Quantifying the Synergistic and Antagonistic Effects of Metal–Organic Complexation on Particulate Matter Oxidative Potential via Redox Kinetics
Year: 2026
Type: preprint
Abstract: Oxidative potential (OP) is an indicator of the ability of redox-active species in particulate matter (PM) to generate reactive oxygen species (ROS) via redox chemistry in lung lining fluid. Previous studies have reported synergistic and antagonistic OP effects in mixtures of metals and non-redox-active organics and attributed them to complexation-induced changes in redox potential and kinetics; however, the quantitative validity of this mechanistic hypothesis remains unclear. Here, we evaluated this hypothesis using a newly developed chemical equilibrium–kinetic DTT assay model for Fe–oxalate system. Experiments showed three distinct stages with increasing oxalate-to-Fe ratio: weak interactions at low ratios, strong antagonism at higher ratios, and strong synergy at extremely high ratios. The model successfully reproduced the weak interactions and antagonism. Fe– oxalate complexation enhanced Fe(II)-driven oxidant reduction kinetics but also shifted the Fe(III)/Fe(II) balance toward Fe(III), decreasing Fe(II) concentrations and offsetting much of the kinetic enhancement. Strong antagonism arose from suppression of Fe(III)-driven DTT oxidation by less reactive Fe(III)–oxalate species. Strong synergy was not reproduced by the model, indicating the involvement of additional pathways. These results indicate that the effects of metal–organic interactions on OP are determined by changes in reaction kinetics, chemical speciation, and metal redox balance.
Source: ChemRxiv
Authors: Satoko Kayaba, Yuji Fujitani
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7211944657