reserved.