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Photochemical transformation and interaction of octachlorodibenzofuran (OCDF) with microplastics in suspended particulate matter-water system
Summary
Researchers investigated how the toxic pollutant octachlorodibenzofuran undergoes photochemical transformation in the presence of microplastics and suspended particulate matter in water. The study found that microplastics serve as carriers for this hydrophobic organic pollutant, and their co-presence with suspended particles affects the pollutant's breakdown behavior under light exposure.
Microplastics (MPs) and suspended particulate matter (SPM) are widely present in the aquatic environment, serving as carriers for various pollutants. Understanding the phototransformation behavior of hydrophobic organic pollutants in the presence of coexisting microplastics and SPM is crucial for assessing their environmental fate and potential impacts. In this study, we investigated the photochemical transformation behavior of octachlorodibenzo-p-dioxin (OCDF) in water under simulated solar irradiation, using polypropylene (PP) microplastics and SPM collected from the Pearl River. The results showed that the degradation rate of OCDF increased with the increase of PP content in the system. Experiments using EPR and probe molecules, as well as quenching experiments of reactive species, demonstrated that the presence of PP significantly elevated the concentration of reactive oxygen species (ROS) in the system. Through product analysis, we identified the main degradation pathways of OCDF to involve carbon-oxygen bond breaking, dechlorination and substitution reactions. These pathways were further rationalized and verified through theoretical calculations. In addition, we calculated the reaction energy barriers of OCDF attacked by ROS on the surface of particulate matter. Compared with SPM, the reaction energy barrier for OCDF reacting with •O on the PP surface was significantly reduced, suggesting that PP can enhance the photochemical transformation of OCDF by facilitating the reactivity of ROS. This study provides new insights into the photochemical transformation of hydrophobic organic pollutants mediated by microplastics in real aqueous environments, highlighting the role of MPs in altering the fate and behavior of persistent organic pollutants.