Photochemical Degradation of Disposable Face Masks and Polypropylene in Aquatic Environments
Mentor 1
Laodong Guo
Start Date
28-4-2023 12:00 AM
Description
During the COVID-19 pandemic, billions of face masks have been disposed and may eventually end up in terrestrial and aquatic environments. However, the degradation mechanisms of disposable face masks and their environmental fate in the environment remain poorly understood. In the present project, photochemical reactivity of disposable face masks (3-ply) and their degradation products were evaluated and compared to pristine polypropylene (PP), the major plastic polymer in disposable face masks. Before UV-irradiation, face masks were separated into three layers; outer (hydrophobic), middle (polypropylene melt blown non-woven fabric) and inner (non-woven fabric), and each layer was cut into small fragments in pre-combusted glass beakers with predetermined weight/volume ratios. Time series samples were collected to monitor the degradation of face masks and PP and the production of dissolved organic matter (DOM) during weathering. DOM was characterized in terms of dissolved organic carbon (DOC), chromophoric DOM (CDOM) and fluorescence DOM (FDOM), including absorption coefficient, specific UV absorbance (SUVA), spectral slope, and fluorescence excitation-emission matrices, as well as zeta potentials and DOM molecular size. All treatments show significant extent of degradation with a linear increase in both DOC and CDOM compared to dark treatments, with an estimated production rate constant followed the order of outer layer > PP > middle layer > inner layer. In addition, the quality of DOM or their intensive properties, such as SUVA at 254 nm (or aromaticity) and spectral slope, also had an observable change during the weathering of face masks, suggesting concurrent DOM degradation accompanied with DOM release. Changes in fluorescence EEM spectra in the time series samples are consistent with the increased DOC and CDOM during weathering. These results indicate that disposable face masks could suffer from rapid photochemical weathering in the environment, releasing considerable amounts of DOM and other by products into aquatic environments. Further studies are needed to quantify the degradation products of disposable face masks and their environmental impacts.
Photochemical Degradation of Disposable Face Masks and Polypropylene in Aquatic Environments
During the COVID-19 pandemic, billions of face masks have been disposed and may eventually end up in terrestrial and aquatic environments. However, the degradation mechanisms of disposable face masks and their environmental fate in the environment remain poorly understood. In the present project, photochemical reactivity of disposable face masks (3-ply) and their degradation products were evaluated and compared to pristine polypropylene (PP), the major plastic polymer in disposable face masks. Before UV-irradiation, face masks were separated into three layers; outer (hydrophobic), middle (polypropylene melt blown non-woven fabric) and inner (non-woven fabric), and each layer was cut into small fragments in pre-combusted glass beakers with predetermined weight/volume ratios. Time series samples were collected to monitor the degradation of face masks and PP and the production of dissolved organic matter (DOM) during weathering. DOM was characterized in terms of dissolved organic carbon (DOC), chromophoric DOM (CDOM) and fluorescence DOM (FDOM), including absorption coefficient, specific UV absorbance (SUVA), spectral slope, and fluorescence excitation-emission matrices, as well as zeta potentials and DOM molecular size. All treatments show significant extent of degradation with a linear increase in both DOC and CDOM compared to dark treatments, with an estimated production rate constant followed the order of outer layer > PP > middle layer > inner layer. In addition, the quality of DOM or their intensive properties, such as SUVA at 254 nm (or aromaticity) and spectral slope, also had an observable change during the weathering of face masks, suggesting concurrent DOM degradation accompanied with DOM release. Changes in fluorescence EEM spectra in the time series samples are consistent with the increased DOC and CDOM during weathering. These results indicate that disposable face masks could suffer from rapid photochemical weathering in the environment, releasing considerable amounts of DOM and other by products into aquatic environments. Further studies are needed to quantify the degradation products of disposable face masks and their environmental impacts.
