Microbial involvement in iodine cycle: mechanisms and potential applications.

Iodine has two natural isotopes – the only stable iodine isotope is 127I, whilst 129I is the only radioactive iodine isotope that is formed in nature (T1⁄2 = 1.57 · 107 years). However, the main sources of 129I in the environment are anthropogenic from nuclear fuel reprocessing plants (NFRP) and nuclear accidents. Current levels of 129I do not represent any radiological hazard to humans, but the liquid discharges of 129I from reprocessing plants into the ocean makes it a unique oceanographic tracer to study the movement of water masses, transfer of radionuclides and marine cycles of stable elements such as iodine. The gaseous releases of 129I from reprocessing plants can be used as an atmospheric and geochemical tracer (Hou, 2004). 129I and 127I have the same chemical properties and therefore it is expected that they also behave similar in environment. Lack of 129I and 127I speciation data makes it difficult to confirm or disprove this assumption. The main problem is the mobility – species of newly introduced and old − natural 129I. The old 129I is in equilibrium with 127I – natural 129I/127I ratio and this is disturbed with 129I from NFRP which is released to the environment in volatile form. As such it is rapidly transferred among surface compartments. Liquid discharges to oceans influence areas in accordance with marine currents. Wet and, to a lesser extent, dry depositions of atmospheric 129I are the main sources for 129I in terrestrial environment, which is distant from 129I sources such as NFRP. The biggest reservoir of iodine is the ocean with an average concentration of approximately 50-60 μg L-1 seawater. From marine environment is iodine transferred to the atmosphere by volatilization mainly as iodomethane (CH3I) and then washed out to terrestrial environment by wet and dry deposition. It is accumulated in soils where it is strongly bound-adsorb to organic matter, and iron and aluminium oxides in soil (Fuge, 2005). In the accumulation processes of iodine in soil besides various physico-chemical parameters including soil type, pH, Eh, salinity, and organic matter content, soil microorganism – especially bacteria were found to play an important role (Muramatsu & Yoshida, 1999, Amachi, 2008). In this way the biogeochemical cycling of 129I is strongly connected to processes in ocean and soil systems – the atmosphere being the bridge between them.

Diagnosis of the causes of thyrotoxicosis (destruction or increased functional activity of the thyroid tissue in nodular and diffuse thyroid pathology) is a key point in determining the management of patients with this pathology. Scintigraphy is the method of choice in differential diagnosis of the causes of thyrotoxicosis assessing the functional state of the thyroid gland. According to variable medical interest, thyroid scintigraphy can be performed using 99mTc-pertechnetate or radioactive iodine isotopes (123I, 124I, 131I). For thyroid uptake evaluation used scintigraphy with 99mTc-pertechnetate radiopharmaceutical, which is not organificates and quickly excretes from thyroid tissue. In case of thyroid iodine pharmacokinetics investigation radiopharmaceuticals labeled by iodine isotopes (123I,131I, 124I) are used. The review includes original scintigrams, tables and diagrams. Article shows thyroid scintigraphy informativity analysis, evaluates the place and role of the thyroid scintigraphy examinations in modern diagnostic algorithms taking into account the history of the disease, laboratory tests, ultrasound (TIRADS) and result ofFNA (Bethesda). Additionally authors focused on existing clinical guidelines analysis. An optimized algorithm for the diagnosis and treatment of diffuse and/or nodular thyroid pathology associated with thyrotoxicosis is proposed.

The zirconium isotope 93 Zr is a long-lived pure β-particle-emitting radionuclide produced from 235 U fission and from neutron activation of the stable isotope 92 Zr and thus occurring as one of the radionuclides found in nuclear reactors. Due to its long half-life, 93 Zr is one of the radionuclides of interest for the performance of assessment studies of waste storage or disposal. This paper describes the determination of 93 Zr in evaporator concentrate (EC) sample from nuclear power plant (PWR). A zirconium selective separation using liquid-liquid extraction and TRU column were used before the ICPMS measurement to remove isobaric interferences. 20-21 93 Nb detection limit of 0.045 μg L -1 was obtained for 93 Zr determination by ICPMS technique.

Radionuclide contamination in Canada: A scoping review

Different decontamination factors for $sup 129$I and $sup 131$I are frequently invoked in environmental impact reports concerned with nuclear fuel recycle. Selected differences, or ratios, have not been justified on the basis of mathematical models or experimental data. A description is given of the origins of these differences in terms of isotopic exchange and material balance equations for the short- and long-lived (or stable) isotopes. The ratios of decontamination factors can be calculated when there is complete attainment of isotopic exchange between gas- or liquid-phase iodine and iodine sorbed by a solid or liquid. If there is no exchange, decontamination factors are isotope- independent unless material recycle occurs within the system. Between these extremes, there can be decontamination factors whose explanation requires experimental determination of the extent of exchange. The model applies to other radioactive isotopes of iodine as well as to other elements with short- and long- lived (or stable) isotopes. (auth)

Different decontamination factors for /sup 129/I and /sup 131/I are frequently invoked in environmental impact reports concerned with nuclear fuel recycle. Selected differences, or ratios, have not been justified on the basis of mathematical models or experimental data. This report presents a description of the origins of these differences in terms of isotopic exchange and material balance equations for the short- and long-lived (or stable) isotopes. The ratios of decontamination factors can be calculated when there is complete attainment of isotopic exchange between gas- or liquid-phase iodine and iodine sorbed by a solid or liquid. If there is no exchange, decontamination factors are isotope independent unless material recycle occurs within the system. Between these extremes, there can be decontamination factors whose explanation requires experimental determination of the extent of exchange. The model applies to other radioactive isotopes of iodine as well as to other elements with short- and long-lived (or stable) isotopes.

Three radioactive isotopes of iodine, 132I, 125I, and 123I, and 99mTc are compared with 131I on the basis of their suitability for the investigation of thyroid disorders. The radiation doses to the adult and foetal thyroid from these various isotopes are also compared. 123I is a cyclotronproduced isotope with a half-life of 13 hours; details relating to its production and to the impurities present are given. 132I gives a low radiation dose to the thyroid compared with 131I but it can only be used for early thyroid uptake tests and it is quite unsuitable for scanning. 125I has limited applications for in vivo work but can be used for a protein bound radioiodine estimation or a urinary excretion test. 123I can be used for all the standard tests, is very suitable for scanning and gives a radiation dose comparable with that of 132I. 99mTc is very suitable for scanning but cannot be used for any of the conventional thyroid function tests. The radiation doses to the foetal thyroid from 123I, 125I and 1...

Chapter 55 - Thyroid Uptake and Scan

Chapter 15 - Radiological contaminants in water: pollution, health risk, and treatment

Phytoplankton in marine surface waters play a key role in the global iodine cycle. The biologically-mediated iodide production under future scenarios is limited. Here we compare growth, iodate to iodide conversion rate and membrane permeability in the diatom Chaetoceros sp. (CCMP 1690) grown under seawater carbonate chemistry conditions projected for 2100 (1000 ppm) and pre-industrial (280 ppm) conditions. We found no effect of CO2 on growth rates, but a significantly higher cell yield under high CO2, suggesting sustained growth from relief from carbon limitation. Cell normalised iodate uptake (16.73 ± 0.92 amol IO3− cell−1) and iodide production (8.61 ± 0.15 amol I− cell−1) was lower in cultures grown at high pCO2 than those exposed to pre-industrial conditions (21.29 ± 2.37 amol IO3− cell−1, 11.91 ± 1.49 amol I− cell−1, respectively). Correlating these measurements with membrane permeability, we were able to ascertain that iodide conversion rates were not linked to cell permeability and that the processes of mediated iodate loss and diatom-iodide formation are decoupled. These findings are the first to implicate OA in driving a potential shift in diatom-mediated iodate reduction. If our results are indicative of diatom-mediated iodine cycling in 2100, future surface ocean conditions could experience reduced rates of iodide production by Chaetoceros spp., potentially lowering iodide concentrations in ocean regions dominated by this group. These changes have the potential to impact ozone cycling and new particle formation in the atmosphere.

For legal and regulatory purposes, the International Atomic Energy Agency (IAEA, 1994) defines radioactive as waste that contains or is contaminated with radionuclides at concentrations or radioactivity levels greater than clearance levels as established by the regulatory body . The radioactive wastes are residues that have been produced by human nuclear activity and for which no future use is foreseen. Besides the nuclear power plants, the nuclear weapons testing, medical uses and various research studies involve a large number of radionuclides. In particular the nuclear accidents such as Three Mile Island Nuclear Power Station, where some gas and water were vented to the environment around the reactor, Chernobyl Nuclear Power Plant, the effects of the disaster were very widespread and Fukushima II Nuclear Power Plant have also released a large amount of radionuclides to environment.

Radioiodine, which is the collective term for all radioactive isotopes of the element iodine, is formed at the Savannah River Site (SRS) principally as a by-product of nuclear reactor operations. Part of the radioiodine is released to the environment during reactor and reprocessing operations at the site. The purpose of this report is to provide an introduction to radioiodine production and disposition, its status in the environment, and the radiation dose and health risks as a consequence of its release to the environment around the Savannah River Plant. A rigorous dose reconstruction study is to be completed by thee Center for Disease Control during the 1990s.

Review of Russian language studies on radionuclide behaviour in agricultural animals: part 2. Transfer to milk

Cancer de la thyroïde après exposition aux rayonnements ionisants

Chapter 5 Radionuclides as Tracers and Timers in Surface and Groundwater