Iodine

About: Iodine is a research topic. Over the lifetime, 8936 publications have been published within this topic receiving 139981 citations. The topic is also known as: I & element 53.

Insights into the Photochemical Transformation of Iodine in Aqueous Systems: Humic Acid Photosensitized Reduction of Iodate

Abstract: Marine aerosol is highly enriched in iodine, mostly in the form of iodate (IO3–) ions, compared to its relative abundance in seawater. This paper describes a laboratory study of the photochemical reduction of IO3– in the presence of humic acid. Spectroscopic analysis showed that ∼20% of IO3– was converted to “free” iodide (I–) ions and this fraction remained constant as a function of time. Direct detection of an organically fixed fraction (i.e., ∼ 80%) was not possible, but a number of test reactions with surrogate organic compounds containing functional groups identified in humic acid structures indicate that efficient substitution of iodine occurs at aromatic 1,2 diol sites. These iodinated humic acids are stable with respect to photolysis at near-UV/visible wavelengths and are likely to account for a significant proportion of the soluble iodine-containing organic material occurring within aerosols. In the lower atmosphere, oxidation of I– to I2 in marine aerosol occurs mostly through the uptake of O3, ...

Iodine assimilation by marine diatoms and other phytoplankton in nitrate-replete conditions

Abstract: Several marine phytoplankton species, primarily diatoms, were examined for the accumulation of iodide (10 species) and iodate (9 species) using radioactive iodine-125 in f/2 artificial seawater, a nitrate-enriched medium. Iodide accumulation (net uptake) rates were variable, and diatoms exhibited the highest rates. Emiliania huxleyi and Synechococcus sp. did not accumulate iodide. Accumulation rates ranged from 0 to 1.7 fmol cell21 d21. The diatom Porosira glacialis accumulated the greatest amount of iodide and was used to determine efflux rates of iodide. Iodide efflux was characterized by two distinct phases of iodide release: an initial rapid release rate of 10 amol cell21 min21 from the free space and a subsequent cellular release rate of 0.13 amol cell21 min21, which corresponds to a daily cellular release rate of 0.19 fmol cell21 d21. Accumulation of iodate ranged from 0 to 19 amol cell21 d21, with P. glacialis displaying the highest rate. Emiliania, Synechococcus, and Chaetoceros did not show significant iodate accumulation. Iodide is the preferred chemical species of iodine for uptake under nitrate-replete conditions: iodide accumulation rates ranged from 3 to 90 times larger than those for iodate for the species studied. If the iodate accumulated is tightly coupled to its reduction to iodide, the accumulation rates suggest that phytoplankton-mediated iodate reduction is not environmentally significant. If diatoms can reduce iodate to iodide, their overall contribution to surface-water iodide, while living, would be further reduced because of their ability to reassimilate released iodide. Inorganic iodine exists in disequilibrium in surface seawater as iodide and the thermodynamically favored form, iodate (Wong 1991). The relatively high concentration of iodide in temperate coastal waters and subtropical– tropical waters is thought to be related to biological productivity (Wong 2001; Wong et al. 2002; Chance et al.

An 129I Mössbauer spectroscopic study of iodine doped in poly(vinylpyridines)

Abstract: The charge densities and the configurations of iodine doped in poly(2‐ and 4‐vinylpyridines) have been studied by using the Mossbauer effect of 129I at 16 K. The ’’outer complex’’ is first formed in the system of poly(2‐vinylpyridine) and iodine. The extent of the charge transfer is estimated to be 0.22 in the outer complex, which is nearly the same as pure pyridine. The iodine of the outer complex varies gradually to the tri‐iodide anion and then to the iodide anion by accepting electrons from the pyridine ring of the polymer. In the system of poly(4‐vinylpyridine) and iodine both the outer complex and the ’’inner complex’’ are first observed, and the iodine species in these complexes vary gradually to the I3− ion and finally to the I− ion in a similar manner as the system of poly(2‐vinylpyridine) and iodine. From the values of the Mossbauer parameters the charge or electron populations of the iodine species are calculated, and the arrangements of these species are discussed.

Radiation-induced thyroid carcinogenesis as a function of time and dietary iodine supply: an in vivo model of tumorigenesis in the rat.

Abstract: It is believed that a combination of environmental factors with mutagens induces carcinomas derived from thyroid follicular cells. In this study we tried to ascertain whether a single short-term exposure to external radiation is sufficient to induce thyroid carcinomas in rats under long-term high or low dietary iodine intake. Rats were tested over a period of 110 wk under high (∼10-fold of normal), normal, and low (∼0.1-fold of normal) daily iodine intake. Forty-day-old animals were subjected to single external radiation of 4 Gy or sham radiation. Thyroid function was tested weekly, and thyroid morphology was determined after 15, 35, 55, and 110 wk. Iodine deficiency, but not high iodine intake, led to a decrease in T3 and T4 plasma levels, but to an increase in TSH, which became significant after 9 and 11 wk of treatment, respectively. Both high and low iodine treatment significantly increased the proliferation rate and induced thyroid adenomas, but no malignancies after 55 and 110 wk. Radiation with 4 G...