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Molecular fractionation on ferrihydrite eroded the disinfection byproduct formation potential of dissolved organic matter derived from microplastics and biochar
Summary
Researchers investigated how dissolved organic matter released from microplastics and biochar interacts with the mineral ferrihydrite at the water-sediment interface. They found that specific organic compounds were preferentially adsorbed onto the mineral surface, reducing the potential for forming harmful disinfection byproducts during water treatment by over 20%. The study reveals that natural mineral interactions may help mitigate some of the secondary pollution risks associated with microplastic-derived organic matter in water systems.
Dissolved organic matter derived from microplastics (MPDOM) and biochar (BDOM), as examples of anthropogenic DOM, have received significant attention. Nonetheless, molecular fractionation particularly the detailed "kinetic architecture" and sequential assembly of MPDOM and BDOM at the mineral-water interface remains elusive, which significantly alters DOM composition and subsequent disinfection byproducts (DBPs) formation. This work systematically investigated these issues using FT-ICR MS, 2D-COS, PARAFAC analysis, and kinetic assays. For MPDOM, polyphenolics-like from plastic additives and breakdown products were rapidly adsorbed onto ferrihydrite, while combustion-derived condensed aromatics-like in BDOM exhibited priority adsorption. These results aligned with the equilibrium adsorption capacity for phenolics and condensed aromatics calculated by the Folin-Ciocalteu and benzenepolycarboxylic acid methods, 13.93 mg g and 0.93 mgC g for MPDOM, 3.66 mg g and 7.16 mgC g for BDOM, respectively. It suggested that mineral affinity of specific compounds relied on both molecular state and origin. The molecular fractionation driven by the co-action of "mineral-OM" and "OM-OM" interactions consequently eroded DBPs formation potential (21.77 % for MPDOM and 23.05 % for BDOM) by preferentially sequestering unsaturated and aromatic substances with higher chlorine reactivity. Our findings highlight molecular fractionation on minerals is a vital geochemical behavior regulating solid-liquid distribution and chlorine reactivity, advancing our understanding of anthropogenic carbon sequestration and cycling.