Iodine Fractions in Soil and Their Determination

Abstract

Iodine is an essential micronutrient for most living beings, including humans. Despite efforts through various iodine deficiency disorders elimination programs, such as salt iodization, this problem still persists. Sub-clinical deficiencies have often an endemic character, and they are characteristic to certain areas, where iodine is low or inaccessible in the geochemical environment. Thus, the monitoring of iodine speciation and fractionation—especially in soil, drinking water, and food—is needed. Therefore, the aim of this work is to review the iodine distribution in most common soil fractions which relate to its bioavailability; and briefly summarize the available methods for their identification in the environmental matrices as well.

Reconstruction of the Sources and Their Contributions to 129I in Northern Xinjiang, China

“…The vegetation could also be beneficial to the infiltration of water and the increase of soil organic matter, 56 which are beneficial to retain 129 I in the soil because about 40−60% of iodine in the soil is associated with organic matters. 57 While low vegetation coverage of the natural Gobi Desert and disturbed sites might have a fragile soil structure and low preservation for surface soil, resulting in the occurrence of soil erosion and soil 129 I depletion. 56 As a result, land utilization and vegetation coverage are also significant determinants for the 129 I distribution in the surface soil in Northern Xinjiang.…”

Iodine: Physiological importance and food sources

“…The concentration of iodine in the soil varies between soil types, locations, and seasons, due to the application of fertilizers and other preparations (such as iodine‐containing compounds used for disinfection), as well as due to the presence of animals. Subclinical iodine deficiencies are often endemic and related to the geochemical environment (Duborská et al, 2021).…”

“…Iodine concentration in topsoil is on average 2.5 mg/kg and approximately 10% is soluble in water (Johnson, 2003). Other forms of iodine are recognized as: (i) exchangeable, (ii) bound to carbonates, (iii) bound to metal oxides, and (iv) bound to organic matter (Duborská et al, 2021). The equilibrium between different forms depends on the constituents and pH of the soil.…”

“…Iodide and iodate are the most abundant forms present in water while iodine incorporated into biomolecules can be found in sediments. Iodomethane (CH 3 I), hypoiodous acid (HIO), and molecular iodine (I 2 ) are in gaseous form and present in the atmosphere (Duborská et al, 2021). Seawater is the largest reservoir of iodine, which evaporates and, after cycling, returns to water.…”

Iodine biofortification of bean (Phaseolus vulgaris L.) and pea (Pisum sativum L.) plants cultivated in three different soils

“…The iodine concentration of soils ranges between <0.1 and 150 mg kg -1 and its chemical form and mobility depend on the soil composition e.g. texture, pH, redox conditions, and anion exchange capacity [12][13][14][15]. In many areas (e.g., Europe, Africa, Southeast Asia), high rainfalls, floods, erosion, and overgrazing can significantly reduce the iodine content of the soil.…”