Abiotic formation of organoiodine compounds by manganese dioxide induced iodination of dissolved organic matter. (May 2018)

• Record Type: Journal Article
• Authors: Hao, Zhineng; Wang, Juan; Yin, Yongguang; Cao, Dong; Liu, Jingfu
• Is Part Of: Environmental pollution. Volume 236(2018)
• Page Start: 672
• Page End: 679
• Publication Date: 2018-05
• Subjects: Organoiodine compounds (OICs) -- Manganese oxide (δ-MnO2) -- Dissolved organic matter (DOM) -- Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS); Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2018.02.001
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Iodination of dissolved organic matter (DOM) initiated by manganese oxide may represent an important source of organoiodine compounds (OICs) for iodide-containing waters. Here, Suwannee River natural organic matter was selected as model DOM, the OICs formation in simulated freshwater samples from iodinated DOM induced by manganese oxide (δ-MnO2 ) was investigated at different pHs and concentrations of iodide and δ-MnO2 by using negative ion electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR MS). While no OIC was observed in DOM control samples without δ-MnO2, hundreds of OICs were detected in the presence of δ-MnO2, suggesting the enhanced role of δ-MnO2 played in DOM iodination. The relative abundance was defined as the value of dividing the peak intensity of OICs by the highest m/z peak intensity constantly occurred in each mass spectrum, and selected as a parameter for partly reflecting the real level of OICs. The relative abundance of most OICs were around or greater than 1%, and several OICs with higher relative abundance were identified as diiodo-5-hydroxy-4-cyclopentene-1, 3-dione, diiodomethane and diiodoacetic acid. The numbers of the formed OICs increased with the increase concentrations of iodide/δ-MnO2 and the decrease of pH, and nearly all OICs formed at lower levels of iodide/δ-MnO2 and/or higher pH were overlapped by that at higher levels of iodide/δ-MnO2 and/or lower pH, indicating the reliability of FT-ICR MS analysis techniques and data processing method. The OICs were formed mainly from the iodination of typical lignin-like and tannin-like compounds, as well as the precursor compounds with higher relative abundance through substitution reactions. Our findings demonstrate that the OICs formation by δ-MnO2 -initiated DOM iodination should receive more attention and the concentration, exact structure and toxicity of the OICs need to be further investigated. Graphical abstract: Image 1 Highlights: Numerous organoiodine compounds were formed during manganese dioxide-induced iodination of dissolved organic matter. The effects of pH, manganese dioxide and iodide content on organoiodine compounds formation were explored. Most newly formed organoiodine compounds were lignin- and tannin-like compounds. Substitution reaction was the predominant formation pathway for dissolved organic matter iodination. Precursor compounds with higher relative abundance preferentially reacted with reactive iodine species. Abstract : Numerous OICs initiated by δ-MnO2 -induced DOM iodination were detected and their corresponding formation pathways were revealed.