Interfacial Molecular Fractionation on Ferrihydrite Reduces the Photochemical Reactivity of Dissolved Organic Matter

Abstract

The selective sorption of dissolved organic matter (DOM) on minerals is a widespread geochemical process in the natural environment. Recent studies have explored the influence of this process on the molecular fractionation of DOM at water–mineral interfaces. However, it remains unclear how molecular fractionation affects the photochemistry of DOM. Here, we demonstrate that the adsorptive fractionation of DOM on ferrihydrite greatly reduces its photoproduction of reactive oxygen species (ROS) including 1O2, O2 •–, and •OH normalized to organic carbon (ROSOC). The ROSOC for 1O2, O2 •–, and •OH were positively correlated with the abundances of polyphenols and oxygenated polycyclic aromatics, which were also observed using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis to be preferentially sequestered by ferrihydrite. The molecules that preferentially remained in the solution after adsorption displayed low levels of ROSOC. The molecular fractionation of DOM induced by adsorption on ferrihydrite therefore influenced the molecular components and also significantly reduced the photoreactive fractions of DOM in waters. These results are very important in promoting our understanding of the effects of molecular fractionation on the biogeochemical features, behaviors, and implications of DOM in the environment.

Loss and Increase of the Electron Exchange Capacity of Natural Organic Matter during Its Reduction and Reoxidation: The Role of Quinone and Nonquinone Moieties

“…Based on a 1:1 stoichiometric reaction, the consumed Na 2 S 2 O 4 provided the reactive quinone amount in NOM . The Folin–Ciocalteu method was employed to measure the total phenolic content in NOM based on the chromogenic specific response. , The thiol content was assessed using the standard addition method through the fluorescence derivative reaction with TG-1 . The aldehyde/ketone content was quantified using N-doped carbon dots (Figure S1) through fluorescence quenching.…”

Singlet Oxygen Quantum Yields in Environmental Waters

“…Palma et al, 256 Chen et al, 257 Wasswa et al, 258 Wan et al, 259 Guo et al, 260 Leresche et al, 261 Wang et al, 262 and Zhou et al 263 ) have been published after March 2020 and are not included in this review.…”

“…Nine additional papers reporting 1 O 2 quantum yield values (Wang et al, Palma et al, Chen et al, Wasswa et al, Wan et al, Guo et al, Leresche et al, Wang et al, and Zhou et al) have been published after March 2020 and are not included in this review.…”

Unexpected molecular diversity of brown carbon formed by Maillard-like reactions in aqueous aerosols

“…The detailed analysis conditions are described in the ESI † following the settings utilized in previous studies. 27,28 Meanwhile, ultrapure water and reactants (i.e., Gly, EA, PA, HA, GX, MG, AC, and GAld) were analyzed to represent the blank samples using the same pretreatment procedures as BrC samples. The ESI (Text S3 †) provides additional details about the operation procedures.…”