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Environ Sci Technol. 2011 Mar 15;45(6):2086-92. doi: 10.1021/es1032162. Epub 2011 Feb 15.

Formation of organic iodine supplied as iodide in a soil-water system in Chiba, Japan.

Author information

1
Department of Earth and Planetary Systems Science, Faculty of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan. shima-yoko@hiroshima-u.ac.jp

Abstract

Speciation of iodine in a soil-water system was investigated to understand the mechanism of iodine mobility in surface environments. Iodine speciation in soil and pore water was determined by K-edge XANES and HPLC-ICP-MS, respectively, for samples collected at a depth of 0-12 cm in the Yoro area, Chiba, Japan. Pore water collected at a 0-6 cm depth contained 50%-60% of organic iodine bound to dissolved organic matter, with the other portion being I(-). At a 9-12 cm depth, 98% of iodine was in the form of dissolved I(-). In contrast, XANES analysis revealed that iodine in soil exists as organic iodine at all depths. Iodine mapping of soil grains was obtained using micro-XRF analysis, which also indicated that iodine is bound to organic matter. The activity of laccase, which has the ability to oxidize I(-) to I(2), was high at the surface of the soil-water layer, suggesting that iodide oxidizing enzymes can promote iodine organification. The distribution coefficient of organic iodine in the soil-water system was more than 10-fold greater than that of iodide. Transformation of inorganic iodine to organic iodine plays an important role in iodine immobilization, especially in a surface soil-water system.

PMID:
21322630
DOI:
10.1021/es1032162
[Indexed for MEDLINE]

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