Low Iodide Concentrations Research Articles

Impact of (nano ZnO/multi-wall CNTs) prepared by arc discharge method on the removal efficiency of stable iodine 127I and radioactive iodine 131I from water

Radioactive iodine isotopes especially 131I are used for diagnosis and treatment of different types of cancer diseases. Due to the leak of radioactive iodine into the patient’s urine in turn, the wastewater would be contaminated, so it is worth preparing a novel adsorption green material to remove the radioactive iodine from wastewater efficiently. The removal of 127I and 131I contaminants from aqueous solution is a problem of interest. Therefore, this work presents a new study for removing the stable iodine 127I− and radioactive iodine 131I from aqueous solutions by using the novel nano adsorbent (Nano ZnO/MWCNTs) which is synthesized by the arc discharge method. It is an economic method for treating contaminated water from undesired dissolved iodine isotopes. The optimal conditions for maximum removal are (5 mg/100 ml) as optimum dose with shacking (200 rpm) for contact time of (60 min), at (25 °C) in an acidic medium of (pH = 5). After the adsorption process, the solution is filtrated and the residual iodide (127I−) is measured at a maximum UV wavelength absorbance of 225 nm. The maximum adsorption capacity is (15.25 mg/g); therefore the prepared nano adsorbent (Nano ZnO/MWCNTs) is suitable for treating polluted water from low iodide concentrations. The adsorption mechanism of 127I− on to the surface of (Nano ZnO/MWCNTs) is multilayer physical adsorption according to Freundlich isotherm model and obeys the Pseudo-first order kinetic model. According to Temkin isotherm model the adsorption is exothermic. The removal efficiency of Nano ZnO/MWCNTs for stable iodine (127I−) from aqueous solutions has reached 97.23%, 89.75%, and 64.78% in case of initial concentrations; 0.1843 ppm, 0.5014 ppm and 1.0331 ppm, respectively. For the prepared radio iodine (131I−) solution of radioactivity (20 µCi), the dose of nano adsorbent was (10 mg/100 ml) and the contact time was (60 min) at (pH = 5) with shacking (200 rpm) at (25 °C). The filtration process was done by using a syringe filter of a pore size (450 nm) after 2 days to equilibrate. The removal efficiency reached (34.16%) after the first cycle of treatment and the percentage of residual radio iodine was (65.86%). The removal efficiency reached (94.76%) after five cycles of treatment and the percentage of residual radio iodine was (5.24%). This last percentage was less than (42.15%) which produces due to the natural decay during 10 days.

Soybean Plants Exposed to Low Concentrations of Potassium Iodide Have Better Tolerance to Water Deficit through the Antioxidant Enzymatic System and Photosynthesis Modulation.

Water deficit inhibits plant growth by affecting several physiological processes, which leads to the overproduction of reactive oxygen species (ROS) that may cause oxidative stress. In this regard, iodine (I) is already known to possibly enhance the antioxidant defense system of plants and promote photosynthetic improvements under adverse conditions. However, its direct effect on water deficit responses has not yet been demonstrated. To verify the efficiency of I concerning plant tolerance to water deficit, we exposed soybean plants to different concentrations of potassium iodide (KI) fed to pots with a nutrient solution and subsequently submitted them to water deficit. A decline in biomass accumulation was observed in plants under water deficit, while exposure to KI (10 and 20 μmol L-1) increased plant biomass by an average of 40%. Furthermore, exposure to KI concentrations of up to 20 μM improved gas exchange (~71%) and reduced lipid peroxidation. This is related to the higher enzymatic antioxidant activities found at 10 and 20 μM KI concentrations. However, when soybean plants were properly irrigated, KI concentrations greater than 10 μM promoted negative changes in photosynthetic efficiency, as well as in biomass accumulation and partition. In sum, exposure of soybean plants to 10 μM KI improved tolerance to water deficit, and up to this concentration, there is no evidence of phytotoxicity in plants grown under adequate irrigation.

A Crosslinked Ionic Organic Framework for Efficient Iodine and Iodide Remediation in Water.

Iodine is widely used as an antimicrobial reagent for water disinfection in the wilderness and outer space, but residual iodine and iodide need to be removed for health reasons. Currently, it is challenging to remove low concentrations of iodine and iodide in water (≈5 ppm). Furthermore, the remediation of iodine and iodide across a broad temperature range (up to 90 °C) has not previously been investigated. In this work, we report a nitrate dimer-directed synthesis of a single-crystalline ionic hydrogen-bonded crosslinked organic framework (HC OF-7). HC OF-7 removes iodine and iodide species in water efficiently through halogen bonding and anion exchange, reducing the total iodine concentration to 0.22 ppm at room temperature. Packed HC OF-7 columns were employed for iodine/iodide breakthrough experiments between 23 and 90 °C, and large breakthrough volumes were recorded (≥18.3 L g-1 ). The high iodine/iodide removal benchmarks recorded under practical conditions make HC OF-7 a promising adsorbent for water treatment.

A Crosslinked Ionic Organic Framework for Efficient Iodine and Iodide Remediation in Water

AbstractIodine is widely used as an antimicrobial reagent for water disinfection in the wilderness and outer space, but residual iodine and iodide need to be removed for health reasons. Currently, it is challenging to remove low concentrations of iodine and iodide in water (≈5 ppm). Furthermore, the remediation of iodine and iodide across a broad temperature range (up to 90 °C) has not previously been investigated. In this work, we report a nitrate dimer‐directed synthesis of a single‐crystalline ionic hydrogen‐bonded crosslinked organic framework (HCOF‐7). HCOF‐7 removes iodine and iodide species in water efficiently through halogen bonding and anion exchange, reducing the total iodine concentration to 0.22 ppm at room temperature. Packed HCOF‐7 columns were employed for iodine/iodide breakthrough experiments between 23 and 90 °C, and large breakthrough volumes were recorded (≥18.3 L g−1). The high iodine/iodide removal benchmarks recorded under practical conditions make HCOF‐7 a promising adsorbent for water treatment.

Enhancing the sensitivity towards iodide detection by coupling SECM and an EĆ catalytic mechanism

In this work, a gold conventional sized electrode (r = 3 mm) and a gold microelectrode (r = 12.5 µm) were employed to investigate the EC’ mechanism involving the anodic oxidation of iodide in the presence of the non-redox-active species thiosulfate. A significant anodic current increase, due to the electrocatalytic process, was noticed in cyclic voltammograms recorded in an iodide solution in the presence of thiosulfate when compared to iodide solution only, at the same experimental conditions. Aiming to enhance the sensitivity of the electroanalytical method towards iodide detection, Scanning Electrochemical Microscopy (SECM) was employed to confine reactants and products in a thin-layer cell defined by the solution region between the microelectrode tip and a Au substrate. Very low iodide concentrations, in the range of a 1–10 µmol/L, can be detected at a short tip-substrate distance, and the method was validated by measuring the analyte content in a synthetic urine sample.

Spontaneous Symmetry Breaking: The Case of Crazy Clock and Beyond

In this work, we describe the crazy-clock phenomenon involving the state I (low iodide and iodine concentration) to state II (high iodide and iodine concentration with new iodine phase) transition after a Briggs–Rauscher (BR) oscillatory process. While the BR crazy-clock phenomenon is known, this is the first time that crazy-clock behavior is linked and explained with the symmetry-breaking phenomenon, highlighting the entire process in a novel way. The presented phenomenon has been thoroughly investigated by running more than 60 experiments, and evaluated by using statistical cluster K-means analysis. The mixing rate, as well as the magnetic bar shape and dimensions, have a strong influence on the transition appearance. Although the transition for both mixing and no-mixing conditions are taking place completely randomly, by using statistical cluster analysis we obtain different numbers of clusters (showing the time-domains where the transition is more likely to occur). In the case of stirring, clusters are more compact and separated, revealed new hidden details regarding the chemical dynamics of nonlinear processes. The significance of the presented results is beyond oscillatory reaction kinetics since the described example belongs to the small class of chemical systems that shows intrinsic randomness in their response and it might be considered as a real example of a classical liquid random number generator.

Photocatalyst assemblies with two halide ions

A series of ruthenium polypyridyl photocatalysts bearing amide functional groups were designed that successfully promoted halide assembly in CH2Cl2 and CH3CN solution. In CH2Cl2, halide assembly was accompanied by a visible color change, and the spectral changes presented clear evidence for two halide binding events, yielding a 1:2 ruthenium:halide assembly. In the more polar solvent CH3CN, 1:2 assembly structures were also observed with chloride, bromide, and iodide, and large equilibrium constants were measured for association of the first and second halide (K11 = 0.04 – 2 × 106 M−1, K12 = 0.01 – 3 × 105 M−1). Varying the functional groups on the ancillary ligands tuned the excited-state reduction potentials (Ru2+⁎/+), resulting in a photocatalyst capable of performing iodide oxidation. Quenching of the photocatalyst excited state resulted in static and dynamic quenching, and a Stern-Volmer analysis yielded two linear regions at low and high iodide concentrations. The dynamic quenching rate constants (kq = 6.8 and 4.0 × 1010 M−1 s−1) and static quenching constants (KS = 2.4 and 0.13 × 104 M−1) at low and high iodide concentrations, respectively, were consistent with dynamic quenching of Ru2+ and [Ru2+,I−]+, and static quenching of [Ru2+,I−]+and [Ru2+,2I−]. Transient absorption spectroscopy revealed that the quenching reaction yielded a reduced ruthenium (Ru+) as the primary photoproduct and diiodide (I2•−) as a secondary photoproduct. The second-order rate constant for I2•− formation was measured to be 2.5 × 1010 M−1 s−1, a value consistent with the diffusion limited reaction. The transient absorption data indicates that oxidized halide photoproducts only result from the diffusional quenching reactions, and not from static quenching with an associated iodide ion. Fast back-electron transfer rates and low cage-escape yields in the ruthenium:iodide assemblies are invoked to explain why the static quenching pathway does not lead to measurable photoproduct yields.

Exploring the physics of cesium lead halide perovskite quantum dots via Bayesian inference of the photoluminescence spectra in automated experiment

Abstract The unique optoelectronic properties of metal halide perovskite quantum dots (QDs) make them promising candidates for applications in light-emitting diodes (LEDs), scintillators, and other photonic devices. The automated micropipetting synthesis platform equipped with an optical reader enables the opportunity for high throughput synthesis and photoluminescent (PL) characterization of metal halide perovskite QDs for the first time. Here, we explore the compositional dependence of the PL behavior and stability of the combinatorial library of cesium lead halide (CsPbX3) perovskites QDs via the automated platform. To study the stability of synthesized QDs in the binary and ternary configurations, we study the time-dependent PL properties using previously developed machine learning analysis. To systematically explore the PL behavior in the ternary CsPbX3 QDs system, we introduce the Bayesian inference framework that allows the probabilistic fit of multiple models to the PL data and establishes both optimal model and model parameter robustly. Furthermore, these behaviors can be used as a control parameter for the navigation of the multidimensional compositional spaces in automated synthesis. This analysis shows the nonuniformity of the PL peak behavior in the ternary CsPbX3 QDs system. Further, the analysis confirms narrow size distribution and good quality of CsPbBr3 QDs alloyed with low concentrations of iodide and chloride. We note that Bayesian Inference fit parameters can be further used as a control signal for navigation of the chemical spaces in automated synthesis.

Simple and Easily Applicable Method for Reducing Freshwater Consumption in Dyeing of Wool Fabric

ABSTRACT Textile wet processing is one of the most water-consuming industries. The deficiency of soft water in some parts of the world urged the researchers to exert effort toward minimization of water consumption during textile wet processes. In this work, we bleach wool fabrics by hydrogen peroxide, followed by utilization of the discharged bleaching bath (DBB) in dyeing of wool with acid, reactive, and basic dyes. The residual H2O2 in the bleaching bath was decomposed into water and oxygen by adding low concentrations of potassium iodide (KI). Results of this investigation clarify that treatment of the DBB with KI is mandatory to make the bath appropriate for wool dyeing. The dyeability of wool toward the said dyes in KI-treated DBB is significantly higher than that upon dyeing with tap water. The fastness properties of the dyed fabric to washing, perspiration, and light were assessed. The turbidity, pH, total dissolved salts (TDS), total suspended salts (TSS), biological oxygen demand (BOD), and chemical oxygen demand (COD) of the bleaching effluent were assessed. Solubility of bleached/dyed wool fabrics in alkali and urea-bisulfite solutions assures the modification of some disulfide bonds along wool keratin macromolecules into cystine oxides/cysteic acid residues, and consequently the dyeability was enhanced.

Formation of emerging iodinated disinfection by-products during ballast water treatment based on ozonation processes

Disinfection by-products (DBPs) generated by ballast water treatment pose a potential threat to marine environment which aroused widespread concern. In recent years, emerging iodinated DBPs have attracted widespread attention because of their stronger cytotoxicity and genotoxicity than brominated/chlorinated DBPs. In this study, the effects of different natural organic matter species, total residual oxidant (TRO) concentrations, storage time, temperature, pH, bromide and iodide concentrations on the generation of iodinated trihalomethanes (I-THMs) during ozonation process of ballast water were investigated. The results showed that bromochloroiodomethane and diiodochloromethane (DICM) were not detected under all conditions during ozonation of humaic acid (HA). Different kinds of precursors had a significantly effect on the formation of I-THMs. For algal cells as precursor, DICM were detected (1.22 μg/L), while DICM were not detected from oxidation of 1,3-etonedicarboxylic acid, fulvic acid (FA), phenol, resorcinol, hydroquinone and HA as precursors. The yields of I-THMs from oxidation of algal cells, FA and phenol were higher than other precursors. Linear relationships were observed between the formation of I-THMs and TRO concentrations. The yields of I-THMs reached a peak at 48 h (180 μg/L) after ozonation treatment of ballast water, and then decreased with storage time extension. An increase in temperature enhanced the formation of dibromoiodomethane and bromodiiodomethane, while wakened the formation of iodoform and dichloroiodomethane. The formation of I-THMs was complicatedly affected by different pH values in the range from 4 to 9. The more bromide concentrations, the more brominated I-THMs were formed. The concentrations of I-THMs increased with increasing iodide concentrations, and low concentrations of iodide had greater effect on the production of I-THMs than high concentrations of iodide.

Vertical and seasonal variations of dissolved iodine concentration in coastal seawater on the northwestern Pacific coast of central Japan

Vertical and seasonal variations in the concentrations of total dissolved iodine (TDI), iodide (I−), iodate (IO3−), and dissolved organic iodine (DOI) were examined for seawaters from the northwestern Pacific coast of central Japan (48 m water depth, ca. 1 km offshore) from 2012 to 2016. The annual averages of TDI and iodate concentrations in the upper layer (water depth < 10 m) were below those from deeper levels. Additionally, the concentrations decreased significantly during summer to autumn. The vertical and seasonal trends in TDI and iodate concentrations were suggested to be originated from the uptake of iodate by settling particles within the water column and partially from the input of river waters. The annual average of iodide concentration in the upper layer was higher than that in deeper levels, and the concentration tended to increase during summer to autumn. Further, the iodide concentration showed a significant positive correlation with the water temperature. The results suggest that the iodide concentration was mainly controlled by the efficiency of vertical mixing in the water column, as deeper seawater generally contains low iodide concentration. The vertical and seasonal variations in DOI concentration were erratic and thus obscured its controlling factors.

An Estimation of Volatile Iodine in a Pool at Low pH and High Iodide Concentrations Under Irradiation

A new empirical model is proposed for estimating the amount of volatile iodine in an aqueous phase. The volatile iodine concentration is estimated for highly irradiated CsI solutions in which the pH of the solution changes. The reaction of CsI solution with water radiolysis products is not balanced because radiolysis products are continuously produced under irradiation. Thus the kinetic of the chemical equation is important to determine iodine behavior in a CsI solution. An empirical model for the kinetic equation including the oxidation and reduction reaction is proposed. The proposed model was validated with a wide range of experimental data. A comparison of the experiments and predictions by the model indicated that the predicted volatile iodine from CsI solution with a concentration of 10−3 to 10−4 M was in good agreement. For 10−5 M CsI solution, the predicted iodine concentration was much smaller than experimental data due to the fact that I− was rapidly converted to IO3−.

Iodine Nutritional Status in Schoolchildren from Public Schools in Brazil: A Cross-Sectional Study Exposes Association with Socioeconomic Factors and Food Insecurity.

National programs of salt iodization were implemented in Brazil to combat iodine deficiency (ID) in children of school age. Currently, there are limited data in Brazil on those still vulnerable to this deficiency and the state of nutritional iodine status in the northeast region of Brazil, where children are vulnerable to malnutrition. The aim of this study was to analyze the iodine nutritional status, household food insecurity, socioeconomic and demographic characteristics among schoolchildren from the public school system living in state the state of Bahia, Brazil. A cross-sectional study was conducted on 1419 schoolchildren in Bahia between the ages of 6 and 14 years old. Anthropometric parameters, urinary iodine concentrations (UIC), and thyrotropin (TSH) measurements were evaluated from blood spots on filter paper. The mean UIC was 206.4 ± 80.5 μg/L, with a median of 221.6 μg/L, indicating sufficient iodine intake in the region. Low urinary iodide concentration (<100 μg/L) was detected in 12.3% of the schoolchildren (n = 174), with 6.2% with mild (<100 μg/L), 3.0% with moderate (20-49 μg/L), and 3.1% with severe ID (<20 μg/L). Moreover, 9.4% (n = 134) had a urinary iodide concentration of >300 μg/L, indicating the coexistence of excessive iodine intake (EII). The mean TSH was 1.0 ± 0.6 mIU/L. The body mass index category "overweight/obesity" was a protective factor against EII (odds ratio [OR] = 0.64 [confidence interval (CI) 0.4-1.0]; p = 0.07). Urban areas (73%) had a mean UIC of 213.1 ± 80 μg/L compared with 176.8 ± 76.1 μg/L in rural areas. The risk for EII increased in children living in a house with more than six people (OR = 1.62 [CI 0.9-2.6]; p < 0.05) and water consumption from shallow wells (OR = 1.70 [CI 0.9-3.1]; p = 0.09). The risk of ID was increased by 70% in schoolchildren who had moderate or severe food insecurity (OR = 1.70 [CI 0.9-3.0]; p > 0.05). A significant proportion of schoolchildren still have ID or EII in the northeast region of Brazil, emphasizing the importance of committed public policies to address this problem. Socioeconomic factors and the lack of education about nutritional importance of iodine were important influencing factors in the presence of ID in schoolchildren.

Peracetic acid oxidation of saline waters in the absence and presence of H ₂O ₂: secondary oxidant and disinfection byproduct formation.

Peracetic acid (PAA) is a disinfectant considered for use in ballast water treatment, but its chemical behavior in such systems (i.e., saline waters) is largely unknown. In this study, the reactivity of PAA with halide ions (chloride and bromide) to form secondary oxidants (HOCl, HOBr) was investigated. For the PAA-chloride and PAA-bromide reactions, second-order rate constants of (1.47 ± 0.58) × 10(-5) and 0.24 ± 0.02 M(-1) s(-1) were determined for the formation of HOCl or HOBr, respectively. Hydrogen peroxide (H2O2), which is always present in PAA solutions, reduced HOCl or HOBr to chloride or bromide, respectively. As a consequence, in PAA-treated solutions with [H2O2] > [PAA], the HOBr (HOCl) steady-state concentrations were low with a limited formation of brominated (chlorinated) disinfection byproducts (DBPs). HOI (formed from the PAA-iodide reaction) affected this process because it can react with H2O2 back to iodide. H2O2 is thus consumed in a catalytic cycle and leads to less efficient HOBr scavenging at even low iodide concentrations (<1 μM). In PAA-treated solutions with [H2O2] < [PAA] and high bromide levels, mostly brominated DBPs are formed. In synthetic water, bromate was formed from the oxidation of bromide. In natural brackish waters, bromoform (CHBr3), bromoacetic acid (MBAA), dibromoacetic acid (DBAA), and tribromoacetic acid (TBAA) formed at up to 260, 106, 230, and 89 μg/L, respectively for doses of 2 mM (ca. 150 mg/L) PAA and [H2O2] < [PAA]. The same brackish waters, treated with PAA with [H2O2] ≫ [PAA], similar to conditions found in commercial PAA solutions, resulted in no trihalomethanes and only low haloacetic acid concentrations.

Emission of iodine-containing volatiles by selected microalgae species

Abstract. In this study we present the results of an emission study of different phytoplankton samples in aqueous media treated with elevated ozone levels. Halocarbon measurements show that the samples tested released bromoform and different iodocarbons, including iodomethane, iodochloromethane and diiodomethane. Iodide and iodate levels in the liquid phase were representative of concentrations of surface water in a natural environment. Measurement of volatile iodine (I2) emissions from two diatom samples (Mediopyxis helysia and Porosira glacialis) and the background sample (F/2 medium from filtered natural seawater) showed that the quantity of evolved I2 depends on the ozone concentration in the air. This behaviour was assumed to be caused by the oxidation reaction mechanism of iodide with ozone. The I2 emission flux agrees with model calculations at different iodide concentrations. The I2 emission of a natural plankton concentrate sample was, however, very low compared to other samples and showed no dependence on ozone. The reason for this was shown to be the low iodide concentration in the algal suspension, which seems to be the limiting factor in the oxidative formation of I2.

Apoptosis of NOD.H2h4Thyrocytes by Low Concentrations of Iodide is Associated with Impaired Control of Oxidative Stress

Enhanced iodide intake in NOD.H2(h4) mice accelerates the incidence and severity of spontaneous autoimmune thyroiditis (SAT) via an unknown mechanism. A plausible hypothesis is that iodide-induced apoptosis of thyrocytes can create imbalances in antigenic load and/or disruption of immunoregulatory mechanisms that facilitate activation of autoreactive T cells in cervical lymph nodes draining the thyroid. We examined whether NOD.H2(h4) thyrocytes, exposed to low NaI concentrations in vitro, are more susceptible to apoptosis compared to thyrocytes from CBA/J mice, which are resistant to iodide-accelerated SAT (ISAT). We also looked, at the transcriptional level, for differential activation of genes involved in apoptosis or oxidative stress pathways that may account for potential differences in iodide-mediated apoptosis between NOD.H2(h4) and CBA/J thyrocytes. We report that NOD.H2(h4) thyrocytes, cultured for 24 h at very low (4-8 μM) concentrations of NaI, exhibit high levels (40-55%) of apoptosis, as assessed microscopically following staining with fluorescent caspase inhibitors. Similar treatment of thyrocytes from CBA/J mice, which are resistant to ISAT, yielded significantly lower (10-20%) apoptotic rates. Expression analysis by real-time polymerase chain reaction using arrays of apoptosis- and oxidative stress-related genes showed that NaI intake upregulates the expression of 22 genes involved in ROS metabolism and/or antioxidant function in CBA/J thyrocytes, whereas only two of these genes were upregulated in NOD.H2(h4) thyrocytes. Among the set of overexpressed genes were those encoding thyroid peroxidase (Tpo; 5.77-fold), glutathione peroxidases (Gpx2, Gpx4, Gpx7; 2.03-3.14-fold), peroxiredoxins (Prdx1, Prdx2, Prdx5; 2.27-2.97-fold), superoxide dismutase 1 (Sod1; 3.57-fold), thioredoxin 1 (Txn1; 2.13-fold), and the uncoupling proteins 2 and 3 (Ucp2, Ucp3; 2.01-2.15-fold). The results demonstrate that an impaired control of oxidative stress mechanisms is associated with the observed high susceptibility of NOD.H2(h4) thyrocytes to NaI-mediated apoptosis, and suggest a contributing factor for the development of ISAT in this strain.

Charge Transport and Recombination in Perovskite (CH3NH3)PbI3 Sensitized TiO2 Solar Cells

We report on the effect of TiO2 film thickness on the charge transport, recombination, and device characteristics of perovskite (CH3NH3)PbI3 sensitized solar cells using iodide-based electrolytes. (CH3NH3)PbI3 is relatively stable in a nonpolar solvent (e.g., ethyl acetate) with a low iodide concentration (e.g., 80 mM). Frequency-resolved modulated photocurrent/photovoltage spectroscopies show that increasing TiO2 film thickness from 1.8 to 8.3 μm has little effect on transport but increases recombination by more than 10-fold, reducing the electron diffusion length from 16.9 to 5.5 μm, which can be explained by the higher degree of iodide depletion within the TiO2 pores for thicker films. The changes of the charge-collection and light-absorption properties of (CH3NH3)PbI3 sensitized cells with varying TiO2 film thickness strongly affect the photocurrent density, photovoltage, fill factor, and solar conversion efficiency. Developing alternative, compatible redox electrolytes is important for (CH3NH3)PbI3 o...

Enhanced apoptosis of NOD.H2h4 thyrocytes by low concentrations of iodide: an intrinsic susceptibility factor in iodide-accelerated thyroiditis? (P4148)

Abstract Enhanced iodide intake in NOD.H2h4 mice accelerates the onset and severity of spontaneous autoimmune thyroiditis (ISAT) via an unknown mechanism. In this study, we have tested two hypotheses: 1) that NOD.H2h4 thyrocytes exhibit increased susceptibility to iodide-mediated apoptosis vs that of thyrocytes from other strains of mice; and 2) that progression of ISAT is associated with a reduction in the number of Treg cells in lymphoid tissues. We report that NOD.H2h4 thyrocytes cultured in vitro for 24 hr with 1-16 μM of NaI exhibited total numbers of apoptotic cells (ranging from 7.2 -32.9% above background) which were significantly higher than similarly treated CBA/J thyrocytes (ranging from 1.5 - 6.3% above background) upon staining with fluorescent caspase inhibitors. In addition, we report that flow cytometry of Treg cells in thyroid-draining lymph nodes (7.6-9.9% of CD4+ cells) or spleens (18.5 -19% of CD4+ cells) of NOD.H2h4 Foxp3-gfp mice did not reveal a significant alteration in their frequency, 7, 11 and 15 days following the initiation of enhanced iodide-intake (0.05 % NaI in drinking water). These results indicate that ISAT is not associated with a decrease of Treg frequency in lymphoid organs during the initial stages of the disease but support the view that an intrinsic high susceptibility of NOD.H2h4 thyrocytes to iodide-mediated apoptosis may be one of the triggering factors in ISAT.

The distribution of iodide and iodate in anchialine cave waters — Evidence for sustained localised oxidation of iodide to iodate in marine water

A study of inorganic iodine speciation in the waters of seven Croatian coastal caves is described. These are anchialine caves as they are connected hydraulically with Adriatic Sea surface water, with the tide inside the cave rising and falling with that outside, but replenishment of the water is restricted by the karst rock. In effect, the water in the cave probably acts more like a piston, and although moving slightly vertically, has a long residence time compared to a fully-flushing cave. Anchialine environments display a number of unusual features, e.g., a well-developed pycnocline, hypoxia and endemic fauna. Iodate and iodide were determined by differential pulse voltammetry and cathodic stripping square wave voltammetry, respectively. Low iodide concentrations (< 10 nM) have been consistently identified in the bottom water of the caves where concentrations of 90–100 nM would ordinarily be expected from intrusion of Eastern Adriatic surface seawater. Where total inorganic iodine concentrations behave conservatively with salinity the loss of the iodide implies oxidation to iodate. As iodide oxidation remains one of the enduring academic problems of the marine iodine system the study of iodine in anchialine caves may help unravel it. Iodate reduction was observed in mid-water, at the halocline, and mechanisms for the reduction involving either respiration or chemolitho-autotrophic bacteria are considered. The respiration mechanism is favoured because of enhanced alkalinity found in the near surface waters of the caves.

Inorganic reactions of iodine(III) in acidic solutions and free energy of iodous acid formation

AbstractAn analysis of the former works devoted to the reactions of I(III) in acidic nonbuffered solutions gives new thermodynamic and kinetic information. At low iodide concentrations, the rate law of the reaction IO + I− + 2H+ ⇌ IO2H + IOH is k+B [IO][I−][H+]2 – k−B [IO2H][IOH] with k+B = 4.5 × 103 M−3s−1 and k−B = 240 M−1s−1 at 25°C and zero ionic strength. The rate law of the reaction IO2H + I− + H+ ⇌ 2IOH is k+C [IO2H][I−][H+] – k−C [IOH]2 with k+C = 1.9 × 1010 M−2s−1 and k−C = 25 M−1s−1. These values lead to a Gibbs free energy of IO2H formation of −95 kJ mol−1. The pKa of iodous acid should be about 6, leading to a Gibbs free energy of IO formation of about −61 kJ mol−1. Estimations of the four rate constants at 50°C give, respectively, 1.2 × 104 M−3s−1, 590 M−1s−1, 2 × 109 M−2s−1, and 20 M−1 s−1. Mechanisms of these reactions involving the protonation IO2H + H+ ⇌ IO2H and an explanation of the decrease of the last two rate constants when the temperature increases, are proposed. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 647–652, 2008