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Xue J, Deng Y, Pi K, Fu QL, Du Y, Xu Y, Yuan X, Fan R, Xie X, Shi J, Wang Y. Enrichment of Geogenic Organoiodine Compounds in Alluvial-Lacustrine Aquifers: Molecular Constraints by Organic Matter. Environ Sci Technol 2024; 58:5932-5941. [PMID: 38502530 DOI: 10.1021/acs.est.3c07314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/21/2024]
Abstract
Organoiodine compounds (OICs) are the dominant iodine species in groundwater systems. However, molecular mechanisms underlying the geochemical formation of geogenic OICs-contaminated groundwater remain unclear. Based upon multitarget field monitoring in combination with ultrahigh-resolution molecular characterization of organic components for alluvial-lacustrine aquifers, we identified a total of 939 OICs in groundwater under reducing and circumneutral pH conditions. In comparison to those in water-soluble organic matter (WSOM) in sediments, the OICs in dissolved organic matter (DOM) in groundwater typically contain fewer polycyclic aromatics and polyphenol compounds but more highly unsaturated compounds. Consequently, there were two major sources of geogenic OICs in groundwater: the migration of the OICs from aquifer sediments and abiotic reduction of iodate coupled with DOM iodination under reducing conditions. DOM iodination occurs primarily through the incorporation of reactive iodine that is generated by iodate reduction into highly unsaturated compounds, preferably containing hydrophilic functional groups as binding sites. It leads to elevation of the concentration of the OICs up to 183 μg/L in groundwater. This research provides new insights into the constraints of DOM molecular composition on the mobilization and enrichment of OICs in alluvial-lacustrine aquifers and thus improves our understanding of the genesis of geogenic iodine-contaminated groundwater systems.
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Affiliation(s)
- Jiangkai Xue
- Key Laboratory of Groundwater Quality and Health, China University of Geosciences, Ministry of Education, Wuhan 430078, China
- School of Environmental Studies, China University of Geosciences, Wuhan 430078, China
| | - Yamin Deng
- Key Laboratory of Groundwater Quality and Health, China University of Geosciences, Ministry of Education, Wuhan 430078, China
- School of Environmental Studies, China University of Geosciences, Wuhan 430078, China
| | - Kunfu Pi
- Key Laboratory of Groundwater Quality and Health, China University of Geosciences, Ministry of Education, Wuhan 430078, China
- School of Environmental Studies, China University of Geosciences, Wuhan 430078, China
| | - Qing-Long Fu
- School of Environmental Studies, China University of Geosciences, Wuhan 430078, China
| | - Yao Du
- Key Laboratory of Groundwater Quality and Health, China University of Geosciences, Ministry of Education, Wuhan 430078, China
- School of Environmental Studies, China University of Geosciences, Wuhan 430078, China
| | - Yuxiao Xu
- Key Laboratory of Groundwater Quality and Health, China University of Geosciences, Ministry of Education, Wuhan 430078, China
- School of Environmental Studies, China University of Geosciences, Wuhan 430078, China
| | - Xiaofang Yuan
- Key Laboratory of Groundwater Quality and Health, China University of Geosciences, Ministry of Education, Wuhan 430078, China
| | - Ruiyu Fan
- Key Laboratory of Groundwater Quality and Health, China University of Geosciences, Ministry of Education, Wuhan 430078, China
- School of Environmental Studies, China University of Geosciences, Wuhan 430078, China
| | - Xianjun Xie
- Key Laboratory of Groundwater Quality and Health, China University of Geosciences, Ministry of Education, Wuhan 430078, China
- School of Environmental Studies, China University of Geosciences, Wuhan 430078, China
| | - Jianbo Shi
- Key Laboratory of Groundwater Quality and Health, China University of Geosciences, Ministry of Education, Wuhan 430078, China
- School of Environmental Studies, China University of Geosciences, Wuhan 430078, China
| | - Yanxin Wang
- Key Laboratory of Groundwater Quality and Health, China University of Geosciences, Ministry of Education, Wuhan 430078, China
- School of Environmental Studies, China University of Geosciences, Wuhan 430078, China
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Du J, Hu Y, Kim K, Choi W. Freezing-Enhanced Photoreduction of Iodate by Fulvic Acid. Environ Sci Technol 2023; 57:20272-20281. [PMID: 37943152 DOI: 10.1021/acs.est.3c07278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2023]
Abstract
Iodate is a stable form of iodine species in the natural environment. This work found that the abiotic photosensitized reduction of iodate by fulvic acid (FA) is highly enhanced in frozen solution compared to that in aqueous solution. The freezing-induced removal of iodate by FA at an initial pH of 3.0 in 24 h was lower than 10% in the dark but enhanced under UV (77.7%) or visible light (31.6%) irradiation. This process was accompanied by the production of iodide, reactive iodine (RI), and organoiodine compounds (OICs). The photoreduction of iodate in ice increased with lowering pH (pH 3-7 range) or increasing FA concentration (1-10 mg/L range). It was also observed that coexisting iodide or chloride ions enhanced the photoreduction of iodate in ice. Fourier transform ion cyclotron resonance mass spectrometric analysis showed that 129 and 403 species of OICs (mainly highly unsaturated and phenolic compounds) were newly produced in frozen UV/iodate/FA and UV/iodate/FA/Cl- solution, respectively. In the frozen UV/iodate/FA/Cl- solution, approximately 97% of generated organochlorine compounds (98 species) were identified as typical chlorinated disinfection byproducts. These results call for further studies of the fate of iodate, especially in the presence of chloride, which may be overlooked in frozen environments.
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Affiliation(s)
- Juanshan Du
- KENTECH Institute for Environmental & Climate Technology, Korea Institute of Energy Technology (KENTECH), Naju 58330, Korea
| | - Yi Hu
- Division of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea
| | - Kitae Kim
- Korea Polar Research Institute (KOPRI), Incheon 21990, Korea
| | - Wonyong Choi
- KENTECH Institute for Environmental & Climate Technology, Korea Institute of Energy Technology (KENTECH), Naju 58330, Korea
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Du J, Kim K, Son S, Pan D, Kim S, Choi W. MnO 2-Induced Oxidation of Iodide in Frozen Solution. Environ Sci Technol 2023; 57:5317-5326. [PMID: 36952586 DOI: 10.1021/acs.est.3c00604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Metal oxides play a critical role in the abiotic transformation of iodine species in natural environments. In this study, we investigated iodide oxidation by manganese dioxides (β-MnO2, γ-MnO2, and δ-MnO2) in frozen and aqueous solutions. The heterogeneous reaction produced reactive iodine (RI) in the frozen phase, and the subsequent thawing of the frozen sample induced the gradual transformation of in situ-formed RI to iodate or iodide, depending on the types of manganese dioxides. The freezing-enhanced production of RI was observed over the pH range of 5.0-9.0, but it decreased with increasing pH. Fulvic acid (FA) can be iodinated by I-/MnO2 in aqueous and frozen solutions. About 0.8-8.4% of iodide was transformed to organoiodine compounds (OICs) at pH 6.0-7.8 in aqueous solution, while higher yields (10.4-17.8%) of OICs were obtained in frozen solution. Most OICs generated in the frozen phase contained one iodine atom and were lignin-like compounds according to Fourier transform ion cyclotron resonance/mass spectrometry analysis. This study uncovers a previously unrecognized production pathway of OICs under neutral conditions in frozen environments.
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Affiliation(s)
- Juanshan Du
- KENTECH Institute for Environmental & Climate Technology, Korea Institute of Energy Technology (KENTECH), Naju 58330, Korea
| | - Kitae Kim
- Korea Polar Research Institute (KOPRI), Incheon 21990, Korea
| | - Seungwoo Son
- Department of Chemistry, Kyungpook National University, Daegu 41566, Korea
| | - Donglai Pan
- Division of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea
| | - Sunghwan Kim
- Department of Chemistry, Kyungpook National University, Daegu 41566, Korea
| | - Wonyong Choi
- KENTECH Institute for Environmental & Climate Technology, Korea Institute of Energy Technology (KENTECH), Naju 58330, Korea
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