Formation of Organic Iodine Supplied as Iodide in a Soil−Water System in Chiba, Japan

Abstract

Speciation of iodine in a soil-water system was investigated to understand the mechanism of iodine mobility in surface environments. Iodine speciation in soil and pore water was determined by K-edge XANES and HPLC-ICP-MS, respectively, for samples collected at a depth of 0-12 cm in the Yoro area, Chiba, Japan. Pore water collected at a 0-6 cm depth contained 50%-60% of organic iodine bound to dissolved organic matter, with the other portion being I(-). At a 9-12 cm depth, 98% of iodine was in the form of dissolved I(-). In contrast, XANES analysis revealed that iodine in soil exists as organic iodine at all depths. Iodine mapping of soil grains was obtained using micro-XRF analysis, which also indicated that iodine is bound to organic matter. The activity of laccase, which has the ability to oxidize I(-) to I(2), was high at the surface of the soil-water layer, suggesting that iodide oxidizing enzymes can promote iodine organification. The distribution coefficient of organic iodine in the soil-water system was more than 10-fold greater than that of iodide. Transformation of inorganic iodine to organic iodine plays an important role in iodine immobilization, especially in a surface soil-water system.

Iodine valence and local environments in borosilicate waste glasses using X-ray absorption spectroscopy

“…1) are similar to those reported previously [4,5,[7][8][9][10][11][12]. Due to shorter core-hole lifetimes during X-ray absorption processes for higher atomic number elements, such as iodine, XANES features are broadened [31].…”

“…A number of earlier studies used XAS to characterize iodine in a wide variety of samples [4][5][6][7][8][9][10][11][12][13], including iodine sorption in cement materials [4], iodine in LAW borosilicate glass [5], as well as iodine in spent solvent from nuclear fuel reprocessing [10]. The XAS studies of iodide (I À ) and iodate (IO 3 À ) sorption in hardened cement paste (HCP) and calcium silicate hydrate (CSH) materials [4] as well as iodine in borosilicate glass [5] are of particular interest because of the general chemical similarity of those materials to the glasses investigated here.…”

Fluoride and iodine enrichment in groundwater of North China Plain: Evidences from speciation analysis and geochemical modeling

“…The Bohai seawater had an iodine concentration of 51.1 μg/L. It can be postulated that during the several events of seawater transgression, seawater iodine was potentially loaded on the sediment at coastal area given the strong assimilation of iodine onto organic matter and metal oxides/hydroxides (Dai et al, 2009;Shetaya et al, 2012;Shimamoto et al, 2011). Under favorable conditions, sediment iodine can be released into groundwater to form iodine-rich Na-Cl type water in coastal area.…”

Hydrogeochemistry of co-occurring geogenic arsenic, fluoride and iodine in groundwater at Datong Basin, northern China

“…Long-term intake of As-or F-contaminated groundwater leads to severe arsenicosis or fluorosis, while excessive iodine intake likely causes hypothyroidism or even thyroid cancers [6][7][8]. The World Health Organization (WHO) has recommended guideline values of 10 μg/L and 1.5 mg/L respectively for As and F in drinking water, but set no provisional limit for I due to data deficiency [9].…”

“…Inorganic I can be largely retained by metal minerals such as Fe, Al and Mn (hydr)oxides widely deposited in sediments [24]. Organic I is closely associated with humic substances probably by incorporation and methylation reactions [8]. Under reducing conditions, I may be migrated via reduction of solid-phase IO 3 2-, reductive dissolution of I-bound metal minerals and degradation of organic I into I -species [23,25].…”