紫外線で使い捨てマスクが環境に与える化学的変化を解明（Sun Exposure Changes Chemical Fate of Littered Face Masks）

2025-07-31 ワシントン大学セントルイス校

＜関連情報＞

• https://source.washu.edu/2025/07/sun-exposure-changes-chemical-fate-of-littered-face-masks/
• https://www.sciencedirect.com/science/article/pii/S0304389425011616

使い捨てマスクの光分解が非生物的マンガン酸化物形成を促進する Photolysis of disposable face masks facilitates abiotic manganese oxide formation

Ping-I Chou, Zhenwei Gao, Minkyoung Jung, Mingyang Song, Young-Shin Jun
Journal of Hazardous Materials  Available online: 10 April 2025
DOI:https://doi.org/10.1016/j.jhazmat.2025.138246

Graphical Abstract

Highlights

• Photolysis of disposable face masks promotes Mn oxidation and MnO₂ formation.
• Mn photo-oxidation rates are correlated with the mask material packing density.
• MnO₂ nanoparticles are concentrated near mask surfaces compared to the bulk water.
• Photoaging of mask layers in aqueous environments further enhances Mn oxidation.
• O₂^•- is the main oxidative contributor in MnO₂ formation, while ROO^• also formed.

Abstract

During the COVID-19 pandemic, billions of face masks were discarded into aquatic environments, releasing micro/nanoplastics. This release threatens aquatic ecosystems, influences pollutant transport, and generates reactive oxygen species (ROS). These ROS can affect redox-active metal ions, such as manganese (Mn), in water. Mn oxide solids are commonly found in nature and serve as both electron donors and acceptors in various biogeochemical reactions of trace elements, metal ions, and organics in the environment. However, it remains unclear how disposable face masks, primarily made of polypropylene (PP), impact Mn oxidation and Mn oxides formation in natural surface waters under sunlight. This study, for the first time, reports the photolysis of PP mask layers and their impacts on the kinetics of Mn²⁺ (aq) oxidation to Mn oxide nanoparticles. We found that mask layers enhanced Mn²⁺(aq) photo-oxidation kinetics as their surface material packing density increased. Furthermore, the local concentrations of oxidized Mn²⁺ near the mask surfaces were two orders of magnitude greater than the bulk solution, facilitating heterogeneous Mn oxide formation near mask surfaces. Photoaging of masks further expedited Mn²⁺ oxidation. Superoxide radicals (O₂^•−) generated by mask photolysis were the main responsible ROS for boosting Mn oxidation. These findings highlight the influences of mask photolysis on Mn redox chemistry. Mn oxides formed on mask materials can alter the fate and transport of pollutants such as heavy metals and organic compounds, impacting surface water quality.