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Molecular insights into the bonding mechanisms between selenium and dissolved organic matter
Citation:
Zhang, Z., L. M. Miller, H. He, M. Nadagouda, T. Borch, K. O'Shea, AND D. Dionysiou. Molecular insights into the bonding mechanisms between selenium and dissolved organic matter. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, Netherlands, 915:169429, (2024). https://doi.org/10.1016/j.scitotenv.2023.169429
Impact/Purpose:
This work provides a deeper insight into the intricate, naturally occurring interactions between Se species and various components of organic matter and serves as a reference for future Se risk assessment and/or treatment.
Description:
Natural organic matter (NOM) plays a critical role in the mobilization and bioavailability of metals and metalloids in the aquatic environment. Selenium (Se), an environmental contaminant of aquatic systems, has drawn increasing attention over the years. While Se is a vital micronutrient to human beings, animals and plants, excess Se intake may pose serious long-term risk. However, the interaction between Se and dissolved organic matter (DOM) remains relatively unexplored, especially the reaction mechanisms and interactions of specific NOM components of certain molecular weight and the corresponding functional group change. Herein, we report an investigation on the interactions between Se and DOM by focusing on the mass distribution profile change of operationally defined molecular weight fractions of humic acid (HA) and fulvic acid (FA). The results showed that across all molecular weights studied, HA fractions were more prone to enhanced aggregation upon introduction of Se into the system. For FA, the presence of Se species results in aggregation, dissociation, and redox reactions with the first two being the major mechanisms. Total organic carbon analysis (TOC), UV-vis spectroscopy (UV-vis), and Orbitrap MS data showed that [10,30] kDa MW fraction had the most aromatic decrease (CRAM-like, lignin-like and tannin-like) upon addition of SeO2 via dissociation as the dominant mechanism. Fourier transform infrared spectroscopy (FT-IR) revealed that Se based bridging or chelation of functional groups from individual DOM components through hydrogen bonding in the form of Se-O···H and possibly Se···H and/or attractive electrostatic interactions lead to aggregated DOM1···Se···DOM2. It was concluded from two-dimensional correlation analyses of excitation emission matrix (EEM) and FT-IR that the preferred Se-binding follows lipidàpeptideàtanninàaromatic compounds. These results provide new understanding of Se interactions with various NOM components in aquatic environments and provide insight for Se assessing health risk and/or treatment of Se contaminated water.
URLs/Downloads:
DOI: Molecular insights into the bonding mechanisms between selenium and dissolved organic matter
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