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Aim: The primary aim of this study was to determine the selenium (Se) and iodine (I) food concentrations and dietary intake of the population living in the Kurdish controlled region of northern Iraq. We also assessed the extent to which iodised salt contributes to dietary iodine intake., Methodology: Foods and samples of salt and drinking water were analysed, including 300 crops samples from 40 local farms. The results, supplemented by food composition data, were used to assess dietary Se and I intake for 410 volunteers using a semi-quantitative food questionnaire. To directly investigate the nutritional status of individuals, urine samples were also collected from participants., Results: Selenium intake was mainly supplied by protein and cereal sources. Calculated median dietary intake of Se was 62.7 µg d -1 (mean = 66.3 µg d -1 ) with c. 72 % of participants meeting or exceeding dietary reference intake recommendations for age. Median dietary intake of I, excluding salt consumption, was 94.6 µg d -1 (mean 100.2 µg d -1 ), increasing to 607.2 µg d -1 when salt (of which >90 % was iodized) was included. Salt intake was estimated to be c.13.5 g d -1 (5400 mg Na d -1 ) which greatly exceeds WHO recommended intake (< 2000 mg d -1 of Na). Urine iodine concentrations indicated that 98 % of school aged children had excessive iodine intake (≥300 µg L -1 ) and 80-90 % of all study participants had above average or excessive iodine intake (≥200 µg L -1 )., Conclusions: Poultry and rice are the main sources of dietary Se to this population but around a third of children receive an inadequate Se intake. Fresh fruit and vegetables are the main sources of dietary I, but consumption of local foods cannot supply adequate I without iodised salt supplementation. Consumption of iodized salt well above recommended amounts is supplying this population with substantial iodine intake. Interventions to reduce salt intake would help to limit excessive iodine intake whilst also reducing cardio-vascular risks from Na consumption., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier GmbH.. All rights reserved.)

Iodine deficiency disorders (IDD) in sub-Saharan African countries are related to low dietary I intake and generally combatted through salt iodisation. Agronomic biofortification of food crops may be an alternative approach. This study assessed the effectiveness of I biofortification of green vegetables (Brassica napus L and Amaranthus retroflexus L.) grown in tropical soils with contrasting chemistry and fertility. Application rates of 0, 5 and 10 kg ha -1 I applied to foliage or soil were assessed. Leaves were harvested fortnightly for ~ 2 months after I application before a second crop was grown to assess the availability of residual soil I. A separate experiment was used to investigate storage of I within the plants. Iodine concentration and uptake in sequential harvests showed a sharp drop within 28 days of I application in all soil types for all I application levels and methods. This rapid decline likely reflects I fixation in the soil. Iodine biofortification increased I uptake and concentration in the vegetables to a level useful for increasing dietary I intake and could be a feasible way to reduce IDD in tropical regions. However, biofortification of green vegetables which are subject to multiple harvests requires repeated I applications.

Iodine is an essential micronutrient for human health; phytofortification is a means of improving humans' nutritional iodine status. However, knowledge of iodine uptake and translocation in plants remains limited. In this paper, plant uptake mechanisms were assessed in short-term experiments (24 h) using labelled radioisotopes; the speciation of iodine present in apoplastic and symplastic root solutions was determined by (HPLC)-ICP-QQQ-MS. Iodine storage was investigated in spinach (Spinacia oleracea L.) treated with I - and IO 3 - . Finally, translocation through the phloem to younger leaves was also investigated using a radioiodine ( 129 I - ) label. During uptake, spinach roots demonstrated the ability to reduce IO 3 . Once absorbed, iodine was present as org-I or I - with significantly greater concentrations in the apoplast than the symplast. Plants were shown to absorb similar concentrations of iodine applied as I - . Once absorbed, iodine was present as org-I or I - , via the roots, grown in an inert growth substrate. We found that whilst leaves were capable of absorbing radioactively labelled iodine applied to a single leaf, less than 2% was transferred through the phloem to younger leaves. In this paper, we show that iodine uptake is predominantly passive (approximately two-thirds of total uptake); however, I - can be absorbed actively through the symplast. Spinach leaves can absorb iodine via foliar fertilisation, but translocation is severely limited. As such, foliar application is unlikely to significantly increase the iodine content, via phloem translocation, of fruits, grains or tubers.3 - , via the roots, grown in an inert growth substrate. We found that whilst leaves were capable of absorbing radioactively labelled iodine applied to a single leaf, less than 2% was transferred through the phloem to younger leaves. In this paper, we show that iodine uptake is predominantly passive (approximately two-thirds of total uptake); however, I - can be absorbed actively through the symplast. Spinach leaves can absorb iodine via foliar fertilisation, but translocation is severely limited. As such, foliar application is unlikely to significantly increase the iodine content, via phloem translocation, of fruits, grains or tubers.

Element cycling in the terrestrial environment is heavily reliant upon processes that occur in soil solution. Here we present the first application of microdialysis to sample iodine from soil solution. In comparison to conventional soil solution extraction methods such as Rhizon™ samplers, centrifugation, and high-pressure squeezing, microdialysis can passively sample dissolved compounds from soil solution without altering the in-situ speciation of trace elements at realistic soil moisture conditions. In order to assess the suitability of microdialysis for sampling iodine, the permeability factors and effect of perfusion flowrate on I - and IO 3 recovery was examined in stirred solutions. Furthermore, microdialysis was used to sample native soluble iodine at a range of water contents and iodine-enriched soils to investigate iodine soil dynamics. Total iodine concentrations were measured using ICP-MS. Inorganic species and the molecular weight distribution of organically bound iodine were determined by anion exchange and size exclusion chromatography (SEC) coupled to an ICP-MS, respectively. The most effective recovery rates in stirred solution were observed with the slowest perfusion flowrate yielding 66.2 ± 7.1 and 70.5 ± 7.1% for I - recovery was examined in stirred solutions. Furthermore, microdialysis was used to sample native soluble iodine at a range of water contents and iodine-enriched soils to investigate iodine soil dynamics. Total iodine concentrations were measured using ICP-MS. Inorganic species and the molecular weight distribution of organically bound iodine were determined by anion exchange and size exclusion chromatography (SEC) coupled to an ICP-MS, respectively. The most effective recovery rates in stirred solution were observed with the slowest perfusion flowrate yielding 66.2 ± 7.1 and 70.5 ± 7.1% for I - , respectively. Microdialysis was proven to be capable of sampling dissolved iodine from the soil solution, which accounted for <2.5% of the total soil iodine and speciation followed the sequence: organic-I > I 3 - . The use of SEC coupled to (i) UV and (ii) ICP-MS analysis provided detail regarding the molecular weight distribution of dissolved org-I compounds. Dissolved org-I was detected with approximate molecular weights between 0.1 and 4.5 kDa. The results in this study show that microdialysis is a suitable technique for sampling dissolved iodine species from soils maintained at realistic moisture contents. In addition, inorganic iodine added to soils was predominately bound with relatively low molecular weight (<4.5 kDa) soluble organic matter.-  > IO 3 - . The use of SEC coupled to (i) UV and (ii) ICP-MS analysis provided detail regarding the molecular weight distribution of dissolved org-I compounds. Dissolved org-I was detected with approximate molecular weights between 0.1 and 4.5 kDa. The results in this study show that microdialysis is a suitable technique for sampling dissolved iodine species from soils maintained at realistic moisture contents. In addition, inorganic iodine added to soils was predominately bound with relatively low molecular weight (<4.5 kDa) soluble organic matter., (Crown Copyright © 2019. Published by Elsevier Ltd. All rights reserved.)

Iodine is an essential micronutrient for human health: insufficient intake can have multiple effects on development and growth, affecting approximately 1.9 billion people worldwide. Previous reviews have focussed on iodine analysis in environmental and biological samples, however, no such review exists for the determination of iodine fractionation and speciation in soils. This article reviews the geodynamics of both stable 127 I and the long-lived isotope 129 I (t 1/2 = 15.7 million years), alongside the analytical methods for determining iodine concentrations in soils, including consideration of sample preparation. The ability to measure total iodine concentration in soils has developed significantly from rudimentary spectrophotometric analysis methods to inductively coupled plasma mass spectrometry (ICP-MS). Analysis with ICP-MS has been reported as the best method for determining iodine concentrations in a range of environmental samples and soils due to developments in extraction procedures and sensitivity, with extremely good detection limits typically <μg L -1 . The ability of ICP-MS to measure iodine and its capabilities to couple on-line separation tools has the significance to develop the understanding of iodine geodynamics. In addition, nuclear-related analysis and recent synchrotron light source analysis are discussed.

The rate of reactions between humic acid (HA) and iodide (I(-)) and iodate (IO3(-)) have been investigated in suspensions spiked with (129)I at concentrations of 22, 44 and 88 μg L(-1) and stored at 10 °C. Changes in the speciation of (129)I(-), (129)IO3(-) and mixed ((129)I(-) + (129)IO3(-)) spikes were monitored over 77 days using liquid chromatography inductively coupled plasma mass spectrometry (LC-ICP-MS). In suspensions spiked with (129)I(-) 25% of the added I(-) was transformed into organic iodine (Org-(129)I) within 77 days and there was no evidence of (129)IO3(-) formation. By contrast, rapid loss of (129)IO3(-) and increase in both (129)I(-) and Org-(129)I was observed in (129)IO3(-)-spiked suspensions. However, the rate of Org-(129)I production was greater in mixed systems compared to (129)IO3(-)-spiked suspensions with the same total (129)I concentration, possibly indicating IO3(-)I(-) redox coupling. Size exclusion chromatography (SEC) demonstrated that Org-(129)I was present in both high and low molecular weight fractions of the HA although a slight preference to bond with the lower molecular weight fractions was observed indicating that, after 77 days, the spiked isotope had not fully mixed with the native (127)I pool. Iodine transformations were modelled using first order rate equations and fitted rate coefficients determined. However, extrapolation of the model to 250 days indicated that a pseudo-steady state would be attained after ∼200 days but that the proportion of (129)I incorporated into HA was less than that of (127)I indicating the presence of a recalcitrant pool of (127)I that was unavailable for isotopic mixing., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The aim of this study was to characterise nutritional-I status in Malawi. Dietary-I intakes were assessed using new datasets of crop, fish, salt and water-I concentrations, while I status was assessed for 60 women living on each of calcareous and non-calcareous soils as defined by urinary iodine concentration (UIC). Iodine concentration in staple foods was low, with median concentrations of 0.01 mg kg(-1) in maize grain, 0.008 mg kg(-1) in roots and tubers, but 0.155 mg kg(-1) in leafy vegetables. Freshwater fish is a good source of dietary-I with a median concentration of 0.51 mg kg(-1). Mean Malawian dietary-Iodine intake from food, excluding salt, was just 7.8 μg d(-1) compared to an adult requirement of 150 μg d(-1). Despite low dietary-I intake from food, median UICs were 203 μg L(-1) with only 12% defined as I deficient whilst 21% exhibited excessive I intake. Iodised salt is likely to be the main source of dietary I intake in Malawi; thus, I nutrition mainly depends on the usage and concentration of I in iodised salt. Drinking water could be a significant source of I in some areas, providing up to 108 μg d(-1) based on consumption of 2 L d(-1).

Long-term trends in iodine and selenium retention in soil, and uptake by herbage, were investigated in archived samples from the Park Grass Experiment, initiated in 1856 at Rothamsted, UK. Soil (0-23 cm) and herbage samples from plots receiving various mineral fertilizers and organic manures, with and without lime, were analysed for selenium (Se) and iodine (I) to assess the effect of soil amendments, annual rainfall, crop yield and changes in soil chemistry from 1876 to 2008. Comparing soil from limed and unlimed control (unfertilized) plots, TMAH-extractable Se and I concentrations both diverged, with time, with greater retention in unlimed plots; differences in concentration amounted to 92 and 1660 μg/kg for Se and I, respectively, after 105 yr. These differences were broadly consistent with estimated additions from rainfall and dry deposition. Offtake of both elements in herbage was negligible compared to soil concentrations and annual inputs (<0.003% of total soil I and <0.006% of total soil Se). A positive correlation was observed between I and Se concentrations in herbage, suggesting some common factors controlling bioavailability. A growth-dilution effect for I and Se was suggested by the positive correlation between growing season rainfall ( GSR) and herbage yield together with soil-to-plant transfer factors decreasing with yield. Phosphate and sulphate fertilizers reduced I and Se herbage concentrations, both through ion competition and increased herbage yield. Results suggest that in intensive agriculture with soil pH control, the I requirement of grazing animals is not likely to be met by herbage alone. [ABSTRACT FROM AUTHOR]