Immobilization of fission iodine by reaction with insoluble natural organic matter

Steinberg, Spencer M.; Schmett, G. T.; Kimble, G.; Emerson, David R.; Turner, M. F.; Rudin, Mark

doi:10.1007/s10967-008-0727-2

Cited by 38 publications

(22 citation statements)

References 11 publications

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“…The presence of high organic matter content (LOI) and the implication that the humus level is higher may have contributed to the assimilation of iodine in the top soil which constitutes the primary reservoir of iodine in most soils. Equally, Metal oxides and hydroxides like Fe(OH) 3 may play an important role in controlling iodine behavior in soils, both through adsorption of inorganic iodine and oxidation of iodide (Steinberg et al, 2008a, Steinberg et al, 2008cand Dai et al, 2009. The findings of this study agree with Fuge (2005) who showed that iodine is concentrated in iron-rich soils.…”

Section: Concentration Of Iodine Na K and Fe 2+ In Soilsupporting

confidence: 88%

Concentration of I2, Na, K, Mg and Fe2+ in Soils, Plants, Ash and Salt Samples of Selected Areas of Western Kenya

2016

IJSR

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Table salt is one of the most used food additives with a unique place in food consumption. The chemical and physical composition of traditional salts is not well understood. Two types of reeds from Lugari and Busia regions of western Kenya were studied to establish the concentration of selected nutrients and determine some of the factors affecting the micronutrient content. Cyperus papyrus and Typha latifolia reeds of Lugari and Busia regions respectively, grow in weak acidic soils of pH range from 4.9-6.5. It was observed that an increase in the soil's percentage clay content increases CEC while an increase in soil bulk density decreases the soil's CEC. Soil iodine was found to depend largely on depth, SBD, percentage clay clay and moisture. An increase in depth led to a decrease in iodine level in soil with the top soils (0-15 cm,) recording higher iodine content than sub-soils (15-30 cm deep). As iodine increased with increase in SBD and % clay, Fe 2+ concentration increased with increase in depth in the dry season. There was higher concentration of iodine in Cyperus papyrus reeds from Bidimbidi than in Ululo during both the wet and dry seasons. The K content of T. latifolia was higher than that of C. papyrus with K levels increasing with increase in iodine concentration in both plants. Busia reeds had more Na and K than Lugari reeds for both the wet (2871.8 mg/kg > 2519 mg/kg) and the dry (367 mg/kg > 223 mg/kg) seasons. In the present study, Iodine, K, Na, concentrations increased with ashing process while a decrease in Mg was noted. The concentrations of K and Na were higher in soils than in plants with a Tf ranking order of Na > K > Mg > I for both Busia and Lugari regions. The order of decreasing concentration of the micronutrients in the salt was of the form Na> K >Mg for Busia while for Lugari it was K >Na >Mg. On average, Busia Cyperus papyrus salt had higher Na, pH and moisture content but lower K, 11,930 mg/kg, 10.3, 10.1 % and 3,736.2 mg/kg compared to Lugari Typha latifolia salt whose Na, K, pH and moisture are 3,943.8 mg/kg, 4,635.8 mg/kg, 9.7 and 0.8 % respectively.. Lugari salt samples had a Na:K ratio of 0.9 while Busia's C. papyrus salt had a Na:K ratio of 3.2. Comparing the Na: K ratio of the types of reed salts, T. latifolia has 0.85:1 while C. papyrus has 3.2:1 compared to 4:1 recommended by WHO 2006. From the results, Cyperus papyrus salt may be a better and ideal food salt than Typha latifolia.

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Section: Concentration Of Iodine Na K and Fe 2+ In Soilsupporting

confidence: 88%

Concentration of I2, Na, K, Mg and Fe2+ in Soils, Plants, Ash and Salt Samples of Selected Areas of Western Kenya

2016

IJSR

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“…Below pH 6 iodate sorption is predominantly to iron and aluminium oxides, with iron oxides becoming increasingly important as pH drops (Whitehead, 1974b). Iodate is non-reactive toward organic matter and studies have shown that it is reduced to electrophilic species such HOI or I 2 before incorporation into the organic structure of humus (Francois, 1987a,b;von Gunten, 1999, 2000;Radlinger and Heumann, 2000;Warner et al, 2000;Reiller et al, 2006;Schlegel et al, 2006;Steinberg et al, 2008c). The reduction of iodate has been shown to be faster under acidic conditions (Brummer and Field, 1979); in soils, humic substances can reduce iodate due to their electrondonor characteristics (Wilson and Weber, 1979).…”

Section: Iodatementioning

confidence: 99%

Iodine dynamics in soils

Shetaya

Young

Watts

et al. 2012

Geochimica et Cosmochimica Acta

135

118

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We investigated changes in iodine ( 129 I) solubility and speciation in nine soils with contrasting properties (pH, Fe/Mn oxides, organic carbon and iodine contents), incubated for nine months at 10 and 20°C. The rate of 129 I sorption was greater in soils with large organic carbon contents (%SOC), low pH and at higher temperatures. Loss of iodide (I À ) from solution was extremely rapid, apparently reaching completion over minutes-hours; iodate (IO À 3 ) loss from solution was slower, typically occurring over hours-days. In all soils an apparently instantaneous sorption reaction was followed by a slower sorption process for IO À 3 . For iodide a faster overall reaction meant that discrimination between the two processes was less clear. Instantaneous sorption of IO À 3 was greater in soils with high Fe/Mn oxide content, low pH and low SOC content, whereas the rate of time-dependent sorption was greatest in soils with higher SOC contents. Phosphate extraction (0.15 M KH 2 PO 4 ) of soils, $100 h after 129 I spike addition, indicated that concentrations of sorbed inorganic iodine ( 129 I) were very low in all soils suggesting that inorganic iodine adsorption onto oxide phases has little impact on the rate of iodine assimilation into humus. Transformation of dissolved inorganic 129 IO À 3 and 129 I À to sorbed organic forms was modelled using a range of reactionand diffusion-based approaches. Irreversible and reversible first order kinetic models, and a spherical diffusion model, adequately described the kinetics of both IO À 3 and I À loss from the soil solution but required inclusion of a distribution coefficient (k d ) to allow for instantaneous adsorption. A spherical diffusion model was also collectively parameterised for all the soils studied by using pH, soil organic carbon concentration and combined Fe + Mn oxide content as determinants of the model parameters (k d and D/r 2 ). The kinetic model parameters were not directly related to a single soil parameter; inclusion of pH, SOC, oxide content and temperature was necessary to describe the observed behaviour. From the temperature-dependence of the sorption data the activation energy (E a ) for 129 IO À 3 transformation to organic forms was estimated to be $43 kJ mol À1 . The E a value was independent of %SOC and was consistent with a reaction mechanism slower than pore diffusion or physical adsorption, but faster than most surface reactions.

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“…Among other potential naturally-occurring sorbents for 129 I, natural organic matter which may be stable for geological storage seems to be the most promising candidate [35].…”

Section: Surface Oxidationmentioning

confidence: 99%

Iodide interaction with natural pyrite

Aimoz

Curti

Mäder

2011

J Radioanal Nucl Chem

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Abstract129 I is one of the major dose-determining nuclides in the safety analysis of deep storage of radioactive waste. Iodine forms anionic species that hardly sorb on the surfaces of common host-rock minerals. Recently, interest has arisen on the role of pyrite, an accessory mineral capable of binding anionic selenium. Whereas the interaction of selenium with pyrite is well documented, corresponding results on iodine sorption are still scarce and controversial. Pyrite is present in argicilleous rocks which are being considered in many countries as potential host rocks for a radioactive waste repository. The uptake of iodide (I -) on natural pyrite was investigated under nearly anoxic conditions (O 2 \ 5 ppm) over a wide concentration range (10 -11 -10 -3 M total I -) using 125 I as the radioactive tracer. Weak but measurable sorption was observed; distribution coefficients (R d ) were less than 0.002 m 3 kg -1and decreased with increasing total iodide concentration. Iodide sorption was connected to the presence of oxidized clusters on the pyrite surface, which were presumably formed by reaction with limited amounts of dissolved oxygen. The results obtained indicated that pyrite cannot be considered as an effective scavenger of 129 I under the geochemical conditions prevailing in underground radioactive waste geologic storage.

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Immobilization of fission iodine by reaction with insoluble natural organic matter

Cited by 38 publications

References 11 publications

Concentration of I2, Na, K, Mg and Fe2+ in Soils, Plants, Ash and Salt Samples of Selected Areas of Western Kenya

Concentration of I2, Na, K, Mg and Fe2+ in Soils, Plants, Ash and Salt Samples of Selected Areas of Western Kenya

Iodine dynamics in soils

Iodide interaction with natural pyrite

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