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Iodine: Radionuclides

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Abstract

This article provides a review of iodine with regard to the basic chemistry, occurrence, speciation, separation, analysis, fate, and transport. Biogeochemical cycling of iodine in the environment is complex because iodine occurs in multiple oxidation states (ranging from −1 to +7), and inorganic and organic species may be hydrophilic, atmophilic, and biophilic. Organically bound iodine can be a significant fraction of total iodine in the atmosphere, biosphere, hydrosphere, and lithosphere. Nuclear-fuel reprocessing facilities constitute the major source (>90%) of ¹²⁹I released to the environment. It has been recognized that ¹²⁹I is a very important dose contributor in risk assessment because of its tendency to concentrate in the human thyroid gland, long half-life, and presumably high mobility. Speciation, input concentration, and residence time effects will influence the biogeochemical cycling of anthropogenic ¹²⁹I deposited on surface soils.

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... 108,111,112 In contrast to many other man-made radionuclides, anthropogenic releases were dominated not so much by nuclear accidents or nuclear weapons testing, but mainly by releases from NFRPs. 108,109,113 According to a recent study, the 129 I releases from Fukushima (estimated 1.2 kg) remained slightly below those from Chernobyl (estimated 1.3−6 kg). 114 However, SI Figure S2 illustrates that the contribution of both accidents to the global 129 I inventory is rather negligible. ...
... The natural 129 I/ 127 I background of the prenuclear era (1.5 × 10 −12 for the hydrosphere, which has not been confirmed for the terrestrial biosphere, though 121,122 ) has been increased by anthropogenic inputs to 10 −11 to 10 −4 . 109 Fortunately, the pre-Fukushima background of 129 I in Japan is quite well documented and investigated. 123 The isotopic ratio between 129 I/ 131 I in the releases from Fukushima was determined by Miyake et al. as 31.6 ± 8.9 as of 15 March 2011. ...
... As the final step prior to AMS measurement, I − is precipitated in the form of AgI, and mixing with conductive materials, such as Ag or Nb powder. 109,110 Organically bound iodine, for example, in soil samples, first needs to be decomposed prior to extraction by alkali fusion or ashing at 800°C. The liberated I 2 is trapped in NaOH or on activated charcoal cooled with liquid nitrogen (cryogenic adsorption). ...
Article
In environmental monitoring campaigns for anthropogenic radionuclides released in the course of the Fukushima nuclear accident (2011), most focus had been on gamma-emitting radionuclides. More than 99% of the released activity was due to radionuclides of the elements Kr, Te, I, Xe, and Cs. However, little work had been done on the monitoring of radionuclides other than (131)I, (132)Te, (134)Cs, (136)Cs, and (137)Cs. Radionuclides such as those of less volatile elements (e.g., (89)Sr, (90)Sr, (103)Ru, (106)Ru, plutonium), pure beta-emitters ((3)H, (14)C, (35)S), gaseous radionuclides ((85)Kr, (133)Xe, (135)Xe) or radionuclides with very long half-lives (e.g., (36)Cl, (99)Tc, (129)I, some actinides such as (236)U) have been understudied by comparison. In this review, we summarize previous monitoring work on these "orphan" radionuclides in various environmental media and outline further challenges for future monitoring campaigns. Some of the understudied radionuclides are of radiological concern, others are promising tracers for environmental, geochemical processes such as oceanic mixing. Unfortunately, the shorter-lived nuclides of radioxenon, (103)Ru, (89)Sr and (35)S will no longer exhibit detectable activities in the environment. Activity concentrations of other radionuclides such as tritium, (14)C, or (85)Kr will become blurred in the significant background of previous releases (nuclear explosions and previous accidents). Isotope ratios such as (240)Pu/(239)Pu will allow for the identification of Fukushima plutonium despite the plutonium background.
... 131 I has a half-life of 8.02 days and high specific activity (4.59 × 10 3 TBqg -1 ). Thus, 131 I was only a short-lived radioiodine (Hu and Moran, 2010;Kaplan et al., 2014;Yeager et al., 2017). Another example is the 129 I contamination in the Hanford Site at Washington State, USA, where subsurface 129 I plumes were > 50 km 2 and the 129 I level in the groundwater was higher than the standard for 129 I (<1pCi/L) listed in the US Federal Registry. ...
... Currently, there is no existing method to remediate 129 I levels below 1pCi/L in the groundwater . Compared to 131 I, 129 I has a halflife of 1.57 × 10 7 years and low specific activity (6.6 MBqg -1 ) (Hu and Moran, 2010;Kaplan et al., 2014;Yeager et al., 2017). Given its very long half-life, high toxicity to humans, highly specific accumulation in the human thyroid gland, high inventory in the Hanford Site, high mobility in groundwater and the uncertainty of its biogeochemical fate and transport in the environment, 129 I is a primary risk driver at the Hanford Site . ...
Article
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Iodine (I) is a trace element with health and environmental significance. Iodate (IO 3 ⁻ ), iodide (I ⁻ ) and organic iodine (org-I) are the major species of iodine that exist in the environment. Dissimilatory IO 3 ⁻ -reducing bacteria reduce IO 3 ⁻ to I ⁻ directly under anoxic conditions via their IO 3 ⁻ reductases that include periplasmic iodate reductase IdrABP 1 P 2 , extracellular DMSO reductase DmsEFAB and metal reductase MtrCAB. IdrAB and DmsEFAB reduce IO 3 ⁻ to hypoiodous acid (HIO) and H 2 O 2 . The reaction intermediate HIO is proposed to be disproportionated abiotically into I ⁻ and IO 3 ⁻ at a ratio of 2:1. The H 2 O 2 is reduced to H 2 O by IdrP 1 P 2 and MtrCAB as a detoxification mechanism. Additionally, dissimilatory Fe(III)- and sulfate-reducing bacteria reduce IO 3 ⁻ to I ⁻ directly via their IO 3 ⁻ reductases and indirectly via the reduction products Fe(II) and sulfide in the presence of Fe(III) and sulfate, respectively. I ⁻ -oxidizing bacteria oxidize I ⁻ to molecular iodine (I 2 ) directly under oxic conditions via their extracellular multicopper iodide oxidases IoxAC. In addition to I 2 , a variety of org-I compounds are also produced by the I ⁻ -oxidizing bacteria during I ⁻ oxidation. Furthermore, ammonia-oxidizing bacteria oxidize I ⁻ to IO 3 ⁻ directly under oxic conditions, probably via their intracellular ammonia-oxidizing enzymes. Many bacteria produce extracellular reactive oxygen species that can oxidize I ⁻ to triiodide (I 3 ⁻ ). Bacteria also accumulate I ⁻ during which I ⁻ is oxidized to HIO by their extracellular vanadium iodoperoxidases. The HIO is then transported into the bacterial cells. Finally, bacteria methylate I ⁻ to org-I CH 3 I, probably via their methyltransferases. Thus, bacteria play crucial and versatile roles in the global biogeochemical cycling of iodine via IO 3 ⁻ reduction, I ⁻ oxidation and accumulation and org-I formation.
... h), 135 I (t 1/2 = 6.57 h), 132 I (t 1/2 = 2.30 h) and 134 I (t 1/2 = 52.5 min) [1]. The isotopes 129 I and 127 I (stable isotopes) represent 87% of the total iodine. ...
... The iodine ( 127 I) concentration in the sediment core AN6 varied from 5.23 to 13.9 mg/g. This range is lower than that in most of marine sediments (~50 mg/g) (Hu and Moran, 2011). Unlike 129 I with its artificial sources, stable iodine in the coastal environment has mainly natural sources and bonded to the sediment materials, and therefore resided in the sediment for a relatively long time (Hou et al., 2009), reflecting the source and/or composition of its matrix. ...
Article
I released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident has been observed in the atmospheric, terrestrial and oceanic environments, and it also entered the marine sediments via dispersion by sea water movement and deposition around Japan. However, there have been few studies of marine sediment cores in contrast to the large number of studies on seawater. In this work, a sediment core collected near FDNPP was analyzed for ¹²⁹I. It is observed that the ¹²⁹I/¹²⁷I atomic ratios in this sediment core are comparable to those in the seawater and sediments collected from offshore Fukushima after the accident, but 2 orders of magnitude higher than those in seawater in this region before the accident, suggesting the significant amount of ¹²⁹I has been transferred and incorporated to the offshore shallow sediments. The difference in environmental behavior between ¹²⁹I and ¹³⁷Cs is discussed based on their depth distributions in the sediment core in comparison with the grain size distribution of sediments. The peak concentrations of iodine isotopes were found in a relatively deeper layer than radiocesium. Radiocesium follows the distribution of fine grains in the sediment core, implying its high association to fine grains.
... Iodine is a trace element widely distributed in the atmosphere, lithosphere, hydrosphere and biosphere at varying concentrations (Hu and Moran, 2010). It is an essential micronutrient in mammals, necessary for the production of thyroid hormones and for the proper functioning of the thyroid gland. ...
Article
Iodine is an important element in studies of human nutrition to combat I deficiency disorders, and in protection of the environment and human health from anthropogenic release of radioactive I. Biogeochemical cycling of I in the subsurface environment is complex, because it occurs in multiple oxidation states and as inorganic and organic species that may be volatile, hydrophilic and biophilic. Predicting the fate and transport of anthropogenic radioiodine deposited from the atmosphere or released into the subsurface requires knowledge of the sorption and degradation behavior of the various I species that may interact with soils and sediments. In this study, sorption, degradation, and transport behavior of I species (iodide, iodate, methyl iodide, and 4-iodoaniline) were examined in 12 geologic samples of differing physico-chemical characteristics, collected at numerous nuclear facilities in the USA. In particular, this work focuses on the sorption and degradation behavior of CH3I in geologic media, for which few studies are available, even though it is recognized as an important gaseous form of I in the marine atmosphere, and as a major form released from nuclear fuel reprocessing facilities and during nuclear accidents. Results from complementary batch and column experiments show that different I species exhibit very different sorption and transport behavior in geologic media. Sorption of I− is in general minimal, but a low concentration (5 × 10−13 M) of radioactive 125I is found to be strongly sorbed onto samples with high organic matter. Sorption of IO3- is consistently greater than that of I−, and sorption of 4-iodoaniline is generally strong and seems to be related to the amount of organic matter in the media. Methyl iodide is weakly sorbed onto 12 geologic samples with a distribution coefficient of about 1 mL/g, but its degradation varies greatly as a function of organic matter content, with a regression line of t1/2 = 0.084 × OM + 0.088 (R2 = 0.898, N = 6) where t1/2 is the degradation half-life and OM is the organic matter content. These results will be useful in predicting the mobility of anthropogenic radioactive I deposited on a soil surface, and highlight the fact that it will exhibit different residence times according to its original chemical form and to the composition of host sediments.
... Iodine is a trace element widely distributed in the atmosphere, lithosphere, hydrosphere and biosphere at varying concentrations (Hu and Moran, 2010). It is an essential micronutrient in mammals, necessary for the production of thyroid hormones and for the proper functioning of the thyroid gland. ...
... There is a large volume of literature on the chemistry, speciation, geochemistry behavior, and remediation technologies of these radionuclides [3][4][5][6]. Comprehensive reviews on the general chemistry, analytical characterization methods, speciation, potential human exposure, separation techniques of Pu [7], U [8], Np [9], Am [10] and Tc [11,12] are available in more recent literature. ...
Article
Pu, U, Np, Am and Tc are among the major risk drivers at nuclear waste management facilities throughout the world. Furthermore, uranium mining and milling operations have generated an enormous legacy of radioactively contaminated soils and groundwater. The sorption process of radionulcides onto ubiquitous Fe (hydr)oxides (FHOs; hematite, magnetite, goethite and ferrihydrite) is one of the most vital geochemical processes controlling the transport and fate of radionuclides and nuclear wastes in the subsurface zones. Meanwhile, understanding molecular-level chemical speciation of radionuclides onto FHOs is crucial to model their behavior in subsurface environments, and to develop new technologies for nuclear waste treatment and long-term remediation strategies for contaminated soils and groundwater. This review article aims (1) to provide risk or performance assessment modelers with macroscopic distribution coefficient (K(d)) data of Pu, U, Np, Am and Tc onto FHOs under different conditions (pH, radionuclide concentration, solution ion strength, sorbent loading, partial pressure of CO(2) ( [Formula: see text] ), equilibrium time) pertinent to environmental and engineered systems, and (2) to provide a microscopic or molecular-level understanding of the chemical speciation and sorption processes of these radionuclides to FHOs.
Article
Large variations in pre-nuclear ¹²⁹I/¹²⁷I ratios in terrestrial environments have been observed, but few investigations have been carried out on how the isotopic composition varies and how it is affected by the terrestrial environment. In this work, lake and river sediments were studied for the first time with the aim of exploring the possible connections between the natural iodine isotopic composition and its sources. The observed higher natural ¹²⁹I/¹²⁷I ratios compared to those in the marine system suggested that the isotopes did not reach a steady state. Decreasing ¹²⁹I/¹²⁷I ratios with increasing ¹²⁷I contents indicated perturbation of old iodine, and a narrower range of initial equilibrium ratios was suggested based on pre-nuclear ratios derived in the studied sediments.
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An improved solvent extraction procedure for iodine separation from brine samples has been applied at Xi’an Accelerator Mass Spectrometry (AMS) center. Oil in the brine sample has to be removed to avoid appearance of the third phase during solvent extraction and to improve the chemical yield of iodine. The small amount of oil remained in the water phase was first removed by phase separation through settling down sufficiently based on their immiscibility, and then by filtration through a cellulose filter, on which oil was absorbed and removed. After oil removed, extraction recovery of iodine could achieve more than 90 %. The sodium bisulfite as an effective reductant should be added before acidification to avoid loss of iodine by formation of I2 in sample via reaction of iodate and iodide at pH 1–2, and then pH was adjusted to 1–2 to reduce the iodate to iodide followed by oxidation of iodide to I2 and solvent extraction to separate all inorganic iodine. As a pre-nuclear era sample, 129I/127I ratio in brine is normally more than two orders of magnitude lower than that in present surface environmental samples, so prevention of cross-contamination and memory effect in apparatus during processing procedure are very critical for obtaining reliable results, and monitoring the procedure blank is very important for analytical quality of 129I. The 129I/127I isotopic ratio in the brine samples and procedure blank of iodine reagents were measured to be (1.9–2.7) × 10−13 and 2.08 × 10−13, respectively, 3–4 orders of magnitudes lower than that in environmental samples in Xi’an, and the result of procedure blank is in the same level as the previous experiments in past 3 years, indicating contamination is not observed in our method.
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Radioactivity from the Fukushima Daiichi Nuclear Power Plant (F-1NPP) accident in deposition samples has been monitored at the National Institute of Radiological Sciences (NIRS) in Chiba Prefecture, Japan, located about 220 km south-southwest of the F-1NPP. Sampling was carried out from 15 March 2011, two to three times a day for 10 d and then once a day until 22 April 2011. Gamma-ray spectrometry of fallout deposition samples revealed the presence of I, I, Te, Cs, and Cs. The largest deposition was observed during 7:00-16:00 on 21 March. The estimated total deposition densities at NIRS were 1.40 × 10 Bq m for I, 4.12 × 10 Bq m for Te, 1.45 × 10 Bq m for Cs, and 1.48 × 10 Bq m for Cs (corrected to 11 March 2011). The obtained densities of Cs and Cs were also supported by the accumulated amount of Cs and Cs in soil near the deposition sampling site. For the vertical profile of those radionuclides in soil at NIRS, about 94% of the total deposition was distributed in the top 10 mm depth on 26 April 2011.
Article
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Iodine has long been recognised as an important element environmentally. Despite this there are many gaps in our knowledge of its geochemistry and even where information is available much of this is based on old data which, in the light of recent data, are suspect. Iodine forms few independent minerals and is unlikely to enter most rock-forming minerals. In igneous rocks its concentration is fairly uniform and averages 0.24 mg/kg. Sedimentary rocks tend to have higher concentrations with average iodine contents of:-recent sediments 5–200 mg/kg, carbonates 2.7 mg/kg, shales 2.3 mg/kg and sandstones 0.8 mg/kg. Organic-rich sediments are particularly enriched in iodine. Soils, generally, are much richer in iodine than the parent rocks with the actual level being decided mainly by soil type and locality. Little soil iodine is water-soluble and much iodine is thought to be associated with organic matter, clays and aluminium and iron oxides. Most iodine in soils is derived from the atmosphere where, in turn, it has been derived from the oceans. Seawater has a mean iodine content of 58 μg/L, while non-saline surface waters have lower and very variable levels. Subsurface brines and mineral waters are generally strongly enriched in iodine. Marine plants are frequently enriched in iodine while terrestrial plants have generally low contents. Iodine is essential for all mammals. Consideration of the geochemical cycle of iodine reveals that its transfer from the oceans to the atmosphere is probably the most important process in its geochemistry.
Article
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The measurement of iodine in natural-water samples by inductively coupled plasma mass spectrometry (ICP-MS) is described. The limit of detection is 10pg/ml. The element is easily determined by this method without separation or preconcentration. Because iodine is highly volatile, the obtained signal is somewhat unstable. Iodine vaporization, however, can be restrained by the addition of an organic alkali (for example tetramethyl ammonium hydroxide), making it possible to obtain a stable signal. Analytical results using the conventional calibration-curve method and the standard addition method agreed well. We determined the iodine concentration of 42 natural-water samples in the northern Kanto area. The concentrations of iodine ranged from 0.65 to 35.9ng/ml.
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Total suspended particle (TSP) samples were collected onboard a round-trip cruise from Shanghai, China to Prydz Bay, Antarctica from November 2005 to March 2006. Water soluble iodine species were measured using ion chromatography coupled to Inductively Coupled Plasma-Mass Spectrometry (IC-ICP-MS). The results reveal that soluble organic iodine (SOI) is the most abundant fraction, accounting for approximately 70 % of total soluble iodine (TSI) on average. One unidentified organic iodine (UOI) signal was present in almost all of the samples and was responsible for up to 38.3% of TSI. The abundance of inorganic iodine species, iodate and iodide, was less than 30% of TSI. Iodide was significantly correlated with SOI suggesting a link between iodide formation and SOI decomposition. TSI levels varied considerably over the length of the voyage. In the coastal Antarctic enhanced level of TSI were found to be correlated with the air mass transport from the ice front sector. Citation: Lai, S. C., T. Hoffmann, and Z. Q. Xie (2008), Iodine speciation in marine aerosols along a 30,000 km round-trip cruise path from Shanghai, China to Prydz Bay, Antarctica, Geophys. Res. Lett., 35, L21803, doi:10.1029/2008GL035492.
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99Tc and 129I are important contributors to risk assessment due to their long half-lives and high mobility as aqueous anionic species. We analyzed 99Tc and 129I in groundwater samples in and near 11 underground nuclear tests and in melt glass and rock samples retrieved from the Chancellor test cavity, Nevada Test Site. The 129I/127I ratio ranges from 10−3 to 10−6 in cavity water and 10−4 to 10−9 in satellite wells. The 99Tc concentration ranges from 3 to 10−4 Bq/l in cavity waters and from 0.3 to 10−4 Bq/l in satellite wells. Downstream migration is apparent for both radionuclides. However, it is affected by both retardation and initial distribution. In-situ 99Tc and 129I K d s calculated using rubble and water concentrations are 3 to 22 ml/g and 0 to 0.12 ml/g, respectively, and are suggestive of mildly reducing conditions. 129I distribution in the melt glass, rubble and groundwater of the Chancellor test cavity is 28%, 24% and 48%, respectively, for 99Tc, it is 65%, 35% and 0.3%, respectively. Our partitioning estimates differ from those of underground tests in French Polynesia, implying that fission product distribution may vary from test to test. Factors that may influence this distribution include geologic conditions (e.g., lithology, water and CO2 content) and the cooling history of the test cavity.
Article
Soil-solution distribution coefficients, Kds, of I- and IO3- were measured by a batch method using 125I for 68 wet (fresh) and autoclaved soils collected from upland fields, paddies, forests and open areas throughout Japan. Nine soil properties, such as Soil-pH, cation exchange capacity (CEC), anion exchange capacity (AEC), active-Al (extractable Al by oxalic acid + ammonium oxalate) and total organic carbon (TOC), were also measured. The Kds for wet sous ranged widely from 1.1 to 10,2001kg-1 for I- and from 2.1 to 82101kg-1 forIO3-. The medians for I- and IO3- were 525 and 437 1 kg-1, respectively. These values were almost two orders of magnitude higher than previously reported Kds for air-dried Japanese soils. The medians of Kds for I and IO3- were the highest for Andosols, followed by Gley soils and Brown Forest soils. The Kds for sandy samples were low. Relatively good correlations (r > 0.65) were found between Kds for wet soils and TOC and total-N, indicating the contribution of organic materials on the sorption of I. The Kds were markedly reduced by autoclaving. The medians of Kds for autoclaved soils for I- and IO3-were 2.4 and 12.41 kg-1, respectively. The effects of autoclaving on the sorption of I were more remarkable than those for IO3-. It was estimated that 86% of I- sorption and 50% of IO3- sorption were attributable to the microbial activities and/or soil fractions which are sensitive to autoclaving.
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[1] A spatial survey of iodine and its long-lived isotope, 129I, in 40 rivers of the USA, Canada, and western Europe, reveals that the ratio of 129I/I is a sensitive indicator for the influence of nuclear fuel reprocessing facilities. Rivers with point sources for 129I in their watersheds are drastically affected, while all rivers sampled show evidence for atmospherically transported 129I from the world's major nuclear fuel reprocessing facilities. Varying mixtures of oceanic cyclic salt and soil-derived iodine account for the observed spatial variation in iodine concentrations. A comparison of 129I concentrations in river and rainwater reveals concentration effects due to evapotranspiration.
Article
To draw the balance of anthropogenic 129I input into European soils, the concentrations of I and 127I in seven soils from Lower Saxony were analyzed down to a depth of 250 cm. In comparison with pre-nuclear soils and Ukrainian soils, we detected a significant anthropogenic input of 129I. Considering the different time periods for the input of 129I and 127I it was possible to assess the dynamics of sorption processes which dominate migration and accumulation. Anthropogenic 129I was successfully used as a tracer for a clarification of the migration processes of trace elements in soils.
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We report on studies of the concentrations of cosmogenic nuclides in the magnetic fraction of cosmic dust particles recovered from the South Pole Water Well (SPWW) and from Greenland. Our results confirm that cosmic dust material from these locations contains measurable amounts of cosmogenic nuclides. The Antarctic particles (and possibly those from Greenland as well) also contain minor amounts of solar Ne. Concentrations of cosmogenic nuclides are consistent with irradiation of this material as small objects in space, with exposure ages similar to the expected Poynting-Robertson (P-R) lifetimes of 50-200 kyr for particles 25-100 μm in size.
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Two simple methods, (1) isotope exchange method and (2) anion exchanger column method, are developed for the determination of chemical forms of radioiodine (iodide and iodate) in water samples. Using these methods, transformations of chemical forms of iodine in various water samples were studied. It was observed that iodate in rain water (unfiltered) and milk tended to change iodide form, whereas iodide was converted to iodate form in seawater and tap water. After the Chernobyl accident both chemical forms of131I (iodide and iodate) were found in rain water samples collected in Japan.
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The Clear Lake area of northern California is the location of hot spring activity, some of which is associated with the formation of Au and Hg deposits. We measured and ratios in nine warm springs (formation springs), six cold springs with elevated levels of Cl and I (mineral springs), and five springs of recent meteoric origin. Dating of the I in the formation waters indicated that sources of I in these waters are formations with minimum ages between 60 and 80 Ma. This age range is in good agreement with the ages of the Franciscan Complex and the Great Valley Sequence, the dominant formations in this area. Because the mineral waters are essentially formation waters diluted with meteoric water, I in these waters is of the same origin.Residence times of the waters were calculated based on the build-up of129I and 36Cl as a consequence of the presence of U and Th in the crust. The residence time of the formation waters in the Great Valley Sequence, the location for most of these springs, was probably not longer than 84,000 yr. The concentrations found for 36Cl and 129I in the mineral waters indicate that these waters have residence times of similar magnitude in formations such as the Franciscan Complex or the Clear Lake Volcanics, which have slightly higher levels of U and Th than the Great Valley Sequence.
Article
The largest reservoir of crustal iodine is found in marine sediments, where it is closely associated with organic material. This presence, together with the existence of a long-lived, cosmogenic radioisotope 129I (t1/2 = 15.7 Ma), make this isotopic system well suited for the study of sediment recycling in subduction zones. Reported here are the results of 129I/I ratios in volcanic fluids, collected during a comprehensive study of fluids and gases in the Central American Volcanic Arc. 129I/I ratios, together with I, Br, and Cl concentrations, were determined in 79 samples from four geothermal centers and a number of crater lakes, fumaroles, hot springs, and surface waters in Costa Rica, Nicaragua, and El Salvador. Geothermal and volcanic fluids were found to have iodine concentrations substantially higher than values in seawater or meteoric waters. 129I/I ratios in most of the geothermal fluids are below the preanthropogenic input ratio of 1500 × 10−15, demonstrating that recent anthropogenic additions are largely absent from the volcanic systems. The majority of the 129I/I ratios are between 500 and 800 × 10−15. These ratios indicate minimum iodine ages between 25 and 15 Ma, in good agreement with the age of subducted sediments in this region. In all four geothermal systems, however, a few samples were found with iodine ages older than 40 Ma—that is, considerably below the expected age range for subducted sediments from the Cocos Plate. These samples probably reflect the presence of iodine derived from sediments in older accreted oceanic terraines. The iodine ages indicate that the magmatic end member for the volcanic fluids originates in the deeper parts of the subducted sediment column, with small additions from older iodine mobilized from the overlying crust. The high concentrations of iodine in geothermal fluids, combined with the observed iodine ages, demonstrate that remobilization in the main volcanic zone (and probably also in the forearc area) is an important part in the overall marine cycle of iodine and similar elements.
Article
A method for the determination of the total amount of iodine in soil by inductively coupled plasma mass spectrometry was developed. Iodine in soil was completely extracted by heating a mixture of 5 mL of 5% tetramethylammonium hydroxide solution and 100 mg of soil for 3 h in an oven at 70°C. Indium as an internal standard was added and the extract was diluted at least more than 10-fold. Iodine amount in the solution was determined by measuring the signal intensity of I against that of In. When the method was tested by analyzing four reference soil samples (GSS-1, 4, 5, and 7), the iodine contents obtained were in good agreement with the certified values for the samples.
Article
In order to analyze the behavior and phytoxicity of iodine in soil, the chemical forms of soil iodine must be identified. Therefore, a method for quantitative speciation of iodine in soil was proposed. Iodine extracted from soil samples with tetrametBPyIammonium hydroxide (TMAH) was separated into humic and fnalvic acid fractions at pH4 1.5 after the addition of ascorbic acid into the TMAH extract to reduce iodate into iodide. Since the iodide in the TMAH extract was recovered in the fdvic acid fraction by this procedure, iodine contained in the haamic acid fraction was considered to be organically bound. Podine in the fulvic acid fraction was separated into organic iodine bound to fnlvic acids and the total inorganic iodine. Furthermore, iodine soluble from soil in 0.1 mol L potassium chloride was assumed to correspond to the amount of total iodide in soil, and from the difference in the concentration of total inorganic iodine and soluble iodide, the amount of iodate was calculated. By the application of this method, iodine in soil was separated into four fractions: organic iodine bound to humic acids, organic iodine bound to fulvic acids, iodate, and iodide. This speciation method was applied to two soils. It was found that s Barge proportion of iodine in soil occurred in an organicalPy bound form.
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The equipment required for the accelerator mass spectrometry (AMS) analysis of heavy elements using small tandem accelerators is reviewed, and examples of the analytical capability for 129I and precious metals, including the platinum group elements, are given.
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The inorganic speciation of soluble iodine has been determined in size-fractionated aerosol samples collected from the tropical Atlantic Ocean in October/November 2002 during Meteor cruise 55, a pilot study of the German SOLAS programme. Iodide concentrations were appreciable (>0.4 pmol m-3) in the fine and coarse modes of all samples whereas iodate was occasionally below detection limit (~0.7 pmol m-3) in samples from northern hemisphere air and was undetectable in all samples from the southern hemisphere. Iodine was enriched, and chlorine and bromine depleted, relative to seasalt concentrations. The majority of Cl- loss was due to the seasalt displacement reaction. Halogen activation (I- + HOX + H+ = IX + H2O) may also have occurred, but did not result in net I- depletion in any aerosol fraction. The observed variations of iodine speciation cannot be reproduced by current models of aerosol iodine chemistry.
Article
Atmospheric iodine models currently predict iodate as the only stable iodine sink species in the troposphere. However, it is shown here using ion chromatograph inductively coupled plasma-mass spectroscopy (IC-ICP-MS) that iodate is the least abundant iodine species in precipitation (rain and snow) collected from various locations in southern Germany, the Swiss Alps, and Patagonia (Chile). The majority of iodine is associated with organic compounds (average 56%) followed by iodide (average 27%). Although the exact structure of the organic fraction remains ambiguous and is probably of higher molecular weight, a smaller portion of the iodo-organic compounds are anionic (5–20% of total I). One of these anionic organo-I peaks is present in all rain and most snow chromatograms and is generally responsible for 5–18% of total iodine. This suggests a ubiquitous atmospheric iodine species. The data indicate that organic iodine compounds play an important role in the global atmospheric iodine cycle and the atmospheric iodine sink. As such, future tropospheric iodine models must consider organic-I reactions.
Article
The concentration and speciation of iodine have been determined in wet and dry deposition at a coastal site over a 15-month period. Deposition fluxes in rain (2.7 μmol m-2 yr-1) and aerosol (3.6-6.5 μmol m-2 yr-1) are the major routes for removal of iodine from the marine atmosphere onto the Earth's surface, with only a minor contribution from direct deposition of methyl iodide (0.003-0.17 μmol m-2 yr-1). Iodate (IO3-) is often considered to be the only species of iodine that is permanently removed to the aerosol phase, and IO3- may therefore be expected to be the dominant form of iodine in precipitation. However, iodide (I-) was found to constitute a significant fraction (5-100%) of iodine in both rain and aerosol. This implies that the rates of iodate formation and iodide volatilization (through reaction with hypohalous acids) are relatively slow. A third pool of aerosol iodine (nonvolatile organic compounds) may also contribute to removal of iodine from the atmosphere in dry or wet deposition.
Article
A simple, fast and sensitive method comprising ion chromatography, eluent suppression columns and spectrophometric methods capable of measuring iodide in concentrations of 0–10 μg 1−1 in natural waters is reported. This method was used to determine the iodide concentrations in water samples from known goitrous and non-goitrous areas in Plateau State, Nigeria. The effects of common substances usually found in water on this method are also reported.
Article
Since February 2006, the new 1MV multielement compact AMS facility SARA (Spanish Accelerator for Radionuclides Analyses) at the Centro Nacional de Aceleradores (CNA) in Sevilla (Spain) is fully operative. During the first one and a half year of operation, the viability of the system for the measurement of 10Be, 14C, 129I and plutonium isotopes, 239Pu and 240Pu, has been evaluated. First results have demonstrated that, in terms of precision and detection limits, the performance of the device compares to other compact AMS facilities, although some progress can still be done in order to optimize its capacities. At this moment, background levels are in the order of 10−14 for 10Be/9Be, 10−13 for 129I/127I, 10−15 for 14C/12C (processed and unprocessed blank) and about 106 atoms for plutonium isotopes: 239Pu, 240Pu and 242Pu. In this work, the current status of the AMS measurements at CNA for the above mentioned radionuclides is described.
Article
Significantly higher efficiencies for 129I measurement by Accelerator Mass Spectrometry (AMS) would be possible if 129I3+ ions could be counted at terminal voltages as low as 1MV. However, at M/Q=3, the molecular interference was anticipated to be severe; this has prevented the use of charge 3+ from being adequately considered. Instead, charge 5+ has been used at higher terminal voltages because of the minimal interference. During a recent performance assessment with charge state 3+, a background of 129I/127I≈10−14 was readily obtained and few 86Sr2+ and 43Ca1+ ions were encountered. This surprising result is possibly due to the very low binding energy and consequent poor stability of anions such as CaSr− and Ca3-. Some triply charged molecular ions were found in the energy spectrum at lower stripping gas pressure but their interference with the detection of 129I3+ was readily suppressed with the Ar gas stripper operated at normal thickness. It now appears that as long as the prepared AMS samples are of good chemical purity, the molecular fragments can be expected to remain quite low in intensity and readily resolved by the final detector. As a result, charge state 3+ can be used for 129I measurements at lower terminal voltages with higher overall efficiency.
Article
Anticipating the application of I-129 as an oceanographic tracer in marine environment studies in the North Pacific, a new beamline has been set up at the AMS facility of the Japan Atomic Energy Research Institute for the measurement of iodine isotopic ratios (I-129/I-127). It is demonstrated that iodine isotopic ratios can be measured with a precision below 2%, and that the detection limit is substantially better than 10(-13). The method of preparing AgI sample material from seawater is described.
Article
In spite of the environmental relevance of 129I, there is still a scarcity of data about its presence in the different natural compartments. In this work, results are presented on the concentration of 129I in rainwater samples taken in Sevilla (southwestern Spain) and in a sediment core taken near the Ringhals coast (Sweden). Typical concentrations of 108 and 109129I at/l are found in rainwater samples, similar to other values in literature. In the case of the sediment core, our results clearly show the impact of anthropogenic sources, with concentrations in the order of 1013129I at./kg and isotopic ratios 129I/127I in the order of 10−8 in the higher layers.
Article
Sample preparation procedures for AMS measurements of 129I and 127I in environmental materials and some methodological aspects of quality assurance are discussed. Measurements from analyses of some pre-nuclear soil and thyroid gland samples and of a systematic investigation of natural waters in Lower Saxony, Germany, are described. Although the up-to-now lowest 129I/127I ratios in soils and thyroid glands were observed, they are still suspect to contamination since they are significantly higher than the pre-nuclear equilibrium ratio in the marine hydrosphere. A survey on all available 129I/127I isotopic ratios in precipitation shows a dramatic increase until the middle of the 1980s and a stabilization since 1987 at high isotopic ratios of about (3.6–8.3)×10−7. In surface waters, ratios of (57–380)×10−10 are measured while shallow ground waters show with ratios of (1.3–200)×10−10 significantly lower values with a much larger spread. The data for 129I in soils and in precipitation are used to estimate pre-nuclear and modern 129I deposition densities.
Article
The current status of sample preparation activities and AMS determination of 129II ratios are described. Determination of 129II ratios is being performed routinely at the precision of 3% (at 10−11 level). A system background of 20−80 × 10−15 of 129II ratio has been achieved without a time-of-flight (TOF) detector and without a low-energy electrostatic deflector. An intercomparison of 129II ratios for AgI samples obtained from other AMS facilities and for the round robin exercise by the International Atomic Energy Agency (IAEA) show an excellent agreement. Potential applications of 129I for tracing groundwater and ocean water are discussed.
Article
A method is described for the measurement of total iodine and sample preparation for accelerator mass spectrometry (AMS) measurement of 129I. Samples were combusted in a stream of oxygen and the iodine liberated was collected in a trapping solution. Aliquots of the trapping solution were used to measure total iodine by gas chromatography and 129I by AMS. The method was tested using standard reference materials 2709 San Joaquin Soil, 2711 Montana Soil and 2704 Buffalo River Sediment from the National Institute of Standards and Technology, IAEA-375 soil from the International Atomic Energy Agency, a bovine thyroid sample from Gomel, KI and KIO3. The recoveries with respect to the reference values were between 89 and 100%. No tracers were used and no efficiency corrections were applied to these results.
Article
At AECL – Chalk River Laboratories, Ontario, Canada solid, low-level radioactive wastes from industrial, academic and medical applications have been stored in trenches above unconsolidated sandy glacial tills and permeable very-fine to fine-grained sands overlying crystalline bedrock. The sandy aquifer system drains into a swamp comprised of approximately 3 m of sphagnum peat. A comprehensive field and analytical program, involving measurements of total iodine, The maximum iodine concentration and
Article
A simple determination method for halogens (Cl, Br, and I) in plant samples using inductively coupled plasma-mass spectrometry (ICP-MS) was developed. In order to extract these halogens into aqueous solution, a leaching step with tetramethyl ammonium hydroxide (TMAH) under mild conditions was carried out, i.e. a 0.1-g dried sample was left overnight (ca. 12h) in contact with 1mL of 25% TMAH in a small PFA vial at 60°C. Then the sample was transferred to a 50-mL centrifuge tube and diluted to 50mL with deionised water. After centrifugation, halogens in the supernatant were determined by ICP-MS. When standard reference materials were measured by the method, the data were within the 95% confidence range of the certified values. The results also agreed well with the values obtained by neutron activation analysis with correlation factor r>0.99.
Article
VOLUME VI: Boron, Aluminum, Gallium, Indium, and Thallium. Silicon, Germanium, Tin, and Lead. Nitrogen, Phosphorus, Arsenic, Antimony, and Bismuth. Sulfur, Selenium, Tellurium, and Polonium. the Halogens: Fluorine, Chlorine, Bromine, and Iodine. Appendix. Ion-Exchange Resins. Index.
Article
A method for the detection of iodide in geologic materials including surface and ground waters, brines, and extracts from sediment, plants, soil and crude oil is presented. The detection limit of the HPLC system under ideal conditions is 0.45 ng. Applications of the method are related to the use of the 129I isotope system in environmental science and geology. Ion chromatography is used to monitor extraction of I and to determine total I concentrations from samples prepared for measurement of 129I/I ratios by accelerator mass spectrometry. Methods of extraction and sample preparation are described.
Article
Iodine is an important element in studies of environmental protection and human health, global-scale hydrologic processes and nuclear nonproliferation. Biogeochemical cycling of iodine in soils is complex, because iodine occurs in multiple oxidation states and as inorganic and organic species that may be hydrophilic, atmophilic, and biophilic. In this study, we applied new analytical techniques to study the content and speciation of stable iodine in representative surface soils, and sorption and transport behavior of iodine species (iodide, iodate, and 4-iodoaniline) in sediments collected at numerous nuclear facilities in the United States, where anthropogenic ¹²I from prior nuclear fuel processing activities poses an environmental risk. The surface soil samples were chosen for their geographic locations (e.g., near the ocean or nuclear facilities) and for their differing physico-chemical characteristics (organic matter, texture, etc). Extracted solutions were analyzed by IC and ICP-MS methods to determine iodine concentrations and to examine iodine speciation (iodide, iodate, and organic iodine). In natural soils, iodine is mostly (nearly 90% of total iodine) present as organic species, while inorganic iodine becomes important (up to 50%) only in sediments with low organic matter. Results from laboratory column studies, aimed at examining transport of different iodine species, showed much greater retardation of 4-iodoaniline than iodide or iodate. Careful attention must be given to potential interconversion among species when interpreting the biogeochemical behavior of iodine in the environment. In addition to speciation, input concentration and residence time effects will influence the biogeochemical cycling of anthropogenic 129I deposited on surface soils.
Article
The sorption of I on a set of selected minerals was examined by: X-ray absorption near edge structure (XANES) and high concentration chemical sorption experiments, as well as very low concentration tracer (using ¹²⁵I) sorption experiments. A XANES method was used to determine I2, I(V) and I (-I) in supernatant solutions and slurries of minerals. This is, we believe, the first reported use of XANES to investigate the redox state of I that is sorbed on minerals. With this technique, it was determined that pyrite, biotite and magnetite sorb I from solutions containing 1000 μg ml⁻¹ I. In the pyrite/water system, IO3⁻ was reduced to what appeared to be I2 in the XANES scans and sorbed on the minerals surface. Magnetite sorbed I⁻ from solution but not IO3⁻. In contrast, biotite sorbed IO3⁻ from solution but did not take up any I⁻. No changes in I redox state were observed in the magnetite and biotite experiments. Based on this association the presence of Fe(II) in the sorbing phase appears to be related to uptake, but not necessarily to a change in I redox.
Article
Since the previous conference, the Australian National University AMS system has undergone a series of refinements, and the research program conducted on the facility has expanded significantly. The system is now used for the measurement of the isotopes 10Be, 14C, 26Al, 36Cl, 59Ni and 129I. The research program includes projects in hydrology, geomorphology, environmental geochemistry and biomedicine. Chlorine-36 remains the principal isotope, but the demand for other heavy isotopes, especially 26Al, has burgeoned during 1992–93. This paper describes the recent advances with AMS measurements on the 14UD, and details the current status and future direction of the AMS research program.
Article
The AMS program at the University of Rochester is described with mention of the development of a gas-filled magnet isobar separator as a means to overcome the anticipated problems with high sulfur in Cl-36 measurements once a high-intensity ion source is installed. Cl-36 is the radioisotope with the largest numbers of samples measured in recent years. A brief overview of Cl-36 and I-129 applications as well as other projects is given with details to be found in other contributions in this issue.
Article
129I/127I ratios measured in meteoric water and epiphytes from the continental United States are higher than those measured in coastal seawater or surface freshwater and suggest long-range atmospheric transport of 129I from the main source for the earth's surface inventory, viz., nuclear fuel reprocessing facilities. The median ratio for 14 meteoric water samples is 2100 × 10-12, corresponding to a 129I concentration of 2.5 × 107 atoms/L, whereas 9 epiphyte samples have a median ratio of 1800 × 10-12. Calculated deposition rates of 129I in the continental United States reveal that a small but significant fraction of the atmospheric releases from the nuclear fuel reprocessing facilities at Sellafield, England, and Cap de La Hague, France, is deposited after distribution by long-range transport. The inferred dominant mode of transport is easterly, within the troposphere, mainly in the form of the organic gas methyl iodide.
Article
A 3MV multi-element accelerator mass spectrometer (AMS) has been installed in Xi'an, China, and prelimi- nary tests have been completed. The results of both background and precision tests for 4 nuclides are 3.1 × 10-16, 0.2% (14C); 1.8 × 10-14, 1.4% (10Be); 2.3 × 10-15, 1.14% (26Al); and 2.0 × 10-14, 1.75% (129I). The unique features of this facility are the newly developed ion source accepting solid and CO2 samples; the specially designed low-energy injector, including a "beam blanking unit" and "Q-snout"; the acceleration tube structure with the combined magnetic and electrostatic suppression; and the function of the slit stabilization in the post-acceleration system. These features are discussed in terms of the end-user's point of view.
Article
The value of the pre-bomb 129I/127I ratio in the hydrosphere is important for the use of this isotope system for dating and tracing purposes. In order to determine this value and to examine spatial variability, 129I/127I ratios were measured in 25 sediment samples from five cores taken at geographically distinct coastal areas. The results indicate a pre-anthropogenic 129I/127I ratio of 1500×10−15, in good agreement with values derived from previous sediment and groundwater studies. Results from shallow sediments show that the layer of bioturbation is dominated by the addition of anthropogenic 129I. The good agreement between results for this layer from different cores supports the understanding that marine iodine is isotopically homogeneous and associated with organic material which is actively remineralized at the sediment–water interface. Lower ratios (down to 354×10−15, corresponding to an age of 32.5 Ma) and larger variations than expected were found in sections of the cores below the layer of bioturbation. These observations can be explained by the presence of refractory fossil organic material, transported by rivers to the sediments from uplifted, continental shales. The results suggest that marine iodine is present in two forms, a labile component which is isotopically homogeneous, and a refractory component which is associated with kerogen (or other fossil organic compounds) whose 129I/127I ratio reflects the age of these compounds. 129I/127I ratios can be used to identify and date fossil organic material in Recent sediments, the presence of which can alter the assumptions underlying models of the global carbon cycle.
Article
Chemical forms of iodine in soil solutions under non-flooded oxidizing and flooded reducing soil conditions were quantitatively analyzed. The results showed that IO3¯ (oxidation number +5) was the dominant chemical form under non-flooded soil condition (85.8% of water soluble iodine), although most of the iodine was combined with the soil in an insoluble form.In contrast, under the flooded soil condition, a considerable portion of the insoluble iodine combined with the soils was transformed to water soluble iodine, where the concentration of soluble iodine became much higher than that under non-flooded soil condition, and I¯ (oxidation number −1) was the dominant chemical form (86.8% of water soluble iodine), followed by IO3¯ (11.9%).It was assumed that the redox potential was an important factor affecting the concentration of soluble iodine or the ratio of I¯ to IO3¯ in the soil solution.
Article
Iodine-129, with a half life of 15.7Myr (ref. 1), is one of the longest lived of the cosmogenic radionuclides. Although the primordial supply of 129I is now extinct, 129I is continuously being produced in the atmosphere primarily by cosmic ray reactions on xenon2, in the Earth primarily by spontaneous fission of 238U (ref. 3), and in meteorites and the Moon primarily by proton and neutron induced reactions on Te and Ba (ref. 4). The relatively large quantity of 129I introduced into the environment from the nuclear age may be useful as a tracer in groundwater hydrology5. Fissiogenic 129I in large granite formations (batholiths) could be used to establish the suitability of these sites for long term nuclear waste storage, because groundwater movement would carry away the more soluble iodides and disturb the equilibrium 129I/238U ratio. The concentration of 129I in meteorites can be combined with results for shorter-lived radionuclides to provide information on the constancy of the galactic cosmic ray flux over longer time scales than previously possible and also on the preterrestrial history of meteorites. We have applied the new atom counting technique to 129I analysis with a sensitivity (the minimum number of atoms in the sample required to obtain a quantitative result) of less than 107 atoms of 129I in a 1-mg sample. An AgI standard with a known 129I/127I ratio of 10−11 was determined to ±10%, and the background contribution from a reagent grade AgI sample gave an upper limit to the ratio of about 3×10−13. We used a time-of-flight measurement to distinguish 129I from the stable 127I ions that were not separated by the mass analysis system. Our results for the meteorites Bruderheim and Dhajala represent the first direct (that is, not inferred6 from radiogenic Xe) determination of 129I in meteorites. A Xe molecular negative ion was discovered but we show that it is not a problem for 129I analysis.
Article
Analytical procedures in the determination of iodine-129 (half-life: 1.6×107 y) have been studied using accelerator mass spectrometry (AMS), with special references to the separation procedures of iodine from soil samples for the AMS measurement. Iodine was successfully volatilized from soil samples by pyrohydrolysis at 1000 °C and collected in a trap solution. Iodine was purified from the matrix by solvent extraction. Finally, it was precipitated as silver iodide to make a target for AMS. In order to obtain information on the 129I/127I ratio in a chemical blank (or iodine carrier), we have determined the ratios in several iodine reagents and found that the ratios fell in a narrow range around 1.7×10−13. The detection limit for soil sample (1 g material) by the present method was about 0.01 mBq/kg or 4×10−11 as the ratio of stable iodine (129I/127I ratio), i.e. these values were much better than that by neutron activation analysis (NAA) used in our previous studies. We have applied this method in the analysis of soil samples collected from different places in Japan. We could successfully determine 129I in soil samples with low 129I concentrations, which could not be detected by NAA. Sample size necessary for the soil analysis by AMS was only about 0.5 g or less, whereas about 100 g of the sample were required for NAA [Muramatsu, Y., Ohmomo, Y., 1986. Iodine-129 and iodine-127 in environmental samples collected from Tokaimura/ Ibaraki, Japan. Sci. Total Environ. 48, 33-43]. Using this method, new data were obtained for the 129I levels in 20 soil samples collected from background areas far from nuclear facilities, and the ranges were 1.4×10−5−4.5×10−3 Bq/kg as 129I concentrations and 3.9×10−11−2.2×10−8 as 129I/127I ratios. These values are useful in understanding the 129I levels in Japanese environments. Higher 129I concentrations were observed in forest soils than those in field and rice paddy soils should be related to the interception effect of atmospheric 129I due to tree canopies. Relatively high 129I/127I ratios found in rice paddy soils could be explained by their low stable iodine concentrations which were caused by the desorption of stable iodine from the rice paddies during the cultivation.
Article
With the recent addition of a high-energy analysis beam line, the capability to measure 129I has been developed at the NSF-Arizona AMS Laboratory. Preliminary measurements have been made using the +4 and +5 charge states at 2.1 MV with a gas stripper. The current system employs a 90° injection magnet (r=0.36 m) following the ion source. Analysis components following the accelerator include an electrostatic quadrupole doublet lens, a 15° electrostatic deflector (r=1.25 m), a 90° analysis magnet (r=1.27 m) and a 77° spherical electrostatic analyzer (r=2.0 m). Detection of 129I is accomplished with a silicon surface barrier detector. Operation of this system with various iodine samples will be discussed.
Article
Laboratory studies were conducted to quantify and identify the key processes by which iodide (I-) sorbs to subsurface arid sediments. A surprisingly large amount of I- sorbed to three alkaline subsurface sediments that were low in organic matter content; distribution coefficients (Kd's) ranged from 1 to 10 mL/g and averaged 3.3 mL/g. Experiments with pure mineral isolates, similar to the minerals identified in the clay fraction of the sediments, showed that there was little or no I- sorption to calcite (Kd = 0.04 ± 0.01 mL/g), chlorite (Kd = −0.22 ± 0.06 mL/g), goethite (Kd = 0.10 ± 0.03 mL/g), montmorillonite (Kd = −0.42 ± 0.08 mL/g), quartz (Kd = 0.04 ± 0.02 mL/g), or vermiculite (Kd = 0.56 ± 0.21 mL/g). Conversely, a significant amount of I- sorbed to illite (Kd = 15.14 ± 2.84 mL/g). Treating the 125I--laden illite mixtures with dissolved F-, Cl-, Br-, or 127I-, caused 43 ± 3%, 45 ± 0%, 52 ± 3%, and 83 ± 1%, respectively, of the adsorbed I- to desorb. Finally, I- sorption to illite was strongly pH-dependent; the Kd values decreased from 46 to 22 mL/g as the pH values increased from 3.6 to 9.4. An appreciable amount of I- sorbed to illite even under alkaline conditions. These experiments suggest that illite removed I- from the aqueous phase predominantly by reversible physical adsorption to the pH-dependent edge sites. Illites may constitute a substantial proportion of the clay-size fraction of many arid sediments and therefore may play an important role in retarding I- movement in these sediments.
Article
Cyanide, sulfide, iodide, and bromide are separated and detected by using ion chromatography (IC) and electrochemical detection via a silver working electrode. The detection limits are 2 ppb, 30 ppb, 10 ppb, and 10 ppb, respectively. Cyanide and sulfide can be determined simultaneously, as well as with other anions commonly determined by IC. Cyanide contained in Cd and Zn complexes is quantitatively determined as total "free" cyanide, while cyanide contained in Ni and Cu complexes is only partially determined as "free" cyanide. The strongly bound cyanide in Au, Fe, or Co complexes is not detected.
Article
High-performance liquid chromatography (HPLC) has been coupled with on-line Inductively coupled plasma mass spectrometry (ICP/MS) for the speciation of iodide ion I- and five iodo amino acids (monolodotyrosine, dilodotyrosine, 3,3',5-and 3,3',5'-trilodothyronine, and thyroxine) commonly found in thyroglobulin. The absolute detection limits were in a range from 35 to 130 pg as iodine: this is roughly 1 order of magnitude lower than those in conventional methods using stable isotope of iodine. The relative standard deviation of peak-ares measurements was less than 6% for each of the six species. Based on these results, the contents of iodine-containing compounds in an enzymatic digest of bovine thyroglobulin were determined.
Article
In order to more effectively use iodine isotope ratios, 129 I/ 127 I, as hydrological and geochemical tracers in aquatic systems, a new high performance liquid chromatography (HPLC) method was developed for the determination of iodine speciation. The dissolved iodine species that dominate natural water systems are iodide, iodate, and organic iodine. Using this new method, iodide was determined directly by combining anion exchange chromatography and spectrophotometry. Iodate and the total of organic iodine species are determined as iodide, with minimal sample preparation, compared to existing methods. The method has been applied to quantitatively determine iodide, iodate as the difference of total inorganic iodide and iodide after reduction of the sample by NaHSO 3 , and organic iodine as the difference of total iodide (after organic decomposition by dehydrohalogenation and reduction by NaHSO 3) and total inorganic iodide. Analytical accuracy was tested: (1) against certified reference material, SRM 1549, powdered milk (NIST); (2) through the method of standard additions; and (3) by comparison to values of environmental waters measured independently by inductively coupled plasma mass spectrometry (ICP-MS). The method has been successfully applied to measure the concentrations of iodide species in rain, surface and ground water, estuarine and seawater samples. The detection limit was ∼1 nM (0.2 ppb), with less than 3% relative standard deviation (R.S.D.) for samples determined by standard additions to an iodide solution of 20 nM in 0.1 M NaCl. This technique is one of the few methods sensitive enough to accurately quantify stable iodine species at nanomolar concentrations in aquatic systems across a range of matrices, and to quantitatively measure organic iodine. Additionally, this method makes use of a very dilute mobile phase, and may be applied to small sample volumes without pre-column concentration or post-column reactions.
Article
The instrumental design for coupling different liquid chromatographic systems such as ion, reversed phase, and size exclusion chromatography as well as capillary gas chromatography, with ICP-MS for the determination of element species is described. For accurate analyses obtaining 'real time' concentrations of chromatographic peaks, the isotope dilution mass spectrometric (IDMS) technique is applied. Two different spiking modes are possible, one using species-specific and another one using species-unspecific spike solutions of isotope-enriched labelled compounds. The species-specific mode is only possible for element species well defined in their structure and composition, for example iodate or selenite, whereas the species-unspecific mode must be applied in all cases where the structure and composition of the species is unknown, for example, for metal complexes with humic substances. For accurate determinations by the isotope dilution technique the mass discrimination effect must also be taken into account. Iodate, iodide and organoiodine species, including those of humic substances, have been analysed in mineral, drinking and environmental water samples by coupling different liquid chromatographic methods with ICP-IDMS. Heavy metal complexes with humic substances in water samples of different origin have been characterized by size exclusion/ICP-IDMS. The possibilities of determining different environmental selenium species are discussed and the results for the analysis of selenite and selenate, which has been carried out by GC/ICP-IDMS after converting these species into a volatile piazselenol compound, are presented. (C) 1998 Elsevier Science B.V.