Sorption and speciation of iodine in groundwater system: The roles of organic matter and organic-mineral complexes

Li, Junxia; Zhou, Hailing; Wang, Yanxin; Xie, Xianjun; Qian, Kun

doi:10.1016/j.jconhyd.2017.04.008

Cited by 29 publications

(13 citation statements)

References 43 publications

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“…Organic I in the concentration range of 0.07–0.38 μmol/L represents a subordinately important yet variable pool of I in the groundwater (Figure C). The prevalence of dissolved organic I has been recognized to derive from the degradation of organic matter in association with IO 3 – reduction. ,, Compared with IO 3 – , the intermediate species HIO and I 2 exert a stronger affinity for DOM, favoring the formation of iodinated organic compounds under reducing conditions . In particular, HIO shows a high preference for unsaturated, nonaromatic bonds, which are particularly prone to oxidation in the assimilation by organic molecules .…”

Section: Resultsmentioning

confidence: 99%

“…22,23 The preferability and extent of DOM degradation may not only determine the amount of I being released and reassimilated but also affect the secondary precipitation of I. 8,24 Changes in the reactivity and solubility of Fe oxides alter electron shunting as well as the formation of secondary Fe(II) minerals that contribute to I reimmobilization. 5,25 The materialized comprehension of I variability therefore calls for a bioenergetics-based interpretation of the redox processes involved in electron transfer and I mobilization.…”

Section: Introductionmentioning

confidence: 99%

“…The binding of I to sedimentary organic matter and metal (e.g., Fe) oxide minerals during early diagenesis favors the preservation of I in the sediments and thus constitutes the most important sinks of solid-phase I (e.g., in total, up to 65% of the total I in the Datong sediments). , Under evolving redox conditions, the transformation of I-bearing dissolved organic matter (DOM) and Fe minerals was considered the primary process constraining the mobilization of I in aquatic and groundwater systems. − Biomineralization of DOM is able to release iodate (I(V)) into the groundwater, and simultaneous electron transfer to the Fe oxides leads to the migration of Fe(II) and I(V). , These pathways of I partitioning depend strongly upon the availability and lability of DOM. ,− The incorporation of I into secondary Fe(II) minerals (e.g., Fe(II) sulfides) may reimmobilize I into the aquifer sediments, but currently, knowledge is limited about the mechanisms and kinetics of I cycling related to Fe mineralogical transformation . During redox zonation, reduced I species including elemental I (I 2 ) and hypoiodious acid (HIO) may be generated and subsequently incorporated into the DOM. , Because of the harder base nature of IO 3 – than I – , the reduction reaction can facilitate the desorptive migration of I in the aquifers .…”

Section: Introductionmentioning

confidence: 99%

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Spatiotemporal Variability of Groundwater Iodine in the Northern Arid Basins: Significance for Safe Water Supply

Xie

et al. 2022

Environ. Sci. Technol.

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The genesis of geogenic iodine (I)-contaminated groundwater poses a significant threat to long-term water exploitation. Safe and sustainable water supply, particularly in the northern arid basins, demands a quantitative prediction of the high variability of I distribution over hydrogeological timescales. Here, bioenergetics-informed reactive transport modeling was combined with high-resolution molecular characterization of fueling organic matter to decipher the time-controlled interactions between vertical flow and (bio)geochemical processes in I transport within the Datong aquifers. The declining reactivities of I-bearing organic matter and Fe oxides in the 15−40 m depth decreased the rate of I release, while a growing number of pore volumes flushed through the aquifers to leach out I − and organic I. This removal effect is compensated by the desorption of I − from Fe oxides and secondary FeS generated from the concurrent reduction of Fe oxides and SO 4 2− . Consequently, peak concentrations of groundwater I − may have appeared, depending upon the vertical recharge rate, at the first several pore volumes flushed through the aquifers. The current vertical distributions of the various I species likely represent a quasisteady state between I mobilization and leaching. These new mechanistic insights into the dynamic hydrogeological− (bio)geochemical processes support secure groundwater use in the I-affected northern arid basins.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Spatiotemporal Variability of Groundwater Iodine in the Northern Arid Basins: Significance for Safe Water Supply

Xie

et al. 2022

Environ. Sci. Technol.

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“…Such sediments provide favorable material conditions for iodine enrichment in sedimentary facies 29 . For example, the iodine content of sediment in Datong basin (0.18 ~ 1.46 μg/g) 30 is comparable to that of marine sediment (0.03 ~ 2.54 μg/g) 29 , implying the iodine enrichment mechanism is similar in sedimentary basins and oceans. Paleochannel swing enhances the reducing environment, cation exchange, and low infiltration recharge of surface water, which can promote iodine release from iodine-rich aquifer sediment into groundwater 28 .…”

Section: Uneven Spatial Distribution Of Total Iodinementioning

confidence: 94%

Deficiency and excess of groundwater iodine and their health associations

Yan

Han

et al. 2022

Nat Commun

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More than two billion people worldwide have suffered thyroid disorders from either iodine deficiency or excess. By creating the national map of groundwater iodine throughout China, we reveal the spatial responses of diverse health risks to iodine in continental groundwater. Greater non-carcinogenic risks relevant to lower iodine more likely occur in the areas of higher altitude, while those associated with high groundwater iodine are concentrated in the areas suffered from transgressions enhanced by land over-use and intensive anthropogenic overexploitation. The potential roles of groundwater iodine species are also explored: iodide might be associated with subclinical hypothyroidism particularly in higher iodine regions, whereas iodate impacts on thyroid risks in presence of universal salt iodization exhibit high uncertainties in lower iodine regions. This implies that accurate iodine supply depending on spatial heterogeneity and dietary iodine structure optimization are highly needed to mitigate thyroid risks in iodine-deficient and -excess areas globally.

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“…Iodine speciation is controlled by complex physico-chemical factors and microbial activities that strongly influence chemical behavior and mobility (reviewed by Kaplan et al, 2014 and Yeager et al, 2017). For example, high levels of organic matter in the soils and sediments at Sellafield and Chernobyl (Hou et al, 2003) as well as the Savannah River Site (Xu et al, 2011) effectively sequester iodine species on solid phases in these systems (Schmitz and Aumann, 1995; Santschi and Schwehr, 2004; Xu et al, 2011; Li et al, 2017; Hao et al, 2018). By contrast, sediments at the Hanford Site are naturally low in organic carbon (< 1 mg/L); thus, the minerology, specifically iron/ manganese oxides and calcium carbonates, as well as pH play a larger role in iodine speciation and sorption to subsurface sediments (Hu et al, 2005; Kerisit et al, 2018; Lawter et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Microbial Methylation of Iodide in Unconfined Aquifer Sediments at the Hanford Site, USA

et al. 2019

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Incomplete knowledge of environmental transformation reactions limits our ability to accurately inventory and predictably model the fate of radioiodine. The most prevalent chemical species of iodine include iodate (IO3−), iodide (I−), and organo-iodine. The emission of gaseous species could be a loss or flux term but these processes have not previously been investigated at radioiodine-impacted sites. We examined iodide methylation and volatilization for Hanford Site sediments from three different locations under native and organic substrate amended conditions at three iodide concentrations. Aqueous and gaseous sampling revealed methyl-iodide to be the only iodinated compound produced under biotic conditions. No abiotic transformations of iodide were measured. Methyl-iodide was produced by 52 out of 54 microcosms, regardless of prior exposure to iodine contamination or the experimental concentration. Interestingly, iodide volatilization activity was consistently higher under native (oligotrophic) Hanford sediment conditions. Carbon and nutrients were not only unnecessary for microbial activation, but supplementation resulted in >three-fold reduction in methyl-iodide formation. This investigation not only demonstrates the potential for iodine volatilization in deep, oligotrophic subsurface sediments at a nuclear waste site, but also emphasizes an important role for biotic methylation pathways to the long-term management and monitoring of radioiodine in the environment.

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Sorption and speciation of iodine in groundwater system: The roles of organic matter and organic-mineral complexes

Cited by 29 publications

References 43 publications

Spatiotemporal Variability of Groundwater Iodine in the Northern Arid Basins: Significance for Safe Water Supply

Spatiotemporal Variability of Groundwater Iodine in the Northern Arid Basins: Significance for Safe Water Supply

Deficiency and excess of groundwater iodine and their health associations

Microbial Methylation of Iodide in Unconfined Aquifer Sediments at the Hanford Site, USA

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