Recycling and persistence of iodine 127 and 129 in forested environments: A modelling approach

Environmental iodine as a natural iodine intake in humans and environmental pollution index: a scientometric and updated mini review

Although almost a third of the world's population is exposed to iodine deficiency (ID), and supplementation programs such as enriching table salt have been carried out or are being carried out at the global and national level, in many regions of the world, people are facing an increase in iodine intake, which is mainly due to the presence of large amounts of iodine in water, soil, agricultural products, or high consumption of seafood. Published articles were indexed in the Scopus database (from 2000 to 1 April 2023) were reviewed and analyzed by VOSviewer software. The results showed the growing interest of researchers over the last 20 years in environmental iodine intake. The results of this study can have a significant impact on the planning and policy-making of relevant officials and communities to supply the needed iodine.

Iodide uptake by forest soils is principally related to the activity of extracellular oxidases

129I is a nuclear fission decay product of concern because of its long half-life (16 Ma) and propensity to bioaccumulate. Microorganisms impact iodine mobility in soil systems by promoting iodination (covalent binding) of soil organic matter through processes that are not fully understood. Here, we examined iodide uptake by soils collected at two depths (0-10 and 10-20 cm) from 5 deciduous and coniferous forests in Japan and the United States. Autoclaved soils, and soils amended with an enzyme inhibitor (sodium azide) or an antibacterial agent (bronopol), bound significantly less 125I tracer (93%, 81%, 61% decrease, respectively) than the untreated control soils, confirming a microbial role in soil iodide uptake. Correlation analyses identified the strongest significant correlation between 125I uptake and three explanatory variables, actinobacteria soil biomass (p = 6.04E-04, 1.35E-02 for Kendall-Tau and regression analysis, respectively), soil nitrogen content (p = 4.86E-04, 4.24E-03), and soil oxidase enzyme activity at pH 7.0 using the substrate L-DOPA (p = 2.83E-03, 4.33E-04) and at pH 5.5 using the ABTS (p = 5.09E-03, 3.14E-03). Together, the results suggest that extracellular oxidases, primarily of bacterial origin, are the primary catalyst for soil iodination in aerobic, surface soils of deciduous and coniferous forests, and that soil N content may be indicative of the availability of binding sites for reactive iodine species.